MicroBiology MCQs with Answer and Explnation | Chapter 50

Answer: They are diploid

Bacteria are haploid, meaning they possess only one copy of each chromosome. This differs from eukaryotes, which are typically diploid with two sets of chromosomes. Diploidy in bacteria is rare and often associated with temporary states like conjugation for genetic exchange.

The other options are incorrect:

• Their genetic material is organized into a single chromosome: This is correct. Bacteria typically have a single, circular chromosome.
• Their DNA has intervening sequences (Introns) in almost all genes: This is correct. Most bacterial genes do contain introns, non-coding regions within the DNA that are spliced out during mRNA production.
• They use the same genetic code as all eukaryotes: This is correct. The vast majority of organisms, including bacteria and eukaryotes, use the same universal genetic code to translate DNA sequences into proteins.

Answer: Opsonization

Opsonization is the process where host proteins coat the surface of foreign particles, like bacteria, making them more recognizable and easier for phagocytic cells (e.g., macrophages, neutrophils) to engulf and destroy. These host proteins act as “opsonins,” providing a bridge between the particle and the phagocyte’s receptors.

The other options are incorrect:

• Chemotaxis: This refers to the directed movement of cells or organisms in response to a chemical stimulus. While chemotaxis plays a role in immune cell recruitment towards the site of infection, it is not directly involved in the binding and ingestion of bacteria.
• Chemokine: Chemokines are small signaling molecules that attract immune cells to the site of infection, similar to chemotaxis. While they facilitate phagocytosis indirectly by guiding phagocytes, they are not directly involved in binding bacteria.
• Membrane attack complex (MAC): This is a group of proteins within the complement system that forms pores in the membranes of bacteria, leading to their lysis. While the complement system contributes to opsonization through protein deposition, the MAC specifically targets bacterial membranes for destruction, not opsonization for phagocytosis.

Answer: Rheumatic fever

The ASO (Antistreptolysin O) test primarily helps diagnose rheumatic fever, a potential complication of untreated group A streptococcal infections like strep throat and scarlet fever. The test measures the level of antistreptolysin O antibodies in the blood, which your body produces in response to streptococcal infection. While elevated ASO levels may suggest past strep infection, they’re particularly indicative of rheumatic fever.

The other options are incorrect:

• Rheumatoid arthritis: This is an autoimmune disease, not caused by bacterial infection, and has different diagnostic tests. ASO levels are typically normal in rheumatoid arthritis.
• Typhoid fever: This is caused by the bacterium Salmonella typhi, not group A streptococcus. Different tests, like blood cultures and serological tests, are used for diagnosing typhoid fever. ASO levels are not relevant for it.
• Rickettsial fever: These are a group of tick-borne infections caused by Rickettsia bacteria. Rickettsial fevers have specific diagnostic tests, and ASO levels are not helpful for their diagnosis.

Answer: Psychrophilic

Psychrophilic bacteria thrive in cold environments with temperatures below 20°C (68°F). They have adapted their biological processes to function efficiently in colder conditions. Examples include bacteria found in deep oceans, glaciers, and permafrost.

The other options are incorrect:

• Mesophilic: These bacteria prefer moderate temperatures, typically between 20°C and 45°C (68°F and 113°F). Most human pathogens fall under this category.
• Thermophilic: These bacteria flourish in high temperatures, ranging from 50°C to 80°C (122°F to 176°F). They occur in hot springs, hydrothermal vents, and compost piles.
• Microaerophilic: These bacteria require low oxygen concentrations for growth. While their temperature preferences can vary, they don’t necessarily thrive in cold environments.

Answer: Bacterial capsule

Negative staining is a technique used to demonstrate the presence of bacterial capsules. In negative staining, acidic stains like India ink or nigrosin are used, and the bacterial background appears stained while the capsules remain unstained and appear as halos around the stained cells. This method helps in highlighting the capsules, which are often difficult to visualize using other staining techniques.

The other options are incorrect:

• Bacterial spore: Spores are not readily visible in negative staining as they are highly refractile and don’t stain well. They require different techniques like heat fixation and specific staining methods for visualization.
• Bacterial flagella: While flagella can be seen in negative staining under optimal conditions, their thinness and movement make them difficult to consistently observe. Other techniques like electron microscopy are better suited for flagella visualization.
• Bacterial fimbriae: Similar to flagella, fimbriae are too thin and delicate to be reliably visualized in negative staining. They are often better observed with electron microscopy or specific staining techniques.

Answer: Through configuration

Bacteria can acquire new characteristics through various mechanisms, except through configuration. Configuration refers to the spatial arrangement of molecules within a cell, which doesn’t directly alter the genetic material or introduce new traits. While configuration can influence how genes are expressed, it doesn’t lead to the acquisition of new characteristics.

The other options are incorrect:

• Through plasmids: Plasmids are small, circular pieces of DNA that can replicate independently of the bacterial chromosome. They can carry genes for various traits, including antibiotic resistance and virulence factors. Bacteria can acquire plasmids through conjugation, a process where they exchange genetic material with other bacteria.
• Incorporating part of host DNA: Sometimes, bacteria can take up DNA from their environment, including host DNA. This process, called transformation, can lead to the acquisition of new genes and traits.
• Through bacteriophages: Bacteriophages are viruses that infect bacteria. Some bacteriophages can carry bacterial genes, which they can inject into other bacteria during infection. This can lead to the transfer of new characteristics.

Answer: Bacterial spores

Bacterial spores are the most resistant form of life known, capable of surviving extreme conditions like boiling water, freezing temperatures, and even radiation. This is due to their complex structure, featuring a thick, multi-layered coat and dehydrated cytoplasm. These adaptations protect the spore’s DNA and essential components, allowing it to remain dormant for extended periods until conditions become favorable for germination and growth.

The other options are incorrect:

• Viruses: While some viruses can be quite stable, they generally lack the protective mechanisms of bacterial spores and are vulnerable to heat inactivation.
• Spirochetes: These spiral-shaped bacteria are relatively sensitive to heat and can be readily inactivated by boiling water.
• Streptococcus mutans: This bacterium is a common cause of dental cavities and is readily killed by pasteurization temperatures used in milk processing.

Answer: Pili

Pili, also known as fimbriae, are hair-like appendages composed of protein filaments that extend from the bacterial surface. These structures play a crucial role in bacterial attachment to various surfaces, including host cells, other bacteria, and inanimate objects. They function like tiny grappling hooks, allowing the bacteria to adhere and colonize different environments.

The other options are incorrect:

• Capsule: While capsules are external structures, they are primarily composed of polysaccharides and do not directly participate in bacterial attachment. They serve other functions like protection against phagocytosis by immune cells.
• Flagella: Flagella are whip-like structures used for bacterial motility, enabling them to move towards or away from stimuli. They are not directly involved in attachment.
• Mesosomes: Mesosomes are internal folds of the bacterial plasma membrane and are not external structures. They play a role in cellular respiration and cell division, not attachment.

Answer: Flagella

Monotrichous, Lophotrichous, Amphitrichous, and Peritrichous are all types of flagellar arrangements in the anatomy of a bacterial cell. These terms describe the organization and distribution of flagella, which are whip-like appendages that bacteria use for motility.

The other options are incorrect:

• Ribosomes: These are found in all cells, including bacteria, and are not specific to flagella arrangement.
• Mesosomes: These are not considered distinct bacterial structures in modern understanding and are primarily folds in the cell membrane.
• None of the above: This is incorrect, as all the listed terms are types of flagella arrangements.

Answer: None of the above

Koch’s postulates are a set of criteria used to establish a causal relationship between a microorganism and a disease. None of the microorganisms listed—Treponema pallidum (causing syphilis), Mycobacterium leprae (causing leprosy), and Neisseria gonorrhoeae (causing gonorrhea)—fulfill all the criteria of Koch’s postulates. Koch’s postulates include factors like isolating the microorganism from individuals with the disease, growing it in pure culture, and causing disease upon inoculation into a healthy host.

The other options are incorrect:

• Treponema pallidum: While T. pallidum is the causative agent of syphilis, fulfilling all of Koch’s postulates for this organism can be challenging due to difficulties in cultivating it in the lab.
• Mycobacterium leprae: Similar to T. pallidum, M. leprae is the causative agent of leprosy but its slow growth and fastidious culture requirements make complete adherence to Koch’s postulates difficult.
• N. Gonorrhoeae: This bacterium is the causative agent of gonorrhea, and fulfilling all of Koch’s postulates is more achievable due to its easier cultivation in the lab. However, depending on the specific criteria and experiments considered, there might be some lingering doubts or nuances.

Answer: Heat stable

Endotoxins are lipopolysaccharide (LPS) complexes found in the outer membrane of Gram-negative bacteria. Unlike exotoxins, which are usually proteins and can be denatured by heat, endotoxins are resistant to high temperatures.

The other options are incorrect:

• Highly antigenic: Endotoxins are not highly antigenic. They are weak antigens and do not usually induce a strong immune response compared to proteins or other more immunogenic substances.
• Proteins in nature: This is incorrect. Endotoxins are not proteins; they are composed of lipopolysaccharides. Exotoxins are the bacterial toxins that are proteins in nature.
• Action is often enzymatic: Endotoxins do not typically exhibit enzymatic activity. Exotoxins, on the other hand, often have enzymatic functions that contribute to their toxic effects.

Answer: Bronchial asthma

Ipratropium bromide is a bronchodilator, meaning it relaxes the muscles surrounding the airways in the lungs, making breathing easier. It is primarily used to treat the symptoms of bronchial asthma, a chronic inflammatory condition that causes narrowing of the airways.

The other options are incorrect:

• Renal colic: This is a severe pain in the lower back and abdomen caused by a blocked ureter (tube carrying urine from the kidney to the bladder). Ipratropium bromide has no effect on the urinary tract.
• Organophosphorus poisoning: This type of poisoning affects the nervous system and requires specific antidotes. Ipratropium bromide does not have an effect on the nervous system and is not used in this situation.
• Miosis: This is a constriction of the pupil of the eye. While some anticholinergics like atropine can cause miosis, ipratropium bromide has a minimal effect on the eyes and is not used for this purpose.

Answer: Bacterial

Botryomycosis is a chronic skin infection caused by bacteria, most commonly Staphylococcus aureus. While the name might suggest a fungal origin (“mycosis”), it is actually due to the presence of sulfur granules within the lesions, which previously led to confusion with fungal infections.

The other options are incorrect:

• Fungal: As mentioned above, botryomycosis is not caused by fungi.
• Viral: Viruses do not cause botryomycosis; it is a bacterial infection.
• Parasitic: Parasites are also not involved in botryomycosis.

Answer: Gram negative bacteria

Endotoxin is a component of the outer membrane of gram-negative bacteria. It’s a lipopolysaccharide (LPS) molecule that can trigger a strong inflammatory response in the body when released.

The other options are incorrect:

• C. albicans: This is a type of fungus, not a bacterium, and doesn’t produce endotoxins.
• S. sanguis: This is a gram-positive bacterium, which means it has a different cell wall structure compared to gram-negative bacteria and doesn’t contain endotoxins.
• Actinomyces viscosus: This is also a gram-positive bacterium and doesn’t produce endotoxins.

Answer: Region III

Region III of the cell wall, specifically the lipid A portion of lipopolysaccharide (LPS), is responsible for the endotoxic activity in Gram-negative bacteria. This lipid A component is released during bacterial lysis and has potent inflammatory properties, contributing to the symptoms associated with endotoxins.

The other options are incorrect:

• Region I: There is no specific indication of a “Region I” in the context of cell wall components responsible for endotoxic activity.
• Region II: There is no specific indication of a “Region II” in the context of cell wall components responsible for endotoxic activity.
• Bovine antigen: Bovine antigen is not a component of the cell wall responsible for endotoxic activity. The endotoxic activity is primarily associated with the lipid A component of lipopolysaccharide (LPS) in Gram-negative bacteria.

Answer: Conjugation

Plasmids are transmitted to other bacteria through a process called conjugation. In conjugation, a donor bacterium transfers genetic material, including plasmids, to a recipient bacterium through direct cell-to-cell contact. This transfer is facilitated by a structure called a pilus.

The other options are incorrect:

• Transformation: Transformation involves the uptake of free DNA from the environment by a bacterial cell. While plasmids can be involved in transformation, the question specifically asks about the transmission of plasmids to other bacteria, and that process is termed conjugation.
• Transduction: Transduction involves the transfer of genetic material from one bacterium to another by a bacteriophage (virus). Plasmids are not typically transmitted through transduction.
• All of the above: This option is incorrect because the primary mode for plasmid transmission to other bacteria is conjugation. While plasmids can be involved in transformation, and transduction can transfer genetic material, the question specifically asks about plasmid transmission.

Answer: Released from bacterial cell wall

Exotoxins are secreted by bacteria, meaning they actively released from the cell and diffuse into the surrounding environment. They do not remain within the bacterial cell wall. This differentiates them from endotoxins, which are integral components of the cell wall and only released upon cell death or lysis.

The other options are incorrect:

• Produced in minute amounts: While some exotoxins are indeed highly potent and require small amounts to cause significant effects, others can be produced in larger quantities. Production amount depends on the specific toxin and bacterial species.
• Destroyed by proteolytic enzymes: Many exotoxins are indeed susceptible to breakdown by enzymes like proteases, but not all. Some possess structures that resist enzymatic degradation.
• Weakly antigenic: Exotoxins can be highly antigenic, meaning they trigger a strong immune response in the host. This is why antibodies against specific exotoxins can be used for vaccination or passive immunization.

Answer: After meals

After meals, there is an influx of food particles and sugars into the oral cavity, providing a readily available source of nutrients for bacteria to multiply. This leads to a temporary increase in bacterial numbers compared to other times of the day.

The other options are incorrect:

• In the morning: While bacteria may have been replicating overnight, the lack of recent food intake limits their available resources, so their numbers are generally lower than after meals.
• At night: Following dinner and throughout the night, there is typically a gradual decrease in bacterial numbers due to reduced food intake and increased salivary flow, which has bacteria-cleansing properties.
• After brushing: Brushing effectively removes bacteria from the oral cavity, significantly reducing their overall numbers compared to any other time of the day.

Answer: Facultative anaerobic

Facultative anaerobes are the only option that can grow both in the presence and absence of oxygen. They adapt their metabolism depending on the oxygen availability, utilizing the more efficient aerobic respiration with oxygen present and switching to fermentation pathways without oxygen.

The other options are incorrect:

• Microaerophilic: These microorganisms require low oxygen concentrations for growth and are inhibited by normal atmospheric levels.
• Obligate aerobic: These organisms strictly require oxygen for their metabolism and cannot survive in its absence.
• Anaerobic: Anaerobes grow exclusively in the absence of oxygen and are often poisoned by its presence.

Answer: Divide by binary fission

Bacteria are prokaryotic organisms, meaning they lack complex membrane-bound organelles like mitochondria. Binary fission is the most common mode of reproduction in bacteria, where a single cell divides into two identical daughter cells through a simple splitting process.

The other options are incorrect:

• Mitochondria always absent: This is true. As mentioned before, bacteria lack mitochondria due to their prokaryotic nature.
• Sterols always present in cell wall: This is false. While some bacteria, like Gram-positive bacteria, have cell walls containing peptidoglycan, others, like Gram-negative bacteria, have cell walls primarily composed of lipopolysaccharides and lack sterols.
• Can be seen only under electron microscope: This is false. While some bacteria are indeed very small and require electron microscopes for detailed visualization, many larger bacterial species can be observed under a light microscope with proper staining techniques.

Answer: Bacteriodes fragilis

While Bacteriodes fragilis is a common bacteria found in the intestines, it is not a typical cause of urinary tract infections (UTIs). UTIs are primarily caused by bacteria that originate from the lower gastrointestinal tract and periurethral region, not the upper intestine where Bacteriodes fragilis resides.

The other options are incorrect:

• Klebsiella pneumoniae: This bacteria can cause UTIs, especially in those with compromised immune systems or catheters.
• Escherichia coli (E. coli): This is actually the most common culprit for UTIs, responsible for up to 80% of cases.
• Proteus mirabilis: This bacteria is another frequent cause of UTIs, particularly in hospital settings and among individuals with urinary tract abnormalities.

Answer: Pneumonia

A throat culture is not typically useful for diagnosing pneumonia. Pneumonia is an infection primarily involving the lower respiratory tract (lungs), and the organisms causing pneumonia are not usually present in the throat. Other diagnostic methods, such as chest X-rays and sputum cultures, are more appropriate for identifying pneumonia.

The other options are incorrect:

• Streptococcal sore throat: A throat culture is commonly used to diagnose streptococcal sore throat caused by Streptococcus pyogenes (group A streptococcus). The culture helps identify the presence of the bacteria.
• Diphtheria: A throat culture is used for diagnosing diphtheria, an infection caused by Corynebacterium diphtheriae. The culture helps confirm the presence of the bacterium.
• Thrush: Thrush is a fungal infection caused by Candida species. While a throat culture may not be the primary diagnostic method for thrush, other methods, such as clinical examination and microscopy, are used to identify fungal infections.

Answer: Enterococcus faecalis

While Enterococcus faecalis is a type of bacteria found in the intestines of some healthy people, it’s not a typical culprit for diarrhea. The other three options, Shigella spp, Salmonella spp, and Campylobacter spp, are all major bacterial causes of this common gastrointestinal issue.

The other options are incorrect:

• Shigella spp: These bacteria invade and damage the intestinal lining, leading to bloody diarrhea, fever, and abdominal cramps.
• Salmonella spp: These bacteria contaminate food and water sources, causing nausea, vomiting, diarrhea, and abdominal pain.
• Campylobacter spp: These bacteria are commonly found in raw poultry and unpasteurized milk, causing watery diarrhea, fever, and abdominal cramps.

Answer: Streptococcus faecalis

Streptococcus faecalis is a representative of the faecal streptococci group. Faecal streptococci are a group of bacteria that inhabit the intestines of humans and animals, and they are often used as indicators of fecal contamination in water. Streptococcus faecalis is a species within this group.

The other options are incorrect:

• Streptococcus bovis: This species is also found in the gut but is less common and primarily associated with opportunistic infections in the elderly and those with underlying conditions.
• Streptococcus equinus: As the name suggests, this species primarily colonizes the intestines of horses and other animals. While it can rarely cause infections in humans, it’s not considered a typical faecalstreptococcus.
• Streptococcus faecium: This species shares some similarities with S. faecalis but is less frequently isolated from human feces and exhibits different pathogenic potential.

Answer: 7-14 days

The development of a stable gut flora in newborns is a dynamic process that occurs over several weeks. While microorganisms begin colonizing the baby’s intestines immediately after birth, it takes some time for a diverse and stable community to establish itself.

The other options are incorrect:

• 1 day: It’s too early for a stable flora to be established at this point. The initial microorganisms are primarily acquired from the mother during birth and breastfeeding.
• 7 days: While significant colonization has occurred by this time, the composition of the flora is still fluctuating and susceptible to changes in diet and environmental factors.
• 30 days: This may be too long for some newborns, especially those breastfed. For most babies, a relatively stable flora is established within 7-14 days, although the composition can continue to refine further over months and even years.

Answer: Staphylococcus aureus

The nose and skin are considered the best anatomic locations for Staphylococcus aureus. Staphylococcus aureus is a common bacterium that is part of the normal flora of the skin and anterior nares (nose) in many individuals.

The other options are incorrect:

• Bacteroides species: Bacteroides species are anaerobic bacteria commonly found in the gastrointestinal tract. They are not typically associated with the nose and skin.
• Gardnerella vaginalis: Gardnerella vaginalis is associated with bacterial vaginosis and is primarily found in the vaginal environment. It is not a common inhabitant of the nose and skin.
• Enterococcus: Enterococcus species are often found in the gastrointestinal tract and can be present in other body sites. However, they are not specifically associated with the nose and skin.

Answer: lt cannot be eradicated by antimicrobial agents

The normal microbial flora present on the skin and mucous membranes cannot be completely eradicated by antimicrobial agents. These microorganisms are part of the body’s natural microbiota and play important roles in maintaining a balanced and healthy environment.

The other options are incorrect:

• It is absent in the stomach due to the acidic pH: This statement is incorrect. While the stomach has a low pH due to gastric acid, it is not completely devoid of microorganisms. Some bacteria, such as Helicobacter pylori, can survive in the acidic environment of the stomach.
• It establishes in the body only after the neonatal period: This statement is incorrect. The establishment of normal microbial flora begins shortly after birth and continues during the neonatal period and beyond.
• The flora in the small bronchi is similar to that of the trachea: This statement is incorrect. The microbial flora in different regions of the respiratory tract can vary. The flora in the small bronchi may differ from that in the trachea and other respiratory structures.

Answer: Gut of human

Klebsiella, particularly Klebsiella pneumoniae, is a common inhabitant of the human gut, particularly the large intestine or colon. It is part of the normal gut microbiome and generally doesn’t cause harm unless it enters other parts of the body, especially those normally sterile, like the bloodstream or lungs, resulting in potential infections.

The other options are incorrect:

• Colon of humans: While Klebsiella primarily resides in the large intestine, including the colon, it’s important to clarify it can also be found in other parts of the gut.
• Nose of humans: Although Klebsiella can transiently be present in the nose of healthy individuals, it’s not a typical or permanent resident. Its primary habitat is the gut.
• Eyes of humans: Klebsiella is not part of the normal flora of the healthy human eye. Its presence in the eyes can indicate an infection requiring medical attention.

Answer: Periodontal disease.

Periodontal disease, also known as gum disease, is a common affliction in humans. It involves inflammation of the gums and, if left untreated, can lead to damage to the soft tissues and bone supporting the teeth. Periodontal disease is prevalent across different age groups and can affect a significant proportion of the population.

The other options are incorrect:

• Severe acute respiratory syndrome: Severe Acute Respiratory Syndrome (SARS) is a respiratory illness caused by a coronavirus. While it can be severe, it is not as commonly prevalent as periodontal disease in the general population.
• Acquired immune deficiency syndrome: Acquired Immune Deficiency Syndrome (AIDS) is caused by the human immunodeficiency virus (HIV). It is a serious condition, but its prevalence is lower compared to periodontal disease, which affects a larger proportion of the population.
• Caries: Caries refers to tooth decay or cavities. While it is a common dental issue, periodontal disease (gum disease) is generally more prevalent and affects a broader population. Periodontal disease involves the inflammation of the gums and supporting structures.

Answer: Ribosomes

Ribosomes are responsible for protein synthesis, a vital process for all living cells, including bacteria. However, these proteins are mainly involved in internal cellular functions and don’t typically interact with the host immune system. Therefore, they are less likely to contain valuable antigens that could trigger an immune response.

The other options are incorrect:

• Cell wall: The bacterial cell wall acts as a barrier between the bacterium and its environment. It often contains unique components not found in human cells, making it a rich source of valuable antigens for vaccine development.
• Flagella: These tail-like appendages help bacteria move and interact with their surroundings. Flagellar proteins can trigger an immune response, especially when specific bacteria are associated with infections.
• Capsule: This slimy outermost layer protects bacteria from various environmental stresses and the host immune system. Capsule composition can vary based on the bacterial species, and some components can elicit strong immune responses, making them valuable antigens.

Answer: Ecoli

N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) are the building blocks of peptidoglycan, a rigid polymer that forms the backbone of the bacterial cell wall. E. coli, like most bacteria, possesses a cell wall and therefore incorporates NAM and NAG into its structure.

The other options are incorrect:

• Mycoplasmas: These unique bacteria lack a true cell wall due to a minimal peptidoglycan layer or complete absence. Consequently, they wouldn’t have significant amounts of NAM and NAG.
• Amoeba: While amoebas are single-celled eukaryotes, they don’t have a bacterial cell wall and wouldn’t require or utilize NAM and NAG. Their outer membrane has a different composition altogether.
• Spheroplast: This term refers to a bacterial cell that has lost its outer cell wall layer but retains the cytoplasmic membrane. While they still possess peptidoglycan remnants, spheroplasts are significantly depleted of NAM and NAG compared to intact bacteria like E. coli due to the incomplete cell wall structure.

Answer: Lipopolysaccharides

Gram-negative bacteria are associated with endotoxin, and this is primarily due to the presence of lipopolysaccharides (LPS) in their outer membrane. LPS is a complex molecule consisting of lipid A, core polysaccharide, and O antigen. The lipid A component is responsible for the endotoxic properties of LPS.

The other options are incorrect:

• Steroids: Steroids are organic compounds with a different structure and function. They are not directly associated with the endotoxic properties of Gram-negative bacteria.
• Peptidoglycan: Peptidoglycan is a component of bacterial cell walls, and it is more prevalent in Gram-positive bacteria. While peptidoglycan itself is not an endotoxin, it is associated with the structural differences between Gram-positive and Gram-negative bacteria.
• Polypeptide: Polypeptides are chains of amino acids and are not directly associated with the endotoxic properties of Gram-negative bacteria. The key component responsible for endotoxin activity in Gram-negative bacteria is lipid A within the LPS.

Answer: Trichoderma

Trichoderma is a type of fungus known for its ability to fight off other, harmful fungi that cause plant diseases. It works through several mechanisms, including direct parasitism, competition for resources, and production of antifungal compounds. Trichoderma is widely used as a biocontrol agent in agriculture and can be applied to seeds, soil, or directly to plants.

The other options are incorrect:

• Lactobacillus: These are bacteria commonly found in fermented foods and yogurt. While they are beneficial for human health, they don’t have any known effects on plant diseases.
• Chlorella: This is a type of green algae known for its nutritional value. It has some potential in promoting plant growth but doesn’t directly control diseases.
• Anabaena: This is another type of blue-green algae that can fix nitrogen in the soil, benefiting plants. However, it also lacks specific properties to combat plant diseases.

Answer: species-specific and inactive on non-target organisms

In an integrated pest management (IPM) program, minimizing harm to other living things (non-target organisms) is crucial. Therefore, the ideal biocontrol agent should be:

• Species-specific: It targets only the pest species causing the problem, reducing impact on beneficial insects, pollinators, and other organisms.
• Inactive on non-target organisms: This ensures minimal collateral damage to the broader ecosystem.

The other options are incorrect:

• species-specific and symbiotic: Symbiotic relationships involve mutual benefit. While specific targeting is good, a symbiotic biocontrol agent might rely on the pest, hindering its pest control effectiveness.
• free-living and broad-spectrum: Free-living organisms aren’t dependent on hosts, but a broad-spectrum agent could harm beneficial organisms alongside the pest, disrupting the ecosystem balance.
• narrow spectrum and symbiotic: Similar to “species-specific and symbiotic,” this approach might limit pest control effectiveness due to the reliance on the pest for survival.

Answer: Cyanobacteria and Rhizobium

Cyanobacteria and Rhizobium are both microbes that can be used as biofertilizers. Cyanobacteria (blue-green algae) are capable of nitrogen fixation, converting atmospheric nitrogen into a form usable by plants. Rhizobium is a genus of nitrogen-fixing bacteria that forms symbiotic relationships with leguminous plants, aiding in nitrogen fixation.

The other options are incorrect:

• Aspergillus and Rhizopus: Aspergillus and Rhizopus are fungi. While certain fungi may have beneficial roles in agriculture, they are not typically used as biofertilizers. Instead, they may play roles in organic matter decomposition.
• Rhizobium and Rhizopus: Rhizobium is a nitrogen-fixing bacterium that can be used as a biofertilizer. However, Rhizopus is a fungus and is not typically used for this purpose.
• Aspergillus and Cyanobacteria: While Cyanobacteria can be used as a biofertilizer, Aspergillus is a fungus and is not commonly used for this purpose in agriculture.

Answer: Clostridium, Actinomyces

While both Clostridium and Actinomyces are gram-positive bacteria, it’s crucial to be specific in multiple-choice scenarios. Therefore, it’s more accurate to choose them both as the correct answer.

The other options are incorrect:

• Actinomyces: This is indeed a gram-positive bacterium known for its role in decomposing organic matter and producing antibiotics.
• Clostridium: This too is a gram-positive bacterium known for its diverse capabilities, including spore formation and producing toxins like botulinum toxin.
• Rhizobium: Rhizobium is a genus of gram-negative bacteria, not gram-positive. It is known for its ability to form nitrogen-fixing symbiotic relationships with leguminous plants.

Answer: Bacteroides fragilis

While many bacterial species can cause urinary tract infections (UTIs), Bacteroides fragilis is not typically one of them. This gram-negative anaerobic bacterium primarily resides in the human gut and plays a role in digestion. It rarely travels to the urinary tract and isn’t known to cause UTIs under normal circumstances.

The other options are incorrect:

• Proteus mirabilis: This gram-negative, motile bacterium is a common cause of UTIs, particularly in women and individuals with urinary catheters. It readily adheres to the bladder lining and can ascend to the kidneys if left untreated.mirabilis bacterium
• Escherichia coli (E. coli): This infamous gram-negative bacterium is the most common culprit behind UTIs, responsible for roughly 80-90% of cases. It also resides in the gut but can easily migrate to the urethra and bladder, causing inflammation and discomfort.
• Klebsiella pneumoniae: Another opportunistic gram-negative bacterium, Klebsiella can cause UTIs, particularly in healthcare settings or among individuals with weakened immune systems. It can be resistant to multiple antibiotics, making treatment challenging.

Answer: Q-fever

Q-fever is diagnosed by serologic means. Serologic tests, such as enzyme-linked immunosorbent assay (ELISA) or immunofluorescence assay (IFA), can detect antibodies produced in response to Coxiella burnetii, the bacterium responsible for Q-fever.

The other options are incorrect:

• Actinomycosis: This bacterial infection is typically diagnosed through culture of the bacterium from tissue samples or abscesses, not serology.
• Pulmonary tuberculosis: While antibodies can be detectable in later stages, diagnosis of tuberculosis primarily relies on chest X-rays, physical examination, and specific tests like the tuberculin skin test or interferon-gamma release assay.
• Gonorrhea: This sexually transmitted infection is usually diagnosed through direct detection of the bacteria from swabs or urine samples, not serologic tests.

Answer: Streptococcus pyogenes

Streptococcus pyogenes, also known as group A streptococcus, primarily causes infections in the throat and skin, such as strep throat and impetigo. While it can contribute to other digestive issues like nausea and vomiting, diarrhoea is not a typical symptom associated with Streptococcus pyogenes infections.

The other options are incorrect:

• Shigella dysenteriae: This gram-negative bacterium invades the intestinal lining, causing severe dysentery with bloody diarrhoea, fever, and abdominal cramps.
• Clostridium difficile (C. Diff): This spore-forming bacterium thrives in antibiotic-disrupted gut environments, causing antibiotic-associated diarrhoea with watery stools, abdominal pain, and fever.
• Salmonella enteriditis: This type of Salmonella bacteria contaminates food and water, leading to food poisoning with symptoms like nausea, vomiting, and watery diarrhoea that can be bloody.

Answer:

Nitrosovibrio tenuis does not correspond to an ammonia-oxidizing bacteria. Ammonia-oxidizing bacteria are involved in the first step of nitrification, converting ammonia to nitrite. Nitrosovibrio tenuis, on the other hand, is not known for its role in ammonia oxidation.

The other options are incorrect:

• Nitrosococcus Oceanus: Nitrosococcus oceanus is a species of ammonia-oxidizing bacteria involved in the oxidation of ammonia to nitrite in the process of nitrification.
• Nitrospina Gracilis: Nitrospina gracilis is a nitrite-oxidizing bacterium rather than an ammonia-oxidizing bacterium. It participates in the second step of nitrification, converting nitrite to nitrate.
• Nitrosomonas Europaea: Nitrosomonas europaea is a well-known species of ammonia-oxidizing bacteria. It plays a key role in the conversion of ammonia to nitrite during nitrification.

Answer: Clostridium botulinum

Canned foods are specifically processed to eliminate Clostridium botulinum, a dangerous bacterium that produces the deadly botulinum toxin. The canning process involves heating the food to high temperatures for extended periods, which effectively kills C. botulinum spores, ensuring the safety of the food.

The other options are incorrect:

• Lactobacillus: These are beneficial bacteria commonly found in fermented foods like yogurt and sauerkraut. They actually play a role in preserving food by producing lactic acid, which inhibits the growth of harmful bacteria like C. botulinum.
• Mycobacterium tuberculosis: This bacterium causes tuberculosis, primarily affecting the lungs. While it can survive in some food products, it’s not typically associated with canned food spoilage and isn’t eliminated by the canning process.
• Coxiella burnetii: This bacterium causes Q-fever, a flu-like illness. It can be present in unpasteurized milk products but isn’t a typical concern for commercially canned foods.

Answer: Amphitrichous

Amphitrichous bacteria have clusters of flagella at both the poles of their cells. The prefix “amphi” means “both,” and “trichous” refers to hair-like structures like flagella. Therefore, amphitrichous bacteria are aptly named for their distinctive flagellar arrangement.

The other options are incorrect:

• Lophotrichous: These bacteria have a single tuft of flagella at one pole of the cell.
• Peritrichous: These bacteria have flagella distributed evenly over the entire surface of the cell.
• Monotrichous: These bacteria have a single flagellum at one pole of the cell.

Answer: Treponema Pallidum

Treponema pallidum is a spirochete bacterium. Spirochetes are a unique group of spiral-shaped bacteria characterized by their helical or corkscrew morphology. Treponema pallidum is the causative agent of syphilis.

The other options are incorrect:

• Streptomyces sp.: Streptomyces is a genus of bacteria known for its filamentous growth and its role in the production of antibiotics. It is not a spirochete.
• Corynebacterium Diphtheriae: Corynebacterium diphtheriae is a rod-shaped bacterium and is not classified as a spirochete. It is the causative agent of diphtheria.
• Spirillum Volutans: Spirillum volutans is a spiral-shaped bacterium but belongs to the genus Spirillum, not Spirochetes. Spirochetes and spirilla are distinct groups of bacteria based on their morphological characteristics.

Answer: alga

Algae are the type of microorganisms that are photosynthetic. Algae encompass a diverse group of photosynthetic organisms, ranging from single-celled forms to complex multicellular seaweeds. They use sunlight to produce their own food through photosynthesis.

The other options are incorrect:

• Yeast: Yeast is a type of fungus. While some fungi may form symbiotic relationships with photosynthetic organisms, yeast itself is not photosynthetic.
• Virus: Viruses are not considered living organisms, and they do not possess the cellular machinery for photosynthesis. They rely on host cells for their replication.
• Helminth: Helminths are parasitic worms, and they do not have the capability for photosynthesis. They obtain nutrients by living in or on host organisms.

Answer: Aspergillus

Aspergillus niger is a common fungus used in industrial production of citric acid through a process called fermentation. It efficiently converts sugary raw materials like molasses or corn steep into citric acid.

The other options are incorrect:

• Pseudomonas: These bacteria are mainly known for their ability to degrade pollutants and hydrocarbons, not for producing citric acid.
• Saccharomyces cerevisiae: This is the well-known yeast used in bread baking and beer fermentation. It primarily produces ethanol and carbon dioxide from sugars, not citric acid.
• Clostridium: These bacteria are often associated with anaerobic environments and can cause foodborne illnesses. Some species produce lactic acid or butyric acid, but not citric acid.

Answer: Anabaena

Anabaena azollae is a nitrogen-fixing cyanobacterium that lives within the cavities of Azolla, a small aquatic fern. This symbiotic relationship benefits both organisms: Anabaena provides fixed nitrogen to Azolla, while Azolla provides Anabaena with shelter and nutrients. This partnership significantly improves rice crop yields in paddies.

The other options are incorrect:

• Frankia: This nitrogen-fixing bacterium associates with actinorhizal plants like alder and casuarina, but not with Azolla.
• Tolypothrix: This is a filamentous cyanobacterium that can fix nitrogen, but it is not typically found in rice fields or associated with Azolla.
• Spirulina: This cyanobacterium is known for its nutritional value and ability to fix nitrogen, but it is primarily found in freshwater lakes and ponds, not rice fields.

Answer: Rhizobium

Rhizobium is used as a biofertilizer for the soybean crop. It forms a symbiotic relationship with the roots of leguminous plants, including soybeans. In this association, Rhizobium bacteria fix atmospheric nitrogen into a form that the plant can utilize, promoting the growth of soybeans.

The other options are incorrect:

• Azotobacter: While also a nitrogen-fixing bacteria, Azotobacter primarily benefits non-leguminous crops like rice and wheat. It thrives in the soil surrounding the plant roots and fixes nitrogen independently.
• Nostoc: This blue-green algae can fix nitrogen but is not specifically adapted to colonize plant roots or form symbiotic relationships like Rhizobium. Its impact on soybean crops would be less significant.
• Azospirillum: Similar to Azotobacter, it’s a nitrogen-fixing bacteria for non-leguminous plants. It promotes plant growth by promoting root development and nutrient uptake, but the nitrogen-fixing benefits for soybeans are limited.

Answer: Bacillus thuringiensis

Bacillus thuringiensis is a soil-dwelling bacterium that produces proteins known as Bt toxins. These toxins are highly specific to caterpillars and disrupt their digestive systems, leading to death. Bt is considered safe for humans, animals, and beneficial insects, making it a popular choice for organic and sustainable pest control.

The other options are incorrect:

• Trichoderma: This is a beneficial fungus that helps protect plants from fungal diseases and promotes root growth. It is not effective against butterfly caterpillars.
• Baculovirus: These viruses are naturally occurring and can infect specific insect species, including caterpillars. However, their use as a biopesticide is less common compared to Bt due to factors like cost and specificity.
• Glomus: This is a type of mycorrhizal fungi that forms symbiotic relationships with plant roots, improving nutrient uptake and plant growth. It has no insecticidal properties.

Answer: Ethanol

Yeast, particularly the species Saccharomyces cerevisiae (Baker’s yeast or Brewer’s yeast), readily converts sugars in various ingredients like grains, fruits, and honey into ethanol and carbon dioxide through a process called fermentation. This is the basis for producing alcoholic beverages like beer, wine, and spirits.

The other options are incorrect:

• Tetracycline: This is an antibiotic produced by bacteria, not yeast.
• Butanol: While certain types of yeast can produce butanol under specific conditions, it’s not their primary or common product. Industrial production of butanol typically relies on different fermentation methods involving clostridia bacteria.
• Citric Acid: Although some yeast strains can contribute to citric acid production under specific circumstances, the primary industrial producers are fungi belonging to the Aspergillus genus.

Answer: Chlorella

Chlorella is an alga that can be used as food for human beings. It is a genus of green microalgae that is rich in proteins, vitamins, and minerals. Chlorella is sometimes consumed as a dietary supplement or as a food source due to its nutritional content.

The other options are incorrect:

• Polysiphonia: This red alga is primarily used in agar production, a polysaccharide with various industrial and culinary applications. While some species are edible, their consumption is less common and widespread compared to Chlorella.
• Ulothrix: This filamentous green alga is not typically consumed by humans due to its tough cell walls and less appealing taste compared to Chlorella. Additionally, its harvesting and processing are less efficient.
• Spirogyra: This filamentous green alga is primarily found in freshwater habitats and holds little nutritional value for humans. Its taste and texture are not suitable for direct consumption.