Cytoplasmic inclusions include
Answer: D
Correct answer: all of these
Cytoplasmic inclusions are the granular and membranous bodies within the cell: ribosomes for protein synthesis, mesosomes as membrane infoldings, and storage bodies such as fat globules, glycogen granules and volutin. They are not bounded by a true membrane in the eukaryotic sense.
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What is Chemotaxis?
Answer: C
Correct answer: In the presence of a chemical compound, swimming towards or away of a bacteria
Chemotaxis is movement in response to a chemical gradient - towards an attractant such as a sugar or amino acid, and away from a repellent. The cell cannot sense a gradient across its own length, so it compares concentrations over time, lengthening its runs when conditions improve and tumbling when they worsen.
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The common word for bacteria which are spherical in shape is
Answer: A
Correct answer: cocci
Cocci are spherical. Bacilli are rods, spirilla helical rods, and pleomorphic describes organisms such as Mycoplasma that have no fixed shape because they have no wall.
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The capsule of Klebsiella pneumoniae is composed of heteropolysaccharides.
Answer: A
Correct answer: True
The capsule of Klebsiella pneumoniae is a heteropolysaccharide, built of more than one kind of sugar, and it is very thick - giving the mucoid colonies characteristic of the organism. It resists phagocytosis, and its many antigenic types are the basis of capsular serotyping.
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A cluster of polar flagella is called
Answer: A
Correct answer: lophotrichous
The prefixes describe the arrangement: lophotrichous is a tuft of several flagella at one pole; monotrichous a single one; amphitrichous flagella at both poles; peritrichous flagella all over the surface.
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Cyanobacteria have
Answer: B
Correct answer: a gram-negative cell wall
Cyanobacteria have a gram-negative wall: a thin peptidoglycan layer with an outer membrane over it, and they stain gram-negative accordingly. Their peptidoglycan layer is unusually thick for a gram-negative organism, but the outer membrane settles the classification.
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A single flagellum or a cluster of flagella at both poles is known as
Answer: C
Correct answer: amphitrichous
Amphitrichous means flagella at both poles - one at each, or a tuft at each. Monotrichous is a single flagellum at one pole, lophotrichous a tuft at one pole, and peritrichous flagella all over.
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Which among the following acts as receptors for bacteriophage attachment in Gram-negative bacteria?
Answer: B
Correct answer: O antigens
The O-antigen of lipopolysaccharide is the most exposed structure on a gram-negative cell, and many bacteriophages use it as the receptor they recognise before injecting their DNA. Lipid A is buried in the membrane, and teichoic acid belongs to gram-positive walls - where it serves the same purpose for their phages.
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Which of these is exposed on the outer surface of a gram-negative bacterium?
Answer: B
Correct answer: O-antigen of lipopolysaccharide (LPS)
The outer face of the gram-negative outer membrane is covered with lipopolysaccharide, whose O-antigen - a long chain of repeating sugars - projects outwards. It is what the immune system recognises, and what serotypes such as E. coli O157 are named for. Braun lipoprotein anchors the outer membrane to the peptidoglycan beneath, lipoteichoic acid belongs to gram-positive walls, and the electron transport chain is in the inner membrane.
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Which of the following structure(s) is /are external to cell wall?
Answer: D
Correct answer: All of these
All three lie outside the cell wall: flagella for motility, stalks (prosthecae) for attachment and for increasing the absorptive surface, and sheaths, the tubes in which some filamentous bacteria live. Capsules, pili and fimbriae belong to the same external category.
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