Bacteria Morphology Questions and Answers

Answer: C

Correct answer: attachment of the cells to surfaces

A stalk or prostheca is an extension of the cell wall and membrane. It anchors the cell to a surface - often with a holdfast at its tip, as in Caulobacter - and by extending the cell it also increases the surface available for absorbing nutrients from dilute water.

Answer: C

Correct answer: Amphitrichous

Amphitrichous means flagella at both poles - a single one at each, or a tuft at each. Lophotrichous is a tuft at one pole only, monotrichous a single flagellum at one pole, and peritrichous flagella all over the surface.

Answer: B

Correct answer: Peritrichous

Salmonella, like E. coli and Proteus, is peritrichous: flagella all over the cell. When they all rotate counter-clockwise they gather into one bundle and the cell runs straight; when one reverses, the bundle breaks up and the cell tumbles into a new direction.

Answer: B

Correct answer: Outer Membrane

The gram-negative basal body has four rings, and the letters name where each sits: L in the outer membrane (L for lipopolysaccharide), P in the peptidoglycan, and S and M at the cytoplasmic membrane. Gram-positive cells, having no outer membrane, have only the S and M rings.

Answer: D

Correct answer: Mot protein

The Mot proteins form the stator, a ring of channels around the motor through which protons flow back into the cell. The energy of that flow is what turns the rotor - the flagellum is driven by the proton-motive force, not by ATP. The Fli proteins are the switch that reverses the direction of rotation.

Answer: B

Correct answer: port of entry of genetic material during mating

The F (sex) pilus is made by a donor cell carrying the F plasmid. It attaches to a recipient and draws the two cells together, and DNA then passes from donor to recipient - the process of conjugation. Ordinary fimbriae, by contrast, are for attachment to surfaces.

Answer: B

Correct answer: nutrient absorption and attachment to surfaces

A prostheca is a stalk-like extension of the cell wall and membrane. It increases the surface area available for absorbing nutrients - a real advantage in dilute water - and, with a holdfast at its tip, anchors the cell to a surface. Caulobacter is the classic example.

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.

Answer: A

Correct answer: positive chemotaxis

Movement towards an attractant is positive chemotaxis. The cell cannot measure a gradient across its own tiny length, so it compares concentrations over time: when things are improving it lengthens its runs, and when they are not it tumbles and sets off in a fresh direction.

Answer: A

Correct answer: Protonmotive force

The flagellar motor is driven by the proton-motive force - protons flowing back into the cell through the Mot channels - and not by ATP. This is why a cell whose respiration is poisoned stops swimming even while it still has ATP, and it distinguishes the bacterial flagellum sharply from the ATP-driven eukaryotic one.