This set of Microbiology Interview Questions and Answers focuses on “Morphology and Fine Bacteria Structure – Size, Shape and Arrangement of Bacterial Cells”.
1. In the classification of bacteria according to shape, which among the following refers to cuboidal arrangement of bacterial cells?
Explanation: In the Sarcinae group of bacteria, the cells divide in three planes, in a regular pattern, producing a cuboidal arrangement of cells. In Staphylococci, cells divide in three planes, in an irregular pattern, producing bunches of cocci.
2. Which group of bacteria among the following have the largest area of contact?
Explanation: Trichomes are similar to chains but have a much larger area of contact between the adjacent cells whereas in palisade arrangement, the cells are in side by side at angles to one another.
3. Which among the following are “Spirochetes”?
a) Spirillum volutans
b) Corynebacterium diphtheriae
c) Streptomyces sp.
d) Treponema pallidum
Explanation: Spirochetes are flexible and can twist and contort their shape, whereas spirilla are relatively rigid. Treponema palldium belongs to the spirochetes group and Spirillum volutans belong to the spirilla group.
4. What is the approximate size of the bacterial cell?
a) 2mm in diameter
b) 1mm in diameter
c) 2 micrometer in diameter
d) 0.5 to 1.0 micrometer in diameter
Explanation: Bacteria are very small, most being approximately 0.5 to 1.0 micrometer in diameter. This is the reason why they cannot be seen by naked eyes and can be observed under the microscope.
5. When rod shaped bacteria appears in pairs, it is known as?
Explanation: When bacilli occur in pairs, it is known as diplobacilli but when they form chains it is known as streptobacilli. Cocci are spherical shaped bacteria and not rod shaped.
6. Surface area/volume ratio of bacteria is exceedingly low compared to the same ratio for larger organisms of similar shape.
Explanation: Due to the small size of microorganisms, the surface area/volume ratio of bacteria is exceedingly high compared to the same ratio for larger organisms of similar shape. A relatively large surface through which nutrients can enter (or waste products leave) compared to a small volume of cell substance to be nourished accounts for the unusually high rate of growth and metabolism of bacteria.
7. Bacteria with less than a complete twist or comma shaped is known as?
Explanation: Bacteria with less than a complete twist or turn have a vibrioid shape, whereas those with one or more complete turns have a helical shape. Spirilla are rigid helical bacteria whereas spirochetes are highly flexible.
8. Which of the following are functions of the stalk?
a) nutrient absorption
c) attachment of the cells to surfaces
d) human infection
Explanation: Stalk are mainly nonliving ribbonlike or tubular appendages that are excreted by the cell. These stalks aid in the attachment of the cells to surfaces.
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