1. Transverse binary fission requires the formation of a crosswall.
a) True
b) False
Explanation: The most important mode of cell division in the usual growth of bacterial population is transverse binary fission, in which a single cell divides after developing a transverse septum(crosswall).
2. Which of the following bacterial species divides by fragmentation?
a) Bacillus subtilis
b) Streptococcus faecalis
c) Rhodopseudomonas acidophila
d) Nocardia sp.
Explanation: Bacteria that produce extensive filamentous growth, such as Nocardia sp. reproduce by fragmentation of the filaments into small bacillary or coccoid cells, each of which gives rise to new growth.
3. Rhodopseudomonas acidophila reproduces by which of the following methods?
a) Binary fission
b) Budding
c) Fragmentation
d) Sporulation
Explanation: Rhodopseudomonas acidophila reproduces by budding, a process in which a small protuberance(bud) develops at one end of the cell; this enlarges and eventually develops into a new cell which separates from the parent.
4. Streptomyces sp. show the budding mode of reproduction.
a) True
b) False
Explanation: Streptomyces sp. produce many spores per organism by developing crosswalls(septation) at the hyphen tips and then each spore gives rise to a new organism.
5. The synthesis of new membrane material during reproduction in Gram-positive cells is performed by which of the following organelles?
a) Nucleus
b) Mesosome
c) Endoplasmic Reticulum
d) Cytoplasmic membrane
Explanation: The first step in reproduction is an inward growth of the cytoplasmic membrane at the middle of the cell. A mesosome which is usually attached to the cytoplasmic membrane in Gram-positive cells have a role in the synthesis of new membrane material.
6. Equatorial ridge formation in the cell wall takes place in which of the following bacteria?
a) Streptomyces sp.
b) Bacillus subtilis
c) Streptococcus faecalis
d) Escherichia coli
Explanation: In Streptococcus faecalis, all of the new wall material formed by the dividing cell is made during synthesis of the septum which begins beneath an equatorial ridge in the cell wall.
7. When septum formation occurs near the pole of cell then it results in the formation of daughter cell known as _________
a) microcell
b) macrocell
c) minicell
d) daughter cell
Explanation: In some mutants of E.coli and B.subtilis, septum forms near the pole resulting in a very small daughter cell termed as minicell which lacks DNA and therefore cannot multiply.
8. A bleb or fold like formation occurs in which of the following bacteria?
a) Rhodopseudomonas acidophila
b) Bacillus subtilis
c) E.coli
d) Streptococcus faecalis
Explanation: In E.coli a bleb or fold of the outer membrane occurs at the site where the septum will be formed; it is not evident in the final stages of septum formation. The cytoplasmic membrane and the peptidoglycan layer grow inward in the early stages but the cytoplasmic membrane does not invaginate until the final stages of septum formation.
9. Which of the following does not occur during binary fission in bacteria?
a) Cell elongation
b) Cytokinesis
c) DNA duplication
d) Spindle formation
Explanation: Binary fission is a form of asexual reproduction that starts with cell elongation followed by division of cytoplasm(cytokinesis) and nucleus and finally DNA duplication occurs resulting in the formation of two daughter cells.
10. The portion of the growth curve where rapid growth of bacteria is observed is known as ____________
a) Lag phase
b) Logarithmic phase
c) Stationary phase
d) Decline phase
Explanation: A typical growth curve has four regions. An initial period of no growth known as the lag phase, followed by rapid growth known as logarithmic phase. No growth is observed in the stationary phase and death phase.