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Bacteria reproduce using a method known as binary fission. The chromosome copies itself during binary fission, resulting in two genetically identical copies. The cell then grows in size and divides into two daughter cells. The parent cell and both daughter cells are identical. Binary fission, an asexual process in which a single cell divides into two, is their primary mode of reproduction. In optimal conditions, some bacterial species can divide every 10–15 minutes, resulting in a population doubling every 10–15 minutes.
- Growth of bacteria or microorganisms refer to __________________
a) an increase in the size of an individual organism
b) an increase in the mass of an individual organism
c) changes in the total population
d) an increase in number of cells
Answer: d
Explanation: Growth denotes the increase in number of cells beyond that present in the original inoculum. It does not refer to an increase in size or mass of an individual organism.
- Transverse binary fission requires the formation of a crosswall.
a) True
b) False
Answer: a
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). - Which of the following bacterial species divides by fragmentation?
a) Bacillus subtilis
b) Streptococcus faecalis
c) Rhodopseudomonas acidophila
d) Nocardia sp.
Answer: d
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.
- Rhodopseudomonas acidophila reproduces by which of the following methods?
a) Binary fission
b) Budding
c) Fragmentation
d) Sporulation
Answer: b
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.
- Streptomyces sp. show the budding mode of reproduction.
a) True
b) False
Answer: b
Explanation: Streptomyces sp. produce many spores per organism by developing cross walls(septation) at the hyphen tips and then each spore gives rise to a new organism.
- 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
Answer: b
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.
- 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
Answer: c
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.
- 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
Answer: c
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.
- 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
Answer: c
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.
- Which of the following does not occur during binary fission in bacteria?
a) Cell elongation
b) Cytokinesis
c) DNA duplication
d) Spindle formation
Answer:d
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
1. Growth of bacteria or microorganisms refer to
- an increase in the size of an individual organism
- an increase in the mass of an individual organism
- changes in the total population
- an increase in number of cells
Answer: D
Explanation: Growth denotes the increase in number of cells beyond that present in the original inoculum. It does not refer to an increase in size or mass of an individual organism.
- Transverse binary fission requires the formation of a crosswall.
- True
- False
Answer: A
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)
3.Which of the following bacterial species divides by fragmentation?
- Bacillus subtilis
- Streptococcus faecalis
- Rhodopseudomonas acidophila
- Nocardia sp.
Answer: D
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.
4.Rhodopseudomonas acidophila reproduces by which of the following methods?
- Binary fission
- Budding
- Fragmentation
- Sporulation
Answer: B
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.
5.Streptomyces sp. show the budding mode of reproduction.
- True
- False
Answer: B
Explanation: Streptomyces sp. produce many spores per organism by developing cross walls(septation) at the hyphen tips and then grows into new organisms.
6.The synthesis of new membrane material during reproduction in Gram-positive cells is performed by which of the following organelles?
- Nucleus
- Mesosome
- Endoplasmic Reticulum
- Cytoplasmic membrane.
Answer: B
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. D
7.Equatorial ridge formation in the cell wall takes place in which of the following bacteria?
- Streptomyces sp.
- Bacillus subtilis
- Streptococcus faecalis
- Escherichia coli
Answer: C
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.
