Acid fast staining targets which of the following compound?
Acid fast staining targets mycolic acid in the cell wall of Mycobacterium species.
1 ml of microbial culture was diluted to 10ml and 1ml of diluted culture was further diluted by adding 99ml of buffer. 0.5 ml of final culture was plated on to an agar plate. Then, 200 colonies were observed. What was the number of bacteria per ml in the original culture?
- 1 ml original diluted to 10ml means 10 times dilution
- 1 ml of diluted culture further diluted to 100 ml means 100 times dilution
Total dilution factor = 1000 times = 10-3
Here. 0.5 ml of final culture contains 200 colonies
In a microbial culture, the maximum synthesis of antibiotics occurs in
Maximum synthesis of antibiotics in a microbial culture occurs in stationary phase because in stationary phase, nutrition and space become limitation. So to prevent excess growth in limited resources and in this stress condition, microbes starts producing antibiotics (as a survival mechanism).
Which of the following is not true for photolithoautotrophic organism.
Photolithoautotrophs are the organisms which use
- CO2 as carbon source (Autotrophs)
- Inorganic ions / compounds as H+/e– source (Litho)
- Sunlight as energy source (Photo)
Find out the mismatch from the following.
Aerotolerant anaerobes grow equally well in the presence or absence of oxygen, eg. Streptococcus pyrogenes.
Correct sequence of events that occur during lytic cycle of bacteriophage infection.
P. Synthesis of viral nucleic acid and protein
Q. Release of new viruses by lysis of host cell
R. Attachment of virus on the surface of bacteria
S. Assembly and packaging of new virus
T. Penetration of viral DNA into the host
Sequence of events that occur during lytic cycle of bacteriophage infection is,
(i) Virus attaches on to the surface of the host bacterium.
(ii) Penetration of viral DNA into the host
(iii) Synthesis of viral nucleic acid and protein
(iv) Assembly and packaging of new virus
(v) Release of new virus by lysis of the host cell
Which of the following does not hold true for retroviruses.
Genome of retroviruses is single stranded RNA and not ds DNA.
Creutzfeldt Jacob disease in humans is caused by
Creutzfeldt Jacob disease in humans is caused by prions. Prions are infectious proteins with no nucleic acid.
Mode of action of penicillin is to inhibit
Penicillin inhibits cell wall synthesis in bacteria by inhibiting the process of transpeptidation reaction, which is essential for cell wall synthesis.
Mode of action of streptomycin is by
Streptomycin inhibits translation in prokaryotes by preventing the formation of 70S ribosomes. It acts on the 30S subunit of prokaryotic ribosomes.
Gentamycin is an antibiotic, which is produced by
Gentamycin is an antibiotic produced by the bacteria belonging to Micromonospora sp. It inhibits translation by inhibiting 16s rRNA.
The presence of D-amino acids in the cross links of peptidoglycan layer is most likely because
D-amino acids are most likely present in cross links of peptidioglycan layer as proteases easily cleave L-amino acids.
Which of the following is/are the characteristic(s) of exotoxin?
Exotoxins are produced by some species of gram positive and gram negative bacteria.
- They are secreted out of the cell
- They are heat labile, and get inactivated rapidly at 60 to 80ºC
- They are polypeptides
- They can be converted to toxoids and used as vaccines.
Select the disease(s) caused by bacteria.
Tetanus is caused by Clostridium tetani
Anthrax is caused by Bacillus anthracis
Whooping cough is caused by Bordetella pertusis
Meningococcal meningitis caused by Bordetella pertusis
Which of the following disease (s) is/are caused by prions?
Kuru disease is caused by prions in humans. Scrapie disease is caused by prions in sheep.
HIV replicates its genome using unique mechanisms. Which of the following statements regarding the same are correct?
HIV is an enveloped virus and contains a RNA dependent DNA polymerase for infection. DNA copy of HIV genome is integrated into host cell DNA.
Gram positive cells
All the characteristic present in options are correct regarding gram positive cells.
A microorganism has a specific growth rate of 2.8 h–1, its doubling time will be _______ minutes. (Round off to two deimal places).
A bacterium of cocci group has a diameter of 3µm . Calculate the ratio of its surface area to volume (in ) _________(Answer should be an integer)
Cocci bacterium has spherical shape.
Surface area of sphere = 4ar2
Volume of sphere = 4/3ar2
0.2 ml of a microbial culture was diluted by adding 9.8ml of buffer to 10 ml. 0.1ml of this was further diluted by adding 9.9 ml of buffer to 10 ml. Plating 0.5 ml from 2nd tube yields 80 colonies. Cell density in original culture was ____________ x 104 cells. (Round off to one decimal place)
Volume of a single microbial cell is 10-3 um3. The number of cells present in its 5ml of culture will be_______________ 1015 cells. (Answer should be an integer)