Questions and Answers

A landfill sample was analyzed by dilution and plating techniques for viable bacterial count. When one gram of the landfill sample was diluted 1 x 10−4^{-4}−4 (w/v), it yielded 400 CFU. The viable bacterial count (in million, rounded off to the nearest integer) in one gram landfill sample is _______.

At t = 0, the bacterial cell number is 10,000 cells/mL. At t = 480 minutes, the cell number increased to 320,000 cells/mL. The mean generation time during this exponential growth period, rounded off to the nearest integer, is ________ minutes.

Which of the following is/are TRUE about the Escherichia coli chromosome?

(A) It is typically bound by histones
(B) It is circular in nature
(C) It is found in the nucleoid
(D) It contains multiple origins of replication

At root nodules, which of the following C4 organic acid(s) is/are transported across the symbiosome membrane and into bacteroids?

(A) Succinate
(B) Pyruvate
(C) Malate
(D) Fumarate

Which of the following is/are consequence(s) of nitrous acid (HNO2_22​) mediated deamination?

(A) Deamination of cytosine, adenine, and guanine
(B) GC-to-AT transitions
(C) AT-to-GC transitions
(D) Addition of an alkyl group to the bases

Which of the following event(s) occur(s) during translation in prokaryotes?

(A) tRNA binding to the start codon of mRNA on the 30S subunit of the ribosome
(B) Anticodon of tRNA binding to the start codon of mRNA on the 50S subunit of the ribosome
(C) The ribosome continues to move along the mRNA to add new amino acids to the polypeptide
(D) The polypeptide is released when the ribosome reaches the stop codon

Which of the following cocci is/are examples of division in one plane?

(A) Staphylococci
(B) Streptococci
(C) Micrococci
(D) Diplococci

Which of the following is/are active transport mechanism(s) in prokaryotes where the substance is chemically altered during transport across the membrane?

(A) Group translocation
(B) Simple diffusion
(C) Facilitated diffusion
(D) Osmosis

Which one of the following redox couples has the highest tendency to donate electrons?

(A) Fumarate / succinate
(B) NAD+^++ / NADH
(C) FAD / FADH2_22​
(D) Pyruvate / lactate

Match the antibiotics in Group I with the microorganisms that produce them in Group II.

(A) (P)-(ii), (Q)-(iii), (R)-(i), (S)-(iv)
(B) (P)-(i), (Q)-(ii), (R)-(iii), (S)-(iv)
(C) (P)-(i), (Q)-(ii), (R)-(iv), (S)-(iii)
(D) (P)-(ii), (Q)-(iv), (R)-(i), (S)-(iii)