You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. Explain the two regulatory pathways for Mel1 that can explain the behavior of the MelA– and MelB– mutations. For each regulatory pathways what is a role for the inducer melibiose?

#Question id: 3046

#Unit 2. Cellular Organization

Which one of the following reagent used in differentiation of gram positive and Gram negative bacteria?

(P) Congo red                        (Q) Safranine

(R) Methylene blue                  (S) Iodine

#Question id: 3047

#Unit 2. Cellular Organization

A rapidly growing bacterial species such as E. coli exhibits a typical phase of growth cycle in liquid nutrient broth. If a bacterial culture has starting density 1000 cells/ml in log phase and after four hours cell density is 4000 cells/ml.  What is specific growth rate per hour? 

#Question id: 3048

#Unit 2. Cellular Organization

 If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell, the regenerated bacterium will probably

#Question id: 3049

#Unit 2. Cellular Organization

E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, what should be true of E. coliʹs generation time

#Question id: 3050

#Unit 2. Cellular Organization

Agar is well suited as a solidifying agent because

A. it has been melted in boiling water

B. it can be cooled to about 40 to 42°C before hardening

C. it will not melt again until the temperature rises to about 80 to 90°C.

D. most microorganisms cannot degrade it.

#Question id: 3051

#Unit 2. Cellular Organization

You have 10^10 cell/L of bacterial stock solution. To prepare 1 liter of growth medium containing 1000 bacteria, the volume in microlitre of this stock solution that should be added is