Question

In the last experiment, you set up the experiment with M. tuberculosis, but again replacing the air in the chamber with nitrogen gas as you did in the second experiment. You get the following results, which you do not need to graph.

There was clearly no CO2 produced in any of the eudiometers. Nothing. Explain in your own words why some sugars were consumed with air in the flask, but not with N2.

Time (minutes)	no sugar	glucose	sucrose	maltose	lactose	galactose
0	0	0	0	0	0	0
5	0	0	0	0	0	0
10	0	0	0	0	0	0
15	0	0	0	0	0	0
20	0	0	0	0	0	0
25	0	0	0	0	0	0
30	0	0	0	0	0	0
35	0	0	0	0	0	0
40	0	0	0	0	0	0
45	0	0	0	0	0	0
50	0	0	0	0	0	0
55	0	0	0	0	0	0
60	0	0	0	0	0	0

Answer 1

Mycobacterium tuberculosis is the aerobic bacteria which utilises oxygen for its oxidative phosphorylation. Initially though less but air in flask had oxygen which the bacteria used for respiration and gained some energy to use some basic sugar.As the air or oxygen started depleting they entered a non-replicating persistant stage which is a microaerobic stage and the bacterial cells ceased replication. So they were not able to either divide or respire hence used no sugar. Morever nitrogen gas cannot be directly used by them and high concentration can be ever harmful so respiration using nitrogen gas as substrate is not possible.