Francois Jacob and Jacques Monod studied Escherichia coli (E. coli) bacteria by using lab experimentation. What revision to their initial hypothesis did they come up with?
A. The lac operon is repressed by allolactose.
B. E. coli are unable to process lactose sugar.
C. All E. coli operons are always turned on.
D. Two operons regulate gene control in E. coli.
Answers
B. E. coli are unable to process lactose sugar.
Escherichia coli is also known as E. coli is a Gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes (EPEC, ETEC, etc.) can cause serious food poisoning in their hosts and are occasionally responsible for food contamination incidents that prompt product recalls. The harmless strains are part of the normal microbiota of the gut and can benefit their hosts by producing vitamin K2, (which helps blood to clot) and preventing colonization of the intestine with pathogenic bacteria, having a mutualistic relationship. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in the fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterward.
E. coli is capable of metabolizing lactose, but only when there are no better (easier) sugars to eat. If glucose or other compounds are present in the environment the genes required to metabolize lactose are turned off.
E. coli can live on a wide variety of substrates and uses mixed acid fermentation in anaerobic conditions, producing lactate, succinate, ethanol, acetate, and carbon dioxide. Since many pathways in mixed-acid fermentation produce hydrogen gas, these pathways require the levels of hydrogen to be low, as is the case when E. coli lives together with hydrogen-consuming organisms, such as methanogens or sulphate-reducing bacteria.