Question

A bacterium was isolated from

the human gut and successfully grown on NA in the lab. Where in thioglycollate medium would you expect to see growth for this organism and why?

AaBbCcDdE ABCD de AaBbCcDde AaBbCD AaBbCcDdE A. A. EEZE, . Normal Preformatted No Spacing Heading 1 Heading 2 1) A bacterium was isolated from the human gut and successfully grown on NA in the lab. Where in thioglycollate medium would you expect to see growth for this organism, and why? (2 pts) One would expect to see growth 2) You plate two organisms, A and B, at many different temperatures. You find the following patterns of growth. Please classify the temperature requirements of both organisms using two descriptors for each. (2 pts) Organism A: Temperature 4°C 25°C 30°C 37°C 42°C Organism B: 3) You are given an unknown Gram+ bacterium and told that it forms endospore. You perform an endospore staining procedure on a culture of this organisms that has been incubated at an appropriate temperature for double its usual growth time. a) What result would you expect? (1 pt) b) What would you expect to see in a Gram stain of the same organism? Please be specific. (1 pt) 4) Interpret the experimental results for Enterobacter cloacae in ornithine decarboxylase broth after incubation for 48hr at 37C (11.Amino Acid Decarboxylation). What happened in this tube? Please be specific. (2 pts) Engshus

Answer 1

Bacterial population in gut mostly compromises of Anaerobic bacteria making up to 99% of the bacterial population.

And according to the question, these bacteria are cultivated in NA. NA is neomycin agar and is used for culturing fastidious anaerobes.

Thioglycollate is a differential media which is used in determining what are the oxygen requirements of the bacteria. Thioglycolate broth contains sodium Thioglycolate which consumes the oxygen from the media, thus facilitating growth of Anaerobic bacteria, especially obligate anaerobes.

In the tube, if the culture is of aerobic bacteria, they will form a layer on top while obligate anaerobes will settle down on the bottom forming a layer there. As for facultative anaerobes, they will grow mostly at top but some layers will be spread downward, showing that they do prefer oxygen but can also grow in lower concentration of it. Microaerophiles will grow on the upper part of the tube but not at the very top since they are poisoned by high concentration of oxygen.

So to answer the question, the gut bacteria are anaerobes which is established by using NA media, they will grow on the bottom part of the thioglycolate broth because they can't tolerate oxygen and prefer to grow where oxygen concentration is lowest, i.e, at the bottom.