What following method can be used to grow O_2-sensitive, obligated anaerobes? a.

Question

What following method can be used to grow O_2-sensitive, obligated anaerobes? a. MSA plates b. Thioglycollate broth c. TSB d. EMB plates ___ are strains that are unable to grow on a minimal medium that supports growth of the wild type strain, but can grow on the minimal medium if one or more nutritional supplements are added a. Prototrophs b. Autotrophs c. Auxotrophs d. Minitxophs A microbiologist is working with two genera of bacteria, A and B, to determine if cells are competent. Strains are grown under optimal conditions, and DNA fragments that carry the gene for green fluorescent protein are added to each culture at 20-minute intervals. Samples from each treatment are plated on a nutrient agar and incubated, after which the plates are examined under an ultraviolet lamp. The microbiologist observes that all plates of bacteria B contain colonies that are fluorescent, while for bacteria A only the plates from stationary phase demonstrate fluorescent colonies. What can be concluded from these results? a. Competence in bacteria B is dependent on the phase of growth b. Bacteria A is competent in the stationary phase of growth. c. Competence in bacteria A is constitutively expressed. d. Neither bacteria A nor bacteria B cells are competent. A plasmid, carrying a desired gene with an antibiotic gene, was used for transformation. The antibiotics incorporated into the culture medium can a. select against organisms that have incorporated a plasmid containing the desired gene. b. select for organisms that have incorporated a plasmid not containing the desired gene c. enhance production of recombinant proteins.

Explanation / Answer

12) Obligate anaerobes are the bacteria that can live only in the absence of oxygen. Obligate anaerobes metabolise energy anaerobically. Clostridia and bacteriodes are obligate anaerobes. Culture of anaerobes is extremely difficult due to the need to exclude oxygen, slow growth and complex energy requirements. Thioglycolate acts as the reducing agent. Deep culture tubes with thioglycollate broth can be used to culture obligate anaerobes. Oxygen is found only at the top due to diffusion from air. Colony formation characteristics can be used to identify the organism. Obligate anaerobes will grow only at the bottom of the deep culture tube, aerobes will grow at the top of the deep culture tube and facultative anaerobes grow throughout the culture tube. So, the answer for this question is option (b) thioglycollate broth.

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