Peptone water and nutrient broth are
Answer: C
Correct answer: basal media
Peptone water and nutrient broth are basal (simple) media: they support the growth of ordinary non-fastidious organisms and serve as the foundation to which blood, serum or inhibitors are added to make enriched or selective media.
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A high dissolved oxygen concentration in the culture medium is toxic and leads to
Answer: D
Correct answer: all of the above
Too much dissolved oxygen generates reactive oxygen species, and all three consequences follow: DNA damage, lipid peroxidation of the membranes, and excessive metabolism of the medium’s nutrients. This is why oxygen is controlled rather than simply maximised in a bioreactor.
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Which of the following is used for the proper maintenance and preservation of pure cultures?
Answer: D
Correct answer: All of the above
All three are standard. Periodic transfer to fresh medium keeps a culture alive but risks contamination and mutation over many passages. Overlaying with mineral oil slows drying and metabolism, extending the interval between transfers. Lyophilisation - freeze drying - is the best for long-term storage, keeping cultures viable for years with no change.
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Which of the following bacteria can grow in alkaline pH?
Answer: D
Correct answer: Vibrio cholerae
Vibrio cholerae is alkalophilic, growing well up to about pH 9 - which is exploited in alkaline peptone water enrichment. The other three are enterobacteria with neutral optima, and lactobacilli prefer acid.
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The major problem associated with the isolation of free cells and cell aggregates from organs is that of
Answer: A
Correct answer: releasing the cells from their supporting matrix
The cells of an organ are held in an extracellular matrix of collagen and other proteins, and the difficulty is freeing them from it without damaging them. Enzymes such as collagenase and trypsin, and chelators such as EDTA, are used for the purpose, and the balance is always between complete release and cell injury.
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The medium which allows the growth of more than one microorganisms of interest but with morphologically distinguishable colonies is known as
Answer: C
Correct answer: differential medium
A differential medium lets several organisms grow but makes them look different - through a fermentable sugar and a pH indicator, or through haemolysis on blood agar. A selective medium, by contrast, stops the unwanted organisms growing at all.
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Which type of culture is prepared by inoculating directly from the tissue of an organism into culture medium?
Answer: A
Correct answer: Primary cell culture
A primary culture is one started directly from tissue taken from the organism. It most closely resembles the tissue of origin, but has a limited lifespan - once subcultured it becomes a cell line.
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In the secondary culture, cells are obtained from _______________________
Answer: A
Correct answer: primary culture
A secondary culture is obtained by subculturing a primary culture - detaching the cells, usually with trypsin, and reseeding them in fresh medium. The organism itself is the source only of the primary culture.
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Toxicity due to the accumulation of ammonia can be overcome
Answer: D
Correct answer: all of the above
All three help. Substituting glutamate for glutamine removes the amide nitrogen that becomes ammonia; feeding glutamine slowly keeps its concentration low, so less is deaminated; and removing the ammonium as it forms - by dialysis or by ion exchange - deals with what is produced. All are used in high-density culture.
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______________ is the primary equipment required for animal tissue culture laboratories
Answer: B
Correct answer: Laminar flow
The laminar flow cabinet is the essential item: it delivers a steady sheet of HEPA-filtered air over the work surface, so that nothing airborne settles on the culture. Everything else in an animal cell laboratory depends on maintaining sterility, and a single contaminated flask can be lost in a day.
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