In the identification of mycobacterial isolates, the catalase test involves the:
a. breakdown of phenolphthalein disulfate into phenolphthalein and other salts.
b. measurement of the height of a column of bubbles of oxygen.
c. production of a lipase that is able to hy-drolyze the catalase.
d. development of a pink-to-red color, indi-cating a positive result.
B
Catalase testing of mycobacterial isolates is assessed in more than one way: by the relative activ-ity of the enzyme, as determined by the height of a column of bubbles of oxygen formed; by the reaction of enzyme and substrate; and by the ability of the catalase enzyme to remain active after heating.
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Why might a large number of competing microorganisms in a food sample result in lack of sensitivity of culture methods for detecting pathogens?
A. Many microbes secrete compounds that can be toxic for their competitors. If you need a pathogenic microbe to grow in a culture in order to detect it, these toxic compounds might inhibit the growth of the pathogen and impede the test. B. You can't obtain a pure culture from a food sample that has a large number of microbes present. It would be impossible to detect only one from within the sample. C. Culture methods often rely on biochemical changes taking place in medium for identification. With multiple microbes present, you may not be sure that the biochemical change observed is from the presence of a pathogen or from some other non-dangerous bacterium that also induces the biochemical change. D. The sheer number of microbes present might shut down the growth/replication of a pathogenic microbe in a food sample due to a 'starving out' effect. If it can't grow/replicate, it won't be detectable by a culturing method test. E. Many microbes secrete compounds that can be toxic for their competitors. If you need a pathogenic microbe to grow in a culture in order to detect it, these toxic compounds might inhibit the growth of the pathogen and impede the test AND culture methods often rely on biochemical changes taking place in medium for identification. With multiple microbes present, you may not be sure that the biochemical change observed is from the presence of a pathogen or from some other non-dangerous bacterium that also induces the biochemical change.
Which choice accurately conveys the complexity of neural connections in the human brain?
A) About 100 billion neurons each contact 1,000 to 10,000 other neurons. B) A million or so neurons each contact up to 100 other neurons. C) 10 million or so neurons each contact up to 10,000 other neurons. D) A billion or so neurons each contact up to a million other neurons.
The most probable consequence of ozone depletion is
a. global warming. b. an increase in skin cancers. c. eutrophication. d. fish kills in shallow lakes. e. groundwater contamination.
If systemic blood pressure were to increase, and no other changes occur, what would happen to urine production?
1.It would increase in volume. 2.It would decrease in volume. 3.The volume would not change. 4.The volume would remain the same, but frequency would increase.