More emphasis is placed, this week, on tying "old" info with new leaps forward.
Grades will be curved providing you correctly answer at least 4 of these:
This is a 14-question quiz. On your answer sheet, CROSS OUT one of the 15 questions you don't want counted.
| NOTE: If you did not specify which question you wanted dropped, only the first 14 were graded.
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| | 1. In an MPN analysis using the Eijkman-Durham method, the higher the proportion of tubes which become turbid overnight with growth...
(a) the more fecal contamination Just a lot of soil bacteria
(b) the more lactase that is being produced Nope: usually only E. coli have lactase.
(c) the more polluted the test water is good bacteria are "pollution"
(d) the higher the BOD is of the test water not much to do with BOD
(e) all of the above
(f) none of the above | | | 8. You are to isolate an axenic bacterial strain from some contaminated environmental source. Which list below contains only some of the equipment necessary to do so?
(a) Spectrophotometer, sterile nutrient broth, UV light
(b) tweezers, paper disks, E. coli and NA plates
(c) serial dilution tubes, micropipetters and tips, a dozen Eijkman-Durham tubes
(d) petri plates, inoculating loop, flame To make streak plates, you'll also need NA and an autoclave
(e) sterile toothpicks, autoclave, Coulter counter
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| | 2. You placed 1 mL samples of well water into 10 Eijkman-Durham tubes and incubated them at 41°c. The next day you found that all were cloudy, and that 6 had bubbles trapped in the small inverted Durham tubes. The E. coli concentration was about
(a) 0.1/mL
(b) 0.5/mL
(c) 0.9/mL
(d) 5/mL
(e) 9/mL
(f) 18 per 100 mL Your MPN table shows you that 40% without bubbles indicates 0.91 E. coli/input volume = 0.91/mL
| | 9. E. coli come in more than 50,000 varieties (combos of underwear, outerwear and flagella types). Most are nonpathogenic. It is important to discern the pathogenic types from the vast majority of necessary "good" ones. The most common type that is involved with cystitis is E. coli K5:O1:H7. Positive tests for the O1 endotoxin or the H7 flagellar protein yields mostly false positives because many nonpathogens possess the O1:H7 traits. They are thus not the pathogenic factors. Thus the K5 capsular acid polysaccharide must be tested for. Unfortunately isolating and maintaining stocks of anti-K5 antibody is expensive, and so a cheaper way was desirable. A lab discovered (from raw sewage water - always the best source for new coliphages!) a phage which attacked only E. coli K5 strains. This they called φ5. In the urology lab, the technician smeared isolates from various patients onto a sectored plate. Small drops of both T4 (inner part of sectors) and φ5 (outer) were applied to the fresh smudges and incubated for 6 hours to give time for the phages to attack, if possible, the bacteria giving plaques as shown. Which patients were presumed to be infected by E. coli K5:O1:H7 (circle all which apply)?  (a) Bonney
(b) Charles
(c) Brewster
(d) Angelica
(e) Epiphany
(f) none
Only Angelica and Brewster had plaques by φ5.
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| | 3. MPN methods are used when cfu/mL in the original are ____, and serial dilution/plate counts are used when cfu/mL in the original is _____.
(a) low / high
(b) high / low
(c) about equal; doesn't matter
(d) E. coli / some other bacterial species
(e) some other bacterial species / E. coli | | 10. Regarding the results in #9, above, they got a spurious result with E. coli K17, and thus to eliminate false positives, they cross-tested with φ17 (inner) and φ5 (outer) with the results shown. Now which patient(s) tested exclusively positive for E. coli K5 (circle all which apply)?  (a) Bonney
(b) Charles
(c) Brewster
(d) Angelica
(e) Epiphany
(f) none
Brewster's culture turned out really to be E. coli K17.
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| | 4. Bubbles in the MPN tubes indicate that
(a) CO2 was formed
(b) the species was a "dairy" bacterium
(c) the tubes had not been presterilized before inoculation with test water
(d) the tap water initially used contained too much dissolved gas
(e) none of the above Fully: the bubbles indicate that the tube contained E. coli which can convert lactose to CO2 above 40°c. | | 11. (Modified question from Post-7) Dr. Sørensen supplied Wilbie with some anti-lactase (goat antibody against E. coli lactase). Cheryl isolated some E. coli lacZ- mutant cells from NA+lactose and, lysed them and normal E. coli and lacO- (off all the time) E. coli, separately with lysozyme. The students then ran three tests on the lysates: Mary Lou, after returning with donuts and drinks did an ONPG test on each lysate; Jimmy and Wilbie did a slide-agglutination test on the three lysates; and Cheryl and Jason(!) put together an Ouchterlony-diffusion test on them (see the color-figure below). First let's look at Mary Lou's results. Which of the following is correct? Cheryl's lacZ mutant... 
(a) makes an operable enzyme
(b) is able to digest lactose
(c) is actually lacO-
(d) does in fact have a defective cistron Yes, the lacZ cistron!
(e) can't be discerned because ML picked up the wrong bottle (not ONPG)
(f) a and b
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| | 5. You placed 5 mL samples of stream water into 10 Eijkman-Durham tubes and incubated them at 41°c. The next day you found that all then were cloudy, and that 6 had bubbles trapped in the small inverted Durham tubes. The E. coli concentration was about
(a) 0.1/mL
(b) 0.5/mL
(c) 0.9/mL
(d) 5/mL
(e) 9/mL
(f) 18 per 100 mL This time it was 0.91 E.coli per 5 mL = ? per 100 mL | | 12. Regarding #11, above, Jimmy and Wilbie's slide agglutination test showed that Cheryl's mutant lacZ cistron... (Hint: know the "Central Dogma!")
(a) was not transcribed
(b) was decoded to make mRNA, which then failed to be translated
(c) like all its lac-operon partners was turned off
(d) had a feedback effect on lacR shutting lacR "off"
(e) all of the above
(f) none of the above It was transcribed AND translated, but into a protein that didn't function to degrade lactose or ONPG, but yet was recognizable by the anti-lactase.
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| | 6. Prof. Bengston made two fresh 100 mL NB cultures of E. coli both at exactly 1x106 cfu/mL: one sparged with air, the other with N2. Then 1x108 pfu's (virions) of T4 were dumped into each culture. Six minutes later 5 μL samples were withdrawn and spread each completely over the agar surfaces of two NA plates. Note that equal numbers of T4 and E. coli were in that 100 mL. But by random attachment of T4s to cells, some cells were attacked by more than one T4, leaving other cells unattacked. (a) No colonies appeared the next day as all the bacteria were infected
(b) A great many colonies grew up because the vast majority of the bacteria did not get infected. About 2/3 were infected.
(c) fewer colonies grew up from the air-sparged culture than from the N2-sparged culture Attachment of phage to cells is unaffected by temperature and rate of host cell growth.
(d) colonies that grew up were from uninfected bacteria
(e) none of the above | | 13. Cheryl and Jason's immunodiffusion plate, in #11 above, showed that (circle all that are correct)... (a) Dr. Sørensen's goat anti-lactase contained more than one type of antibody Notice the two precipitin bands between the antibody well and the lysate from the normal E. coli.
(b) one part of Cheryl's mutant lacZ cistron was normal One type of antibody was made against the normal portion.
(c) one part of Cheryl's mutant lacZ cistron was abnormal The other type of antibody was made against the other section of the lactase.
(d) their immunodiffusion work conflicted with the slide-agglutination results
(e) was supported by Mary Lou's ONPG findings
(f) the lacO- mutant likely produced lactose permease
(g) the lac+ strain produced two types of lactase
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| | 7. Back to #6, above: Jason and Wilbie wanted to see the effect of aeration had on viral replication. After several hours, they took identical samples from the two infected cultures, shook them with chloroform to kill any residual bacteria, and then spread them on freshly seeded lawns of E. coli growing on NA.
(a) The plaques from the aerated culture grew in diameter faster than those from the N2-sparged culture Here individual plaques should all grow at the same rate because the lawn's host cells are all aerobic.
(b) There were more plaques from the aerated culture than from the N2-sparged culture During those several hours, the aerated cells grew more vigorously, and thus infected cells produced phage more vigorously also.
(c) The pfu/mL from the aerated culture indicated that all the input virions had been used up.
(d) The pfu/mL from the aerated culture indicated that there were now fewer than 1x108 pfu's (virions) of T4 in the culture
(e) both a and c only
(f) both b and d only | | 14. Let's talk chemical analogs again. Analogs look a lot like something else, and can fool enzymes, phages, etc., some times or all of the time. From information you already know about the lac-operon and about the viruses in this quiz, which one of the horizontal lines in the following chart is completely true.
| | analog | analog
of what | fools
(uses or is used by) | doesn't fool
| | e.g. | counterfeit
20-dollar bill | 20-dollar bill | John Q. Public | fraud detection pen
| | (a) | ONPG | glucose | lactase | lac-represser protein
| | (b) | IPTG | lactose | lac-repressor protein | lactase
| | | IPTG is a powerful lac-inducer, thus must react with and inactivate lac-repressor. But it is not degraded by lactase.
| | (c) | sulfa | PABA
para-amino-benzoic acid | humans | bacteria
| | (d) | penicillin | pyruvic acid | humans | bacteria
| | (e) | φ5 | T4 | E. coli K25 | E. coli K17
| | (f) | mal-formed
lactase | lactase | ONPG | anti-lactase
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| | 15. Again, return to #6, above. After two hours Jimmy and Mary Lou took 5 μL of the anaerobic culture and plated them on freshly seeded lawns of susceptible E. coli on both NA and MacConkey agar. As the hours went by, they noticed... (a) that plaques became evident first on the NA plate and later on the MacConkey plate
(b) first on the MacConkey plate and then on the NA plate
(c) no plaques formed on the NA plate
(d) no plaques formed on the MacConkey plate
(e) none of the above choices MacConkey agar forces E. coli to grow anaerobically and less efficiently. Thus plaques should develop more slowly than on aerobic NA.
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