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  #1  
Old 08-08-2010
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Bacteria Bacteriology Questions

Bacterial identification by serology depends on agglutination of intact bacteria by antibody. Antibodies
to some antigens are better at agglutination than antibodies to others. Antibodies to which antigen
would you expect to be least effective at agglutination?
A. O-antigen.
B. Capsule.*
C. Pili.
D. Porin protein
E. Ribosomal protein.
F. Teichoic acid
G. Peptidoglycan.

An outbreak of intestinal illness is traced to contamination by E. coli of potato salad served in a local
cafeteria. Isolates from all patients are of the same serotype and all but one are sensitive to three
antibiotics: ampicillin, trimethoprim/sulfa, and tetracycline. One isolate, of identical serotype, is
resistant to all three antibiotics.
What process most likely mediated simultaneous acquisition of three antibiotic-resistance genes?
A. Conjugation.
B. Transformation.
C. Generalized transduction.
D. Specialized transduction.

When an antibiotic resistance gene is transferred to a bacterial cell, it may require integration into the
chromosome if it is not to be lost. Integration may take place by homologous recombination, which
requires that participating DNA molecules be highly similar in sequence, or by enzyme-catalyzed
insertion, which has no such requirement.
Which mode of transfer would result in stable persistence of an antibiotic-resistance gene only if donor
and recipient cells were closely-related, typically of the same species?
A. Transfer of an R-factor (=R-plasmid) by conjugation.
B. Transfer of the F-factor by conjugation.
C. Transfer of chromosomal DNA by conjugation.
D. Specialized transduction.
E. Movement of a transposon from the DNA genome of a virus to DNA of the bacterial chromosome.

A patient with bacterial infection of the bloodstream developed fever and shock, produced by
lipopolysaccharide (LPS). What part of LPS was responsible for these toxic effects?
A. Long repeating polysaccharide (O-antigen).
B. Complex phosphorylated polysaccharide core.
C. Unsaturated fatty acids, released by hydrolysis.
D. Disaccharide substituted with saturated fatty acids.*
E. Protein, freed from covalent linkage to polysaccharide by plasma proteases.

A pot of leftover stew was boiled for half an hour, covered, and left to cool. Those who later ate it
developed nausea and cramps, due to bacterial “food poisoning”. What form of bacteria was most
likely to have contaminated the stew?
A. Cells of acid-fast bacteria.
B. Cells of bacteria that lack cell walls.
C. Cells of Gram-negative bacteria.
D. Cells of Gram-positive bacteria.
E. Spores of Gram-positive bacteria.* C.perfringes?
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Old 08-08-2010
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E. Ribosomal protein.
A. Conjugation.
D. Specialized transduction.
C. Unsaturated fatty acids, released by hydrolysis.
E. Spores of Gram-positive bacteria.
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Old 08-09-2010
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i think just answering is not sufficient....better will be to explain the reason why u chose a particular option..wil be more helpful to others...like me..
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Old 12-19-2010
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I really wanna know these answ as well! Can anybody explain them???
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Old 12-20-2010
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Quote:
Originally Posted by khushboo View Post
E. Ribosomal protein.
A. Conjugation.
D. Specialized transduction.
C. Unsaturated fatty acids, released by hydrolysis.
E. Spores of Gram-positive bacteria.
I am not good at bacterial genetics, so i would take a shot at the other answers...

E. Ribosomal protein.
Its the only antibody representing an antibody against an intracellular component.

C. Unsaturated fatty acids, released by hydrolysis.
The main pathogenic part of LPS is Lipid A.

E. Spores of Gram-positive bacteria
Heating & cooling.
Bacillus Cereus ?
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Old 12-21-2010
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Thank you so much!
Genetics..... Not easy for me...
Thnk you again for helping me!
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Old 12-21-2010
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E. Spores of Gram-positive bacteria
Heating & cooling.
Bacillus Cereus ?

Im not sure if I agree with that, spores are highly resistant to just regular heating and antiseptics/bactericidal agents.

Since its cooking, as in heating, which actives it.. then I would think it has a Heat Labile Protein, which gets denatured at a higher temp, Im not sure if this part is right, but they are secretion of the heat-labile enterotoxin B, an example of this would be Staph., and staph is a GPB.

So choice would be D?
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Old 12-21-2010
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Quote:
Originally Posted by patelMD View Post
E. Spores of Gram-positive bacteria
Heating & cooling.
Bacillus Cereus ?

Im not sure if I agree with that, spores are highly resistant to just regular heating and antiseptics/bactericidal agents.

Since its cooking, as in heating, which actives it.. then I would think it has a Heat Labile Protein, which gets denatured at a higher temp, Im not sure if this part is right, but they are secretion of the heat-labile enterotoxin B, an example of this would be Staph., and staph is a GPB.

So choice would be D?
I would go for E rather than D.
I think the biggest hint in the stew question is the boiling. Since the stew was boiled for half an hour, heat-labile enterotoxin would be destroyed. In all probability, most Bacillus spores would be destroyed as well (although they probably survived the lower temp at which the stew was originally cooked, allowing them to colonise and poison the stew as it sat). Cereulide (the emetic toxin of B. cereus) would not be destroyed. The second thing speaking against heat-labile enterotoxin is the nausea and cramps rather than a watery diarrhoea.
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