Bacteria Questions and Answers

Q: The attachment structures of bacteria are the

Correct answer: all of the aboveAll three are names for the structures by which bacteria stick to a surface. Fimbriae and pili are the short hair-like appendages themselves - the words are often used interchangeably, though pilus is also used for the longer sex pilus - and colonisation factors is the general term for the adhesins that let a pathogen attach to a particular host tissue. Attachment is the first step of almost every infection.

Q: How many systems does the complement fixation reaction include?

Correct answer: 2 systemsThe test uses two systems. The first is antigen, antibody and complement; if they match, the complement is consumed. The second - the haemolytic indicator system of sheep red cells and haemolysin - is then added to reveal whether any complement is left.

Q: K antigen is a

Correct answer: capsular antigenK is the capsular antigen - from the German Kapsel. The other two in the Kauffman-White scheme are O, the somatic antigen of the lipopolysaccharide, and H, the flagellar antigen. Together they define the serotype of an enterobacterium.

Q: For penetration, viruses use

Correct answer: The mechanism called viropexiaViropexis is the engulfment of the attached virus particle by the cell membrane, which folds round it and takes it in as a vesicle - receptor-mediated endocytosis. Enveloped viruses have a second option, fusing their envelope directly with the plasma membrane.

Q: The antigen causing agglutination is called

Correct answer: agglutinogenThe agglutinogen is the antigen; the agglutinin is the antibody that clumps it; and the agglutinate is the visible clump they form. The parallel set for precipitation is precipitinogen, precipitin and precipitate.

Q: Fixation of the smear is necessary for

Correct answer: all of the aboveFixing serves all three purposes: it kills the organisms, making the slide safe to handle; it makes them stick to the glass so they are not washed off during staining; and it alters the cells so that they take up the dye more readily.

Q: Flagella are demonstrated by

Correct answer: Morozov’s stainingA flagellum is far too thin to see by ordinary light microscopy, so it must first be thickened. Morozov’s silver impregnation deposits metal along it until it is visible - the same principle as the mordant-and-silver flagella stains generally.

Q: Bacteria that cannot grow in the presence of oxygen are

Correct answer: Strict anaerobesStrict (obligate) anaerobes are killed by oxygen, because they lack the enzymes that dispose of the toxic products of oxygen chemistry. Strict aerobes require it; facultative anaerobes grow with or without it; microaerophiles need it but only at low concentration.

Q: Naked viruses are

Correct answer: NonenvelopedA naked virus is simply one with no envelope - the capsid is its outermost layer. Such viruses are the tougher: having no lipid, they survive drying, detergents and the acid and bile of the gut, which is why so many of them spread by the faecal-oral route.

81.

The attachment structures of bacteria are the

A.pili
B.fimbriae
C.colonization factors
D.all of the above

Answer: D

Correct answer: all of the above

All three are names for the structures by which bacteria stick to a surface. Fimbriae and pili are the short hair-like appendages themselves - the words are often used interchangeably, though pilus is also used for the longer sex pilus - and colonisation factors is the general term for the adhesins that let a pathogen attach to a particular host tissue. Attachment is the first step of almost every infection.

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82.

How many systems does the complement fixation reaction include?

A.2 systems
B.4 systems
C.3 systems
D.5 systems

Answer: A

Correct answer: 2 systems

The test uses two systems. The first is antigen, antibody and complement; if they match, the complement is consumed. The second - the haemolytic indicator system of sheep red cells and haemolysin - is then added to reveal whether any complement is left.

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83.

K antigen is a

A.somatic antigen
B.capsular antigen
C.flagellar antigen
D.virulent antigen

Answer: B

Correct answer: capsular antigen

K is the capsular antigen - from the German Kapsel. The other two in the Kauffman-White scheme are O, the somatic antigen of the lipopolysaccharide, and H, the flagellar antigen. Together they define the serotype of an enterobacterium.

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84.

For penetration, viruses use

A.Specific receptors
B.Lysozyme
C.The mechanism called viropexia
D.The synthetic machinery of host cell

Answer: C

Correct answer: The mechanism called viropexia

Viropexis is the engulfment of the attached virus particle by the cell membrane, which folds round it and takes it in as a vesicle - receptor-mediated endocytosis. Enveloped viruses have a second option, fusing their envelope directly with the plasma membrane.

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85.

Epidemic disease is

A.constantly present in particular area
B.spreads rapidly, involving many persons in an area at the same time
C.spreads through many areas of the world involving many persons within a short period
D.spreads slowly, involving several persons in an area at the same time

Answer: B

Correct answer: spreads rapidly, involving many persons in an area at the same time

An epidemic is an outbreak affecting many people in one area at one time, well above the expected level. A disease constantly present at a low level is endemic; one spreading across many countries is a pandemic.

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86.

The antigen causing agglutination is called

A.agglutinogen
B.agglutinate
C.agglutinin
D.precipitinogen

Answer: A

Correct answer: agglutinogen

The agglutinogen is the antigen; the agglutinin is the antibody that clumps it; and the agglutinate is the visible clump they form. The parallel set for precipitation is precipitinogen, precipitin and precipitate.

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87.

Fixation of the smear is necessary for

A.to kill the bacteria
B.for preventing bacteria washing off during staining
C.for best staining
D.all of the above

Answer: D

Correct answer: all of the above

Fixing serves all three purposes: it kills the organisms, making the slide safe to handle; it makes them stick to the glass so they are not washed off during staining; and it alters the cells so that they take up the dye more readily.

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88.

Flagella are demonstrated by

A.Ozeshki’s staining
B.Burri’s technique
C.Loeffler’s technique
D.Morozov’s staining

Answer: D

Correct answer: Morozov’s staining

A flagellum is far too thin to see by ordinary light microscopy, so it must first be thickened. Morozov’s silver impregnation deposits metal along it until it is visible - the same principle as the mordant-and-silver flagella stains generally.

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89.

Bacteria that cannot grow in the presence of oxygen are

A.Strict anaerobes
B.Strict aerobes
C.Facultative anaerobes
D.Microaerophilic

Answer: A

Correct answer: Strict anaerobes

Strict (obligate) anaerobes are killed by oxygen, because they lack the enzymes that dispose of the toxic products of oxygen chemistry. Strict aerobes require it; facultative anaerobes grow with or without it; microaerophiles need it but only at low concentration.

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90.

Naked viruses are

A.Enveloped
B.Nonenveloped
C.Viruses that are genetically deficient and so incapable of producing infectious daughter virions
D.Infective agents free of protein, with low molecular weight RNA

Answer: B

Correct answer: Nonenveloped

A naked virus is simply one with no envelope - the capsid is its outermost layer. Such viruses are the tougher: having no lipid, they survive drying, detergents and the acid and bile of the gut, which is why so many of them spread by the faecal-oral route.

Discuss in Forum

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