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Exam 2 MIM Microbiology > Microbial Genetics I & II > Flashcards

Microbial Genetics I & II Flashcards

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1
Q

What genetic diversity of bacteria is composed of what two categories of genetic information?

A

1) core gene pool of chromosomal DNA

2) flexible gene pool

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2
Q

What are some genes that the flexible gene pool may contain?

A

1) pathogenicity factors

2) abx resistance

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3
Q

What does the core gene pool contain?

A

Genes that are essential to the bacteria such as those for ribosomes, cell envelope, DNA replication, etc.

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4
Q

The DNA for bacteria has a noticeable lack of what element which is present in eukaryotic DNA?

A

1) non-coding DNA

2) introns

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5
Q

Which gene pool is larger?

A

Flexible gene pool is considerably larger. Has ~16k genes which are distinct

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6
Q

What is the approximate size of the different gene pools for an E. coli?

A

Core: 2k genes
Variable: 2-3.5k genes

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7
Q

What are phages?

A

bacterial viruses

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8
Q

What is a prophage?

A

A phage already integrated into a bacteria’s genome

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9
Q

What are some flexible genetic elements?

A

1) plasmids
2) phages
3) integrons
4) transposons
5) genomic islands/islets

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10
Q

What are genomic islands?

A

Long block of DNA which is from another organism and is associated with a particular function

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11
Q

The integration of things like a phage, or a plasmid into the DNA of a commensal E. coli might do what?

A

-confer toxicity or pathogenicity to the bacteria

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12
Q

What are the three mechanisms of horizontal gene transfer?

A

1) transformation
2) transduction
3) conjugation

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13
Q

What is transformation?

A

transfer of free DNA

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14
Q

What is transduction?

A

transfer by viral delivery

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15
Q

What is conjugation?

A

plasmid transfer

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16
Q

How do free fragments of DNA enter the cell in transformation?

A

through DNA binding proteins

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17
Q

In what form does bacteria take up DNA?

A

single strand

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18
Q

What proteins facilitate the recombination of free ssDNA?

A

recA, and rec proteins

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19
Q

How does transformed DNA add into the genome?

A

true recombination, so alleles are traded for one another or the same one

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20
Q

What is competence?

A

the preparation necessary to make a cell ready for taking up free DNA

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21
Q

When does transformation and competence usually happen in the bacterial cell cycle?

A

stationary phase

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22
Q

Which strains are constitutively competent?

A

Neisseria and H. influenzae

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23
Q

What is one phenotypic change that bacteria undergo to become competent?

A

includes the expression of pore proteins

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24
Q

How does a bacterium normally protect itself from foreign DNA?

A

restriction modification systems

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25
Q

How do restriction enzymes work?

A

These enzymes make cuts at certain points in the DNA thus cutting it out of the genome

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26
Q

How does a bacterium differentiate between its own DNA and foreign DNA?

A

methylation protects the bacterium’s own DNA

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27
Q

How do we induce E.coli to become competent in the lab?

A
  • salt treatments

- electroporation

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28
Q

What is the general shape of a bacteriophage?

A
  • filamentous
  • icosahedral head
  • head and tail form together in “sputnik”-like shape
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29
Q

What location on the bacteriophage does it recognize cell surface receptors?

A

at the base plate

30
Q

What limits host ranges for phages?

A

cell surface protein specificity

31
Q

What are the two types of phage?

A

1) virulent

2) temperate`

32
Q

What are the two life cycles of the phage?

A

lytic and lysogenic

33
Q

Describe the lytic cycle.

A

The lytic cycle is when a phage will enter a bacterium, and use the cell’s machinery to produce daughter phages. The cell is killed in the process.

34
Q

Describe the lysogenic cycle.

A

The lysogenic cycle is when a phage’s DNA integrates with the bacterial genome and propagates itself in this fashion.

35
Q

What is a bacterial cell with a prophage called?

A

A lysogenic cell

36
Q

At what sites do phages combine their DNA in the lysogenic cycle?

A

ATT sites

37
Q

What types of infections, diseases, etc. are effectively treated with bacteriophages?

A
  • wounds
  • suppurative infections
  • gut infections
38
Q

What is lysogenic conversion?

A

A new phenotypic property is conferred on a bacteria carrying that phage

39
Q

What usually causes the toxigenicity of bacteria?

A

incorporation of phage elements and viral dna

40
Q

What is transduction?

A

the transfer of DNA to another bacterium by viral delivery

41
Q

What are the two types of transduction?

A

1) generalized

2) specialized

42
Q

Which type of transduction is more common?

A

generalized

43
Q

Describe generalized transduction.

A

Phage enters the cell and while assembling phage components a portion of bacterial DNA gets into a phage. The phage then propagates this DNA

44
Q

What cycle does generalized transduction depend upon?

A

lytic cycle

45
Q

Describe specialized transduction.

A

Phage DNA will integrate with the bacterial DNA and enter the lysogenic cycle. This segment can pop in and out and sometimes will take bacterial DNA with it

46
Q

What is CRISPR?

A

Clustered regularly interspaced short palindromic repeats

47
Q

What is thought to be the function of CRISPR in bacteria?

A

bacterial immunity

48
Q

How does CRISPR work in general?

A

In general, there is an array of repeated sequences which allow the integration of foreign DNA in between. These sequences then get transcribed and eventually act as primers for foreign DNA.

49
Q

How long are the non-repeating sections of the CRISPR array?

A

20-25 base pairs

50
Q

What chops up foreign DNA to put it into CRISPR DNA?

A

cas complex

51
Q

What is conjugation?

A

DNA transfer through plasmid DNA

52
Q

What is F factor?

A

fertility factor

53
Q

What does F factor confer to the bacterium?

A

Ability to transfer DNA via conjugation

54
Q

What is a bacterium with F factor called? one without F factor?

A

with F factor: F+; without: F-

55
Q

What are incompatibility groups?

A

groups which are defined by a set of genes that cannot coexist in bacteria to successfully reproduce, although they can exist in a bacterium at the same time

56
Q

What types of genes are on the F plasmid?

A
  • transfer genes
  • insertional sequences
  • incompatibility group genes
57
Q

What is Hfr?

A

A bacterium which has had plasmid DNA inserted into its genome

58
Q

Can a HFr bacterium conjugate with a F- bacterium?

A

Yes.

59
Q

What are the two types of resistance?

A

1) intrinsic

2) acquired

60
Q

What is intrinsic resistance?

A

intrinsic mechanisms of bacteria that might make them resistant to antibiotics

61
Q

To what types of antibiotics is mycoplasma resistant?

A

those that target the cell wall, as it has none

62
Q

What are the two types of acquired resistance?

A

1) vertical transfer

2) horizontal transfer

63
Q

How is vertical transfer of antibiotic resistance conferred?

A

through mutations

64
Q

How is horizontal transfer of abx resistance conferred?

A

through plasmids

65
Q

Plasmids contain what kind of DNA?

A

circular dsDNA

66
Q

What is “selfish DNA”?

A

DNA that copies itself numerous times in the genome and confers no advantage to its host

67
Q

Why do some plasmids have selfish DNA?

A

if their DNA is gotten rid of it will kill the bacterium

68
Q

What the three types of transfer of plasmid DNA?

A

1) conjugative
2) non-conjugative but mobilizable
3) non-conjugative non-mobilizable

69
Q

What are the two most medically-important function of plasmids?

A

1) confer resistance to antibiotics

2) confer resistance to heavy metals

70
Q

What are the three main ways that plasmids can specify resistance?

A

1) efflux pumps
2) modifying enzymes, modifying target of abx or the abx itself
3) degrading enzymes

71
Q

How is antibiotic resistance to tetracycline commonly conferred?

A

efflux pumps, but sometimes thru modification of the elongation element it identifies

Exam 2 MIM Microbiology (5 decks)

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