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Microbiology > Bacterial characteristics and genetics > Flashcards

Bacterial characteristics and genetics Flashcards

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Biology 101 flashcards
1
Q

What is the endotoxin of Gram-negative bacteria?

A

Lipopolysaccharide

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2
Q

What is the pathogenetic part of the gram-positive bacteria?

A

Teichoic acid

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3
Q

Peptidoglycan is composed of long
polysaccharide chains made up of two
main sugars:

A

N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)

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4
Q

The NAG and NAM units alternate
and are linked together by?

A

β(1→4)
glycosidic bonds

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5
Q

What is the function of the peptydoglycan?

A

structural support, protection, and shape maintenance.

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6
Q

In how many stages does biosynthesis of peptidoglycan take place?

A

3:
1) synthesis of UDP-N-acetylmuramyl-pentapeptide and UDP-N-acetylglucosamine.
2) Intermediate lipid precursor is synthesized.
3) Polymerization of the newly synthesized disaccharide - peptide units.

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7
Q

what are microaerophilic bacteria?

A

they grow well in low O2 concentrations, but are killed by high O2 concentrations.

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8
Q

beta-hemolysis?

A

colonies of blood agar plates are surrounded by a zone of complete clearing ( lysis of red blood cells )

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8
Q

alpha-hemolysis?

A

partial blood hemolysis, surrounded by a greenish halo ( due to the transformation of hemoglobin to methemoglobin.

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9
Q

Gamma-hemolysis?

A

no change of the surrounding

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10
Q

vertical transmission of bacterial genetic material?

A

distribution to daughter cells following cell division

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11
Q

Horizontal transmission of bacterial genetic material?

A

with an unidirectional mechanism from a donor cell to an acceptor cell

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12
Q

Mechanisms of horizontal transfer of genetic material:

A

Transformation, Transduction, Conjugation

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13
Q

The ability to take up the DNA from the environment is called?

A

Competence

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14
Q

types of plasmids?

A

Conjugative, Col plasmids, virulence plasmids, metabolic plasmids.

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15
Q

what are bacteriocins?

A

Bacteriocins are proteinaceous or peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s).

16
Q

Mobile genetic elements:

A

Insertion sequences and transposons

17
Q

What are transposable elements?

A

genetic units that are able to replicate independently and mediate their own transfer from one chromosome to another, from one position on the same chromosome to another.

18
Q

What are transposons?

A

these genes may code for antimicrobial resistance, substrate metabolism

18
Q

What are insertion sequences?

A

simple transposable elements, its presence in the chromosome is hard to detect

19
Q

What is bactericide?

A

a substance that kills bacteria. Bactericides are
disinfectants, antiseptics, or antibiotics

20
Q

What is Bacteriostatic?

A

“bacteriostatic” means that the agent prevents the growth of bacteria (i.e., it keeps them in
the stationary phase of growth), and “bactericidal” means that kills bacteria.

21
Q

What are the phases of bacterial growth in liquid medium?

A

Exponential (the highest rate of growth), stationary (the number of cells doesnt increase), death ( death of bacteria due to the lack of nutrients)

22
Q

What is a LAG phase?

A

It is phase during which the bacteria do not grow yet as they were just introduced to the liquid media.

23
Q

How can we obtain isolated colonies of single species of bacteria?

A

We can use a technique such as isolated spreading with the use of a Loop.

24
Q

What is the limiting factor for bacteria metabolism and doubling?

A

Water

25
Q

What chemicals gram-positive bacteria cannot withstand?

A

Bile salts, Crystal violet dye

26
Q

What color does MacConkey agar turns in the presence of lactose fermenting bacteria?

A

Red or pink

27
Q

why is there a greenish halo during the Alpha hemolysis?

A

it is due to the transformation of hemoglobin to methemoglobin.

28
Q

what is the episomic state of the plasmid?

A

plasmid is free in the cytoplasm

29
Q

what is the integrated state of the plasmid?

A

the plasmid genes are integrated into the bacterial chromosome

30
Q

what can cells with F+ produce?

A

sexx pilus, through which the gene for sex pilus is transferred to the F- cell

31
Q

what do invertible elements do?

A

they switch the genes

32
Q

what are the types of transduction?

A

Generalized and Specialized

33
Q

how can we induce the competence state?

A

by the use of cations or by electroporation.

34
Q

what is generalized transduction?

A

is when the bacteria chromosomes get integrated into the capsid of the virus and eventually transferred to other bacteria (lytic cycle)

35
Q

what is specialized transduction?

A

is when the bacteriophage gene takes up some of bacterial gene and then after lysis of the cell transfers it to other bacteria

Microbiology (6 decks)

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