Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology of Microbes > Selective and Diagnostic Culturing L17 > Flashcards

Selective and Diagnostic Culturing L17 Flashcards

1
Q

what is a phototroph

A

organism that is nutritionally able to synthesise all its required growth factors from simple substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how do substances vary

A

depending on the nutritional classification of the organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are physical conditions that should be met

A

Temperature
pH
O2 levels
Osmolarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are general nutritional requirements

A 
carbon source
nitrogen source
sodium
phosphorus 
sulphur 
iron
trace elements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the carbon sources available for nutrition

A

CO2 (AUTOTROPHS)
Organic molecules (HETEROTROPHS)
e.g. glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the nitrogen sources available for nutrition

A

inorganic e.g. N2 NH4

organic e.g. amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is sodium for in nutritional requirement

A

transporters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the phosphorus elements in nutritional requirements

A

nucleotides and ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the sulphur elements in nutritional requirements

A

SOv4^2- sulfate
H2S hydrogen sulphide
as aminoacids (Cys)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the iron elements in nutritional requirements

A

(Fe2+): cytochromes, catalase & other enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the trace elements in nutritional requirements

A

Zn2+; Cu2+; Mn2+; Mo6+; Co2+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the trace elements for in nutritional requirements

A

required for a range of enzyme activities
required at very low levels (mg l-1)
sufficient present as contaminants in most media

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is defined media

A

made from mixtures of pure chemicals and contain precisely controlled amounts of each chemical
requires a thorough knowledge of cell metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the growth media prepared as

A

mixtures of extracts:

  • yeast extracts: vitamins and amino acids
  • peptones: amino acids and TE’s from hydrolyzed protein
  • meat infusions: soups
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

where are peptones produced

A

Peptones are produced from a variety of raw materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the effect of a different growth media

A

end product will contain a different range of aa’s and minerals which favour growth of different organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what peptones are from milk

A

casein peptones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what peptones are from meat

A

general peptones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what peptones are from soya

A

plant peptones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the methods of isolating a particular organism

A

using

  • selective medis
  • differential medium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is selective media

A

contains selective agents which prevent growth of some organisms but allows others to grow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does selective media often contain

A

antibiotics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what does selective media require

A

requires an understanding of the growth parameters of the whole population

24
Q

what is differential medium

A

particular organism has a characteristic appearance on the medium

25
Q

which agar is used for staphylococcus aureus

A

baird parker

26
Q

what does staphylococcus look like on baird parker agar, under what particular conditions

A

produces grey/black shiny colonies with a clear halo in 24h at 37°C

27
Q

what do other staphylococci look like on baird parker agar

A

dont produce a clearing

28
Q

what does bacillus look like on baird parker agar

A

brown, matt colonies

29
Q

what does proteus look like on baird parker agar

A

produces brown/black colonies

30
Q

what agar is E. coli and Salmonella grown on

A

MacConkey agar

31
Q

how are E.coli and Salmonella differentiated on agar

A

pH change (media contains a pH indicator) due to their different ability to ferment lactose

32
Q

what colour does lactose positive turn and which bacteria on what agar

A

pink
E.coli
MacConkey

33
Q

what colour is lactose negative

A

yellow

34
Q

what is bacillus cereus selective agar used for

A

Precipitates Lecithin in egg yolk

Cannot utilise mannitol so medium stays blue

35
Q

what bacteria grows well on mannitol salt agar, what does the bacteria do

A

Staphylococcus aureus grows in presence of high salt (S) and ferments mannitol to produce acid (D)
agar changes from normal red to yellow

36
Q

what are the three general modes of antibiotic action

A

1) prevent synthesis of bacterial cell wall (e.g. all β-lactams)
2) damage cytoplasmic membrane (e.g. polymxyin)
3) interfere with biochemical synthesis

37
Q

what does Rifampicin do, where is it used

A

inhibit transcription

antibiotics - interfere with biochemical syntheis

38
Q

what does Chloramphenicol, Streptomycin, Tetracycline do, where is it used

A

inhibit ribosome function

antibiotics - interfere with biochemical synthesis

39
Q

what does Fluroquinolones do, where is it used

A

inhibit DNA replication

antibiotics - interfere with biochemical synthesis

40
Q

what can lead to antibiotic resistance

A

1) Absence of a target site
2) Variants/point mutations in target sites that prevents the antibiotic binding
3) Enzymes to detoxify the antibiotics
4) Efflux pumps that remove the antibiotic before it damages the cell

41
Q

when are enrichment procedures used

A

Used where essential to detect very low numbers of a specific organism
e.g. food borne pathogens in food samples
Also helps to revive damaged cells
e.g. those that have survived a processing step or have been in an unfavourable environment and may be sub-lethally injured

42
Q

what is the enrichment procedure steps STEP1

A

Pre-enrichment
increase cells present
allows resuscitation/recovery of damaged cells
non-selective broth used

43
Q

what is the enrichment procedure steps STEP2

A

Selective enrichment (broth)
promotes desired organism growth
prevents/retards growth of other organisms
combinations of:
substances toxic to unwanted bacteria
inhibitory growth conditions
conditions increasing growth of target organism

44
Q

what is the enrichment procedure steps STEP3

A 
Selective plating (agar)
isolates organism of interest on selective /diagnostic agar
= presumptive positive
45
Q

what is the enrichment procedure steps STEP4

A

Confirmative tests

further testing is required to confirm identification

46
Q

what are confirmatory tests

A

1st 2 common tests are Catalase and Oxidase tests

47
Q

what does the catalase test do

A

detects enzyme that detoxifies Hydrogen peroxide

Typical of obligate aerobes and most facultative anaerobes

48
Q

what does the oxidase test do

A

detects cytochrome c oxidase

Tells you that organism is able to use oxygen as a terminal electron acceptor

49
Q

what is defined medium

A

ability to utilise specific sugars or amino acids

50
Q

what is medium containing defined substrates

A

ability to metabolise specific compounds

51
Q

what is the more common small scale rapid tests

A

API or Biolog

52
Q

what biochemical tests are carried out by preparing small cultures

A

defined medium
medium containing defined substrates
more common to carry out small scale, rapid tests e.g. API or Biolog

53
Q

what is antibiotic testing

A

serology

54
Q

what happens in antibiotic testing, serology

A

Agglutination tests carried out using antisera specific for the target organism

55
Q

what does it mean if clumping occurs in serology

A

cells have cross-reacted with the antibody

56
Q

what DNA based tests detect specific genes

A

DNA hybridisation methods

PCR amplification of genes

57
Q

how is media prepared

A

Components of media provided as dry powders
- Correct amounts weighed out
- Mixed with correct amount of distilled water
- Sterilised by autoclaving
- Cool and pour into Petri dishes
> Before pouring, heat sensitive components can be mixed into the molten agar
> Includes many antibiotics, vitamins, proteins, lipids

Physiology of Microbes (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions