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Flashcards in lecture 1.8 Deck (19):
1

Planctonic=

free floating in culture medium

2

Biofilm/Sessile=

communities of single or multiple species growing on surfaces

3

Oligotrophic growth=

growth on/ a requirement for a complex mixture of nutrients that are preset at low concentrations

4

Describe the characteristics of a biofilm

complex, slime enclosed communities called a biofilm
Biofilms are ubiquitous in nature in water
Can be formed on any conditioned surface
heterogeneity is differences in metabolic activity and locations of microbes
exchanges take place metabolically: DNA uptake and communication

5

Whats the problem with biofilms in health?

When formed on medical devices, such as implants, often lead to illness
Sometimes difficult to cure with antibiotics – there may be persisters that are more resistant to antibiotics
Sloughing off of organisms can result in contamination of water phase above the biofilm such as in a drinking water system

6

quorum sensing=

density-dependent manner in which biofilms communicate

7

How do biofilms uptake DNA?

DNA uptake occurs, bacteriocins are released
bacteriocins are chemical that kill (cannibalize?) bacteria of the same species as the ones making the bacteriocins
bacteriocin producing strains carry a resistance factor against the bacteriocin

8

How does Quorum Sensing work?

Acylhomoserine lactone (AHL) --molecule produced by many gram-negative organisms
diffuses across plasma membrane
once inside the cell, induces expression of target genes regulating a variety of functions

9

What are the different ways in which culture media can be classified

chemical constituents from which they are made
physical nature
function

10

peptones=

protein hydrolysates prepared by partial digestion of various protein sources

11

Extracts=

aqueous extracts, usually of beef or yeast

12

Agar=

sulfated polysaccharide used to solidify liquid media; most microorganisms cannot degrade it

13

What are the advantages of a complex media?

can support rapid growth (because the bacteria don’t have to make lots of biosynthetic precursors

14

What are the disadvantages of a complex media?

we don’t know and can’t control composition

15

What are the different types of media?

Supportive or general purpose media
Enriched media (e.g. blood agar/ media supplemented by blood or other special nutrients)
Selective
Differential

16

How does selective media work?

MacConkey agar
contain bile salts that are toxic to gram-positives
selects for gram-negative bacteria

17

How does blood agar differentiate?

hemolytic versus nonhemolytic bacteria

18

How does MacConkey agar differentiate?

lactose fermenters versus nonfermenters: Lac+ (e.g. E. coli) are red on MacConkey, Lac- (e.g. Salmonella) are white

19

What percent of bacteria observed can be cultured in lab media and why?

approx 1%
Medium used is too rich or too poor
Medium does not contain a necessary supplement
O2 tension, temperature not right
Organism requires some other species to feed it
Who knows?