Biofilm physiology

Question 1

what is the dominant life form of bacteria?

Answer 1

biofilms

Question 2

what percentage of surgical wound infections are due to pseudomonas aeruginosa?

Answer 2

8%

Question 3

what percentage of deaths in immunocomprimised patients are due to pseudomonas aeruginosa?

Answer 3

30%

Question 4

what percentage of bloodstream infections are due to pseudomonas aeruginosa?

Answer 4

10%

Question 5

what percentage of deaths associated with intubated patients are due to pseudomonas aeruginosa?

Answer 5

38%

Question 6

what percentage of death under outbreaks in burn units are associated with pseudomonas aeruginosa?

Answer 6

60%

Question 7

what percentage of deaths in the expanding AIDS population are associated with pseudomonas aeruginosa?

Answer 7

50%

Question 8

what percentage of nosocomial pneumonia cases are due to pseudomonas aeruginosa?

Answer 8

16%

Question 9

what percentage of hospital acquired urinary tract infections are due to pseudomonas aeruginosa?

Answer 9

12%

Question 10

what is the most frequent severe genetic disease among caucasians?

Answer 10

cystic fibrosis

Question 11

A minimum of ____ of these problematic wounds are infected with P. aeruginosa.

Answer 11

50%

Question 12

how d obacteria use cell-cell signalling to coordinate expression of virulence

Answer 12

in a density related process called ‘quorum sensing’

Question 13

What is QS characterised by ?

Answer 13

QS is characterised by an accumulation of autoinducing signal molecules in and around high density colonies

• QS allows cells to co-ordinate their gene expression in a cell density dependant manner
• QS controls the transcription of many virulence genes of pathogenic bacteria

Question 14

what quorum sensing signals are used by gram-negative bacteria

Answer 14

= N-acyl-l-homoserine lactones (AHL) AI-1
= furanone (E. coli, Salmonella, H. pylori) AI-2
= adrenaline/noradrenaline AI-3

Question 15

what quorum sensing singals are used by gram postive bacteria

Answer 15

 Gram positive = Auto inducing peptide (AIP)

Question 16

what is required for synthesis of periplasmic anionic glucans

Answer 16

ndvB

Question 17

what is the central regulator of the stress response?

Answer 17

RpoS

Question 18

does high cell density induce stress reposne?

Answer 18

yes induces RpoS

Question 20

give an example of a osmoprotectant

Answer 20

trehalose

Question 21

what is the global stress response sigma factor

Answer 21

(rna polymerase alternate factor so it can only bind to rpos sensitive genes)

Question 22

what is lasl and what happens when its deleted from p.aeruginosa

Answer 22

• Deletion of lasI, structural gene for N-(3-oxydodecanoyl)-L-homoserine lactone synthetase, causes loss of EPS production and defects in biofilm formation (Davies et al., 1998)

Question 23

give two examples of quorum sensing chemicals produced by p.aeruginosa in the CF lung

Answer 23

• P. aeruginosa has been shown to produce both N-butyryl-L-acyl HSL and N-(3-oxydodecanoyl)-L-homoserine lactone in the CF lung (Erickson et al., 2002; Singh et al., 2000).

Question 24

when are genes for synthesis of pili and flagella repressed in biofilms?

Answer 24

during maturation

Question 25

how many genes in the p.aeruginosa microarray showed differential expression in two growth mdoes

Answer 25

73 out of 5500

Question 26

what are some issues with analysing averages of gene expression in biofilms

Answer 26

– which are heterogeneous groups of cells exhibiting different activities
– certain subpopulations in the biofilm may have substantially different patterns of gene expression
– than did the homogeneous planktonic population or most of the metabolically active cells in the biofilm.