Biofilm formation and Quorom sensing

Question 1

Cell to cell communication in bacteria cells is acomplished through -

Answer 1

the exchange of chemical signal molecules known as autoinducers in a process known quorom sensing

Question 2

What parameter is quorom sensing used to monitor

Answer 2

Cell density

Question 3

What processes does quorom sensing regulate

Answer 3

Motility, biofilm formation, toxins

Question 4

What are the 3 basic components for quorom sensing in both (+) and (-) bacteria

Answer 4

1. The production of autoinducer molecules, at low densitiies the AI diffuse away, at high cell densities they trigger the expressing of quorom inducible genes
2. Receptors monitor AI levels
3. When a sufficient concentraion of AI is reached, expression of AI responsive genes is increased

Question 5

Describe the process of quorom sensing in gram positive bacteria

Answer 5

Gram (+) bacteria use peptides, known as autoinducing peptides (AIPs) as signalling molecules. AIPs are produced and secreted into the extracellular enviroment. When extracellular AIP concentration reaches a threshold concentration, AIP bins to membrane bound kinase receptors which activates the cells kinase activity. The signal is passed to intramolecular signalling molecules which activate qourom sensing regulon

Question 6

Describe the process of quorom sensing in gram negative bacteria

Answer 6

Acyl homoserine lactones (AHLs) are used as autoinducers. Once produced they diffuse through both cell membranes. At high densities they trigger the expression of quorom inducible genes. AHL can pass through both cell membranes to bind to intramolecular receptors to change gene expression.

Question 7

What are biofilms

Answer 7

3-D multilayer bacterial populations embedded in a polysaccharide matrix. The biofilms has water channels embedded which allow for the flow of oxygen and nutrients through the structure.

Question 8

Name the 4 stages of biofilm formation

Answer 8

Attachment
Colonisation
Development
Dispersal

Question 9

Name 2 bacteria that form biofilms and state where they form biofilms

Answer 9

Vibrio cholerea - in infected gut tissue

E.coli - on medical devices and in human tissue