Microbial communities

Question 1

Describe positive and negative interactions

Answer 1

Positive - E.g Bacteria produces toxin that is the other ones food
Negative - Competition/prey

Question 2

What is quorum sensing?

Answer 2

Bacteria sends out signal (autoinducers) to sense population.
If cell density is high then more autoinducers.
These bind to receptor that regulates transcription of genes that produce autoinducers, produces a positive feedback producing more signal

Question 3

What is the Agr system

Answer 3

E.g of quorum sensing
At low cell density AIP concentration is low so no RNA III so no biofilm production.
At high density AIP high so more RNA III which drives invasion and toxin
Switch from biofilm to pathogen

Question 4

How is biofilm formed?

Answer 4

Polymer matrix attaches to cell surface.
Change of expression = irreversible attachment
2 maturation stages make sticky coat, supress flagella and QS