Originally Posted by admin
Yup its true the colonised bacteria will compete for the food of the new bacteria, making it tough for the new bacteria to survive.
Also the old bacteria usually make biofilms, meaning they stick onto the surface as colonies working together to generate a film that will prevent other new bacterial colonies / species from colonizing the area.
The crucial thing is to have biofilms established by "good" bacteria, as usually happens when an infant is fed with mothers milk (plenty of bifidobacteria were found in intestined of infants and toddlers).
Another thing discovered is that "good" or rather probiotic bacteria (mainly lactic acid bacteria) ans some symbiotic bacteria somehow activate human immune response when they have contant with pathogenic bacteria.
It has something to do with TLR receptors.
Group of researchers led by PhD Yasmine Belkaid discovered that during infection DNA particles are released from symbiotic bacteria (maybe due to their lysis caused by pathogenic bacteria - thing yet unknown) and those DNA bind to TLR9 receptor and that trigger immune response. "Good" microorganisms may therefore act as an adjuvant.
This is interesting but many mechanisms are still to be discovered.
Jorge1907 - why do you thing the mechanisms I described are odd? It was proved that metabolsm products like lactic acid inhibit the growth of some bacteria, so do bacteriocins. The latter substances are ecologically important - they seem to play role in bacterial competition in the environment (especially soil) where bacteria compete for nutrients and try to outgrow other bacteria.