In order to ensure the survival of their own population, bacteria must develop some strategies to differentiate their own species from other bacteria. One strategy might include the production of antibiotics that kill others but not themselves. How do you think bacteria could develop such effective strategy, ie, developing antibiotic synthesis genes after gaining the resistant genes? Does quorum sensing system help them to recognize themselves from other bacteria?
Quorum sensing (QS) and the production of antimicrobials are tightly connected. QS is the most widely recognized means by which cells recognize their own population size. The most researched means of quorum sensing is by the production of diffusible molecules, such as acyl-homoserine lactones (AHLs). Modifications to the structure of these AHLs allow them to become species or strain specific. In the classical example, AHLs are produced constitutively, and when the population reaches a certain density, the elevated concentration of AHLs will trigger changes in gene expression in the QS regulon. Antimicrobial production is often within this regulon, because a single cell could not produce enough antimicrobial to inhibit a competing population. Interestingly there are some AHLs that are shared between multiple species. This allows the organisms to know both their own population and the population of nearby organisms. Often a species will produce multiple AHLs that are produced at different concentrations and different states of growth.
I hope this helps. There are many reviews out there that may also be useful.
I think that cooperation between different species of bacteria plays more important role in their evolution and life comparing to competition. See Griffin AS, West SA, Buckling A. Cooperation and competition in pathogenic bacteria. Nature. 2004 26;430(7003):1024-7.
Here's an interesting paper that investigates bacterial population interactions in Vibrionaceae. There isn't much about quorum sensing here, but it is a great paper nonetheless.
http://www.sciencemag.org/content/337/6099/1228.long
Using multiple Quorum sensing systems might be a possibility. For gram positive bacteria, there might be no problem, as they typically use small peptides which allows for a huge number of different types, species specific or so.
For the typical gram negative bacteria using AHLs as signalling molecules, the number of different types of AHLs is rather restricted. So, there might be overlaps from other species, cross-talk cannot be excluded.
It is interesting that how own species recognise themselves as many of bacteria produces same QS signals..
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