Is there a degree of “Social Etiquette” present among marine bacterial populations?

Marine bacteria were formerly thought to have solitary lifestyles, with each individual acting independently, any concept of community structure absent. However, now it is commonly recognized that bacteria can utilize mechanisms to simultaneously act as a population and interact with one another to influence the surrounding environment. Bacteria can cooperatively interact through ‘talking’ to each other on a chemical level, this mechanism is quorum-sensing (QS).                                          

However, in the natural environment where there is a limited and often sparsely distributed concentration of nutrients available to microbes, it would be reasonable to think that bacteria would not hesitate to compete with their relatives in order to survive, that bacteria are “selfish” and thrive for individual “fitness” with no regard to their kin. Cordero et al. (2012) analyzed interference competition; mediated by antibiotic production between different populations of the Vibrionaceae family from the coastal marine realm. A Burkholder plate assay was used in the investigation. This method allows testing for local growth inhibition between bacteria that have been co-plated on nutrient agar. This technique used is significant as it provides somewhat realistic conditions for ocean bacteria, as interference competition is prevalent among individuals where density can be high i.e. biofilm formation. In the study 35,000 interactions, from 185 strains were examined. Repetition of the assay for a number of selected strains demonstrated 97% replicability of the interactions, of which; 44% were found to be able to inhibit growth of another strain, 86% of which were inhibited by another. However hostile interactions were revealed to be between rather than within Vibrio populations; with 96% of the interactions, facilitated by small antibiotic molecules. These results indicate that the majority of the competition present was between opposing, un-related populations. That related bacteria could almost have a sense of "comradeship" within in the population and do not compete with their kin for resources.

This research is significant and was chosen because it has given novel insight into bacterial interactions. Cordero et al. have suggested that bacteria are not the simplistic microorganisms previously imagined but are reproducing with a sense of social structure, organization and with direction. Indicating that competition between microbes is regulated by social hierarchy and etiquette between individuals: similar to mammals, birds and insect communities where complex social structures are present, in which resources can be defended and also shared among the population. It has been implied through this paper that bacteria are also capable of these relations, that within a population of related bacteria, antibiotics are produced by a few and shared among the many. The related bacteria are resistant to the secreted antibiotics, which are distributed like “public goods” that benefit the congregation as a whole rather than just the individual.

            Cordero, O. X., Wildschutte, H., Kirkup, B., Proehl, S., Ngo, L., Hussain, F., Le Roux, F., Mincer, T. and Polz, M.F. (2012)

           

            "Ecological Populations of Bacteria Act as Socially Cohesive Unites of Antibiotic Production and Resistance." Science, 1228-1231.

            http://www.ncbi.nlm.nih.gov/pubmed/22955834