Chemical Communication within the genus Marinobacter may Mediate Niche Competition

Because of its wide ecological distribution the Marinobacter genus is considered ubiquitous in the ocean and can be described as “opportunitrophs” able to survive under a wide-range of conditions often colonizing the surfaces of marine snow or algae. While Marinobacter spp. account numerically for only a small proportion of the total bacteria present in the “phycosphere” of algae-associated environments, either in culture or in the field they are almost universally present in the core microbiome of microalgae in general and dinoflagellates in particular. Although many potentially algal associated bacteria occur in seawater only a few individuals actually colonize the surface of a phytoplankton host at the same time, suggesting a possible intraspecies competition for this niche. Thus there must be various ways that bacteria and/or algae control the colonization population of an algal surface, most of which likely invoke some sort of cell to cell communication.

Here we show that Marinobacter do not produce or utilize an acylhomoserine lactone based quorum sensing system. Rather in the absence of a classical acyl homoserinelactone based quorum sensing system “sibling” colonies of some species of Marinobacter exhibit a new form of non-lethal chemical communication which prevents colonies from overrunning each others niche space. We further show that this inhibition is the result of a loss in motility for cells at the colony interface mediated by the protein glycerophosphoryl diester phosphodiesterase. The potential ecological consequences of this chemical communication are also discussed.