Antimicrobial activity of Pseudoalteromonas strains isolated from the Ross Sea (Antarctica) versus Cystic Fibrosis opportunistic pathogens

In Antarctica, the selective pressure may have led to the evolution of novel capabilities by indigenous organisms, including microorganisms, to achieve competitive advantages. In this work, the ability of thirteen Antarctic Pseudoalteromonas isolates from different sources (sponges, seawater and sediments) to synthesize antimicrobial compounds was analysed. The antibacterial activity was tested against Cystic Fibrosis opportunistic pathogens belonging to the Burkholderia cepacia complex (Bcc). Data obtained revealed that all the Pseudoalteromonas strains synthesize a plethora of microbial volatile organic compounds (mVOCs) and diffusible molecules that strongly interfere with the growth of Bcc bacteria and that this synthesis may be influenced by the growth media essentially in terms of amount of each mVOC. The finding that mVOCs profiles can be obtained from bacteria belonging to very different taxa strongly suggests that the synthesis of such compounds might have a great relevance from an evolutionary and/or ecological viewpoint. Since these mVOCs are able to completely inhibit the growth of Bcc bacteria, thus exhibiting an antibacterial activity, it is possible that such compounds might represent one of the forces driving the structuring of bacterial communities inhabiting the same ecological niche.