Temperature, not LuxS, mediates AI-2 formation in hydrothermal habitats.

Quorum sensing provides the basis for coordinating community-wide, microbial behaviors in many mesophilic bacteria. However, little attention has been directed toward the possibility that such phenomena occur in extremely thermal microbial environments. Despite the absence of luxS in hyperthermophile genomes, autoinducer-2 (AI-2), a boronated furanone and proposed 'universal' interspecies mesophilic bacterial communication signal, could be formed by Thermotoga maritima and Pyrococcus furiosus through a combination of biotic and abiotic reaction steps. AI-2 did not, however, induce any detectable quorum-sensing phenotypes in these organisms, although transcriptome-based evidence of an AI-2-induced stress response was observed in T. maritima. The significance, if any, of AI-2 in hydrothermal habitats is not yet clear. Nevertheless, these results show the importance of considering environmental factors, in this case high temperatures, as abiotic causative agents of biochemical and microbiological phenomena.