Changes in archaeal and bacterial community composition following entombment in halite crystals

The general aim of this project was to identify whether microorganisms from salt-saturated brines are preferentially entombed inside halite brine inclusions. This involved direct comparison of microbial communities (Archaea and Bacteria) in in-situ brine and halite samples collected from Trapani Salterns in Sicily, as well as, comparison between parent brines and experimentally-entombed halite communities over a course of 21-weeks. Quantification of archaeal and bacterial numbers showed that Archaea are exceptionally more abundant in both brine and halite, and that Bacteria are about 0.25% of the overall community in both conditions. Remarkably, few differences were observed in terms of abundance and community structure between communities in 21-week-old halite and those found in the parent brines. Evidently, all organisms of a mixed microbial community are entombed equally and most that are trapped in this way are capable of surviving inside halite for short to moderate lengths of time. This is presumably due to a complex web of interspecies interactions, co-operations and the sharing of usable metabolites. Nevertheless, some organisms are poor survivors inside halite and showed a decrease in their relative abundance in halite. In this study, this was highlighted by the decreased abundance of Haloquadratum, Candidatus Nanosalina and Cyanobacteria VII inside halite. Finally, comparisons made between communities from different Pond (brine) origins showed some significant differences and suggests that communities in halite can vary considerably depending on the environmental conditions (e.g. ionic composition and water activity) at the point of halite precipitation.