Abstract:
Terrestrial Antarctica is one of the most extreme environments on the planet Earth. Despite the harsh conditions, the continent is able to host a surprisingly high diversity of microorganisms comparable to temperate environments, even in areas with total absent of phototrophs organisms. A recent study demonstrates how high-affinity hydrogenases, carbon monoxide dehydrogenases and a RuBisCo lineage are capable to scavenge atmospheric trace gases to support chemosynthetic carbon fixation. Notwithstanding this insightful approach, only two sites in Antarctica have been used to support this discovery, leading to the necessity of increasing the sampling depth and the potential of other kind of enzymes involved in the gas scavenging process. Here we analyzed 19 soil metagenomes from a region north of McMurdo Dry Valleys, Eastern Antarctica. We identified the main groups of genes encoding enzymes implicated in the scavenging of atmospheric hydrogen and carbon monoxide to produce carbon biomass. We also propose additional gene groups involved in the uptake of different atmospheric gases including methane and ammonia as alternative chemosynthetic pathways of primary production. In our metagenomes we identified 25 complete genes (and 1224 partial sequences. belonging to high-affinity NiFe-hydrogenases (group 1h. and 6 complete genes (and 277 partial sequences. with sequence homology to carbon monoxide dehydrogenases (Mo-Cu CoxL., responsible for the scavenging of the molecular H2 and CO from the atmosphere, respectively. Moreover, we identified 45 complete genes (and 736 partial sequences. for non-classical methane oxygenases, potentially involved in the aerobic oxidation of methane. With respect to the ammonia scavenge we found a wide distribution for high-affinity ammonium/ammonia transporters able to introduce atmospheric ammonia into the bacterial cell that, in conjunction with glutamine synthetase (54 complete genes and 948 partial sequence., are responsible for the conversion of this metabolite into glutamate. Evolutionary relationships confirmed their phylogenetic assignment into every single family of enzymes. This work gives a comprehensive overview of how non-photosynthetic communities from Antarctica are able to use trace gases from the atmosphere as alternative pathways to support primary production in an ubiquitous way. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.
