Members of the archaeal phylum are among the most abundant microorganisms on Earth. Although versatile metabolic capabilities such as acetogenesis, methanogenesis, and fermentation have been suggested for bathyarchaeotal members, no direct confirmation of these metabolic functions has been achieved through growth of in the laboratory. Here we demonstrate, on the basis of gene-copy numbers and probing of archaeal lipids, the growth of subgroup Bathy-8 in enrichments of estuarine sediments with the biopolymer lignin. Other organic substrates (casein, oleic acid, cellulose, and phenol) did not significantly stimulate growth of Meanwhile, putative bathyarchaeotal tetraether lipids incorporated C fromC-bicarbonate only when added in concert with lignin. Our results are consistent with organoautotrophic growth of a bathyarchaeotal group with lignin as an energy source and bicarbonate as a carbon source and shed light into the cycling of one of Earth's most abundant biopolymers in anoxic marine sediment.

In marine sediments, microorganisms are known to play important roles in nitrogen cycling; however, the composition and quantity of microbes taking part in each process of nitrogen cycling are currently unclear. In this study, two different types of marine sediment samples (shallow bay and deep-sea sediments) in the South China Sea (SCS) were selected to investigate the microbial community involved in nitrogen cycling. The abundance and composition of prokaryotes and seven key functional genes involved in five processes of the nitrogen cycle [nitrogen fixation, nitrification, denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonia oxidation (anammox)] were presented. The results showed that a higher abundance of denitrifiers was detected in shallow bay sediments, while a higher abundance of microbes involved in ammonia oxidation, anammox, and DNRA was found in the deep-sea sediments. Moreover, phylogenetic differentiation of bacterial amoA, nirS, nosZ, and nrfA sequences between the two types of sediments was also presented, suggesting environmental selection of microbes with the same geochemical functions but varying physiological properties.

No abstract