Neutral Lipid Biosynthetic Potential in Sediment Microbial Communities from Subantarctic Environments

GALVÁN V, PASCUTTI F, ARABOLAZA A, GRAMAJO H,; MAC CORMACK, WALTER; DIONISI HM; SANDOVAL N, LANFRANCONI M, ÁLVAREZ H,; LOZADA, MARIANA

Congreso; World Microbe Forum; 2021

ASM FEMS

Bacteria from a limited number of taxa areknown to accumulate wax esters (WE) and triacylglycerol (TAG) as an adaptationresponse to stressful environmental conditions, although this capability ispoorly understood at the microbial community level. The goal of this work wasto uncover the prevalence and diversity of bacteria with the potential tosynthesize neutral lipids in coastal sediments of Subantarctic and Antarctic environments,and to characterize the gene clusters related to this process. More than 48,000sequences containing the PF03007 domain (specific of the key enzyme wax estersynthase/acyl-CoA:diacylglycerol acyltransferase, WS/DGAT) were retrieved from13 metagenomes, including subtidal and intertidal sediments of Ushuaia Bay,Argentina (54° 48? S, 68° 17? W), and subtidal sediments of Potter Cove, 25 deMayo Island, Antarctica (62° 13? S, 58° 39? W). Abundance of putative WS/DGATsequences in the sediment metagenomes was 1.23 ± 0.42 timesrelative to 12 single-copy genes encoding ribosomal proteins, much higher than inseawater (0.13 ± 0.31 times in 338 metagenomes). In an ordination analysis, themetagenomes were grouped by geographic location, although closely relatedsequences were present in both environments despite a 1,000 km distance and thepotential barrier of the Antarctic Circumpolar Current. Most sequences werebinned to the Proteobacteria or the Actinobacteria phyla. Phylogenetic analysisrevealed that the majority of the identified sequences were most closely relatedto sequences from genomes assembled from metagenomes, originated fromenvironmental samples including seawater, marine sediments, groundwater,freshwater and biological wastewater treatment plants. The genomic context of putativeWS/DGAT sequences included genes encoding putative Type-2 PAPs and HAD-typehydrolases, glycerol- and acylglycerol- phosphate O-acyltransferases, some ofthem potentially responsible for specific steps in WE and TAG biosynthesis. Inaddition, some scaffolds contained genes of related pathways such as fatty-acidsmetabolism, suggesting carbon recycling might drive the flux to neutral lipidsynthesis. These results indicate the presence of abundant and diverse bacterialpopulations with the potential to synthesize lipid storage compounds. Thisinformation increases our understanding on the mechanisms used by bacteria fromextreme environments to adapt to environmental stressors.