RECONSTRUCTING NEUTRAL-LIPIDS METABOLIC PATHWAYS OF A METAGENOMIC DATASET FROM USHUAIA BAY SEDIMENTS

PASCUTTI FEDERICO; LANFRANCONI MARIANA; GRAMAJO HUGO; SANDOVAL NATALIA; ARABOLAZA ANA; DIONISI HEBE M; GALVAN VIRGINIA; ALVAREZ HECTOR

Congreso; Congreso conjunto SAIB - SAMIGE 2020; 2020

Bacterial production of neutral lipids such as triacylglycerides, wax-esters and polyhydroxyalcanoates (TAG, WE and PHA-B, respectively) has been reported in Gammaproteobacteria and Actinobacteria. Within them, there is a short list of microorganisms with an in-depth study of the metabolic route involved in the synthesis of these compounds. To increase our knowledge of the potential of sediment bacteria in relation to this process, we analyzed homolog sequences of the key enzyme involved in TAG biosynthesis, the wax synthase/diacylglycerol acyltransferase (WS/DGAT), from a metagenomic dataset of a chronically-polluted Subantartic coastal environment, and their genomic context. Almost half of putative WS/DGAT sequences were related to those identified in genomes from members of the Actinobacteria phylum, mainly from the Acidimicrobiia, Actinobacteria and Nitriliruptoria classes, while 34% of the sequences shared higher identity values with WS/DGAT homologs from Proteobacteria (Gammaproteobacteria, followed by Alpha-, Beta- and Deltaproteobacteria). Phylogenetic analyses showed that most metagenomic sequences were more related to sequences from genomes assembled from metagenomes, generated from environmental samples collected worldwide, including seawater, marine sediments, groundwater, seashore sand and freshwater, as well as biological wastewater treatment plants. Gene clusters potentially related to neutral lipid biosynthesis pathways were identified in scaffolds of the metagenomic dataset containing putative WS/DGAT sequences. A number of scaffolds shared highly similar genetic arrangements with genome fragments from a variety of organisms. Among them, some loci included genes that potentially encode other steps in neutral lipid biosynthesis, such as putative Type-2 PAPs and HAD-type hydrolases, glycerol- and acylglycerol- phosphate O-acyltransferases. In Proteobacteria, the gene clusters presented novel distributions of genes involved in TAG, WE and/or PHA, suggesting that they are intertwined. Most scaffolds contained genes from related metabolic pathways, such as fatty-acids metabolism and its regulation, implying that recycling of carbon might drive the flux to one or another neutral lipid synthesis. In addition, genes encoding osmoregulated periplasmic transporters for uptake of organic acids were present, revealing how the environment could also be influencing the studied process. This work is a pioneer study on the diversity of neutral lipid metabolic routes present in sediment bacteria based on metagenomic data. It enriches our knowledge of the metabolic potential of these microbial communities in relation to a process with an inherent biotechnological interest.