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

PASCUTTI F; SANDOVAL, N.E; GALVÁN V; LANFRANCONI M.P.; ARABOLAZA, A.; ALVAREZ H.M.; GRAMAJO, H.; DIONISI H

Congreso; SAIB-SAMIGE Joint Meeting 2020 on line; 2020

SAIB-SAMIGE

Bacterial production of neutral lipids such as triacylglycerides,wax-esters and polyhydroxyalcanoates (TAG, WE and PHA-B, respectively) has beenreported in Gammaproteobacteria and Actinobacteria. Within them, there is ashort list of microorganisms with an in-depth study of the metabolic routeinvolved in the synthesis of these compounds. To increase our knowledge of thepotential of sediment bacteria in relation to this process, we analyzed homologsequences of the key enzyme involved in TAG biosynthesis, the waxsynthase/diacylglycerol acyltransferase (WS/DGAT), from a metagenomic datasetof a chronically-polluted Subantartic coastal environment, and their genomiccontext. Almost half of putative WS/DGAT sequences were related to those identifiedin genomes from members of the Actinobacteriaphylum, mainly from the Acidimicrobiia,Actinobacteria and Nitriliruptoria classes,while 34% of the sequences shared higher identity values with WS/DGAT homologsfrom Proteobacteria (Gammaproteobacteria,followed by Alpha-, Beta- and Deltaproteobacteria). Phylogeneticanalyses showed that most metagenomic sequences were more closely related tosequences from genomes assembled from metagenomes, generated from environmentalsamples collected worldwide, including seawater, marine sediments, groundwater,seashore sand and freshwater, as well as biological wastewater treatmentplants. Gene clusters potentially related to neutral lipid biosynthesis pathwayswere identified in scaffolds of the metagenomic dataset containing putativeWS/DGAT sequences. A number of scaffolds shared highly similar geneticarrangements 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-typehydrolases, glycerol- and acylglycerol- phosphate O-acyltransferases. InProteobacteria, the gene clusters presented novel distributions of genesinvolved in TAG, WE and/or PHA, suggesting that they are intertwined. Mostscaffolds contained genes from related metabolic pathways, such as fatty-acidsmetabolism and its regulation, implying that recycling of carbon might drivethe flux to one or another neutral lipid synthesis. In addition, genes encodingosmoregulated periplasmic transporters for uptake of organic acids were present,revealing how the environment could also be influencing the studied process. This work is apioneer study on the diversity of neutral lipid metabolic routes present insediment bacteria based on metagenomic data. It enriches our knowledgeof the metabolic potential of these microbial communities in relation to aprocess with an inherent biotechnological interest.