HIGH POTENTIAL FOR THE BIOSYNTHESIS OF NEUTRAL LIPID STORAGE COMPOUNDS IN CHRONICALLY-POLLUTED SUBANTARCTIC SEDIMENTS

GALVAN V; PASCUTTI F; SANDOVAL N; LANFRANCONI, MARIANA P.; ARABOLAZA A; ALVAREZ, HÉCTOR M; GRAMAJO H,; DIONISI HM

Buenos Aires

Congreso; LVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2020

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Microorganisms in intertidal sediments of Ushuaia Bay (Tierra del Fuego,Argentina) are adapted to extreme conditions, including low temperatures, high UV-B radiation levels and the presence of various environmental pollutants. Due to tidal cycles, these organisms are also exposed to periods of drought, as well as rapid changes in temperature, salinity and nutrient availability. Members of a limited number of phyla are known to accumulate wax esters (WE) and triacylglycerol(TAG) as an adaptation response tostressful environmental conditions similar to those present in intertidal sediments of Ushuaia Bay. The goal of this work was to studythe abundance and diversity of bacteria with the potential to biosynthesize these neutral lipid storage compounds in intertidal sediments polluted with aliphatic and polycyclic aromatic hydrocarbons, retrieved near a pier of a fuel storage facility. Homolog sequences of the key enzyme for WE and TAG biosynthesis, thewax ester synthase/acyl-CoA diacylglycerolacyltransferase (WS/DGAT), were identified in a metagenomic datasetfrom sediments of this site.Out of the 682,972 protein coding sequences of the dataset, 166 contained thewax ester synthase-like Acyl-CoA acyltransferasepfam domaincommonly used to identify this enzyme (PF03007, E-value ≤10−5), the 74% of them full-length.AWS/DGAT C-terminal domain (PF06974) was also detected in the majority of the sequences. The relative abundance of WS/DGAT homolog sequencesin the dataset was 1.42 ± 0.18 times the number of sequences of single-copy genes coding for ribosomal proteins (average ± standard deviation of 12 genes), suggesting a high prevalence of WE/TAG biosynthesis potential in the microbial community. Sequences were highly diverse, as 108 and 44 clusters were recoveredusing distance thresholds of 80% and 40% identity at the amino acid level, respectively. Furthermore, 64% of the putative enzymes shared low to moderate identity values with WS/DGAT homologs identified in bacterial genomes, indicating the presence of novel organisms with WE/TAG biosynthesis potential in the sediments. The taxonomic assignment of scaffolds containing WS/DGAT homologs (1 to 43.4 Kb, N50 = 35 Kb) indicatedthat members of the Actinobacteria (46 %), Proteobacteria (33 %), Bacteroidetes (3 %) and Acidobacteria (1 %) phyla could be the origin of the majority of the scaffolds, while 17% of them could only be assigned to Bacteria. These results suggest the presence of phylogenetically diverse and abundant microbial populations with the potential to biosynthesize neutral lipid storage compounds in intertidal sediments of this polluted site. This study is the starting point for more in-depth analysesof these metagenomic fragments, in order to increase our understanding of the mechanisms used bythese diverse bacterial populations to adapt to environmental stressors in this extreme environment.