Pseudoalteromonas sp. PA2MD11 Genome sequencing and assembly. Pseudoalteromonas sp. PA2MD11

Active heterotrophic metabolism is amongst the critical metabolic roles exerted by sponge-associated microorganisms, but little is known about their capacity in metabolizing marine polysaccharides. Here, we investigate the genomic content of a sponge-derived Pseudoalteromonas sp. PA2MD11 strain centring our comprehensive in silico survey on its catabolic potential over macroalgal polysaccharides. Phylogenetic and phylogenomic inferences indicated the strain PA2MD11 might represent a new species in the Pseudoalteromonas genus. The genome of Pseudoalteromonas sp. PA2MD11 also houses a number of genes putatively related to the adaptation to the sponge host. Carbohydrate-active enzymes (CAZymes) for the depolymerization of agar and alginate were specifically uncovered in the genome of PA2MD11, namely glycoside hydrolases (GHs) from the families 16, 50 and 117 and polysaccharide lyases (PLs) from the families 6 and 17. Interestingly, a gene for a carrageenan-specific sulfatase was discovered, which is in the likely basis of the consumption of different types of carrageenan by this strain. The complete metabolism of agar and alginate was also predicted from the genomic information, in agreement with the results obtained in physiological assays and solid media screening. From the discovered polysaccharide utilization loci (PULs), the one dedicated to the metabolism of agarose and carrageenan exhibiting signs of is acquisition by horizontal gene transfer from other marine Gammaproteobacteria. Homology modelling and additional structural predictive analyses of the agarases, alginate lyases and carrageenan sulfatase depict clear catalytic and protein folding conservation but lower protein sequence similarity in relation to their known homologues. We advocate the extensive investigation of these marine polysaccharide-degrading enzymes unveiled in Pseudoalteromonas sp. PA2MD11 as potentially novel industrial biocatalytic resources.