Alteromonas are ecologically relevant microorganisms, which are widespread in marine environments and can proliferate in response to pulses of organic matter. Furthermore, they feature a wide ability to degrade polymers, such us polysaccharides produced during algal blooms. Here, we studied two Alteromonas isolates with different capabilities to degrade marine polysaccharides (i.e., laminarine and alginate) with focus on understanding the molecular and cellular mechanisms employed to degrade different carbon (C) sources. The consumption of the polysaccharides was faster than that of glucose for both strains, suggesting their specialization in the utilization of polymeric C. By combining different omics approaches, we identified potential Polysaccharide Utilization Loci and analysed their expression patterns during growth on different C sources. Additionally, by high resolution microscopy we visualized a dense exopolysaccharide (EPS) matrix in Alteromonas strains when growing on some carbohydrates.  Up to four different gene clusters involved in EPS synthesis were identified in their genomes, which were differentially expressed under different growth conditions. By comparative genomics we found that the EPS synthesis clusters were generally present and highly conserved in a set of 24 Alteromonas genomes, suggesting a widespread distribution. Our results suggest that Alteromonas modulates the secretion of specialized extracellular matrices for degrading different carbohydrates, unveiling a potential role of this cellular mechanism for marine C remineralization.

Primary Presenter: Laura Alonso-Sáez, AZTI (lalonso@azti.es)

Authors:

Carla Pérez-Cruz, AZTI  (carlaperez@azti.es)

Uxue Arrizabalaga-Luzuriaga, AZTI  (uarrizabalaga@azti.es)

Raquel Liébana, AZTI  (rliebana@azti.es)

Elisabete Bilbao, AZTI  (ebilbao@azti.es)

Anders Lanzen, AZTI  (alanzen@azti.es)

Laura Alonso-Sáez, AZTI  (lalonso@azti.es)