Extracellular polysaccharides (EPS) secreted by a model marine bacterium (Alteromonas spp.)

Alteromonas are model copiotrophic marine bacteria that are able to produce highly hydrated extracellular biopolymers mainly composed of polysaccharides (i.e., extracellular polysaccharides, EPS), which have a role in biofilm formation in oceans. Some of the functions of EPS are related to protection against environmental stressors, adhesion to particles, carbon storage and nutrient acquisition. Microbial EPS are largely heterogeneous in composition and structure, and some strains produce different types of EPS in response to different conditions. This study aimed at characterizing the synthesis of polysaccharides secreted from an Alteromonas spp. marine strain isolated from the Biscay Bay, targeting the genes involved in its synthesis. First, the genome of this strain was sequenced and different gene clusters related to the synthesis of EPS were identified. Then, a transcriptomic study was carried out to analyse the expression of EPS synthesis related genes in response to glucose and the EPS composition was preliminary characterized.  The long-term objective is to increase our understanding of the patterns of EPS secretion in Alteromonas, which may have a key role in their association with phytoplankton blooms and adaptation to different environmental conditions.