Complex algal polysaccharides as substrates for Maribacter strains

Abstract

Marine bacteria play a crucial role in global nutrient cycles, yet much remains to be understood about their ecophysiological niches, metabolic dependencies, and the functions of essential proteins. The research unit FOR 2406 Proteogenomics of Marine Polysaccharide Utilization investigates the mechanisms behind bacterial polysaccharide utilization during marine phytoplankton blooms. The focus is particularly on the functional analyses of marine bacteria within the phylum Bacteroidota. Flavobacteriia, a prominent class within the phylum Bacteroidota, are a significant component of marine bacterioplankton. Free-living members of this class play a pivotal role in the degradation of polysaccharides from lysed algae. They often harbour carbohydrate-active enzymes within polysaccharide utilization loci, operon- like genetic regions encoding proteins responsible for the hydrolysis and transport of polysaccharides. Fierce competition among free-living bacteria has led to genomic streamlining, typically focusing on a select few polysaccharides. In contrast, particle-associated bacteria face diverse substrate challenges. Some have the ability to sense and migrate toward nutrient sources, while others reside attached to particulate organic matter (POM), resulting in larger genomes compared to their free-living counterparts. Despite their ecological importance, polysaccharide utilization by particle-associated bacteria has received limited attention. Maribacter, observed in particle-associated fractions within marine systems, represent a significant gap in physiological studies. To address this gap, we employed proteomics to investigate the complexity of polysaccharide utilization mechanisms in Maribacter.