Project description:Polysaccharides from macroalgae are important bacterial nutrient source and central biogeochemical component in the oceans. To illuminate the cellular mechanisms of polysaccharide degradation by marine bacteria, growth of Alteromonas macleodii 83-1 on a mix of laminarin, alginate and pectin was characterized using transcriptomics, proteomics and exometabolomics. A. macleodii 83-1 showed two distinct growth stages, with exponential growth during laminarin utilization followed by maintenance during simultaneous alginate/pectin utilization. The biphasic growth coincided with major temporal shifts in gene expression and metabolite secretion, enabling to define major/accessory polysaccharide utilization loci, reconstruct the complete degradation pathways for each polysaccharide, as well as identify temporal phenotypes in other relevant traits. FT-ICR-MS revealed a distinct suite of secreted metabolites for each growth phase, with pyrroloquinoline quinone exclusively produced with alginate/pectin. The finding of substrate-unique phenotypes indicates an exquisite adaptation to polysaccharide utilization with probable relevance for the degradation of macroalgal biomass, which comprises a complex mix of polysaccharides. Moreover, substrate-unique exometabolomes possibly influence metabolic interactions with other community members. Overall, the presence of fine-tuned genetic machineries for polysaccharide degradation and the widespread detection of related CAZymes in global locations indicate an ecological relevance of A. macleodii in marine polysaccharide cycling and bacteria-algae interactions.
Project description:Sulfoquinovose (SQ) and sulfoquinovosyl glycerol (SQGro), derived from abundant membrane sulfolipids termed sulfoquinovosyl diacylglycerols (SQDG) produced by photosynthetic organisms, serve as sources of carbon and sulfur for bacteria. The conversion processes of these sulfoquinovosyl compounds (SQ, SQGro, and SQDG) within marine ecosystems, and their quantitative contributions to the marine organic matter pool, are poorly understood. We have identified Alteromonas macleodii, a cosmopolitan marine bacterium, as a novel organism capable of metabolizing SQ and SQGro. A. macleodii possesses a sulfoquinovosidase that converts SQGro to SQ, and is a member of a distinct clade within glycoside hydrolase family 31 distinct from other sulfoqinovosidases. The ubiquitous presence of sulfoquinovosidases and their transcripts throughout marine environments suggests active metabolism of sulfoquinovose glycosides, particularly in the sunlit surface ocean. Complementing these observations, we demonstrate that marine algae and cyanobacteria produce significant quantities of SQGro, and field samples from coastal and open ocean environments enabled estimation of the annual turnover of SQGro in the teragram range. Together with SQDG and SQ, these sulfoquinovosyl compounds constitute a substantial portion of the marine organic sulfur, estimated at around 1.5 petagrams of carbon turnover per annum. These findings reveal a vast, previously unappreciated pool of organosulfonates within the microbial food web that contributes significantly to the marine carbon and sulfur cycles.
Project description:Sulfoquinovose (SQ) and sulfoquinovosyl glycerol (SQGro), derived from abundant membrane sulfolipids termed sulfoquinovosyl diacylglycerols (SQDG) produced by photosynthetic organisms, serve as sources of carbon and sulfur for bacteria. The conversion processes of these sulfoquinovosyl compounds (SQ, SQGro, and SQDG) within marine ecosystems, and their quantitative contributions to the marine organic matter pool, are poorly understood. We have identified Alteromonas macleodii, a cosmopolitan marine bacterium, as a novel organism capable of metabolizing SQ and SQGro. A. macleodii possesses a sulfoquinovosidase that converts SQGro to SQ, and is a member of a distinct clade within glycoside hydrolase family 31 distinct from other sulfoqinovosidases. The ubiquitous presence of sulfoquinovosidases and their transcripts throughout marine environments suggests active metabolism of sulfoquinovose glycosides, particularly in the sunlit surface ocean. Complementing these observations, we demonstrate that marine algae and cyanobacteria produce significant quantities of SQGro, and field samples from coastal and open ocean environments enabled estimation of the annual turnover of SQGro in the teragram range. Together with SQDG and SQ, these sulfoquinovosyl compounds constitute a substantial portion of the marine organic sulfur, estimated at around 1.5 petagrams of carbon turnover per annum. These findings reveal a vast, previously unappreciated pool of organosulfonates within the microbial food web that contributes significantly to the marine carbon and sulfur cycles.