Different utilization of alginate and other algal polysaccharides by marine Alteromonas macleodii ecotypes

Abstract

The marine bacterium Alteromonas macleodii is a copiotrophic r-strategist, but little is known about its potential to degrade polysaccharides. Here, we studied the degradation of alginate and other algal polysaccharides by A. macleodii strain 83-1 in comparison to other A. macleodii strains. Cell densities of strain 83-1 with alginate as sole carbon source were comparable to those with glucose, but the exponential phase was delayed. The genome of 83-1 was found to harbour an alginolytic system comprising five alginate lyases, whose expression was induced by alginate. The alginolytic system contains additional CAZymes, including two TonB-dependent receptors, and is part of a 24 kb genomic island unique to the A. macleodii 'surface clade' ecotype. In contrast, strains of the 'deep clade' ecotype contain only a single alginate lyase in a separate 7 kb island. This difference was reflected in an eightfold greater efficiency of surface clade strains to grow on alginate. Strain 83-1 furthermore hydrolysed laminarin, pullulan and xylan, and corresponding polysaccharide utilization loci were detected in the genome. Alteromonas macleodii alginate lyases were predominantly detected in Atlantic Ocean metagenomes. The demonstrated hydrolytic capacities are likely of ecological relevance and represent another level of adaptation among A. macleodii ecotypes.

Coastal bacterioplankton community response to diatom‐derived polysaccharide microgels

“…Alteromonadales, Rhodobacterales and Flavobacteriales are regarded as ‘master recyclers’, with growing evidence that they utilize a suite of enzymes to directly and in‐directly exploit algal‐derived polysaccharides (Teeling et al ., ; Buchan et al ., ; Taylor et al ., ; Neumann et al ., ; Teeling et al ., ). In this study, we present experimental evidence to progress this paradigm by demonstrating that the Alteromonadales ( Alteromonas ) respond to diatom‐derived TEP and assimilate TEP carbon, and that the Rhodobacterales increase in activity in response to the same biogenic substrate.…”

Polysaccharide Utilization Loci: Fueling Microbial Communities

“…1) (78), the C. japonicus XyGUL lacks genes encoding a keystone extracellular endoxyloglucanase, which is provided elsewhere in the genome (127,128). The lack of genes encoding a SusD (SGBP-A) homolog and a sensor/regulator system in the C. japonicus XyGUL, both of which are ubiquitous in Bacteroidetes PULs, mirrors observations in bacteria from other phyla (120). Furthermore, the TBDTs from C. japonicus and B. ovatus XyGULs have distinct amino acid sequences, despite being functionally homologous (50,126).…”

“…TBDTs are not specific to Bacteroidetes bacteria but are broadly distributed across Gram-negative bacteria, including alpha-and gammaproteobacteria living in association with biomass debris. Inspection of the genomes of such organisms reveals that TBDT-and CAZyme-encoding genes may be colocalizedanalogous to canonical Bacteroidetes PULs-although susD homologs and sensor/ regulator systems are notably absent (108,(120)(121)(122). Despite their limitations, these TBDT/CAZyme-encoding clusters thus arguably comprise a type of "polysaccharide utilization locus."…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…They can degrade and utilize a broad spectrum of organic substrates, including deep-sea recalcitrant organic matter (245,(250)(251)(252). Alteromonas produces and secretes a variety of extracellular enzymes that contribute to the hydrolysis of biopolymers, including polysaccharides (253)(254)(255)(256)(257), proteins (258,259), nucleic acids (260,261), and lipids (262), the major components of marine POM. Alteromonas and related species respond rapidly to phytoplankton blooms and especially to elevated POC concentrations (109,(263)(264)(265).…”