Abstract
Alginate-degrading bacteria play an important role in alginate degradation by harboring highly efficient and unique alginolytic genes. Although the general mechanism for alginate degradation by these bacteria is fairly understood, much is still required to fully exploit them. Here, we report the isolation of a novel strain, Falsirhodobacter sp. alg1, the first report for an alginate-degrading bacterium from the family Rhodobacteraceae. Genome sequencing reveals that strain alg1 harbors a primary alginate degradation pathway with only single homologs of an endo- and exo-type alginate lyase, AlyFRA and AlyFRB, which is uncommon among such bacteria. Subsequent functional analysis showed that both enzymes were extremely efficient to depolymerize alginate suggesting evolutionary interests in the acquirement of these enzymes. The exo-type alginate lyase, AlyFRB in particular could depolymerize alginate without producing intermediate products making it a highly efficient enzyme for the production of 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH). Based on our findings, we believe that the discovery of Falsirhodobacter sp. alg1 and its alginolytic genes hints at the potentiality of a more diverse and unique population of alginate-degrading bacteria.
Highlights
Alginate-degrading bacteria are bacteria that have the ability to degrade the algal polysaccharide, alginate, composed of long heteropolymeric chains of randomly aligned monosaccharides, β-D-mannuronate and α-L-gluronate
As previously reported, based on the initial draft genome provided, we briefly described that Falsirhodobacter sp. alg1 harbored two alginate lyases, an alginate lyase precursor (AlgFR1; renamed to AlyFRA) and an oligo alginate lyase (AlgFR2; renamed to AlyFRB), and similar genes found within the alginolytic clusters of other alginate-degrading bacteria [23]
Based on our protein expression results (Fig 3A), we showed that AlyFRA and AlyFRB each degraded alginate in an endolytic and exolytic manner correlating to their PL classification and protein similarity analyses to currently reported alginate lyases
Summary
Alginate-degrading bacteria are bacteria that have the ability to degrade the algal polysaccharide, alginate, composed of long heteropolymeric chains of randomly aligned monosaccharides, β-D-mannuronate and α-L-gluronate. These bacteria harbor unique genes expressing “alginolytic” enzymes comprised of alginate lyases, membrane transporters, reductases and kinases. Basic Technology for Improved Bioenergy Production through Functional Analysis and Regulation of Algae and Other Aquatic Microorganisms flagship (http:// www.jst.go.jp/presto/bioenergy/english/index.html) with the Research Theme title of Focused biotechnologies suitable for complete utilization of marine macroalgae. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript
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