Zobellia galactanivorans
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PROVIDER: PRJNA393796 | ENA |
REPOSITORIES: ENA
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Project description:Macroalgae contribute substantially to primary production in coastal ecosystems. Their biomass, mainly consisting of polysaccharides, is cycled into the environment by marine heterotrophic bacteria (MHB), using largely uncharacterized mechanisms. In Zobellia galactanivorans, we discovered and characterized the complete catabolic pathway for carrageenans, major cell wall polysaccharides of red macroalgae, providing a model system for carrageenan utilization by MHB. We further demonstrate that carrageenan catabolism relies on a multifaceted carrageenan-induced regulon, including a non-canonical polysaccharide utilization locus (PUL) and several distal genes. The genetic structure of the carrageenan utilization system is well conserved in marine Bacteroidetes, but modified in other MHB phyla. The core system is completed by additional functions which can be assumed by non-orthologous genes in different species. This complex genetic structure is due to multiple evolutionary events including gene duplications and horizontal gene transfers. These results allow for an extension on the definition of bacterial PUL-mediated polysaccharide digestion.
2017-12-06 | GSE101142 | GEO
Project description:Response of an alga-associated marine flavobacteria to polysaccharide degradation
| PRJNA390150 | ENA
Project description:Previous studies have demonstrated that the iron content in marine heterotrophic bacteria is comparatively higher than that of phytoplankton. Therefore, they have been indicated to play a major role in the biogeochemical cycling of iron. In this study, we aimed to investigate the potential of viral lysis as a source of iron for marine heterotrophic bacteria. Viral lysates were derived from the marine heterotrophic bacterium, Vibrio natriegens PWH3a (A.K.A Vibrio alginolyticus). The bioavailability of Fe in the lysates was determined using a model heterotrophic bacterium, namely, Dokdonia sp. strain Dokd-P16, isolated from Fe-limited waters along Line P transect in the Northeastern Pacific Ocean. The bacteria were grown under Fe-deplete or Fe-replete conditions before being exposed to the viral lysate. Differential gene expression following exposure to the viral lysate was analyzed via RNA sequencing to identify differentially expressed genes under iron-replete and iron-deplete conditions. This study would provide novel insights into the role of viral lysis in heterotrophic bacteria in supplying bioavailable iron to other marine microorganisms under iron-limiting and non-limiting conditions. First, the marine heterotrophic bacterium genome, Dokdonia sp. strain Dokd-P16, was sequenced to provide a genomic context for the expression studies. Subsequently, the relative gene expression in Dokdonia sp. strain Dokd-P16 grown under Fe limiting and non-limiting conditions were analyzed. This transcriptomic approach would be utilized to elucidate genes regulated by Fe availability in Dokdonia sp. strain Dokd-P16, which indicate its Fe-related response viral lysate exposure. Taken together, in this study, the transcriptomic responses of Fe-limited and non-limited marine heterotrophic bacteria were analyzed, which provided novel insights into the biological availability of Fe from the viral lysates.
2021-11-01 | GSE166618 | GEO
Project description:Marine bacterium that produces agarase and carageenanase
| PRJNA16099 | ENA
Project description:Mannitol is a polyol that occurs in a wide range of living organisms, where it fulfills different physiological roles. In particular, mannitol can account for as much as 20 to 30% of the dry weight of brown algae and is likely to be an important source of carbon for marine heterotrophic bacteria. Zobellia galactanivorans (Flavobacteriia) is a model for the study of pathways involved in the degradation of seaweed carbohydrates. Annotation of its genome revealed the presence of genes potentially involved in mannitol catabolism, and we describe here the biochemical characterization of a recombinant mannitol-2-dehydrogenase (M2DH) and a fructokinase (FK). Among the observations, the M2DH of Z. galactanivorans was active as a monomer, did not require metal ions for catalysis, and featured a narrow substrate specificity. The FK characterized was active on fructose and mannose in the presence of a monocation, preferentially K(+). Furthermore, the genes coding for these two proteins were adjacent in the genome and were located directly downstream of three loci likely to encode an ATP binding cassette (ABC) transporter complex, suggesting organization into an operon. Gene expression analysis supported this hypothesis and showed the induction of these five genes after culture of Z. galactanivorans in the presence of mannitol as the sole source of carbon. This operon for mannitol catabolism was identified in only 6 genomes of Flavobacteriaceae among the 76 publicly available at the time of the analysis. It is not conserved in all Bacteroidetes; some species contain a predicted mannitol permease instead of a putative ABC transporter complex upstream of M2DH and FK ortholog genes.
| S-EPMC4325148 | biostudies-literature
Project description:Zobellia galactanivorans strain:OII3 Genome sequencing and assembly
| PRJNA377409 | ENA
Project description:Zobellia galactanivorans is an emerging model bacterium for the bioconversion of algal biomass. Notably, this marine Bacteroidetes possesses a complex agarolytic system comprising four ?-agarases and five ?-porphyranases, all belonging to the glycoside hydrolase family 16. Although ?-agarases are specific for the neutral agarobiose moieties, the recently discovered ?-porphyranases degrade the sulfated polymers found in various quantities in natural agars. Here, we report the biochemical and structural comparison of five ?-porphyranases and ?-agarases from Z. galactanivorans. The respective degradation patterns of two ?-porphyranases and three ?-agarases are analyzed by their action on defined hybrid oligosaccharides. In light of the high resolution crystal structures, the biochemical results allowed a detailed mapping of substrate specificities along the active site groove of the enzymes. Although PorA displays a strict requirement for C6-sulfate in the -2- and +1-binding subsites, PorB tolerates the presence of 3-6-anhydro-l-galactose in subsite -2. Both enzymes do not accept methylation of the galactose unit in the -1 subsite. The ?-agarase AgaD requires at least four consecutive agarose units (DP8) and is highly intolerant to modifications, whereas for AgaB oligosaccharides containing C6-sulfate groups at the -4, +1, and +3 positions are still degraded. Together with a transcriptional analysis of the expression of these enzymes, the structural and biochemical results allow proposition of a model scheme for the agarolytic system of Z. galactanivorans.
| S-EPMC3436304 | biostudies-literature
Project description:Alginate is a major compound of brown macroalgae and as such an important carbon and energy source for heterotrophic marine bacteria. Despite the rather simple composition of alginate only comprising mannuronate and guluronate units, these bacteria feature complex alginolytic systems that can contain up to seven alginate lyases. This reflects the necessity of large enzyme systems for the complete degradation of the abundant substrate. Numerous alginate lyases have been characterized. They belong to different polysaccharide lyase (PL) families, but only one crystal structure of a family 17 (PL17) alginate lyase has been reported to date, namely Alg17c from the gammaproteobacterium Saccharophagus degradans. Biochemical and structural characterizations are helpful to link sequence profiles to function, evolution of functions and niche-specific characteristics. Here, we combined detailed biochemical and crystallographic analysis of AlyA3, a PL17 alginate lyase from the marine flavobacteria Zobellia galactanivorans DsijT, providing the first structure of a PL17 in the Bacteroidetes phylum. AlyA3 is exo-lytic and highly specific of mannuronate stretches. As part of an "alginate utilizing locus", its activity is complementary to that of other characterized alginate lyases from the same bacterium. Structural comparison with Alg17c highlights a common mode of action for exo-lytic cleavage of the substrate, strengthening our understanding of the PL17 catalytic mechanism. We show that unlike Alg17c, AlyA3 contains an inserted flexible loop at the entrance to the catalytic groove, likely involved in substrate recognition, processivity and turn over.
| S-EPMC8600288 | biostudies-literature
Project description:Marine flavobacteria possess dedicated Polysaccharide Utilization Loci (PULs) enabling efficient degradation of a variety of algal polysaccharides. The expression of these PULs is tightly controlled by the presence of the substrate, yet details on the regulatory mechanisms are still lacking. The marine flavobacterium Zobellia galactanivorans DsijT digests many algal polysaccharides, including alginate from brown algae. Its complex Alginate Utilization System (AUS) comprises a PUL and several other loci. Here, we showed that the expression of the AUS is strongly and rapidly (<30 min) induced upon addition of alginate, leading to biphasic substrate utilization. Polymeric alginate is first degraded into smaller oligosaccharides that accumulate in the extracellular medium before being assimilated. We found that AusR, a GntR family protein encoded within the PUL, regulates alginate catabolism by repressing the transcription of most AUS genes. Based on our genetic, genomic, transcriptomic and biochemical results, we propose the first model of regulation for a PUL in marine bacteria. AusR binds to promoters of AUS genes via single, double or triple copies of operator. Upon addition of alginate, secreted enzymes expressed at a basal level catalyze the initial breakdown of the polymer. Metabolic intermediates produced during degradation act as effectors of AusR and inhibit the formation of AusR/DNA complexes, thus lifting transcriptional repression.
| S-EPMC7641319 | biostudies-literature