A mesophilic, aerobic, non-flagellated, gliding bacterium, forming yellow colonies and designated DsijT, was isolated from a red alga on the sea-shore of Roscoff, Brittany, France. DsijT was selected for its ability to actively degrade both agars and carrageenans. The Gram-negative cells occurred singly or in pairs as long rods. The temperature range for growth was 13-45 degrees C, with an optimum at 35 degrees C. The pH range for growth at 35 degrees C was from 6.0 to 8.5, with an optimum around pH 7.0. The NaCl concentrations required for growth at 35 degrees C and pH 7.0 ranged from 5 to 60 g l(-1), with an optimum around 25 g l(-1). The G+C content of the genomic DNA was 42-43 mol%. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain DsijT is closely related to [Cytophaga] uliginosa DSM 2061T. Phenotypic features, however, allowed DsijT and [Cytophaga] uliginosa strains to be distinguished on the basis of ten traits (spreading behaviour, assimilation of eight compounds and amylase production). Their total protein profiles were also different and DNA-DNA hybridization experiments confirmed that DsijT constitutes a new species, distinct from [Cytophaga] uliginosa. Based on the phenotypic features and the phylogenetic relationships of the Flavobacteriaceae, a new genus designated Zobellia gen. nov. is proposed to include Zobellia galactanovorans gen. nov., sp. nov., while [Cytophaga] uliginosa becomes Zobellia uliginosa comb. nov. The type strain of Zobellia galactanovorans is DsijT (= DSM 12802T = CIP 106680T).

Two β-agarase genes, agaA and agaB, were functionally cloned from the marine bacterium Zobellia galactanivorans. The agaA and agaB genes encode proteins of 539 and 353 amino acids respectively, with theoretical masses of 60 and 40 kDa. These two β-agarases feature homologous catalytic domains belonging to family GH-16. However, AgaA displays a modular architecture, consisting of the catalytic domain (AgaAc) and two C-terminal domains of unknown function which are processed during secretion of the enzyme. In contrast, AgaB is composed of the catalytic module and a signal peptide similar to the N-terminal signature of prokaryotic lipoproteins, suggesting that this protein is anchored in the cytoplasmic membrane. Gel filtration and electrospray MS experiments demonstrate that AgaB is a dimer in solution, while AgaAc is a monomeric protein. AgaAc and AgaB were overexpressed in Escherichia coli and purified to homogeneity. Both enzymes cleave the β-(1→4) linkages of agarose in a random manner and with retention of the anomeric configuration. Although they behave similarly towards liquid agarose, AgaAc is more efficient than AgaB in the degradation of agarose gels. Given these organizational and catalytic differences, we propose that, reminiscent of the agarolytic system of Pseudoalteromonas atlantica, AgaA is specialized in the initial attack on solid-phase agarose, while AgaB is involved with the degradation of agarose fragments.

Fucoidans are matrix polysaccharides from marine brown algae, consisting of an α-l-fucose backbone substituted by sulfate-ester groups and masked with ramifications containing other monosaccharide residues. In spite of their interest as biologically active compounds in a number of homologous and heterologous systems, no convenient sources with fucanase activity are available yet for the degradation of the fucalean algae. We here report on the isolation, characterization, and culture conditions of a bacterial strain capable of degrading various brown algal fucoidans. This bacterium, a member of the family Flavobacteriaceae, was shown to secrete fucoidan endo-hydrolase activity. An extracellular enzyme preparation was used to degrade the fucoidan from the brown alga Pelvetia canaliculata. End products included a tetrasaccharide and a hexasaccharide made of the repetition of disaccharidic units consisting of α-1→3-l-fucopyranose-2-sulfate-α-1→4-l-fucopyranose-2,3-disulfate, with the 3-linked residues at the nonreducing end.

Summary: Arylsulphatase activity was identified in cultures of the marine bacterium Alteromonas carrageenovora, using methylumbelliferyl sulphate as substrate. In contrast with most other microbial arylsulphatases, arylsulphatase production in A. carrageenovora was not repressed by sulphate. The structural gene of arylsulphatase (atsA) was cloned and sequenced. An ORF of 984 bp was found, specifying a primary translation product of 328 amino acids with a molecular mass of 35797 Da. Arylsulphatase was partially purified from cell extracts of both A. carrageenovora and recombinant Escherichia coli. Both the recombinant and native enzymes exhibited a pl of 5-5, a Michaelis constant for methylumbelliferyl sulphate of 68 μM, and a molecular mass of approximately 35000 Da in SDS-PAGE analysis. Secondary structure comparisons using hydrophobic cluster analysis suggest functional analogies between the arylsulphatase of A. carrageenovora, that of Mycobacterium leprae and a 33-5 kDa protein from Porphyromonas gingivalis. It is speculated that these proteins are all glycosulphohydrolases, involved with desulphatation of sulphated polysaccharides.

Three rod-shaped, Gram-negative, chemo-organotrophic, heterotrophic, strictly aerobic, gliding bacterial strains, KT02ds18-4, KT02ds18-5 and KT02ds18-6T, were isolated from North Sea surface waters near the island of Helgoland, Germany. Their taxonomic position was investigated by a polyphasic approach. The three strains were light yellow, oxidase- and catalase-positive, and grew optimally at 25 °C, at pH 7.5, and in the presence of 2.5 % (w/v) NaCl. The Chargaff's coefficient was 34.2–34.4 mol%. The three strains shared >90 % DNA–DNA relatedness and an identical 16S rRNA gene sequence. Comparative 16S rRNA gene sequence analysis allocated the three strains to the genus Maribacter in the family Flavobacteriaceae, with similarities of 97.0–97.4 % to five of the recognized Maribacter species. Their low level of DNA–DNA relatedness (<20 %) with these species and differentiating phenotypic characteristics demonstrated that they constitute a new Maribacter species for which the name Maribacter forsetii sp. nov. is proposed. Strain KT02ds18-6T (=CIP 109504T=DSM 18668T) is the type strain. An emended description of the genus Maribacter is also proposed.

A rod-shaped, Gram-negative, chemo-organotrophic, heterotrophic, strictly aerobic, gliding bacterial strain, SW5T, capable of degrading sulphated fucans from brown algae was isolated from a water-treatment facility that recycles the effluent of an alginate-extraction plant in Landerneau (Brittany, France). Its taxonomic position was investigated by a polyphasic approach. Strain SW5T formed dark-yellow colonies, was oxidase-negative and catalase-positive and grew optimally at 25 °C and pH 7.5 and in the presence of 2.5 % (w/v) NaCl. The DNA G+C content was 34.5 mol%. Phylogenetic analysis based on the sequence of the 16S rRNA gene allocated strain SW5T to the genus Mariniflexile in the family Flavobacteriaceae, with a similarity of 98.4 % to the type strain of Mariniflexile gromovii, the only recognized Mariniflexile species. Its low level of DNA–DNA relatedness (<25 %) with the type strain of this species and differentiating phenotypic characteristics demonstrated that strain SW5T constitutes a novel Mariniflexile species, for which the name Mariniflexile fucanivorans sp. nov. is proposed. Strain SW5T (=CIP 109502T =DSM 18792T) is the type strain.