Pelagibacterium halotolerans B2T is a marine halotolerant bacterium that was isolated from a seawater sample collected from the East China Sea. Here, we present the complete genome sequence of the type strain P. halotolerans B2T, which consists of one chromosome (3,944,837 bp; 61.4% G+C content) and one plasmid (4,050 bp; 56.1% G+C content). This is the first complete genome of a member of the Pelagibacterium genus.

A new agarase, AgaACN41, cloned from Vibrio sp. strain CN41, consists of 990 amino acids, with only 49% amino acid sequence identity with known β-agarases. AgaACN41 belongs to the GH50 (glycoside hydrolase 50) family but yields neoagarotetraose as the end product. AgaACN41 was expressed and characterized.

A chitosanase gene, csn, was cloned from Penicillium sp. D-1 by inverse PCR. The cDNA sequence analysis revealed that csn had no intron. The deduced CSN protein consists of 250 amino acids including a 20-amino acid signal peptide, and shared 83.6% identity with the family 75 chitosanase from Talaromyces stipitatus (B8M2R4). The mature protein was overexpressed in Escherichia coli and purified with the affinity chromatography of Ni2+-NTA. The novel recombinant chitosanase showed maximal catalytic activity at pH 4.0 and 48°C. Moreover, the activity of CSN was stable over a broad pH range of 3.0-8.0, and the enzymatic activity was significantly enhanced by Mg2+ and Mn2+. The CSN could effectively hydrolyze colloidal chitosan and chitosan, while could not hydrolyze chitin and carboxymethylcellulose (CMC). Due to the particular acidophily, CSN has the potential application in the recycling of chitosan wastes.

The GenBank/EMBL/DDBJ accession numbers for the 18S rRNA gene and chitosanase gene of strain D-1 are JF950269 and JF950270, respectively.