Cloning and sequencing analysis of alginate lyase genes from the marine bacterium Vibrio sp. O2.

摘要

A new marine bacterium, which displayed alginate-depolymerizing activity in plate assays, was isolated from sea water in Mihonoseki Harbour, Japan. Analysis of the 16S ribosomal RNA gene sequence of 1 of the isolates proved that this alginate-depolymerizing bacterium belonged to the genus Vibrio and it was named Vibrio sp. O2. The alginate lyase genes of Vibrio sp. O2 were cloned and expressed in Escherichia coli. 2 alginate lyase-producing clones, pVOA-A4 and pVOA-B5, were obtained. The alginate lyase gene alyVOA from pVOA-A4 was composed of an 858-bp open reading frame (ORF) encoding 285 amino acids, while alyVOB from pVOA-B5 was composed of an 828-bp ORF encoding 275 amino acids. The degree of identity between the deduced amino acid sequences of AlyVOA or AlyVOB and Photobacterium sp. ATCC 43367 alginate poly(ManA)lyase AlxM was 92.3 and 32.6%, respectively. Alginate lyase consensus regions corresponding to the sequences YFKAGXYXQ and RXELR were observed in all 3 of these sequences. AlyVOA and AlyVOB both degraded polymannuronate in plate assays and were therefore confirmed to be poly( beta-D-mannuronate)lyases.