Showing papers by "Zong-Jun Du published in 2011"

Agarivorans gilvus sp. nov. isolated from seaweed.

Abstract: A novel agarase-producing, non-endospore-forming marine bacterium, WH0801T, was isolated from a fresh seaweed sample collected from the coast of Weihai, China. Preliminary characterization based on 16S rRNA gene sequence analysis showed that WH0801T shared 96.1 % similarity with Agarivorans albus MKT 106T, the type species of the genus Agarivorans. A polyphasic taxonomic study was conducted and confirmed the phylogenetic affiliation of strain WH0801T to the genus Agarivorans. Isolate WH0801T produces light-yellow-pigmented colonies; cells are Gram-stain-negative, straight or curved rods, which are motile with a single polar flagellum. Strain WH0801T grew in 0.5–5 % NaCl, with optimum growth at 3 % NaCl, and its optimal pH and cultivation temperature were 8.4–8.6 and 28–32 °C, respectively. Data from biochemical tests, whole-cell fatty acid profiling, 16S rRNA gene sequence studies and DNA–DNA hybridization clearly indicated that isolate WH0801T represented a novel species within the genus Agarivorans, for which the name Agarivorans gilvus sp. nov. is proposed. The type strain of Agarivorans gilvus sp. nov. is WH0801T (=NRRL B-59247T =CGMCC 1.10131T).

Identification of a marine agarolytic bacterium Agarivorans albus QM38 and cloning and sequencing its beta-agarase genes

Abstract: A total of 117 agar-decomposing cultures were isolated from coastal seawater around Qingdao, China The phenotypic and agarolytic features of an agarolytic isolate, QM38, were investigated The strain was gram negative, strictly aerobic, curved rod and polar flagellum On the basis of several phenotypic characters, biochemical and morphological characters and phylogenetic analysis of the gene coding for the 16S rRNA, the strain was identified as Agarivorans albus strain QM38 This strain can liquefy the agar on the solid agar plate An excellular agarase activity was determined in liquid culture The enzyme exhibited maximal activity at 40 °C, pH 76 Its activity was greatly affected by different concentrations of agarose The highest activity 32 U/ml was achieved in the culture supernatant The hydrolytic product was analyzed by fluorophore-assisted carbohydrate electrophoresis (FACE) After complete hydrolysis of agarose, a series of agaro-oligosaccharides were produced The main products of the enzymes were oligosaccharides in the degree of polymerization (DP) of 2, 4, 6 and 8 Three genes agaD01, agaD02 and agaD03, encoding β-agarases, had been cloned from genomic DNA of Agarivorans albus strain QM38 The open reading frame of agaD01, consisted of 2 988 bp, and shared 955%–989% identity to the β-agarase genes of some strains of Vibrio and Agarivorans Gene agaD02 comprised 2 868 bp and encoded a 955- amino-acid protein It showed 974% and 987% identity to the β-agarase genes of strain Vibrio sp PO-303 and strain Vibrio sp JT0107, respectively Only partial sequence of agaD03 gene has been cloned It showed 965% identity to β-agarase gene (agaB) of Pseudoalteromonas sp CY24, and shared 968% identity to β-agarase-c gene of Vibrio sp PO-303