Li Shaowu

Isolation of Yersinia ruckeri Strain H01 from Farm-Raised Amur Sturgeon Acipenser schrencki in China

Yersinia ruckeri is the causative agent of enteric redmouth disease or yersiniosis, which affects salmonids and several other species of fish. However, there are no reports on the characteristics and pathogenicity of Y. ruckeri isolated from farm-raised Amur Sturgeon Acipenser schrencki. Here, we isolated and characterized Y. ruckeri strain H01 from the diseased Amur Sturgeon in China. The phenotypic and genotypic characteristics of Y. ruckeri were observed, and its virulence was tested by examining experimentally infected sturgeons. Examination of the flagellar morphology of Y. ruckeri by transmission electron microscopy showed five to eight peritrichous flagella located on the cell body. Actively dividing cells with an obvious cell membrane were approximately 0.64 μm in diameter and between 1.7 and 2.5 μm in length. The dose that was lethal to 50% of the test fish after intraperitoneal injection was determined to be 7.2×10(6) CFU, and Y. ruckeri could be reisolated from the liver and kidneys of infected sturgeon. Antimicrobial susceptibility tests showed that H01 was susceptible to 10 antimicrobial agents. Part of the 16S rRNA sequences (563 base pair) was amplified and sequenced to study the genotypic characterization in Y. ruckeri (GenBank accession number JQ657818). The phylogenetic tree revealed H01 was clustered together with Y. ruckeri strains. Together, this study describes the isolation, characterization, and phenotypic-genotypic analysis of a Y. ruckeri strain isolated from farm-raised Amur Sturgeon. The results discovered may provide some theoretical basis for the prevention and control of yersiniosis in Amur Sturgeon.

Assessing genetic diversity in three wild Brachymystax lenok populations using AFLP markers

The genetic diversities of 72 individuals from three wild Lenok populations of Mudanjiang River (MD), Yalujiang River (YL) and Wusulijiang River (WSL) in the northeast of China were analysed using amplified fragment length polymorphism (AFLP) markers. The results showed that 541 polymorphic loci out of 559 were amplified by 12 primer pairs and the percentage of polymorphic loci was 96.78%. Shannon indices for the MD, YL and WSL populations were 0.3988±0.2913, 0.3254±0.3037, 0.2125±0.2862, respectively, and Neis gene diversity indices were 0.2737±0.2062, 0.2229±0.2129, 0.1446±0.1985, respectively. The average total genetic diversity ( H t ) was 0.3512±0.0.0208 and the average genetic diversity within populations ( H s ) was 0.2137±0.0152. Among the three populations, the average genetic distance ( D st ) was 0.1375 and the gene differentiation coefficient ( G st ) was 0.3914. The genetic diversity was 60.85% within populations and 39.15% among populations. The gene flow index ( N m ) was 0.7776. The analysis of molecular variance (AMOVA) indicated that the average fixation index ( F st ) was 0.55336. The variance was 55.16% within populations and 44.84% among populations. The highest polymorphism ratio was in the MD group and the lowest in the WSL group.