Lu Tongyan

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.

Characterization and genetic diversity of the sturgeon Acipenser schrenskii Ig heavy chain.

It is still unknown about the VH gene organization and diversity of the immunoglobulin (Ig) heavy chain locus in Amur sturgeon. In this study, Ig heavy chain alleles were cloned by RT-PCR using the specific primers. Sequence analysis showed that Amur sturgeons VH regions belonged to the same family with higher than 90% identities of their leader peptide (LP). Moreover, a number of conserved motifs in the D segment were identified, and the variability of the CDR3 region was substantial. Further, we speculated that there were at least 12 different JH segments in the locus, contributing to the antibody repertoire of the sturgeon. The genetic diversity of the sturgeon Ig should be associated with the random rearrangement of VH, D and JH segments, action of exonuclease and insertion of N and/or probably P nucleotides at the site of rearrangement.

Cloning and bioinformatics analysis of matrix protein from IHNV-Sn isolate

Matrix protein is one of the structure proteins of infectious haematopoietic necrosis virus(IHNV),and its synthesis leads to apoptosis or programmed cell death in the transfected cells.To study its structure and function,the open reading frame of matrix protein gene was amplified by RT-PCR from IHNV-Sn isolate and cloned into plasmid pET27b(+)vector.The structure and characteristics of the gene were studied by means of bioinformatics software.The results are described as follows:the length of the M gene,encoding 195 aa,was 588 bp.The molecular weight was 21.88 ku and the isoelectric point was 9.35.The matrix protein was rich in serine,threonine and alkaline amino acid,and was composed of plenty of α-helix,extended β and coil.The protein is hydrophobic with no signal peptide and transmembrane regions.The antigenicity of matrix protein was good.According to the protein structure prediction,there might be no N-glycosylation sites,and there were 7 O-glycosylation sites and 15 phosphorylation sites in matrix protein.Phylogenetic analysis showed that the IHNV-Sn isolate was in the same branch with the isolates from America.The study established the foundation for genetic background information,pathogenesis,molecular epidemiology research of IHNV.

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.