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A strain of Vibrio diabolicus named SX-2018 was isolated from Callista chinensis in the Zhejiang coastal region of China. The isolate was identified as V. diabolicus by sequencing of the 16S rRNA, housekeeping genes and subclade-associated genes. Antibiotic resistance as well as biochemical and growth characteristics were determined. Animal studies were performed to evaluate the in vivo virulence of SX-2018. The results indicated that SX-2018 was highly related to the known deep-sea hydrothermal vent V. diabolicus and V. diabolicus from Homo sapiens. Artificial infection showed that SX-2018 exhibited strong pathogenicity toward Gomphina aequilatera, but it did not express pathogenicity toward Mactra veneriformis Reeve, Callista chinensis, Mactra chinensis Philippi, Ruditapes philippinarum, Cyclina sinensis, Dosinia corrugate Meretrix meretrix, Tegillarca granosa, Sinonovacula constricta or Danio rerio. Mortality in Gomphina aequilatera at 25 °C and 15 °C was 100% and 27%, respectively. Virulence-related gene sequence analysis showed that SX-2018 encoded the tlh gene but lacked tdh and trh genes. Tlh and hemolysin coregulated protein genes of SX-2018 shared 99.36–99.79% homology to the deep-sea V. diabolicus strain, 98.65.36–99.79% homology to the V. diabolicus strain from Homo sapiens, and 97–97.79% and 84–89.79% similarity to Vibrio alginolyticus and Vibrio parahaemolyticus, respectively. This study will aid in understanding the evolutionary relationship between V. diabolicus and related pathogenic Vibrio species.

In this paper we present a novel algorithm for the multi-degree reduction of Bezier curves with geometric constraints. Based on the given constraints, we construct an objective function which is abstracted from the approximation error in L"2-norm. Two types of geometric constraints are tackled. With the constraints of G^2-continuity at one endpoint and G^1-continuity (or C^r-continuity) at the other endpoint, we derive the optimal degree-reduced curves in explicit form. With the constraints of G^2-continuity at two endpoints, the problem of degree reduction is equivalent to minimizing a bivariate polynomial function of degree 4. Compared with the traditional methods, we derive the optimal degree-reduced curves more effectively. Finally, evaluation results demonstrate the effectiveness of our method.

The usual B-spline basis is not orthogonal. In order to resolve the theoretical problem that there is not a well-expressed orthogonal basis in spline space to date, we construct an orthogonal basis for the n-degree spline space in which n is an arbitrary natural number. We extend the traditional Legendre method to spline space and obtain a unified and explicit expression for the orthogonal basis. We first define a set of auxiliary functions, which have simple and explicit expressions. Then the proposed orthogonal splines are given as the derivatives of these auxiliary functions. We also provide some examples of cubic orthogonal splines to demonstrate our process. Finally, the orthogonal basis is applied to the problem of the least-square approximation of curves.

Vibrio alginolyticus, a Gram-negative bacterium, is one of the Vibrio pathogens common to human and marine animals. Outer membrane proteins of bacteria play an important role during infection and induction of host immune response. In present research, the OmpK gene of V. alginolyticus was cloned and expressed. The open reading frame contains 846 bp, and the mature protein consists of 261 amino acid residues. The alignment analysis indicated that OmpK was highly conserved, which could serve as a surface antigen for good vaccine candidate. SDS-PAGE indicated the OmpK could over-express in E. coli BL21 (DE3). The recombinant protein was purified by affinity chromatography on Ni-NTA Superflow resin. Western blot analysis revealed that the OmpK protein had immunoreactivity. The large yellow croakers vaccinated with the OmpK were significantly protected against the infection by V. alginolyticus. This study showed that the conserved OmpK was an effective vaccine candidate against infection by V. alginolyticus.

Infectious bursal disease virus (IBDV), a double-stranded RNA virus, is a member of the Birnaviridae family. Four pathotypes of IBDV, attenuated, virulent, antigenic variant, and very virulent (vvIBDV), have been identified. We isolated and characterized the genomic reassortant IBDV strain ZJ2000 from severe field outbreaks in commercial flocks. Full-length genomic sequence analysis showed that ZJ2000 is a natural genetic reassortant virus with segments A and B derived from attenuated and very virulent strains of IBDV, respectively. ZJ2000 exhibited delayed replication kinetics as compared to attenuated strains. However, ZJ2000 was pathogenic to specific pathogen free (SPF) chickens and chicken embryos. Similar to a standard virulent IBDV strain, ZJ2000 caused 26.7% mortality, 100% morbidity, and severe bursal lesions at both gross and histopathological levels. Taken together, our data provide direct evidence for genetic reassortment of IBDV in nature, which may play an important role in the evolution, virulence, and host range of IBDV. Our data also suggest that VP2 is not the sole determinant of IBDV virulence, and that the RNA-dependent RNA polymerase protein, VP1, may play an important role in IBDV virulence. The discovery of reassortant viruses in nature suggests an additional risk of using live IBDV vaccines, which could act as genetic donors for genome reassortment.