Molecular characterization and pathogenicity of a grouper iridovirus (GIV) isolated from yellow grouper, Epinephelus awoara (Temminck & Schlegel)

Molecular characterization was carried out on an iridovirus isolated from yellow grouper, Epinephelus awoara . The major capsid protein (MCP) gene was located, sequenced and compared with homologous genes from other iridoviruses. The nucleotide sequence is 1392 bases long and contains a single open reading frame beginning at an ATG codon from the 5' end and terminating at a TAA codon at the 3' end. The open reading frame encodes a protein of 463 amino acids with a predicted molecular weight of 50 272 Da. Pairwise amino acid alignments detected a high degree of sequence identity between grouper iridovirus (GIV) MCP and the homologous genes of other iridoviruses. The MCP gene of GIV was most similar to the MCP gene from frog virus 3 (FV3) with 70% nucleotide and 73% amino acid sequence identity. The predicted molecular weight of the protein of this gene is comparable with the apparent weight obtained by SDS–PAGE. Pathogenicity of the GIV was investigated in yellow grouper by intraperitoneal injection of 10⁷ and 10⁴ TCID₅₀ virus. Cumulative mortalities reached 100% within 11 and 25 days post-infection, respectively, while no grouper died in the control group. The molecular studies demonstrated that GIV is a member of the genus Ranavirus .     

First isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata (Moreau)

The first isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata, is reported. The pathogen was recovered from ulcers of cultured fish, from three different outbreaks. The six isolates obtained were biochemically and serologically characterized and diagnosis was confirmed by polymerase chain reaction using specific primers and partial 16S rRNA gene sequencing. The isolates constituted a homogeneous phenotypic group; however, they belong to two of the different serotypes described within this species. A virulence evaluation of the isolates using Wedge sole fry was also performed.     

Isolation and Characterization of Pepsin-Soluble Collagen from the Skin of Peru Squid (Dosidicus gigas)

Pepsin-soluble collagen (PSC) was isolated from Peru squid (Dosidicus gigas) skin and physicochemical properties of the PSC were determined. The PSC exhibited a maximum absorbance at 220 nm. Sodium dodecyl sulfate polyacrylamide gel electrophoresis suggested the collagen containing α1 and α2 chain was classified as type I collagen. Amino acid composition indicated that the collagen had lower amino acid content than that of mammalian collagen. Denaturation temperature (T_d) of the PSC was 26.8°C. The PSC had relatively high solubility in alkaline condition or NaCl concentrations below 2%. Fourier transform infrared spectroscopy investigations showed the existence of helical arrangements of collagen. The lyophilized collagen had a uniform and regular network structure. These results suggested that Peru squid skin was a potential source of collagen for further research and application.     

Detection and characterization of a rhabdovirus causing mortality in black bullhead catfish,Ameiurus melas

This study fully describes a severe disease outbreak occurred in 2016 in black bullhead catfish farmed in Italy. Affected fish showed nervous clinical signs as well as emaciations and haemorrhagic petechiae on the skin at the fin bases, abdomen and gills. Viral isolation in cell culture allowed the subsequent identification of a rhabdovirus, tentatively named ictalurid rhabdovirus (IcRV), through electron microscopy, immunofluorescence and whole genome sequencing (WGS). The newly isolated virus, together with 14 additional viral strains stored in our repository and detected during similar mortality episodes in the period 1993–2016, was phylogenetically analysed on the basis of the nucleoprotein and the glycoprotein nucleotide and amino acid sequences. The genetic distances among Italian IcRV strains were also estimated. Our results show that all the IcRV strains belong to the genus Sprivivirus and are closely related to the tench rhabdovirus (TenRV). Italian catfish production is constantly decreasing, mainly due to viral infections, which include the newly characterized IcRV. Data presented in this work will assist to investigate the molecular epidemiology and the diffusive dynamics of this virus and to develop adequate surveillance activities.     

Extracellular Polymeric Substances Produced by the Thermophilic Cyanobacterium Gloeocapsa gelatinosa: Characterization and Assessment of Their Antioxidant and Metal-Chelating Activities

Cyanobacteria, particularly thermophilic strains, represent an important potential source of EPSs, harboring structural complexity that predicts diverse and specific bioactive potential. The thermophilic cyanobacteria Gloeocapsa gelatinosa, isolated from a natural hot source in Ain Echfa (Tunisia), was cultivated in a cylindrical reactor, and the production of biomass and EPSs was investigated. Results revealed that the strain is amongst the most efficient EPSs producers (0.89 g L⁻¹) and that EPSs production was not correlated with the growth phase. EPSs were sulfated heteropolysaccharides containing carbohydrates (70%) based on nine different monosaccharides, mainly mannose (22%), and with the presence of two uronic acids. EPSs were formed by two polymers moieties with a molecular weight of 598.3 ± 7.2 and 67.2 ± 4.4 kDa. They are thermostable in temperatures exceeding 100 °C and have an anionic nature (zeta potential of −40 ± 2 mV). Atomic force microscopy showed that EPSs formed multimodal lumps with 88 nm maximum height. EPSs presented high water holding capacity (70.29 ± 2.36%) and solubility index (97.43 ± 1.24%), and a strong bivalent metal sorption capacity especially for Cu²⁺ (91.20 ± 1.25%) and Fe²⁺ (75.51 ± 0.71%). The antioxidant activity of G. gelatinosa EPSs was investigated using four methods: the β-carotene-bleaching activity, DPPH assays, iron-reducing activity, and metal-chelating activity. EPS has shown high potential as free radicals’ scavenger, with an IC₅₀ on DPPH (0.2 g L⁻¹) three-fold lower than ascorbic acid (0.6 g L ⁻¹) and as a metal chelating activity (IC₅₀ = 0.4 g L⁻¹) significantly lower than EDTA. The obtained results allow further exploration of the thermophilic G. gelatinosa for several biotechnological and industrial applications.     

溶藻细菌的分离及溶藻特性研究

从爆发蓝藻水华的鱼池采集水样,以铜绿微囊藻为对象进行溶藻细菌筛选,得到R1、R2、R3、R5、R6、R8和R9共7株溶藻细菌,生理生化特征初步鉴定R5为海鱼弧菌,另6株为非发酵型细菌.R1、R3、R5、R8和R9细菌含量为105～108 cfu/ml时,对微囊藻的抑制率很高,效果优于R2和R6.对R1、R3、R5和R9...     

Occurrence of multiple antibiotic resistance and genotypic characterization in Edwardsiella tarda isolated from cage‐cultured hybrid red tilapia (Oreochromis sp.) in the Ping River,Northern Thailand

Edwardsiella tarda is a pathogen that causes edwardsiellosis in aquatic animals. The emergence of multiple antibiotic‐resistant strains makes antibiotic treatment difficult. This study aimed to investigate the antibiotic susceptibility patterns and the genotypic characterization of E. tarda isolated from cage‐cultured red tilapia in Thailand. A total of 30 isolates were identified as E. tarda using biochemical and molecular analysis. The disc diffusion method for testing antibiotic susceptibility showed all the isolates were resistant to colistin sulphate and oxolinic acid. High levels of resistance to amoxicillin, ampicillin, ceftazidime, oxytetracycline and sulphamethoxazole/trimethoprim were observed as well. The multiple antibiotic resistance index ranged from 0.25 to 0.92, indicating that these isolates had been exposed to high risk sources of contamination where antibiotics were commonly used. All the isolates carried the bla_TEM gene based on polymerase chain reaction (PCR). The tetA and sul3 genes were detected in 90% (27/30) and 26.7% (8/30) of the isolates respectively. Nine different genetic groups of isolates were obtained using enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC‐PCR). A correlation between genetic types and multiple antibiotic‐resistant patterns was found. These results highlight the potential risks of multiple antibiotic‐resistant isolates for humans and the environment.     

草鱼干扰素的分离纯化及某些理化和生物学特性

通过ＤＥＡＥ－Ｓｅｐｈａｒｏｓｅ阴离子交换层析、Ｓｅｐｈａｃｒｙｌ Ｓ－２００凝胶层析、高效液相层析和梯度聚丙烯酰张胶电泳等技术,对病毒诱生的草鱼血清干扰素进行了分离纯化。纯化的草鱼干扰素在ＳＤＳ－聚丙烯酰胺凝胶电泳中呈现单一组份,分子量为３８ｋＤ,等电点为５．２５,过碘酸－Ｓｃｈｉｆｆ试剂反应表现为典型的糖蛋白染色特征。理化和生物学特性研究表明,草鱼干扰素具有１０００００ｇ（２ｈ）离心不沉降、耐     

冀东滦下灌区种植结构调整策略的研究

分析了冀东滦下灌区四县稻田土壤耕层的全盐含量和地下水矿化度,并依据我国盐渍土壤划分标准和不同作物的耐盐能力,将该稻区划分为宜稻区、盐生植物种植区、耐盐作物种植区和大田旱作物种植区,并提出了各个区域的种植技术方案及配套的工程技术措施。