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     

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.     

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.     

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.     

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 .     

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...     

硼对不同专用小麦品种种子萌发和幼苗生长的影响

为了明确施硼对小麦种子萌发和幼苗生长的效应,以不同的专用小麦品种为材料,研究了不同硼浓度对小麦种子淀粉酶活性、发芽势、发芽率、根系活力、根尖结构及幼苗生长的影响。结果表明,低浓度硼对小麦种子发芽势和发芽率有促进作用,其中硼浓度以20μmol·L-1促进效果最佳,高浓度时有明显的抑制作用;小麦根系活力、根长、芽长、根重和芽重均随硼浓度的升高呈现先促进后抑制的变化趋势,但对根比芽敏感,地下部生物量受影响程度低于地上部;一定的硼浓度能促进根尖分生区表皮细胞和外皮层细胞体积变大及数量增多。不同专用小麦品种对硼浓度响应的敏感程度有差异,中筋小麦扬麦16>弱筋小麦扬麦19>强筋小麦罗麦8号。     

几种海藻中溴过氧化物酶的筛选及酶学性质

溴过氧化物酶(BrPOD)是具有特殊功能的过氧化物酶,海藻是其主要来源。对几种中国海域的红藻如角叉菜(Chondrus ocellatus)、龙须菜(Gracilaria sjoestedtii)、珊瑚藻(Corallina officinalis)进行了溴过氧化物酶的藻种筛选,并对酶活较高的珊瑚藻进行溴过氧化物酶分离纯化及性质的研究。通过硫酸铵沉淀、DEAE-cellulose 52离子交换层析、Sephadex G-100凝胶层析等方法,从珊瑚藻中分离得到溴过氧化物酶。对该酶性质研究表明,该酶分子量较大,表观分子量为64 kD;溴化单氯甲酮的最适pH值为6.0;pH在5.0-9.0时酶活性稳定;在30-70℃温度范围内酶活性稳定;Ca2 、Co2 、Cu2 、Mn2 、NaF和EDTA等化合物使溴过氧化物酶活性下降,钒酸盐能提高酶活性。反应动力学实验表明,该酶对Br-、H2O2的Km分别为7.40 mmol/L和96.09μmol/L。     

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.