A predatory bacterial strain H2was isolated from the Litopenaeus vannamei farming water using Vibrio cholerae as the host bacterium.Strain H2was identified as a Bacteriovoraxsp.strain(GenBank accession No.JX122409)through morphology observation,specific PCR detection and phylogenetic analysis.The 16SrRNA sequence of strain H2had 94%-98% of homology with those of Bacteriovoraxstrains in GenBank,and was most close to Bacteriovoraxstrain NE1(GenBank accession No.EF092445).In addition,strain H2could lyze the other bacterial pathogens such as Vibrio alginolyticus,Vibrio harveyi,Vibrio vulnificus,Vibrio parahaemolyticus and Vibrio anguillarum,and exhibited good lytic activity under pH 7.5and 0.2mg/L nitrite nitrogen.However,its lysis activity could be inhibited at≥0.2mg/L ammonia nitrogen.The present study determined the taxonomic position of strain H2,analyzed its lysis effects on well-known Vibrio,which not only enrich the predatory microbial resources against Vibrio,but laid a solid basis for its application in the removal of Vibrio in farming waters.

<正>黄河下游地区地质多偏盐碱性,尤其是郑州一带,pH普遍偏高,基本在以上,鲤鱼急性烂鳃多发生于6-10月尤其是6月至7月中旬和8月下旬至月中旬期间天气不稳定,温度容易发生剧变,导致鱼经常受到较大刺激,抵抗力下降,极易暴发烂鳃疾病。笔者就今年此地区鲤鱼烂鳃情况做一个汇报,供大家参考,相互学习,借此希望能减少因此病产生的损失。1流行病学调查:6-10月为烂鳃病的流行季节,各个阶段的鲤鱼均可能感染,导致疾病的发生,发病前无任何征

Bdellovibrio bacteriovorus is a predatory invader of other bacteria,foreign and domestic researchers have made great progresses in the design of Bdellovibrio-targeted specific primers,improvement on the isolation and detection methods of B.bacteriovorus as well as its strains' isolation,bacteriolytic mechanism,ecological significance,application effect,etc.However,in contrast with the overseas current study level on B.bacteriovorus for aquaculture use and the position of China's aquaculture in the world,many problems on the study of B.bacteriovorus for aquaculture use still exist in China,involving the control technique on its strains' variation,its bacteriolytic mechanism,effective safety evaluation systems and methods,its new preparations' innovation,and its rational application technology.Thus,in order to promote the application processes of B.bacteriovorus in aquaculture in China,new technologies and achievements in human and domestic animal probiotics should be introduced to resolve the present problems in the study and application of B.bacteriovorus.

In order to provide important scientific basis on the safe use of PVP-I in Carassius auratus gibelio farming,we evaluate the safety of fishery povidonum-iodum(PVP-I)on C.auratus gibelio farming according to the national standards and related regulations.Based on observation on growth inhibition of the PVP-I on Chlorella sp.,aquatic probiotic bacteria,we analyzed the acute toxicity of PVP-I to Daphnia magna straus,Brachydanio rerio,and C.auratus gibelio,as well as the influence on main harmful physicochemical factors of the farming water.The results showed that the growth of Chlorella sp.was promoted with PVP-I at the final concentrations of 6.00-14.00 mg/L,its minimum inhibitory concentration to aquatic probiotics were varied from 128 mg/L to 512 mg/L,its 50% inhibitory concentration to Chlorella sp.was estimated to be above 14.00 mg/L,and its 50% lethal dose to D.magna straus,B.rerio were 13.44 mg/L,17.63 mg/L,respectively.In addition,the 50% lethal dose of PVP-I to C.auratus gibelio was 74.77 mg/L,and in the period of 14 days after the adding of the PVP-I into the farming water at 0.20-1.40 mg/L,the contents of the ammonia and nitrite in C.auratus gibelio farming water were gradually reduced with the increased concentration of the PVP-I.The present study confirmed that the PVP-I had low toxicity,its safe concentration for C.auratus gibelio farming should be no more than 1.34 mg/L in view of its potential threat to zooplankton such as D.magna straus.PVP-I would not lead to the increase of the ammonia and nitrite in the C.auratus gibelio faming water under its safe concentration.

To evalauate the safety of enrofloxacin for Carassius auratus gibelio,the acute toxicity of enrofloxacin and its influences on blood biochemical indicators were studied,based on the conventional dose of enrofloxacin in aquaculture.The results showed that the median lethal dose and safe dose of enrofloxacin for C.auratus gibelio were 1 949.84 mg/kg and 194.98 mg/kg,respectively.Compared with the control group,the content of serum total protein(TP),glutamic-pyruvic transaminase(ALT),aspartate aminotransferase(AST),and γ-glutamine transferase(γ-GT) were not significantly changed with the continuous oral administration at 20 mg/kg as a conventional dose for 30 days,while after the continuous oral administration at 40 mg/kg,80 mg/kg,160 mg/kg,320 mg/kg for 30 days,the serum AST content was significantly increased by 23%,30%,46%,86%(P<0.05),and the ALT content was significantly increased by 37%,42%,69%,86%(P<0.05),respectively.This study determined the safe dose of enrofloxacin and its administration dose range causing liver dysfunction for C.auratus gibelio,and provided a scientific basis for the safe use of enrofloxacin in C.auratus gibelio.Enrofloxacin at 20 mg/kg as a conventional dose does not result in liver dysfunction in C.auratus gibelio.

黄河中下游面积大约是8.7万平方公里,区内气候湿润,年平均相对湿度为65％～85％,降水时段集中在7-8月,尤其7月下旬(或8月上旬)多有较强的暴雨发生,属于温带季风气候.该区域主要养殖草鱼、黄河鲤鱼、鲢鳙鱼、斑点叉尾鲴、云斑鲴等.

Recent studies have revealed that the use of bdellovibrios is an alternative to control bacteriosis. However, no bdellovibrios are available against Aeromonas hydrophila infections in sturgeons. In the present study, a potential Bdellovibrio strain F16 was isolated from sturgeon gut samples, using a sturgeon-pathogenic A. hydrophila as the prey bacterium. It was initially identified as a Bdellovibrio strain using morphological characteristics and specific PCR amplification, and confirmed to be Bdellovibrio sp. strain ETB (GenBank Accession No. DQ302728) and Bdellovibrio bacteriovorus strain SRA9 (GenBank Accession No. AF263833) by phylogenetic analysis. In addition, it was shown to be safe for mammalians and sturgeons, had a wide prey range, and exhibited significant bacteriolytic effects on the pathogenic A. hydrophila. To the best of our knowledge, this is the first report on a promising gut Bdellovibrio strain against pathogenic A. hydrophila.

Recent studies have revealed that the use of denitrifying bacteria is an alternative to eliminate nitrite accumulation in the wastewaters. However, no information is available about Acinetobacter species as a denitrifying agent for reducing nitrite in aquaculture. In the present study, a potential denitrifying strain H1 was isolated from shrimp farming ponds using nitrite as nitrogen source, which displayed almost complete nitrite removal. It was initially identified as Acinetobacter baumannii using API identification kits, and confirmed to be A. baumannii strain (GenBank accession no. JF751054) by phylogenetic analysis. Three key denitrification genes nirS, norB and nirK were detected from strain H1 by PCR amplification. In addition, it was demonstrated to be safe for mammals and giant freshwater prawns, and showed in vitro high nitrite removal activities at a wide range of initial pH 5-9 and 15 to 35 degrees C with a final cell density of 105-107 cfu/ml. To the best of our knowledge, this is the first report on a promising denitrifying A. baumannii strain from shrimp farming ponds.