Isolation, Identification And Safety Evaluation Of Bacteriovorax Sp.H2

Bdellovibrio-and-like organisms,BALOS is a predatory invader of other bacteria and has the potential of substituting antibiotics to become promising probiotics. Thus, In replacement of antibiotics, with better prospects for development. In this article, the current domestic and overseas study and application situations of B. Bdellovibrio-and-like organisms,BALOS used in aquaculture were introduced, problems in its research and application were analyzed, and the suggestions were further proposed to strengthen its studies and applications, so as to promote its application processes in aquaculture of China.A predatory bacterial strain H2was isolated from the Litopenaeus vannamei farming water using Vibrio cholerae as the host bacterium, and identified as a Bacteriovorax sp. strain (GenBank accession no:JX122409) through morphology observation, specific PCR detection and phylogenetic analysis. The16S rRNA sequence of strain H2had94%-98%of homology with those of Bacteriovorax strains in GenBank, and was most close to Bacteriovorax strain NE1(GenBank accession no:EF092445). In addition, strain H2could lyze the other bacterial pathogens such as V. alginolyticus, V. harveyi, V. vulnificus V. parahaemolyticus and V. anguillarum, and exhibited good lytic activity under pH7.5and0.2mg/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 Vibrios, which not only enrich the predatory microbial resources against vibrios, but laid a solid basis for its application in the removal of vibrios in farming waters.The present study was to evaluate the safety of A predatory bacterial strain H2used for aquaculture. According to Chemicals—Alga growth inhibition test (GB/T21805-2008), Water quality—Determination of the acute toxicity of substance to freshwater fish (Brachydanio rerio Hamilton-Buchanan)(GB/T13267-91) and Clinical experiment technical practice for fishery drugs, its acute toxicity of the Strain H2to Daphnia and Yellow catfish were observed, and its influence on main physicochemical factors of aquaculture water was also assayed, and its LD50to Daphnia and Yellow catfish were all>2000μL/L. In addition, in the period of14days after the input of the strainH2into the farming water at0.2μL/L-2000μL/L, the nitrite nitrogen concentration, the contents of the ammonia and sulfide as well as the pH values were gradually reduced, the nitrite removal bacterium H2has well dnitrification characteristics and the ability to adapt to the harmful environment.