两株芽孢杆菌的鉴定

通过对2株芽孢杆菌的形态学、生理生化试验及16S rDNA序列同源性分析,发现B02号菌株与Ba-cillus cereus的同源性为100%,系统发育树分析与Bacillus cereus遗传关系最近,确定该菌株为Bacillus ce-reus。而B03号菌株与Bacillus cereus的同源性为98%,要确定其种还需进一步DNA杂交;该2株芽孢杆菌的芽胞数在1.0×1012个/kg体重以下安全无毒。2株芽孢杆菌的药敏性试验和拮抗性试验结果表明,参试菌对5类抗菌药物大多数都很敏感;对4种动物肠道病原菌无明显拮抗作用。通过酶系测定,参试菌都具有一定SOD酶活性。喂养实验结果表明,2株菌对雏鸡具有一定的防病治病效果。以上结论初步证明该菌株的抑病促生机理主要是生物夺氧和有益代谢产物的作用,而非优势种群、生物拮抗作用。

The Separation and Identification of Two Bacillus Strains

The B02 strain was identified as Bacillus cereus,based on the results of morphological,physiological characteristics and the homological analysis of 16S rDNA sequence.The phylogenetic tree built on the 16S rDNA sequence indicated B02 strain was the nearest to one of Bacillus cereus.The B03 strain needs more tests of DNA hybridization to ascertain its genus.The animal toxicity textidentified that two strains of Bacillus are safe for producting medicament or submedicament when level of addition don''t exteed 109 per gram.The results of antibiotic susceptibility test and antagonistic assay show two bacillus are sensitive to mass of antibacterial and without apparent antagonistc effect.By mensurating the enzymic activity,we can conclude that two bacillus have some superoxide dismutase and hydrolase activities.The feeding test identified that two strains have some effect on disease resistance and cure.All conclusion preliminarily proved that the disease resistance and growth stimulation mechanism of these strains mostly is the effect of biology scrambling oxygen and available metabolites,rather than the effect of dominant species and biological antagonism.