Xenorhabdus luminescens菌株菌落功能二型性的特殊性

THE DISPARITIES BETWEEN MORPHOLOGICAL AND FUNCTIONAL DIMORPHISM IN XENORH ABDUS LUMINESCENS

Akhurst(1980)注意到 Xenorhabdus 属细菌在指示培养基平板上呈现两种菌落形态,定为初生型及次生型。初生型菌可从感染期线虫肠腔中分离到。它不稳定,在体外培养时易转为次生型。初主型及次生型菌的区别在于色素、溴百里酚兰和甲基红的吸收,抗菌能力的差异和卵磷脂酶的存在(Akhurst 1980;Akhurst & Boemare 1988)。初生型还对线虫繁殖有促进作用(Akhurst 1980;Bedding 1981)。

The antimicrobial activity of the primary and secondary form of several X.luminescens(X1)isolates(including a non-luminescent H3 and a pale-pigment-producing G12 isolated from Guangdong, Hainan,China)against each other was determined.The two forms were identified by the colour and mucoid condition of their colonies on indicator agar media.Only the primary form adsorbs bromothymol blue and neutral red from NBTA and MacConkey agar media respectively.Except for the secondary form of X1HNZ,both forms of all isolates showed antimicrobial activity against at least two X enorhabdus isolates.The degree of inhibition,against the various isolates in the test range,was different for each isolate with the exception of X1G12 and X1H3.It is suggested that the bacterial isolates may produce different antimicrobial compounds and that each compound may identify a subspecies of X.luminescens. In the said liquid broth,various bacterial isolates differ in their abilities to maintain the primary form.It was found that the differences between two forms in nematode production are related with the nematode strains and bacterial isolates.Nematode could better grow on the secondary form of some isolates of symbionts with sponge culture medium(1% peptone,1% beef extract,20% eggs,15% soya flour,5% corn oil, 8% polyether polyurethane sponge,and 50% distilled water)than the corresponding primary form.The disparities between morphological and functional dimor- phism in X,lurninescens were discussed.