Evaluation of phase variation in Pseudomonas fluorescens b1 and its effect on some bacterial phenotypic and biocontrol characteristics

Phase variation is one of the adaptive mechanisms in fluorescent pseudomonads; this process caused by reversible genetic modification that generate subpopulation diversity with phenotypic differences that eventually lead to bacterial survival and their fitness under certain environmental conditions and is important in niche adaptation. In the present study¡ phase variation was observed in P. fluorescens strainB1 that carrying gene for phase variation. P. fluorescens B1 had two colony types¡ wild-type colony was small and opaque whereas the second type colony was larger in size and more fluorescent pigment production. These two types colony were tested for production of several enzymes such as protease¡ lipase¡ phosphatase and some metabolites production such as hydrogen cyanide¡ siderophore and auxin and for motility behaviors¡ biofilm formation and antagonistic activity against some phytopathogenic fungi. The results showed significant difference between the two types. Both of two types produced protease¡ lipase¡ phosphatase¡ but production of hydrogen cyanide in second type decreased strongly¡ in contrast production of siderophore and auxin in secondry type Increased. The second cell types was more motile than the wild-type and biofilm formation in wild-type was more than the secondry type. Antifungal activity of wild-type was higher than the secondary type. DNA fingerprint using BOX-PCR confirmed the identity of the second colony type with the parental isolate.