Evidence for the Involvement of Plasmids in Sporophore Initiation and Development in AgaricusBisporus

Abstract

Rainey, P. B. and Cole, A. L. J. (1986). Evidence for the involvement of plasmids in sporophore initiation and development in Agaricus bisporus . The role of bacteria in sporophore initiation of Agaricus bisporus was investigated. Fluorescent pseudomonads, which are regarded as important in sporophore initiation, were isloated from the casing layer of commercial mushroom houses. These isolates were all identified as Pseudomonas putida and found to inhibit the growth of A. bisporus mycelium in vitro , but in a modified ‘Halbschalentest’ the reverse occurred - mycelial growth was stimulated. In addition, primordia initiation and sporophore development was promoted. A sporophore inducing isolate was examined for the presence of plasmids. This isolate was shown to be resistant to mercury, an ability which is usually plasmid borne in pseudomonads and able to utilize camphor, the genes for which are plasmid encoded. Mercury resistance and camphor utilization served as markers for the detection of plasmid (s). Loss of mercury resistance and camphor utilizing ability following treatment with mitomycin C, was associated with loss of sporophore development. Extrachromosomal DNA was extracted by alkaline lysis and separated by agarose gel electrophoresis. Evidence for the presence of at least one large plasmid was obtained.