A novel bacterium has been found that causes a soft rot disease of Agaricus bisporus, the cultivated mushroom. It has been characterized using nutritional, physiological, chemical and molecular techniques. Based on these data, it was shown t o have many characteristics in common with members of the genus Janthinobacterium. Despite similarities to the only described species within this genus, Janthinobacterium lividurn, there were a number of differences between the mushroom pathogen isolated and this species. Despite the high degree of genotypic similarity between members of the genus Janthinobacterium and Herbaspirilhm, as evidenced by DNA-RNA hybridization, and the high degree of 165 rDNA sequence similarity between members of the genera Janthinobacterium, Herbaspirillurn, Oxalobacter and Duganella, as well as the generically misnamed Pseudomonas lemoignei, it was possible to show that members of the genus Janthinobacterium could be easily distinguished from these taxa. The data also indicated that the mushroom pathogenic strains represent a novel species within the genus Janthinobacterium for which the name Janthinobacterium agaricidamnosum sp. nov. is proposed. The type strain of this species has been deposited in the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany, as DSM 9628' and a t the National Collection of Plantpathogenic bacteria, UK, as NCPPB 3945'. To aid practical control of the disease, the effect of the relative humidity on symptom expression on Agaricus bisporus was determined.

A new pathovar of Pseudomonas gladioli, pv, agaricicota is described to accommodate a bacterium pathogenic to Agarieus bitorquis. The bacterium causes a rapid soft rot of cultivated mushrooms at temperatures above 25 C, The pathotype culture has been deposited at the National Collection of Plant Pathogenic Bacteria, Harpenden, UK and designated NCPPB 3580,

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Agaricus bisporus, the cultivated mushroom, was able to mineralize dead 14C-labelled Bacillus subtilis and utilize the cellular components as sole source of carbon and nitrogen for growth. Consistently higher levels of bacteriolytic activity were obtained when A. bisporus was grown on lower concentrations of bacteria, 1.5 mg ml-1 as opposed to 3mg ml-1 basal liquid medium. A. bisporus also mineralized 14C-labelled bacteria in the presence of readily available alternative carbon and nitrogen sources such as glucose and ammonium sulphate. 14C-labelled bacteria were degraded to 14C02 more efficiently than [14C]cellulose. A. bisporus was able efficiently to mineralize biomass produced in situ ( > 20% of total label released as 14C02) where label was incorporated into the microbial biomass by composting rather than added as killed bacteria. This is the first time that quantitative data have been produced to show that the microbial biomass in wheat straw/animal manure compost might be significant in the nutritional strategy of basidiomycetes.

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