Bacteria, yeasts and filamentous fungi colonizing immature, mature and senescing primary leaves of field grown Beta vulgaris (sugar beet) were analysed over a complete growing season. Greatest microbial numbers were detected on senescing primary leaves and these numbers increased over most of the season. The number of colonizers detected on mature leaves was found to be stable over most of the study.Filamentous fungi and yeasts were identified to the genus level and the communities found to have greatest diversity during the summer months. There was no consistent pattern of diversity according to leaf type. Two genera of filamentous fungi, Cladosporium and Alternaria and two yeast genera, Cryptococcus and Sporobolomyces were the most numerous fungal populations isolated. Only 8 filamentous fungi and 3 yeast genera were commonly isolated on PDA (potato dextrose agar).Bacterial strains (1236) were isolated on Tryptic Soy Broth (TSB) agar and identified to species, or in some cases sub-species level, by analysis of their fatty acid methyl ester (FAME) profiles. Isolated bacteria were grouped into 78 named and 37 unnamed species clusters. Greatest number of bacterial species were isolated from young plants and leaves, sampled during the autumn months. Bacterial community diversity was lowest in mid-summer and winter months. Pseudomonas was the most commonly isolated genus and Erwinia herbicola the most common species. P. aureofaciens was the only species isolated from soil that was also isolated from the phyllosphere of B. vulgaris throughout the season.

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.

Agaricus bisporus and other fungi (Basidiomycetes, Ascomycetes, Fungi Imperfecti and Phycomycetes) grew and produced transparent zones in opaque media containing killed Bacillus subtilis as sole carbon and nitrogen source. Other Gram-positive and Gram-negative bacteria were also degraded by A . bisporus. Degradation of B. subtilis by A . bisporus was examined by light and electron microscopy. Liquid cultures were assayed for extracellular fungal enzymes which included EN-acetylglucosaminidase, lipase, nucleases and acid, neutral and alkaline proteases.Microbial biomass in compost may serve as a source of nitrogen, carbon and minerals, and as a water reserve for the growth of A. bisporus.

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