Native polyacrylamide gels of extracellular proteins produced by several Streptomyces isolates grown with suberin were assayed in situ for esterase activity. Two pathogenic isolates of Streptomyces scabies from different geographical regions were found to produce a similar esterase activity that was not produced by nonpathogenic strains. After treatment with EDTA, suberin no longer induced esterase production. Expression was restored when EDTA-treated suberin was supplemented with zinc. The optimal concentration of zinc required for esterase production was 2 microM. This esterase was purified from one of the pathogenic isolates and characterized. The enzyme was 38,000 daltons when determined by gel filtration on Sephadex G-100 and 36,000 daltons when determined by denaturing polyacrylamide gel electrophoresis. The esterase showed maximal activity in sodium phosphate buffer above pH 8.0, was stable to temperatures of up to 60 degrees C, and had an apparent Km of 125 microM p-nitrophenyl butyrate.

A taxonomic study by Naczi, Reznicek, and Ford (American Journal of Botany, 85, 434-447, 1998) has determined that three species (Carex willdenowii, C. basiantha, and C. superata) can be recognized within the C. willdenowii complex. To determine the amount of genetic divergence within and between these species, allozyme analyses were conducted on 14 populations distributed from Pennsylvania to eastern Texas. Seventeen loci were surveyed, 13 of which were polymorphic, with all populations being polymorphic at one or more loci. Interspecific genetic identities ranged from 0.560 (C. willdenowii and C. basiantha) to 0.807 (C. basiantha and C. superata). Alleles for the isozymes Aat-1, Dia-1, Idh-2, Mdh-2, Per-1, Pgm-1, and Pgm-2 served to distinguish C. willdenowii from C. basiantha and C. superata. Carex basiantha and C. superata were recognized by alleles of Mdh-2, Pgm-1, and Tpi-2. The genetic identities of populations within species were high and exceeded 0.957. A caespitose growth habit and perigynia in close proximity to the staminate flowers suggest adaptations for selfing and therefore low levels of heterozygosity. Paradoxically, the values for expected heterozygosities (Hexp) were always lower than those obtained by direct count (Hobs): F values were highly negative, indicating heterozygous excess. Disassortative mating and selection are discussed as possible mechanisms for maintaining heterozygous excess within populations.

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Nine different strains of Streptonijws ('S. scabies') have been isolated from scab lesions on potato tubers. These strains were obtained from different cultivars grown in different geographical areas. Four different types of inhibitory reactions were observed when these strains were tested in pairs with each other. Three of these inhibitory reactions resembled the lethal zygosis phenotype that has been reported for other species of Streptomyces. All of the strains exhibited at least two of these inhibitory reactions and were sensitive to the inhibitory reactions of at least six of the other isolates. Five of these isolates were shown to harbour plasmid DNA.