Search

Plants serve as critical links between above- and below-ground microbial communitites, both influencing and being influenced by microbes in these two realms. Below-ground microbial communities are expected to respond to soil resource environments, which are mediated by the roots of plants that can, in turn, be influenced by the above-ground community of foliar endophytes. For instance, diverse plant communities deposit more, and more diverse, nutrients into the soil, and this deposition is often increased when foliar pathogens are removed. DiFFerences in soil resources can alter soil microbial composition and phenotypes, including inhibitory capacity, resource use, and antibiotic resistance. In this work, we consider plots differing in plant richness and application of foliar fungicide, evaluating consequences on soil resource levels and root-associated Streptomyces phenotypes. Soil carbon, nitrogen, phosphorus, potassium, and organic matter were greater in samples from polyculture than monoculture, yet this increase was surprisingly offset when foliar fungal communities were disrupted. We find that Streptomyces phenotypes varied more between richness plots--with the Streptomyces from polyculture showing lower inhibitory capacity, altered resource-use profiles, and greater antibiotic resistance--than between subplots with/without foliar fungicide. Where foliar fungicide affected phenotypes, it did so differently in polyculture than in monoculture, for instance decreasing niche width and overlap in monoculture while increasing them in polyculture. No diffserences in phenotype were correlated with soil nutrient levels, suggesting the need for further research looking more closely at soil resource diversity and particular compounds that were found to differ between treatments. [ABSTRACT FROM AUTHOR]

Pathogens traverse disciplinary and taxonomic boundaries, yet infectious disease research occurs in many separate disciplines including plant pathology, veterinary and human medicine, and ecological and evolutionary sciences. These disciplines have different traditions, goals, and terminology, creating gaps in communication. Bridging these disciplinary and taxonomic gaps promises novel insights and important synergistic advances in control of infectious disease. An approach integrated across the plant-animal divide would advance our understanding of disease by quantifying critical processes including transmission, community interactions, pathogen evolution, and complexity at multiple spatial and temporal scales. These advances require more substantial investment in basic disease research.

Antibiotic activity is known to affect interactions among soil microbes but very little information is available on the ecology of antibiotic microbial population in soil. To understand this activity better the abilities of streptomycete isolates from prairie soil were studied.

The PCR DNA fingerprinting technique using repetitive intergenic DNA sequences is effective in determining strain identity rapidly. The PCR technique efficiently identifies unique DNA fingerprints of pathogenic and disease-suppressive streptomyces strains. The PCR DNA fingerprints of these strains using BOXA1R primers, rather than the REP1R-I and REP2 primers, are unique, stable and reproducible.

Outer leaves of broad-leaved endive plants have higher fluorescent and pectolytic epiphytic bacterial population densities than inner leaves. The frequency distribution and variability of bacterial population size are influenced by the age of the leaves. Immigration of fluorescent bacteria on new leaves is inhibited by adjacent leaves. Leaves of younger plants have higher bacterial population sizes.

Coexisting Pseudomonas syringae strains are injected into plants to determine their ability to invade and exclude the leaves. The presence of an already existing population on the leaf surface decreases the development of newly introduced challenge strains. P. syringae strains exhibit differences in their capacity to coexist, invade and exclude on the phylloplane. In 107 pairwise combinations, 29 strains are injected into plants for the examination of their ability to invade and exclude.

The article discusses the development of new techniques, which can be used for the quantification of Streptomyces scabiei and antibiotic-producing Streptomyces lavendulae strains. The assays are shown to be extremely beneficial for studying the competitive dynamics of these compounds in the complex soil communities.