We tested the hypothesis that different minerals in soil select distinct bacterial communities in their microhabitats. Mica (M), basalt (B) and rock phosphate (RP) were incubated separately in soil planted with Trifolium subterraneum, Lolium rigidum or left unplanted. After 70 days, the mineral and soil fractions were separated by sieving. Automated ribosomal intergenic spacer analysis was used to determine whether the bacterial community structure was affected by the mineral, fraction and plant treatments. Principal coordinate plots showed clustering of bacterial communities from different fraction and mineral treatments, but not from different plant treatments. Permutational multivariate anova (permanova) showed that the microhabitats of M, B and RP selected bacterial communities different from each other in unplanted and L. rigidum, and in T. subterraneum, bacterial communities from M and B differed (P<0.046). permanova also showed that each mineral fraction selected bacterial communities different from the surrounding soil fraction (P<0.05). This study shows that the structure of bacterial communities in soil is influenced by the mineral substrates in their microhabitat and that minerals in soil play a greater role in bacterial ecology than simply providing an inert matrix for bacterial growth. This study suggests that mineral heterogeneity in soil contributes to the spatial variation in bacterial communities.

This study tests the hypothesis that altering the mineral composition of soil influences microbial community structure in a nutrient-deficient soil. Microcosms were established by adding mica (M), basalt (B) and rock phosphate (P) to soil separately, and in combination (MBP), and by planting with Lolium rigidum, Trifolium subterraneum or by leaving unplanted. The effects of mineral and plant treatments on microbial community structure were assessed using automated ribosomal intergenic spacer analysis. Bacterial community structure was significantly affected by both mineral (global R=0.73 and P<0.001) and plant (global R=0.71 and P<0.001) treatments, as was the fungal community structure: mineral (global R=0.65 and P<0.001) and plant (global R=0.65 and P<0.001) treatments. All pairwise comparisons of bacterial and fungal communities between different mineral treatments and between different plant treatments were significantly different (P<0.05). This study has shown that mineral addition to soil microcosms resulted in substantial changes in both bacterial and fungal community structure, dependent on the type of mineral added and the plant species present. These results suggest that the mineral composition of soil may be an important factor influencing the microbial community structure in soil.

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This is a repository copy of The use of campus based field teaching to provide an authentic experience to all students.

Caves are extreme and specialised habitats for terrestrial life that sometimes contain moonmilk, a fine-grained paste-like secondary mineral deposit that is found in subterranean systems worldwide. While previous studies have investigated the possible role of microorganisms in moonmilk precipitation, the microbial community ecology of moonmilk deposits is poorly understood. Bacterial and fungal community structure associated with four spatially isolated microcrystalline, acicular calcite moonmilk deposits at Ballynamintra Cave (S. Ireland) was investigated during this study. Statistical analyses revealed significant differences in microbial activity, number of bacterial species, bacterial richness and diversity, and fungal diversity (Shannon's diversity) among the moonmilk sites over an area of approximately 2.5 m(2). However, the number of fungal species and fungal community richness were unaffected by sampling location. SIMPER analysis revealed significant differences in bacterial and fungal community composition among the sampling sites. These data suggest that a rich assemblage of microorganisms exists associated with moonmilk, with some spatial diversity, which may reflect small-scale spatial differences in cave biogeochemistry.