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© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in O'Brien, F. J. M., Almaraz, M., Foster, M. A., Hill, A. F., Huber, D. P., King, E. K., Langford, H., Lowe, M., Mickan, B. S., Miller, V. S., Moore, O. W., Mathes, F., Gleeson, D., & Leopold, M. Soil salinity and pH drive soil bacterial community composition and diversity along a lateritic slope in the Avon River critical zone observatory, Western Australia. Frontiers in Microbiology, 10, (2019): 1486, doi:10.3389/fmicb.2019.01486., Soils are crucial in regulating ecosystem processes, such as nutrient cycling, and supporting plant growth. To a large extent, these functions are carried out by highly diverse and dynamic soil microbiomes that are in turn governed by numerous environmental factors including weathering profile and vegetation. In this study, we investigate geophysical and vegetation effects on the microbial communities of iron-rich lateritic soils in the highly weathered landscapes of Western Australia (WA). The study site was a lateritic hillslope in southwestern Australia, where gradual erosion of the duricrust has resulted in the exposure of the different weathering zones. High-throughput amplicon sequencing of the 16S rRNA gene was used to investigate soil bacterial community diversity, composition and functioning. We predicted that shifts in the microbial community would reflect variations in certain edaphic properties associated with the different layers of the lateritic profile and vegetation cover. Our results supported this hypothesis, with electrical conductivity, pH and clay content having the strongest correlation with beta diversity, and many of the differentially abundant taxa belonging to the phyla Actinobacteria and Proteobacteria. Soil water repellence, which is associated with Eucalyptus vegetation, also affected beta diversity. This enhanced understanding of the natural system could help to improve future crop management in WA since the physicochemical properties of the agricultural soils in this region are inherited from laterites via the weathering and pedogenesis processes., This work was funded by the WUN and the individual authors’ institutions. MA and MF were funded by the Critical Zone Observatory Program, NSF ICER 1445346.

Marine sediments harbour vast and diverse prokaryotic communities. With ongoing burial and ageing of respective sediment layers, however, available organic matter becomes more recalcitrant. Thus, sedimentary microorganisms face starvation and ultimately death. Nonetheless, live and active cells are present in old and deeply buried sediments, up to 111 Ma (Roussel et al., 2008). During IODP Leg 307 an organic-matter poor, cold-water, buried coral carbonate mound was sampled. Nineteen isolates, mainly Proteobacteria, were obtained from the mound and surrounding sediments. Additionally, one putative new species belonging to the genus Ornithinimicrobium (Actinobacteria) was isolated. Strains were subsequently phylogenetically and phenotypically characterised. Selected isolates and other sedimentary bacteria were subsequently subjected to anaerobic starvation-survival experiments and their responses to substrate limitation were compared to those of near-surface relatives. All strains survived long periods of starvation (incubated up to 3 years). This was confirmed by constant total cell counts and only slowly increasing proportions of dead cells (20% after one year). Culturability and FISH detectability decreased with time but radiotracer experiments conducted after starvation confirmed viability and potential metabolic activity of many strains. No significant correlations between FISH detectability and other viability measures occurred. Instead starvation time was significantly positively correlated with percentages of dead cells and inversely with culturability. Pure culture starvation experiments were complemented by a study on an estuarine, surface-sediment microbial community, which was stressed in sediment slurry sequential heating experiments. This mimicked burial and resulted in decreasing total counts, culturability, and FISH detcctability but these were still present even after heating to 90 °C. Temperatures above 42 °C were significantly correlated wit

Marine sediments harbour vast and diverse prokaryotic communities. With ongoing burial and ageing of respective sediment layers, however, available organic matter becomes more recalcitrant. Thus, sedimentary microorganisms face starvation and ultimately death. Nonetheless, live and active cells are present in old and deeply buried sediments, up to 111 Ma (Roussel et al., 2008). During IODP Leg 307 an organic-matter poor, cold-water, buried coral carbonate mound was sampled. Nineteen isolates, mainly Proteobacteria, were obtained from the mound and surrounding sediments. Additionally, one putative new species belonging to the genus Ornithinimicrobium (Actinobacteria) was isolated. Strains were subsequently phylogenetically and phenotypically characterised. Selected isolates and other sedimentary bacteria were subsequently subjected to anaerobic starvation-survival experiments and their responses to substrate limitation were compared to those of near-surface relatives. All strains survived long periods of starvation (incubated up to 3 years). This was confirmed by constant total cell counts and only slowly increasing proportions of dead cells (20% after one year). Culturability and FISH detectability decreased with time but radiotracer experiments conducted after starvation confirmed viability and potential metabolic activity of many strains. No significant correlations between FISH detectability and other viability measures occurred. Instead starvation time was significantly positively correlated with percentages of dead cells and inversely with culturability. Pure culture starvation experiments were complemented by a study on an estuarine, surface-sediment microbial community, which was stressed in sediment slurry sequential heating experiments. This mimicked burial and resulted in decreasing total counts, culturability, and FISH detcctability but these were still present even after heating to 90 °C. Temperatures above 42 °C were significantly correlated wit