Search

peer-reviewed, Biochar has shown great potentials in plant growth promotion but its effect on soil bacteria that potentially support plant growth is less well understood. In this study, the effect of biochar soil amendment was investigated on the growth of spring barley, its rhizobacteria diversity and the abundance of sulfur (S) and phosphorus (P) mobilizing bacteria. Furthermore, the S oxidation status was determined in soil, feedstock and biochar. Soil amendment with biochar made from Miscanthus x giganteus resulted in significantly increased growth of barley and grain formation four to seven fold. Further significant increases were found for the soil pH and abundances of rhizosphere soil bacteria capable of growing with tri-calcium phosphate, phosphate-esters, phosphonates or aromatic sulfonates as sole source of S or P. A stepwise regression model attributed 74% of the variation in plant growth to the abundances of P and S mobilizing bacteria. 16S rRNA gene based fingerprint analysis revealed a significant shift in the bacterial community structure upon biochar amendment that correlated significantly with the above mentioned changes (pH, plant growth, bacterial abundances). Under biochar amendment, up to 100 times increases in genera Brevundimonas known for P cycling and Arthrobacter and Cupriavidus previously involved in sulfonate desulfurization were identified via quantitative PCR. S k-edge XANES confirmed that the key S source sulfonate was largely absent in the applied biochar, thus bacterial mobilization of sulfonate-S may have originated from the soil. (C) 2016 Elsevier GmbH. All rights reserved., ACCEPTED, peer-reviewed

peer-reviewed, Hyphae of symbiotic arbuscular mycorrhizal (AM) fungi extend into the soil, affecting the hyphosphere and interact with beneficial soil bacteria. This study aimed to elucidate differences in hyphosphere, hyphoplane and bulk soil bacterial communities and their role in mobilization of sulfonate-sulfur. Abundances of cultivable hyphosphere and hyphoplane bacteria were significantly increased over bulk soil. Cultivation independent fingerprinting revealed significantly different community structures of both hyphosphere and hyphoplane bacteria, fungi and AM fungi over bulk soil. However, cultivation dependent and independent analysis did not identify a difference between bacterial hyphoplane and hyphosphere (hyphospheric) communities. Isolated bacteria capable of aromatic sulfonate desulfurization were almost exclusively of hyphospheric origin. Members of the hyphospheric Gammaproteobacteria and Actinobacteria were found to possess marker gene asfA for aromatic sulfonate desulfurization and hrcR for attachment to fungal hyphae with a type III secretion system, that were not detected in bulk soil. These findings suggest that AM hyphae host a distinct population of sulfonate desulfurizing bacteria putatively capable of hyphal attachment with potential to increase plant sulfur supply. (C) 2014 Elsevier B.V. All rights reserved., ACCEPTED, peer-reviewed

peer-reviewed, Bauxite residue is the alkaline byproduct generated when alumina is extracted from bauxite ores and is commonly deposited in impoundments. These sites represent hostile environments with increased salinity and alkalinity and little prospect of revegetation when left untreated. This study reports the establishment of bacterial communities in bauxite residues with and without restoration amendments (compost and gypsum addition, revegetation) in samples taken in 2009 and 2011 from 0 to 10 cm depth. DNA fingerprint analysis of bacterial communities based on 16S rRNA gene fragments revealed a significant separation of the untreated site and the amended sites in both sampling years. 16S amplicon analysis (454 FLX pyrosequencing) revealed significantly lower alpha diversities in the unamencled in comparison to the amended sites and hierarchical clustering separated the unamended site from the amended sites. The taxonomic analysis revealed that the restoration resulted in the accumulation of bacterial populations typical for soils including Acidobacteriaceae, Nitrosomonadaceae, and Caulobacteraceae. In contrast, the unamencled site was dominated by taxonomic groups including Beijerinckiaceae, Xanthomonadaceae, Acetobacteraceae, and Chitinophagaceae, repeatedly associated with alkaline salt lakes and sediments. While bacterial communities developed in the initially sterile bauxite residue, only the restoration treatments created diverse soil-like bacterial communities alongside diverse vegetation on the surface., ACCEPTED, peer-reviewed

peer-reviewed, Sulfur (S) is an essential macronutrient that is increasingly limiting to crop yield as a result of reduced atmospheric deposition and high yielding crop varieties rapidly depleting soil S stocks. Plants obtain S from soil via their root networks, however, in soil up to 95% of S is organically bound as either sulfate esters or sulfonates which are not directly accessible. In this instance, plants rely on distinct functional soil microbial populations to mineralise the respective organo-S pool. Sulfonate mineralisation is catalysed solely by specific bacteria, while sulfate ester mineralisation is achieved by both bacteria and fungi. Arbuscular mycorrhizal (AM) fungi are ubiquitous soil microbes that have been shown to be very important for both nitrogen and phosphorus cycling, so intuitively they may play a role in the S cycle. AM fungi have many beneficial characteristics that would render them useful in organo-S mobilisation including improved nutrient exchange, extensive hyphal networks, modified rhizodeposition, and increased access to soil aggregates. The study set out to ascertain (i) the microbial diversity associated with AM hyphae in a native ecosystem and analyse their functionality, (ii) the effect of AM inoculation on plant growth and organo-S mobilising communities, and (iii) the interaction between AM fungi and bacteria to improve uptake of labelled organo-S. The results obtained demonstrate that (i) hyphospheric bacterial communities in native grassland swards are enriched in sulfonate mobilisers that can putatively attach to AM hyphae to explore the extended soil environment, (ii) AM inoculation promotes plant growth, significantly impacts bacterial community composition and abundance, and harbours distinct and abundant populations of sulfonate mobilising bacteria, and (iii) an undisturbed AM symbiosis increases uptake of 34S from organo-34S enriched soil at early stages of growth when S requirement is high. Mycorrhizal treatments harbour larger popu

peer-reviewed, Sulfur (S) is an essential macronutrient that is increasingly limiting to crop yield as a result of reduced atmospheric deposition and high yielding crop varieties rapidly depleting soil S stocks. Plants obtain S from soil via their root networks, however, in soil up to 95% of S is organically bound as either sulfate esters or sulfonates which are not directly accessible. In this instance, plants rely on distinct functional soil microbial populations to mineralise the respective organo-S pool. Sulfonate mineralisation is catalysed solely by specific bacteria, while sulfate ester mineralisation is achieved by both bacteria and fungi. Arbuscular mycorrhizal (AM) fungi are ubiquitous soil microbes that have been shown to be very important for both nitrogen and phosphorus cycling, so intuitively they may play a role in the S cycle. AM fungi have many beneficial characteristics that would render them useful in organo-S mobilisation including improved nutrient exchange, extensive hyphal networks, modified rhizodeposition, and increased access to soil aggregates. The study set out to ascertain (i) the microbial diversity associated with AM hyphae in a native ecosystem and analyse their functionality, (ii) the effect of AM inoculation on plant growth and organo-S mobilising communities, and (iii) the interaction between AM fungi and bacteria to improve uptake of labelled organo-S. The results obtained demonstrate that (i) hyphospheric bacterial communities in native grassland swards are enriched in sulfonate mobilisers that can putatively attach to AM hyphae to explore the extended soil environment, (ii) AM inoculation promotes plant growth, significantly impacts bacterial community composition and abundance, and harbours distinct and abundant populations of sulfonate mobilising bacteria, and (iii) an undisturbed AM symbiosis increases uptake of 34S from organo-34S enriched soil at early stages of growth when S requirement is high. Mycorrhizal treatments harbour larger popu

peer-reviewed, Plant growth is highly dependent on bacteria, saprophytic, and mycorrhizal fungi which facilitate the cycling and mobilization of nutrients. Over 95% of the sulfur (S) in soil is present in an organic form. Sulfate-esters and sulfonates, the major forms of organo-S in soils, arise through deposition of biological material and are transformed through subsequent humification. Fungi and bacteria release S from sulfate-esters using sulfatases, however, release of S from sulfonates is catalyzed by a bacterial multi-component mono-oxygenase system. The asfA gene is used as a key marker in this desulfonation process to study sulfonatase activity in soil bacteria identified as Variovorax, Polaromonas, Acidovorax, and Rhodococcus. The rhizosphere is regarded as a hot spot for microbial activity and recent studies indicate that this is also the case for the mycorrhizosphere where bacteria may attach to the fungal hyphae capable of mobilizing organo-S. While current evidence is not showing sulfatase and sulfonatase activity in arbuscular mycorrhiza, their effect on the expression of plant host sulfate transporters is documented. A revision of the role of bacteria, fungi and the interactions between soil bacteria and mycorrhiza in plant S supply was conducted.