Search

Soil management practices such as organic matter input can ameliorate soil health, including microbial com munities that are crucial for ecological processes. In this study, the effect of successive application of cattle dung and/or dung beetle on the diversity and ecological guild of topsoil fungal assemblages on a post-coal mining reclaimed site was investigated. Three experimental treatments namely: dung plus dung beetles (dung + beetle), dung only (dung-only), and no dung, no dung beetle (control) was established on 4-m2 subplots on a ≥16-year old post-coal mining reclamation area. Following a 17-month experimental period, topsoil fungal assemblage was determined using next-generation sequencing of fungal ribosomal internally transcribed spacer 2 region. The highest operational taxonomic unit (OTU) richness and Shannon-Wiener diversity were obtained in the dung only treatment while the lowest OTU richness and diversity was obtained in control treatment. Although not statistically significant, a trend towards lower OTU richness in the topsoil was observed with the addition of dung beetle compared to the only dung treatment. In multivariate space, fungal communities were differentiated between dung-only and control, suggesting the influence of dung addition. Overall, dung addition primarily improved topsoil fungal diversity and the abundance of beneficial plant-fungal symbionts important for nutrient mobilisation in the soil, with a trend towards lower diversity observed with dung beetle addition suggesting possible vertical displacement of organic matter and ecologically relevant fungal species to deeper soil depths

Anthropogenic disturbances of soil environments predispose loss of soil ecosystem functions, including its habitat support function. In this study, the potential ecosystem support and habitat functions of soils from stockpiles and post-mining reclamation areas (ranging from 3 to 25 years) in two coal mining sites were assessed using Eisenia andrei bioassays. Endpoints such as avoidance response, mortality, relative growth rate and fecundity were determined. By taking into cognisance the ages of the reclamation areas, inference was drawn on the potential restoration of ecosystem support functions over the years since reclamation. Mortality and fecundity of earthworms did not suggest limited support functions of control and test soils. Net avoidance response (AR) indicated significant differences (P < 0.05) among treatments with only the net AR in a 3-year old reclaimed soil >80%. Earthworms generally preferred (P < 0.05) undisturbed (“reference”) soils to OECD and test soils. Furthermore, trends in AR suggested a negative effect (P < 0.05) of anthropogenic disturbance and a general improvement of soil habitat function in older reclaimed areas. Of all endpoints, the avoidance test was the most sensitive, which generally reflected the differences in soil physicochemical properties among test soils. Although high intra-site variations in soil properties suggest lack of strict adherence to best reclamation practices, coal mining soil environments are not ecologically derelict with regards to supporting biocoenosis

Soil microbial communities are suitable soil ecosystem health indicators due to their sensitivity to management practices and role in soil ecosystem processes. Presently, information on structural and functional differentiation of bacterial communities in post-coal mining reclamation soils of South Africa is sparse. Here, bacterial communities in three post-coal mining reclamation soils were investigated using community-level physiological profiling (CLPP), enzyme activities, and next-generation sequencing of 16S rRNA gene. Inferences were drawn in reference to adjacent unmined soils. CLPP-based species diversity and proportionality did not differ significantly (P > 0.05) whereas activities of β-glucosidase, urease and phosphatases were significantly (P < 0.05) influenced by site and soil history (reclaimed vs unmined). Bacterial communities were influenced (PERMANOVA, P < 0.05) by soil history and site differences, with several phylotypes differentially abundant between soils. Contrastingly, predicted functional capabilities of bacterial communities were not different (PERMANOVA, P > 0.05), suggesting redundancy in bacterial community functions between reclamation and unmined soils. Silt content, bulk density, pH, electrical conductivity, Na and Ca significantly influenced soil bacterial communities. Overall, results indicate that bacterial community structure reflects underlying differences between soil ecosystems, and suggest the restoration of bacterial diversity and functions over chronological age in reclamation soils

The adaptation of Zulu (Nguni) sheep (Ovis aries) to environmental stress and survival under extensive conditions makes them uniquely important to rural Nguni farmers of South Africa. Here, the faecal bacterial community of five Zulu sheep populations managed under extensive conditions across summer and winter seasons was investigated in order to understand the influence of prevailing seasonal factors. Bacterial operational taxonomic units (OTUs)/species (at 97% 16S rRNA gene similarity) in Zulu sheep faeces were more diverse in winter than in summer at most (80%) sites and varied between seasons at specific sites. Firmicutes was the most abundant phyla in both summer and winter seasons, while the relative abundance of Actinobacteria reduced in 80% of sites from summer to winter. The genera (or family) such as Akkermansia, Eubacterium coprostanoligenes group, Intestinibacter, R-7 group (family Christensenellaceae), Ruminococcus, Ruminoclostridium, Treponema and UCG-005 (family Ruminococcaceae) were relatively more abundant and belonged to a ‘core microbiome’ of Zulu sheep faeces. Between seasons, Acinetobacter, Jeotgalicoccus, Methanobrevibacter, Phascolarctobacterium and Planomicrobium were differentially abundant. Overall, results suggest increased richness and diversity of bacteria from summer to winter which may be related to spatio-seasonal variations in grazing management, forage types and availability. This observation serves as baseline evidence, justifying further controlled studies investigating, amongst other factors, effects of forage type and availability across seasons on ruminal microbiota of Zulu sheep grazing in communally managed rangelands

Arbuscular mycorrhizal (AM) fungi contribute to the restoration of soil ecological functions and processes during ecosystem development. Here, diversity and differentiation of AM fungi in rhizosphere soils and roots of the dominant vegetation along a post-coal mining reclamation soil chronosequence of 3, 11, 15, 19 and 24 years after reclamation were investigated. High-throughput sequence analysis of partial Glomeromycotan 18S rRNA in soils and roots revealed a high number of core operational taxonomic units (OTUs) across chronosequence. Arbuscular mycorrhizal fungal (AMF) OTU richness, Shannon-Weiner index and species dominance were not significantly different across soil and root but were significantly (P < 0.05) correlated with ammonium, nitrate, silt fraction, litter, pH, foliar and/or basal covers. AMF community structure was significantly different (P < 0.05) across unmined and reclamation chronosequence soils, with differentiation between younger reclaimed areas (3 and 11 years) and older reclamation ages (19 and 24 years) in multivariate space. In contrast, structural differentiation in the AMF community colonising the single plant-host across the chronosequence was not significant (PERMANOVA, P > 0.05), although community composition and structure were heterogeneous within 3–11 years but similar within 15–24 years. Seven Glomeromycotan genera were detected in soil and roots, including the relatively dominant Glomus genus, and the differentially abundant Acaulospora, Diversispora, Paraglomus and Scutellospora in either earlier or later years since post-mining reclamation. Canonical correspondence analysis revealed that nitrates (NO3-N), clay content and bulk density significantly influenced (P < 0.05) the AMF community structure in soil, whereas, the AMF community in root was not significantly influenced (P > 0.05) by environmental variables. Overall, the study suggests that AMF community differentiation reflect ecosystem development over chronological space

Biofuel research and development roadmap is currently underway in several countries and is expected to pave a way for the establishment of a viable renewable energy sector that can compete with petroleum-based fuels. Ethanol fermentation has garnered increasing attention amongst various stakeholders (industries, governments, and academia) due to its economic and environmental merits. However, microbial contamination continues to be one of the major barriers in ethanologenic processes, resulting in low ethanol yields and thereby translating into economic losses. To this end, technological innovations geared towards effective elimination of microbial contamination are constantly being developed. This review explores and discusses the fermentation conditions that facilitate the growth of undesired microorganisms during ethanol fermentation processes. It highlights the methods that are currently used in biorefineries as well as innovative and advanced biotechnological methods currently being evaluated as viable alternative strategies to control or eliminate microbial contaminants in ethanol fermentations. These methods have the potential to minimize or control the contamination problem and could pave a way for the development of an efficient biofuel sector

At present, there is no comprehensive soil quality assessment practice for soil stockpiles in the South African coal mining industry. Soil microorganisms and enzymes are suitable indicators for soil quality monitoring. Therefore, this study investigated the microbial community and enzyme (beta-glucosidase and urease) activities in soil stockpiles of opencast coal mines in the coal-rich region of South Africa. Soil stockpiles of three opencast coal mines were sampled at depths of 0–20 cm (‘topsoil’) and >20 cm (‘subsoil’) across three seasons. Beta-glucosidase and urease activities were mostly higher in soil stockpiles than in unmined soils and were significantly influenced (P < 0.05) by the interaction of site and seasonal factors. However, analyses of PCR-denaturing gradient gel electrophoresis (PCR-DGGE) profiles of partial 16S rRNA gene and internally transcribed spacer 2 (ITS2) sequences revealed higher microbial diversity in unmined (reference) soils compared to soil stockpiles across all seasons. Redundancy analysis further revealed that microbial communities of topsoil were not significantly (P > 0.05) influenced by soil properties, whereas microbial communities of subsoils were significantly (P < 0.05) influenced by pH, organic carbon, total nitrogen and phosphorus contents. Furthermore, operational taxonomic units (OTUs) belonging to genera of known phytobeneficial species such as Azomonas, Aureobasidium, Phialocephala, Phoma and Sordariomycetes were detected in these soils. Overall, results suggest that the microbial community structure and diversity observed in stockpiles is impaired (compared to the unmined site), although variations in the microbial community structure of soil stockpiles across seasons are site-specific. The impaired microbial community of stockpiles may have negative implications on soil biological processes driven by microbes; especially those that are critical for nutrient cycling and ecosystem sustainability. More importantly, such