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Inhabitants of extreme and polluted environments are attractive as candidates for environmental bioremediation. Bacteria growing in oil refinery effluents, tannery dumpsite soils, car wash effluents, salt pans and hot springs were screened for microcystin-LR biodegradation potentials. Using a colorimetric BIOLOG MT2 assay; Arthrobacter sp. B105, Arthrobacter junii, Plantibacter sp. PDD-56b-14, Acinetobacter sp. DUT-2, Salinivibrio sp. YH4, Bacillus sp., Bacillus thuringiensis and Lysinibacillus boronitolerans could grow in the presence of microcystin-LR at 1, 10 and 100 µg L−1. Most bacteria grew optimally at 10 µg L−1 microcystin-LR under alkaline pH (8 and 9). The ability of these bacteria to use MC-LR as a growth substrate depicts their ability to metabolize the toxin, which is equivalent to its degradation. Through PCR screening, these bacteria were shown to lack the mlr genes implying possible use of a unique microcystin-LR degradation pathway. The study highlights the wide environmental and taxonomic distribution of microcystin-LR degraders.

Long-term exposure to anthropogenic stressors can lead to perturbations in microbiomes, either selecting for novel and biotechnologically important biotypes, or reductions in the microbial diversity and disequilibrium of ecosystem services. Consequently, analysis of variations in microbial structure and function in stressful environments remains a critical issue in microbial ecology. In this study, the taxonomic structure of bacterial communities inhabiting tannery waste dumpsite soils was evaluated comparatively with those from non-contaminated soils using 16S rRNA gene sequencing. Furthermore, the metabolic potential of these communities was inferred from community level physiological profiling fingerprints. The dumpsite has been receiving tannery waste since 1982; hence, the soils are laden with heavy metals including chromium, zinc, sodium, and potassium. Consequently, the following significant differences between bacterial communities from contaminated and non-contaminated soils were observed: (1) bacterial communities from the contaminated soils were characterized by lower species diversity, albeit at comparable species evenness (Simpson index); (2) long term contamination of soil shifted the bacterial community structure to a distinct core microbiome dominated by bacterial groups such as Halomonas, Balneolaceae, Aliifodinibius, Serinicoccus, Gracilimonas, Marinobater, Penticoccus, Fordinicurvata, Dietzia, and Norcadioides. These are characteristic of saline, metal-laden environments and have potentially high organo-pollutant degradative properties; and (3) bacterial communities from the contaminated soils exhibited a robust metabolic potential utilizing both natural and anthropogenically derived polymers at a higher rate. Overall, these results highlight tannery waste dumpsite soils as microbial diversity hotspots and potential reservoirs for exploration of novel biotechnological tools for bioremediation and industrial applications.

Oil refinery effluents are among stressful environments, and they are characterized by alkaline pH, high concentrations of dissolved solids, electrical conductivity, and metals (mainly Fe, Al, B, Sr, Mn, Cu, Ni). In this study, bacterial diversity in these habitats was inferred from full-length 16S rRNA gene sequences obtained from the PacBio® sequencing platform. The results have shown low bacterial diversity in both raw and treated effluents, with sequences representing only two phyla: Firmicutes and Proteobacteria. Sequences from the raw effluents represent four major genera: Bacillus, Wenzhouxiangella, Rhodabaculum, and Halomonas. Whilst bacterial communities from the treated effluents are relatively more diverse as sequences represent five dominant genera: Pseudoxanthomonas, Brevundimonas, Pseudomonas, Rhodobaculum and Rhizobium. Most of the genera represented in the dataset are halophilic or halotolerant microbes known to have the competency to catabolize a broad spectrum of organic and inorganic pollutants. Hypothetically, these bacteria may be relevant for biotechnological and industrial applications, particularly for the remediation of saline industrial wastes.

The last decade has witnessed growth in scientific interest towards studying the biodiversity and ecology in extreme environments. Acid Mine Drainage (AMD), formed through the bio-oxidation of metal sulphides, is a typical extreme environment that is inhospitable to most life forms. Through the application of traditional culture-based molecular techniques, it has been established that AMD is home to a low diversity, specialized and novel microbial community that plays a critical role in its formation. Intensive efforts have been channeled towards understanding the ecology, microbial biodiversity, processes and metabolic networks within these simple ecosystems. Molecular techniques using high-throughput next-generation sequencing platforms have taken center stage in discerning both the taxonomic and functional diversity in these microbial communities. Recently developed post-genomic approaches as well have been particularly instrumental in deciphering in situ interactions within microbial communities and the environment. In this review, a critical synopsis of the current applications of advanced molecular techniques in probing microbial and functional diversity in AMD environments is presented.

Rapanea melanophloeos is traditionally used in South Africa in the treatment of ailments of the skin, pulmonary and gastro intestinal tract. This study was aimed at giving an overview of these traditional uses and comparing the phytochemicals and antibacterial activities of various crude extracts of the leaves, fruits and bark in order to validate these uses. The three plant parts were extracted using petroleum ether (PE), ethyl acetate (EtOAc), methanol (MeOH) and water. Various phytochemicals were compared using TLC, while alcohol precipitable solids (APS), non-polar terpenes and amino acids were analysed by GC-MS. Antibacterial activity was determined against three Gram-positive and three Gram-negative strains by microdilution assays. Caryophyllene oxides, α-cadinol and (−)-spathulenol were identified in the PE extracts. All nine essential amino acids were present in fruit extracts in significantly higher levels than in the leaves and bark; 255.1, 23.4 and 21.3 mg/g respectively. Most of the extracts showed good antibacterial activity, especially against the Gram-positive pathogens (MIC of ≤1 mg/mL), the EtOAc extracts exhibited the best activity with the fruit having an MIC values of 0.1 ± 0.2 mg/mL against Staphylococcus epidermidis and Enterococcus faecalis, 0.05 mg/mL against Bacillus cereus. Results from this study validate the ethnomedicinal uses of R. melanophloeos extracts for ailments of bacterial etiology. The plant had a rich supply of secondary metabolites, APS and amino acids and TLC and antibacterial activities of the extracts showed slight variations in chemical composition due to geographic distribution.

Oil refinery effluents are among stressful environments, and they are characterized by alkaline pH, high concentrations of dissolved solids, electrical conductivity, and metals (mainly Fe, Al, B, Sr, Mn, Cu, Ni). In this study, bacterial diversity in these habitats was inferred from full-length 16S rRNA gene sequences obtained from the PacBio

This study surveyed physicochemical properties and bacterial community structure of water and sediments from an acid mine drainage (AMD) dam in South Africa. High-throughput sequence analysis revealed low diversity bacterial communities affiliated within 8 dominant phyla; Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes, Nitrospirae, Proteobacteria, Saccharibacteria, and ca. TM6_(Dependentiae). Acidiphilium spp. which are common AMD inhabitants but rarely occur as dominant taxa, were the most abundant in both AMD water and sediments. Other groups making up the community are less common AMD inhabitants; Acidibacillus, Acidibacter, Acidobacterium, Acidothermus, Legionella, Metallibacterium, Mycobacterium, as well as elusive taxa (Saccharibacteria, ca. TM6_(Dependentiae) and ca. JG37-AG-4). Although most of the taxa are shared between sediment and water communities, alpha diversity indices indicate a higher species richness in the sediments. From canonical correspondence analysis, DOC, Mn, Cu, Cr, Al, Fe, Ca were identified as important determinants of community structure in water, compared to DOC, Ca, Cu, Fe, Zn, Mg, K, Mn, Al, sulfates, and nitrates in sediments. Predictive functional profiling recovered genes associated with bacterial growth and those related to survival and adaptation to the harsh environmental conditions. Overall, the study reports on a distinct AMD bacterial community and highlights sediments as microhabitats with higher species richness than water.