Biostabilization of Gold Mine Tailings: Co-Inoculation of Cyanobacteria Under Sterile and Non-Sterile Conditions

Cyanobacterial crust formation has attracted attention for stabilizing erosion-susceptible soils in desert regions. However, limited information exists on its application in waste impoundments such as mine tailings. Identifying suitable inoculants with the ability to develop biocrusts in the more toxic conditions of mine tailings represents a challenge for exploiting this biotechnology for such applications. In this study, the performance of two nitrogen-fixing cyanobacteria (Anabaena sp. and Nostoc muscorum), individually and as a consortium, in creating biocrusts over gold mine tailings were investigated under sterile and non-sterile conditions. The results showed that Anabaena sp. and the co-inoculation of the species promoted higher synthesis of chlorophyll-a and total EPS compared to N. muscorum. The inoculated strains also exhibited different responses in the amount of the EPS fractions. The less soluble and more condensed tightly bound EPS represented a higher fraction of total EPS with co-inoculation and N. muscorum. With respect to wind erosion resistance and compressive strength of the biocrusts generated, co-inoculation showed better performance, followed by N. muscorum, while Anabaena sp. appeared to be less effective. The presence of indigenous microbial community within the tailings influenced the biostabilization performance of Anabaena sp., while the influence was insignificant under co-inoculation and N. muscorum. Overall, inoculating the cyanobacteria in a mixture with complementary traits (higher chlorophyll-a synthesis and total EPS secretion of Anabaena sp. vs. higher TB-EPS fraction and filamentous growth of N. muscorum) presented an effective strategy in the development of a resistant biocrust against wind erosion. With this inoculation strategy, the beneficial effects of the individual strains on biocrust formation could be combined, thus a comparatively stronger structure could be formed. Besides chlorophyll-a content, factors such as cyanobacteria morphology and EPS fractions would contribute to the biostabilization process. The results also suggested that sterilization of the tailings would influence the performance of cyanobacteria depending on the inoculant. Thus, the response of inoculants to other microbial communities should be considered prior to field-scale application.

Identification and Profiling of Microbial Community from Industrial Sludge

This study aims to identify microbial communities and their taxonomical profiling basis of order, species, genus, family, and class at the level in the sludge of pulp and paper industry. Studies showed dominant phyla in 16S rDNA Illumina Miseq analysis inside sludge were Anaerolinea, Pseudomonas, Clostridia, Bacteriodia, Gammaproteobacteria, Spirochetia, Deltaproteobacteria, Spirochaetaceae, Prolixibacteraceae and some unknown microbial strains are also dominant. The results of metabarcoding of the V3-V4 16S rRNA regions acquired from paired-end Illumina MiSeq sequencing were used to analyze bacterial communities and structure. Microorganisms can produce a vast variety of secondary metabolites, all of which are playing a crucial in biogeochemical cycle processes. The present work demonstrates the potential approach to sludge treatment in the open environment via the naturally adapted microorganism, which could be an essential addition to the disposal site. In summary, these investigations indicate that the indigenous microbial community is an acceptable bioresource for remediation or detoxification following secondary treatment. This research aims at understanding the structure of microbial communities and their taxonomic diversity (%) in highly contaminated sludge to perform in-situ bioremediation.

The Impacts of Different Biological Treatments on the Transformation of Explosives Waste Contaminated Sludge

The dinitrotoluene isomers 2,4 and 2,6-dinitrotoluene (DNT) represent highly toxic, mutagenic, and carcinogenic compounds used in explosive manufacturing and in commercial production of polyurethane foam. Bioremediation, the use of microbes to degrade residual DNT in industry wastewaters, represents a promising, low cost and environmentally friendly alternative technology to landfilling. In the present study, the effect of different bioremediation strategies on the degradation of DNT in a microcosm-based study was evaluated. Biostimulation of the indigenous microbial community with sulphur phosphate (2.3 g/kg sludge) enhanced DNT transformation (82% transformation, from 300 g/L at Day 0 to 55 g/L in week 6) compared to natural attenuation over the same period at 25 °C. The indigenous microbial activity was found to be capable of transforming the contaminant, with around 70% transformation of DNT occurring over the microcosm study. 16S rDNA sequence analysis revealed that while the original bacterial community was dominated by Gammaproteobacteria (30%), the addition of sulphur phosphate significantly increased the abundance of Betaproteobacteria by the end of the biostimulation treatment, with the bacterial community dominated by Burkholderia (46%) followed by Rhodanobacter, Acidovorax and Pseudomonas. In summary, the results suggest biostimulation as a treatment choice for the remediation of dinitrotoluenes and explosives waste.

Impacts of NO2 Impurities on the Indigenous Microbial Community Structure and Diversity in CO2-Saline-Sandstone Interaction System

Laboratory experiments (150 days) were performed to analyze the influence of NO2 impurities on indigenous microbial communities and diversity with 16S rRNA sequence at real GCS site (Geological CO2 Sequestration, ordos, China) conditions (pressure: 15 MPa, temperature: 55 °C). The possible impact of metabolic activity on the GCS process was investigated through the BLASTn search. Compared with the pure CO2, results demonstrate that the biomass and biodiversity were lower, due to the lower pH, within 60 days after the co-injection of 0.1% NO2. Subsequently, the pH was quickly buffered through the corrosion of feldspar and clay, and the impact of NO2 had almost no obvious effect on the microbial structure except the abundance of phylum and genus after 90 days. In addition, acid-producing bacteria appeared after 60 days, such as Bacillus, Acinetobacter, and Lactococcus, etc., lower the pH in the solution and accelerate the dissolution of minerals. The Fe (III)-reducing microbes Citrobacter freundii reduce the Fe (III) released from minerals to Fe (II) and induce siderite (FeCO3) biomineralization through biogeochemical processes. Therefore, the co-injection of trace NO2 will not significantly affect the growth of microorganisms on long timescale.

Environmental Risk Assessment of Living Modified Microorganisms (LMM) on the Indigenous Microbial Community

Recent advance of biotechnology enabled development of various living modified microorganisms (LMMs) uses in the field of environmental remediation, food industry, biopesticide, and so on. Consequently, such LMMs have the potential to be released into the natural environment, either intentionally or unintentionally, or exposed to the natural ecosystem during the applications. To investigate the unintended effects of LMMs on soil microorganism populations and communities, microcosm study was conducted using the recombinant microorganism, Corynebacterium glutamicum SEM002 carrying the D-psicose-3-epimerase from Agrobacterium tumefaciens as a model LMM. In addition, potential gene transfer from the LMMs into the soil environment in the microcosm was examined. As a result, small differences in LMMs were observed in populations of soil microorganism such as total bacteria, kanamycin-resistant bacteria, total fungi and total actinomycete. Also, more than 93% of the kanamycin resistance gene from the LMMs was degraded in the microcosm during the 90 days. On the basis of the experimental results, the LMMs showed no distinct impact on soil microorganism populations and communities.

Actinomycoses

Human actinomycoses are always synergistic polymicrobial infections in which fermentative actinomycetes—predominantly Actinomyces israelii, A. gerencseriae, or Propionibacterium propionicum—are the principal pathogens, usually needing the assistance of so-called concomitant microbes to produce disease. Nearly all of the members of the mixed actinomycotic microflora belong to the indigenous microbial community of human mucous membranes, hence actinomycoses present as sporadic endogenous infections which are not transmissible. Antibacterial drugs used for treatment should be active against both the causative actinomycetes and all concomitant bacteria. For cervicofacial actinomycoses, the rare cutaneous processes, and most thoracic forms of the disease, this requirement is best fulfilled by amoxicillin plus clavulanic acid in medium to high doses. The prognosis of cervicofacial and cutaneous actinomycoses is good provided that treatment is adequate; thoracic and abdominal forms are more serious, with grave prognosis without proper treatment.

Genome Analyses and Genome-Centered Metatranscriptomics of Methanothermobacter wolfeii Strain SIV6, Isolated from a Thermophilic Production-Scale Biogas Fermenter

In the thermophilic biogas-producing microbial community, the genus Methanothermobacter was previously described to be frequently abundant. The aim of this study was to establish and analyze the genome sequence of the archaeal strain Methanothermobacter wolfeii SIV6 originating from a thermophilic industrial-scale biogas fermenter and compare it to related reference genomes. The circular chromosome has a size of 1,686,891 bases, featuring a GC content of 48.89%. Comparative analyses considering three completely sequenced Methanothermobacter strains revealed a core genome of 1494 coding sequences and 16 strain specific genes for M. wolfeii SIV6, which include glycosyltransferases and CRISPR/cas associated genes. Moreover, M. wolfeii SIV6 harbors all genes for the hydrogenotrophic methanogenesis pathway and genome-centered metatranscriptomics indicates the high metabolic activity of this strain, with 25.18% of all transcripts per million (TPM) belong to the hydrogenotrophic methanogenesis pathway and 18.02% of these TPM exclusively belonging to the mcr operon. This operon encodes the different subunits of the enzyme methyl-coenzyme M reductase (EC: 2.8.4.1), which catalyzes the final and rate-limiting step during methanogenesis. Finally, fragment recruitment of metagenomic reads from the thermophilic biogas fermenter on the SIV6 genome showed that the strain is abundant (1.2%) within the indigenous microbial community. Detailed analysis of the archaeal isolate M. wolfeii SIV6 indicates its role and function within the microbial community of the thermophilic biogas fermenter, towards a better understanding of the biogas production process and a microbial-based management of this complex process.