Tanneries are generating a significant amount of toxic chromium-containing sludges that severely threaten the soil ecosystem. Remediation of chromium from tannery sludge and contaminated soils using metal-resistant microbial diversity is receiving increasing global focus. The metagenomics technique is a potent tool for examining the biodiversity of soil microbial communities. The present study employed metagenomics techniques to decode and screen metagenomes to assess their diversity in chromium-contaminated soil. The 16S rDNA genes were amplified using versatile primers from the isolated total microbial DNA from the soil. The PCR amplicons were sequenced to evaluate the prokaryotic diversity and metagenomes were assessed. The finding of this study revealed that the ten most abundant dominant bacteria in soil samples were Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Cyanobacteria, Acidobacteria, and Archaea. Meanwhile, Nitrososphaerales exhibited the highest abundance in the control samples it accounts for 48% of microbial diversity used for contaminated soil remediation. This study provides an in-depth analysis of microbial composition and metagenomics for bioremediation of metal contamination soil. It suggests that metagenomes can effectively degrade chromium from the environment. However, more research is needed to investigate the potential of Acidobacteria and other microbes, focusing on their resistance and transformation abilities to combat heavy metal contamination.

The chemical composition and microbial diversity influence the safety, quality and utility of digestate. This study investigated the minimum temperature and time for conversion of digestate to a safe biofertilizer. Digestate, a byproduct of anaerobic digestion was treated at various temperatures, 28 ± 2, 55, 60, 70 and 80 °C at varying durations, 0, 20, 30, 40 and 60 minutes. The potential for rhizobacteria was examined and essentially, at 70 °C and 40 min bacterial counts were 8.05 ± 0.71 × 102 cfu/ml and less than the 1000 cfu/ml permissible limits. At this temperature and time, there were no recorded counts of Salmonella or Escherichiae. Identified species were Pseudomonas sp, Proteus spp., Enterobacter sp., Escherichia coli, Citrobacter sp., Klebsiella sp, Enterococcus sp., Streptococcus sp., Bacillus sp., Yersinia sp., Salmonella sp and Shigella sp. Physicochemical result suggests that digestate processed at 70 °C and 40 mins possess pH, total nitrogen, nitrate and total phosphorus within defined standards while heavy metal concentration was below permissible limits. The rhizobacterial screening showed that Pseudomonas sp., Proteus sp., Bacillus sp. and Streptococcus sp. tested positive for phosphate solubilization, nitrogen fixation, ammonia production and induction of indole acetic acid. Overall, digestate may be successfully deployed as a safe biofertilizer when treated at suitable temperature and time for enhance plant growth.

Seepage control in unlined channels is critical for efficient water resource management, as excessive water loss through channel beds and walls leads to inefficiencies. Microbial-induced calcite precipitation (MICP) offers a promising solution to enhance soil stability and reduce seepage in cohesionless soils. This study investigates the application of MICP using Bacillus subtilis to mitigate water leakage in sandy soils through controlled experiments. A bacterial solution was introduced into soil samples, followed by urea and calcium chloride solutions, facilitating calcite precipitation and bioclogging. pH monitoring and calcium carbonate quantification confirmed the process. Results showed a 26% increase in calcium carbonate content in treated soil, significantly reducing permeability from 6.8 × 10−3 to 1.11 × 10−3 cm/s, as measured by a flexible wall permeameter. Soil strength increased from 234 to 1407 kPa, determined by triaxial compression tests. Validation was achieved using XRD, EDS, and SEM analyses. An interdisciplinary co-occurrence network graph from Scopus data highlighted key concepts like calcium carbonate, calcite precipitation, B. subtilis, bioclogging, and soil stabilization. MICP aligns with several UN Sustainable Development Goals (SDGs), notably SDG 6 by enhancing water retention, SDG 9 by promoting sustainable construction, and SDG 13 by improving soil stability against climate-related hazards. Thus, MICP is a sustainable and effective method for constructing impermeable channels, offering significant water management benefits.

The Northern Indian Ocean (NIO) is one of the most characteristic regions of the world oceans with diverse oceanographic features. Understanding of the microbial community structure in these unique habitats has rapidly increased in the last decade, especially with the advent of molecular tools and the application of NGS technologies. Studies on marine microbial ecology in the NIO regions, from the pre-genomics era relied on culture techniques, microscopic observations, qualitative plate assays and biochemical tests. Molecular techniques and 16S rRNA gene sequencing introduced after the late 1990s significantly enhanced the understanding of bacterial diversity. These molecular tools revealed the presence of bacterial phyla and provided insights into their functional characteristics. Recent, NGS-based metagenomic studies further expanded the understanding of bacterial community structures, especially in the oxygen minimum zones and deep-sea sediments. These tools have identified bacterial taxa in-depth, revealing the existence of numerous Candidatus taxa known only by their genomic makeup. Despite these advancements, a large part of the bacterial diversity from the NIO remains unexplored, with many unanswered questions related to microbial carbon pump. Further transcriptome based studies can greatly improve the understanding of the microbial processes in the NIO, which is a dynamic, oceanographic habitat.

The main causes of this environmental catastrophe are pollutants such as iron, zinc, lead, nickel, and chromium that have entered the water system as a result of uncontrolled industrial effluent discharge in the area. This study finds resistant bacteria and shows the toxicity of heavy metals in industrial effluent near the steel industry. Five separate locations were used for water sampling, and 16s RNA sequencing of the microorganisms that were found was done along with physicochemical parameter analysis and atomic absorption spectrophotometer use. Different water samples’ conductivity, TDS, salinity, DO, turbidity, and pH levels indicate changes in the quality of the water. In addition to having higher values for each of these characteristics, Sample D3’s water samples had greater concentrations of heavy metals, suggesting contamination. Aspergillus niger and Aspergillus terreus were identified in all samples. Both Gram-negative and Gram-positive Bacilli’s resistance to heavy metals has been found to be a sign of microbial adaptation to exposure to heavy metals. 16s rRNA sequencing of microorganisms revealed their roles in heavy metal bioremediation processes. The delicate balance between the flora and fauna in the affected water bodies has been upset by the devastating losses in aquatic life. In this study, we presented the biological methods for eliminating heavy metals, which comprised both metabolically dependent and independent techniques.

The high sulfur content in North-East Indian coal is one of the primary challenges with using it as an energy source. Therefore, the present study uses Burkholderia sp. GR 8-02 to explore coal beneficiation from the Tipong mine (T20 and T60) in Assam (North-East India). Various particle size fractions (−125 to +210 µm, −210 to +250 µm, −250 to +297 µm, −297 to +400 µm and −400 to +500 µm) were treated and subjected to petrographic and chemical analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), Thermogravimetric analysis (TGA), and Raman spectral analysis. The results revealed a 39.04% and 32.43% reduction in total sulfur for T20 and T60 samples, respectively. The ash content decreased by 19.79% in the T20 coal sample and by 24.52% in the T60 coal samples, with a relative decrease in the mineral matter content of approximately 17.43%. Following beneficiation with Burkholderia sp. GR 8-02, the −125 to +250 µm coal fraction exhibited maximum ash removal. The T20 sample useful heating value increased from 8116 to 8203 kcal/kg and the T60 sample from 8060 to 8210 kcal/kg. X-ray diffraction and FTIR patterns showed mineral phases like quartz, kaolinite, and pyrite. The FTIR spectra indicated altered C-S, SO2, and C=O bonds. The thermal profile showed a 12.54% mass loss difference between untreated and treated coal samples, suggesting lower thermal stability post-treatment without affecting the useful heating value (UHV). The treated coal’s surface leaching and morphological structure changes were investigated using Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) images. Raman analysis revealed increased carbon crystallinity and molecular structure in treated coal. This study offers an environmentally friendly and efficient approach to clean coal production.

Mineral weathering played a critical role in removing highly concentrated carbon dioxide (CO2) from the Precambrian atmosphere. Currently, it plays an important role in biogeochemical cycles and soil formation in terrestrial ecosystems. We aimed to fix CO2 by crystallizing carbonated minerals obtained from weathered rocks into calcium carbonate (CaCO3). In this study, we isolated a new Enterobacter bacteria (UT18) species from soil containing many rocks and plants by comparing the ability of the isolated bacteria to decrease pH. In combination with the results of high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), we demonstrated that UT18 participates in mineral weathering by secreting gluconic acid and acetic acid. These organic acids can release Ca, Al, and Si from anorthite. Traces of weathering on the anorthite surface were observed using scanning electron microscopy (SEM). The released Ca ions can be recrystallized by the addition of Na2CO3 into the formation of CaCO3 in the form of aragonite. Our study describes a new characteristic of acid production in UT18 and demonstrates an example of an H+-releasing pattern in microbial mineral weathering. This study will help elucidate the mechanism of microbial mineral weathering and can be applied to soil improvement and greenhouse effect mitigation.

The most varied ecosystem on Earth has been the subject of study for soil scientists and microbiologists for more than three centuries. Using a wide range of methods, they have characterized the composition, structure, and function of the soil microbial community. However, model systems and isolated organisms continue to be the main sources of our knowledge regarding the soil microbiome and the reciprocal dynamics with metal speciation and bioavailability. On the other hand, metals are vital to life processes and are widely present in agriculture and the environment. This chapter’s goal is to highlight the current gaps in metal-microbiome research by reviewing our current understanding of the soil factors that control metal bioavailability and combining it with our understanding of the dynamics of metals and metalloids with microbial communities in soil. In the end, only a complete knowledge of the interactions between soil microbiome and the soil, plant communities that they are associated with, and the molecular mechanisms underlying their biogeochemical function will allow for the restoration of ecosystem function, improved soil health and quality, and any kind of management for microbial metal transformations.

Halophilic microorganisms play a crucial role in plant health and growth in salinity affected lands. The objective of this study was to evaluate the haloarchaeal diversity from the rhizosphere of halophytes and plant growth promoting abilities of these strains. The whole genome sequences of two haloarchaeal strains, Halorubrum lacusprofundi HL1RP11 and Halobacterium noricense NRS2HaP9, were analyzed, and genes related to plant growth promoting traits were identified. Phylogenetic analysis showed that archaeal strains of Halococcus, Halorubrum, Halobacterium and Natrinema were dominant in the rhizosphere of halophytes. More than 60% of the strains were positive for phosphate solubilization and IAA production. About 33% were siderophore producers. More than 40% of haloarchaeal strains showed the heavy metal resistance for Nickel, Cadmium, Chromium and Zinc at a concentration of 5 mM. Genes involved in plant growth promotion were identified through annotation. Gene clusters related to secondary metabolites including phenazine, siderophore production and terpene were also identified in this study. Our results suggested that these haloarchaeal strains can be used as an eco-friendly biofertilizer to improve growth and productivity in hypersaline environment.

In order to transform hazardous substances into their less harmful or nontoxic constituent elements, microorganisms are used in the remediation process known as “bioremediation.” Any biological process that uses microorganisms such as fungi, algae, yeast, bacteria, or green plants, or the enzymes produced by the microorganisms, can restore the natural environment altered by heavy metal pollutants. Among the heavy metals, hexavalent chromium (Cr (VI)) is the most toxic pollutant in the environment. Several human activities are responsible for its release into the environment. The chemical, physical, and biological characteristics have a positive influence on the dissolution within the aqueous medium. Exposure to Cr (VI) may have an influence on both human health and the flora and fauna of the environment. Because of its mutagenic and carcinogenic properties, chromium (VI) is a much more hazardous substance than other chromium species, such as Cr (V) and Cr (III). Dermatitis, asthma, pneumonitis, and bronchiogenic cancer are all possible outcomes of chronic Cr (VI) exposure. The effective management of Cr (VI) to address concerns about public health is absolutely essential from an environmental point of view. This study focuses on the toxicity of chromium and its interactions with various strains of microbes, specifically examining how they might bio-reduce Cr (VI).