The behaviour of M.thermautotrophicus under suboptimal conditions is described and the need for further optimization to improve methane production yields is highlighted.
Abstract
Underground biomethanation represents a promising solution for green energy storage. An isolate of Methanothermobacter thermautotrophicus was obtained in previous study from an underground gas reservoir where it played a key role in a successful in-situ biomethanation experiment. In this study, the physiological and environmental tolerances of the strain are characterised. Optimal methane evolution rates were observed at 55-65 °C and pH 6.5-7.0, methane production was significantly increased by agitation (up to 2.29 mmol CH4·h-1·L-1). The strain showed higher tolerance to NH4Cl (up to 0.6 M) than to NaCl (optimal 0.04-0.4 M). The strain was also tested for its resistance to silver nanoparticles. The whole-genome sequence of the strain was determined, and the corrosion potential was evaluated. To visualise the cells, Scanning Electron Microscopy (SEM) and a method of Advanced Environmental Scanning Electron Microscopy (A-ESEM) were used. These findings describe the behaviour of M.thermautotrophicus under suboptimal conditions and highlight the need for further optimization to improve methane production yields.
Till to date, there is no report on isolation of microorganisms from the Mahiwal hot water spring in Balochistan, Pakistan. In the current manuscript, we report on isolation and morphological, biochemical and molecular characterization of a thermophilic microorganism from this hot water spring. The isolated bacterial strain, MAS2, is rod shaped with 1 µm width and 5 µm length. It forms cream-colored slimy colonies. The strain has the ability to grow in the presence of air between 40 and 75 °C with an optimum growth temperature and pH of 65 °C and 6.5, respectively. It can utilize various sugars, hydrocarbons and carboxylic acids as sole carbon source. No additional salt is required for its growth, though relatively higher yield was achieved with the addition of 0.5% NaCl. The strain MAS2 is capable of producing several important extracellular enzymes of industrial use including an amylase, a lipase, an oxidase and a protease. The 16S rRNA gene sequence of strain MAS2 exhibited high homology with various species belonging to genus Geobacillus. The highest homology of 98.66% was observed with Geobacillus kaustophilus. However, the biochemical characteristics of the strain were more similar to Geobacillus thermopakistaniensis and Geobacillus uzenensis. These results indicate that strain MAS2 represents an unidentified species belonging to genus Geobacillus.
Keywords: Thermophiles; 16S rRNA sequence: Geobacillus sp. MAS2; biochemical characterization; extracellular enzymes.
N. Taj, M. A. Siddiqui, Osama Ahmed Siddiqui et al.· The Journal of Animal and Pl...· 0 citations
Hydrothermal systems contain diverse alkanes derived from biological and geological processes, providing potential carbon and energy sources for microorganisms. However, cultivated thermophilic alkane-utilizing bacteria from hydrothermal environments remain poorly characterized. In this study, a strain L01 was isolated from a deep-sea hydrothermal vent and identified as an alkane-degrading bacterium. The strain L01 grew at 55 °C and pH 7.0 in medium supplemented with n-hexadecane under microoxic conditions. Cells were elongated rods approximately 10–20 μm long and ~0.2 μm wide. Phylogenetic analyses based on 16S rRNA gene sequence similarity (93.11% to the closest described relative), average amino acid identity (AAI, 66.27–66.58%), average nucleotide identity (ANI, 80.80–83.05%), and digital DNA-DNA hybridization (dDDH, 12.5–20.8%) demonstrated that strain L01 represents a previously unrecognized genus within the family Symbiobacteriaceae, for which the provisional name “Thermalkanevorax longiformis” is proposed. An isotope tracing experiment together with genomics and transcriptomics revealed coordinated physiological and metabolic responses associated with n-hexadecane utilization by strain L01. These findings provide a cultivated representative of the family Symbiobacteriaceae with physiological and metabolic responses to n-hexadecane, thereby providing a basis for further investigation of hydrocarbon metabolism.
Huilin Wen, Ge Liu, Chaomin Sun et al.· Microorganisms· 0 citations
Among the 20 isolates, one isolate was identified as Brevibacillus parabrevis PS12, representing the first report from Iraqi soil, which contributed to an increase in bacterial biomass which led to a rise in the specific activity of arginase.
Ayah Muwafaq Hussein, Aqeel Mohammed Majeed Al-Ezee, Zaid Raad Abbas· Journal of the College of B...· 0 citations
Polyhydroxyalkanoates (PHAs) are biodegradable microbial polyesters that may reduce dependence on petroleum-derived plastics, but broader use remains constrained by production costs and tightly controlled cultivation. Thermophilic microorganisms have attracted increasing attention as promising PHA producers because they can be cultivated at elevated temperatures, reducing contamination risks and operational costs. In this study, a thermophilic Geobacillus sp. strain SL28 isolated from a Vietnamese hot spring was evaluated for its PHA-producing capability. Temperature, initial pH, carbon and nitrogen sources, C/N ratio, and cultivation time were examined. Intracellular inclusions were assessed by Sudan Black B and Nile Blue A staining and transmission electron microscopy, whereas the recovered polymer was characterized by FE-SEM, Fourier-transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC–MS), 1H- and 13C-nuclear magnetic resonance (NMR) spectroscopy, capillary viscometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. Under the optimized cultivation conditions identified by one-factor experimentation (50 °C, pH 7.0, sucrose, peptone, C/N 25:1, and 72 h), SL28 reached a dry cell weight of 2.215 ± 0.16 g/L and a PHA concentration of 1.383 ± 0.04 g/L, equivalent to 62.57 ± 2.82% of DCW. Structural characterization confirmed that the recovered polymer was poly(3-hydroxybutyrate) (PHB). The purified PHB also exhibited favorable thermal stability, a relatively high molecular weight, and satisfactory mechanical properties. These results demonstrate the potential of thermophilic Geobacillus sp. SL28 as a promising candidate for PHB production.
D. Q. Nguyen, T. Do, N. Lai et al.· Processes· 0 citations
ABSTRACT Nitrous oxide (N2O) is a potent greenhouse gas and ozone-depleting substance, with a global warming potential 273 times greater than CO2 over a 100-year horizon. Microbial reduction of N2O to dinitrogen represents a key pathway for mitigating emissions under diverse environmental conditions. Here, we report the first comprehensive genomic and physiological characterization of Stutzerimonas frequens strain E49, a newly isolated N2O-reducing bacterium obtained from activated sludge treating landfill leachate. Whole-genome sequencing revealed a 4.51-Mbp circular chromosome and a 35.3-kbp plasmid with high completeness. Functional annotation identified a complete denitrification gene set, including nosZ, as well as the ectABCD-ask gene cluster associated with ectoine biosynthesis, suggesting adaptation to osmotic stress. Strain E49, a uniform rod-shaped bacterium (1.5–2.5 μm), efficiently reduced N2O under anaerobic conditions in the absence of an externally supplied organic carbon source, achieving a biomass-specific rate of 0.70 ± 0.02 µmol-N2O/mg-biomass/h and a cell-specific rate of 7.93 ± 0.23 × 10−10 µmol-N2O/cell/h. Among the cultivation regimens tested, nitrate-free DSMZ 1180 medium supplemented with NH4Cl yielded the highest activity, indicating medium-dependent regulation of N2O respiration. Comparative analysis showed that strain E49 outperformed several reported N2O-reducing isolates under carbon-limited conditions. These findings demonstrate the metabolic versatility of strain E49 and highlight its potential role as a biological sink for N2O in low-nutrient environments. IMPORTANCE Nitrous oxide is a powerful greenhouse gas that contributes to climate change and ozone depletion. Microorganisms that convert nitrous oxide into nitrogen gas play an essential role in reducing these emissions. In this study, we investigated Stutzerimonas frequens strain E49, a bacterium isolated from wastewater treatment sludge. We found that this organism can efficiently reduce nitrous oxide even without an external supply of organic carbon, which is typically required by most bacteria. This suggests that the bacterium can rely on internal energy reserves to carry out this process. We also identified the genetic basis for its nitrous oxide reduction and its ability to adapt to environmental stress. These findings improve our understanding of how nitrous oxide-reducing bacteria function in nutrient-limited environments and may support the development of strategies to mitigate emissions in wastewater treatment and other engineered systems. Nitrous oxide is a powerful greenhouse gas that contributes to climate change and ozone depletion. Microorganisms that convert nitrous oxide into nitrogen gas play an essential role in reducing these emissions. In this study, we investigated Stutzerimonas frequens strain E49, a bacterium isolated from wastewater treatment sludge. We found that this organism can efficiently reduce nitrous oxide even without an external supply of organic carbon, which is typically required by most bacteria. This suggests that the bacterium can rely on internal energy reserves to carry out this process. We also identified the genetic basis for its nitrous oxide reduction and its ability to adapt to environmental stress. These findings improve our understanding of how nitrous oxide-reducing bacteria function in nutrient-limited environments and may support the development of strategies to mitigate emissions in wastewater treatment and other engineered systems.
