Genome sequence of the anaerobic bacterium Bacillus sp. strain ZYK, a selenite and nitrate reducer from paddy soil

Selenium volatilization in plants, microalgae, and microorganisms

The augmented prevalence of Se (Se) pollution can be attributed to various human activities, such as mining, coal combustion, oil extraction and refining, and agricultural irrigation. Although Se is vital for animals, humans, and microorganisms, excessive concentrations of this element can give rise to potential hazards. Consequently, numerous approaches have been devised to mitigate Se pollution, encompassing physicochemical techniques and bioremediation. The recognition of Se volatilization as a potential strategy for mitigating Se pollution in contaminated environments is underscored in this review. This study delves into the volatilization mechanisms in various organisms, including plants, microalgae, and microorganisms. By assessing the efficacy of Se removal and identifying the rate-limiting steps associated with volatilization, this paper provides insightful recommendations for Se mitigation. Constructed wetlands are a cost-effective and environmentally friendly alternative in the treatment of Se volatilization. The fate, behavior, bioavailability, and toxicity of Se within complex environmental systems are comprehensively reviewed. This knowledge forms the basis for developing management plans that aimed at mitigating Se contamination in wetlands and protecting the associated ecosystems.

Microbial reduction and resistance to selenium: Mechanisms, applications and prospects

Selenium is an essential trace element for humans, animals and microorganisms. Microbial transformations, in particular, selenium dissimilatory reduction and bioremediation applications have received increasing attention in recent years. This review focuses on multiple Se-reducing pathways under anaerobic and aerobic conditions, and the phylogenetic clustering of selenium reducing enzymes that are involved in these processes. It is emphasized that a selenium reductase may have more than one metabolic function, meanwhile, there are several Se(VI) and/or Se(IV) reduction pathways in a bacterial strain. It is noted that Se(IV)-reducing efficiency is inconsistent with Se(IV) resistance in bacteria. Moreover, we discussed the links of selenium transformations to biogeochemical cycling of other elements, roles of Se-reducing bacteria in soil, plant and digestion system, and the possibility of using functional genes involved in Se transformation as biomarker in different environments. In addition, we point out the gaps and perspectives both on Se transformation mechanisms and applications in terms of bioremediation, Se fortification or dietary supplementation.

Characterization and Potential Applications of a Selenium Nanoparticle Producing and Nitrate Reducing Bacterium Bacillus oryziterrae sp. nov

A novel nitrate- and selenite reducing bacterium strain ZYK^T was isolated from a rice paddy soil in Dehong, Yunnan, China. Strain ZYK^T is a facultative anaerobe and grows in up to 150, 000 ppm O₂. The comparative genomics analysis of strain ZYK^T implies that it shares more orthologues with B. subtilis subsp. subtilis NCIB 3610^T (ANIm values, 85.4–86.7%) than with B. azotoformans NBRC 15712^T (ANIm values, 84.4–84.7%), although B. azotoformans NBRC 15712^T (96.3% 16S rRNA gene sequence similarity) is the closest Bacillus species according to 16S rRNA gene comparison. The major cellular fatty acids of strain ZYK^T were iso-C_14:0 (17.8%), iso-C_15:0 (17.8%), and C_16:0 (32.0%). The polar lipid profile consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminophospholipid. Based on physiological, biochemical and genotypic properties, the strain was considered to represent a novel species of the genus Bacillus, for which the name Bacillus oryziterrae sp. nov. is proposed. The type strain is ZYK^T (=DSM 26460^T =CGMCC 1.5179^T). Strain ZYK^T can reduce nitrate to nitrite and ammonium and possesses metabolic genes for nitrate reduction including nar, nap and nrf. Biogenic selenium nanoparticles of strain ZYK^T show a narrow size distribution and agree with the gaussian distribution. These selenium nanoparticles show significant dose-dependent inhibition of the lung cancer cell line H157, which suggests potential for application in cancer therapy.

Evidence for the biogenic origin of manganese-enriched layers in Lake Superior sediments

Manganese (Mn) and iron (Fe)-enriched sediment layers were discovered in Lake Superior within, above and below the oxic-anoxic interface. While the role of bacteria in redox reactions with Mn is known to be significant, little information exists about indigenous microbial communities in many freshwater environments. This study examined the bacterial communities of Mn-enriched layers in Lake Superior to identify the potential Mn(II) oxidizers responsible for the formation of Mn oxides. Anaerobic Mn(II) oxidation occurring in the Mn-enriched layers at the oxic-anoxic interface was investigated using Mn(II)-enriched cultures. High-resolution microscopic and spectroscopic investigations provided evidence of the biogenic formation of Mn oxides on cell surfaces. Spectroscopic mapping confirmed high levels of Mn in structures resembling biogenic Mn oxides. These structures were observed in enrichment cultures and in Mn-enriched layer sediment samples, indicating the significance of biogenic Mn oxidation occurring in situ. 16S ribosomal DNA pyrosequencing was used to identify the bacteria potentially responsible for Mnoxide formation in the enrichment cultures and Mn-enriched layers, revealing that the Mn-enriched layer contains classes with known Mn(II)-oxidizing members. Pyrosequencing of bacterial cultures suggested that these bacteria may be Bacillus strains, and that anaerobic microbial-mediated Mn(II) oxidation contributes to the formation of the layers.

Draft genome sequence of Bacillus azotoformans MEV2011, a (Co-) denitrifying strain unable to grow with oxygen

Bacillus azotoformans MEV2011, isolated from soil, is a microaerotolerant obligate denitrifier, which can also produce N₂ by co-denitrification. Oxygen is consumed but not growth-supportive. The draft genome has a size of 4.7 Mb and contains key genes for both denitrification and dissimilatory nitrate reduction to ammonium.

Draft genome sequence of Bacillus azotoformans MEV2011, a (Co-) denitrifying strain unable to grow with oxygen

Bacillus azotoformans MEV2011, isolated from soil, is a microaerotolerant obligate denitrifier, which can also produce N₂ by co-denitrification. Oxygen is consumed but not growth-supportive. The draft genome has a size of 4.7 Mb and contains key genes for both denitrification and dissimilatory nitrate reduction to ammonium.