Abstract:Manganese is an essential trace metal that is not as readily oxidizable like iron. Several bacterial groups posses the ability to oxidize Mn effectively competing with chemical oxidation. The oxides of Mn are the strongest of the oxidants, next to oxygen in the aquatic environment and therefore control the fate of several elements. Mn oxidizing bacteria have a suit of enzymes that not only help to scavenge Mn but also other associated elements, thus playing a crucial role in biogeochemical cycles. This article… Show more
“…The Cr(III) or Cd oxidation capacities of biogenic Mn oxides were 0.24 mmol g −1 and 2.04 mmol g −1 , respectively, which even higher than the chemically synthesized Mn oxides in the aquatic environment [38], [52]. Such studies would be greatly helpful in the feasibility and designing of industrial-scale bioreactors for treating heavy metals contaminated wastewater, and highlight the potential for the application of this bioremediation friendly system, as products could be removed from effluents in the form of a precipitate [8].…”
Section: Discussionmentioning
confidence: 91%
“…MCOs are a class of copper proteins that utilize copper as a cofactor to catalyze four one-electron oxidations of various substrates concomitantly with the reduction of O 2 to water [7], [8]. MCOs have been found in a wide range of organisms including bacteria, fungi (laccase), plants, insects and vertebrates (ceruloplasmin) [7], [9].…”
Multicopper oxidases (MCOs) are a family of enzymes that use copper ions as cofactors to oxidize various substrates. Previous research has demonstrated that several MCOs such as MnxG, MofA and MoxA can act as putative Mn(II) oxidases. Meanwhile, the endospore coat protein CotA from Bacillus species has been confirmed as a typical MCO. To study the relationship between CotA and the Mn(II) oxidation, the cotA gene from a highly active Mn(II)-oxidizing strain Bacillus pumilus WH4 was cloned and overexpressed in Escherichia coli strain M15. The purified CotA contained approximately four copper atoms per molecule and showed spectroscopic properties typical of blue copper oxidases. Importantly, apart from the laccase activities, the CotA also displayed substantial Mn(II)-oxidase activities both in liquid culture system and native polyacrylamide gel electrophoresis. The optimum Mn(II) oxidase activity was obtained at 53°C in HEPES buffer (pH 8.0) supplemented with 0.8 mM CuCl2. Besides, the addition of o-phenanthroline and EDTA both led to a complete suppression of Mn(II)-oxidizing activity. The specific activity of purified CotA towards Mn(II) was 0.27 U/mg. The Km, Vmax and kcat values towards Mn(II) were 14.85±1.17 mM, 3.01×10−6±0.21 M·min−1 and 0.32±0.02 s−1, respectively. Moreover, the Mn(II)-oxidizing activity of the recombinant E. coli strain M15-pQE-cotA was significantly increased when cultured both in Mn-containing K liquid medium and on agar plates. After 7-day liquid cultivation, M15-pQE-cotA resulted in 18.2% removal of Mn(II) from the medium. Furthermore, the biogenic Mn oxides were clearly observed on the cell surfaces of M15-pQE-cotA by scanning electron microscopy. To our knowledge, this is the first report that provides the direct observation of Mn(II) oxidation with the heterologously expressed protein CotA, Therefore, this novel finding not only establishes the foundation for in-depth study of Mn(II) oxidation mechanisms, but also offers a potential biocatalyst for Mn(II) removal.
“…The Cr(III) or Cd oxidation capacities of biogenic Mn oxides were 0.24 mmol g −1 and 2.04 mmol g −1 , respectively, which even higher than the chemically synthesized Mn oxides in the aquatic environment [38], [52]. Such studies would be greatly helpful in the feasibility and designing of industrial-scale bioreactors for treating heavy metals contaminated wastewater, and highlight the potential for the application of this bioremediation friendly system, as products could be removed from effluents in the form of a precipitate [8].…”
Section: Discussionmentioning
confidence: 91%
“…MCOs are a class of copper proteins that utilize copper as a cofactor to catalyze four one-electron oxidations of various substrates concomitantly with the reduction of O 2 to water [7], [8]. MCOs have been found in a wide range of organisms including bacteria, fungi (laccase), plants, insects and vertebrates (ceruloplasmin) [7], [9].…”
Multicopper oxidases (MCOs) are a family of enzymes that use copper ions as cofactors to oxidize various substrates. Previous research has demonstrated that several MCOs such as MnxG, MofA and MoxA can act as putative Mn(II) oxidases. Meanwhile, the endospore coat protein CotA from Bacillus species has been confirmed as a typical MCO. To study the relationship between CotA and the Mn(II) oxidation, the cotA gene from a highly active Mn(II)-oxidizing strain Bacillus pumilus WH4 was cloned and overexpressed in Escherichia coli strain M15. The purified CotA contained approximately four copper atoms per molecule and showed spectroscopic properties typical of blue copper oxidases. Importantly, apart from the laccase activities, the CotA also displayed substantial Mn(II)-oxidase activities both in liquid culture system and native polyacrylamide gel electrophoresis. The optimum Mn(II) oxidase activity was obtained at 53°C in HEPES buffer (pH 8.0) supplemented with 0.8 mM CuCl2. Besides, the addition of o-phenanthroline and EDTA both led to a complete suppression of Mn(II)-oxidizing activity. The specific activity of purified CotA towards Mn(II) was 0.27 U/mg. The Km, Vmax and kcat values towards Mn(II) were 14.85±1.17 mM, 3.01×10−6±0.21 M·min−1 and 0.32±0.02 s−1, respectively. Moreover, the Mn(II)-oxidizing activity of the recombinant E. coli strain M15-pQE-cotA was significantly increased when cultured both in Mn-containing K liquid medium and on agar plates. After 7-day liquid cultivation, M15-pQE-cotA resulted in 18.2% removal of Mn(II) from the medium. Furthermore, the biogenic Mn oxides were clearly observed on the cell surfaces of M15-pQE-cotA by scanning electron microscopy. To our knowledge, this is the first report that provides the direct observation of Mn(II) oxidation with the heterologously expressed protein CotA, Therefore, this novel finding not only establishes the foundation for in-depth study of Mn(II) oxidation mechanisms, but also offers a potential biocatalyst for Mn(II) removal.
“…Considering that the bacterial strains were isolated from metal rich environments, hence the presence of HSPs is very likely. GO analysis reveals several gene functions like manganese ion binding, metal ion transport, high-affinity iron ion transmembrane transport, regulation of pH, copper oxidase activity and response to stress 42 . These functions are essential for metal solubilisation and are especially true in the case of ferro manganese ores which is found in bounty in the area of study.…”
To extend the knowledge on the microbial diversity of manganese rich environments, we performed a clone library based study using metagenomic approach. Pyrosequencing based analysis of 16S rRNA genes were carried out on an Illumina platform to gain insights into the bacterial community inhabiting in a manganese mining site and the taxonomic profiles were correlated with the inherent capacities of these strains to solubilise manganese. The application of shot gun sequencing in this study yielded results which revealed the highest prevalence of Proteobacteria (42.47%), followed by Actinobacteria (23.99%) in the area of study. Cluster of orthologous group (COG) functional category has 85,066 predicted functions. Out of which 11% are involved in metabolism of amino acid, 9% are involved in production and conversion of energy while Keto Encyclopedia of Gene and Genomes (KEGG) functional category has 107,388 predicted functions, out of which 55% are involved in cellular metabolism, 15% are environmental and information processing and 12% are genetic information processing in nature. The isolated microbial consortia demonstrated visible growth in presence of high concentrations of Mn. Solubilisation studies resulted in 86% of manganese recovery after 20 days. The result presented in this study has important implications in understanding the microbial diversity in manganese contaminated mine tailings and their role in natural geochemical cycling of Mn.
“…It is hypothesised that microbial activities, especially of sedimentary bacteria, may contribute towards precipitation of metal hydroxides and play a role in formation and growth of the nodules 4 . These bacteria possibly adsorb metals, including Mn, Fe, Co, Cu and Ni from the deep-sea water and enrich the nodules 5,6 . Sedimentary bacteria are already known to play crucial roles in nutrient cycling in the deep-sea environment 7 , with the help of extracellular enzymes 8 .Figure 1Map showing sampling locations in the Central Indian Ocean Basin.…”
Sedimentary bacteria play a role in polymetallic nodule formation and growth. There are, however, limited reports on bacterial diversity in nodule-rich areas of the Central Indian Ocean Basin (CIOB). In this study, bacterial abundance in thirteen sediment cores collected from the CIOB was enumerated, followed by phylogenetic characterisation and, screening of select heterotrophic bacteria for extracellular enzyme activities. Total bacterial counts (TBC) were in the order of 10
7
cells g
−1
; there was a significant difference (p > 0.05) among the cores but not within the sub-sections of the cores. The retrievable heterotrophic counts ranged from non-detectable to 5.33 × 10
5
g
−1
; the heterotrophic bacteria clustered within the phyla Firmicutes, Proteobacteria and Actinobacteria.
Bacillus
was the most abundant genus. The extracellular enzyme activities were in the order: amylase > lipase > protease > phosphatase > Dnase > urease. Major findings are compared with previous studies from the CIOB and other areas.
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