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1.
Current knowledge of microbial community structures in landfills and its cover soils 总被引:2,自引:0,他引:2
Semrau JD 《Applied microbiology and biotechnology》2011,89(4):961-969
Landfills are a vital component of our waste handling processes. Our lack of knowledge on the microbial processes in these
systems, however, hampers our ability to design the next generation of landfills that: (1) enhance the rate and extent of
waste decomposition, (2) produce byproducts of some value (e.g., methane that can be used for energy generation), and, (3)
minimize their overall impact on driving climate change through the emission of greenhouse gases. In this review, the current
state of knowledge the microbial community structure and activity in both the refuse and overlying cover soils is discussed,
and suggestions provided for future research in this critical aspect of our infrastructure. 相似文献
2.
Alexey Vorobev Sheeja Jagadevan Bipin S. Baral Alan A. DiSpirito Brittani C. Freemeier Brandt H. Bergman Nathan L. Bandow Jeremy D. Semrau 《Applied and environmental microbiology》2013,79(19):5918-5926
Many methanotrophs have been shown to synthesize methanobactin, a novel biogenic copper-chelating agent or chalkophore. Methanobactin binds copper via two heterocyclic rings with associated enethiol groups. The structure of methanobactin suggests that it can bind other metals, including mercury. Here we report that methanobactin from Methylosinus trichosporium OB3b does indeed bind mercury when added as HgCl2 and, in doing so, reduced toxicity associated with Hg(II) for both Alphaproteobacteria methanotrophs, including M. trichosporium OB3b, M. trichosporium OB3b ΔmbnA (a mutant defective in methanobactin production), and Methylocystis sp. strain SB2, and a
Gammaproteobacteria methanotroph, Methylomicrobium album BG8. Mercury binding by methanobactin was evident in both the presence and absence of copper, despite the fact that methanobactin had a much higher affinity for copper due to the rapid and irreversible binding of mercury by methanobactin. The formation of a gray precipitate suggested that Hg(II), after being bound by methanobactin, was reduced to Hg(0) but was not volatilized. Rather, mercury remained associated with methanobactin and was also found associated with methanotrophic biomass. It thus appears that although the mercury-methanobactin complex was cell associated, mercury was not removed from methanobactin. The amount of biomass-associated mercury in the presence of methanobactin from M. trichosporium OB3b was greatest for M. trichosporium wild-type strain OB3b and the ΔmbnA mutant and least for M. album BG8, suggesting that methanotrophs may have selective methanobactin uptake systems that may be based on TonB-dependent transporters but that such uptake systems exhibit a degree of infidelity. 相似文献
3.
Benjamin R. Stenzler Rui Zhang Jeremy D. Semrau Alan A. DiSpirito Alexandre J. Poulain 《Environmental microbiology》2022,24(7):3212-3228
Methylmercury is a potent neurotoxin that biomagnifies through food webs and which production depends on anaerobic microbial uptake of inorganic mercury (Hg) species. One outstanding knowledge gap in understanding Hg methylation is the nature of bioavailable Hg species. It has become increasingly obvious that Hg bioavailability is spatially diverse and temporally dynamic but current models are mostly built on single thiolated ligand systems, omitting ligand exchanges and interactions, or the inclusion of dissolved gaseous phases. In this study, we used a whole-cell anaerobic biosensor to determine the role of a mixture of thiolated ligands on Hg bioavailability. Serendipitously, we discovered how the diffusion of trace amounts of exogenous biogenic H2S, originating from anaerobic microbial ligand degradation, can alter Hg speciation – away from H2S production site – to form bioavailable species. Regardless of its origins, H2S stands as a mobile mediator of microbial Hg metabolism, connecting spatially separated microbial communities. At a larger scale, global planetary changes are expected to accelerate the production and mobilization of H2S and Hg, possibly leading to increased production of the potent neurotoxin; this work provides mechanistic insights into the importance of co-managing biogeochemical cycle disruptions. 相似文献
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5.
The ability of Methylosinus trichosporium OB3b, expressing soluble methane monooxygenase, to oxidize a range of ortho-substituted biphenyls was examined to better understand how substituents affect both the rate and products of oxidation in comparison to biphenyl. Inhibition of oxidation was observed over the tested substrate range for both biphenyl and ortho-halogenated biphenyls (2-chloro-, 2-bromo-, and 2-iodobiphenyl). No inhibition was observed during the oxidation of 2-hydroxybiphenyl and 2-methylbiphenyl. Analysis of the products of oxidation showed that, depending on the substituent, ring hydroxylation, substituent oxidation, and elimination pathways could occur. The type and abundance of products formed along with the relatively high kinetic isotope effect observed for deuterated vs. nondeuterated biphenyl (k(h)/k(d) = 3.4+/-0.02) are consistent with mechanisms that include both hydrogen abstraction and NIH-shift pathways. Knowledge of these substituent-dependent reaction rates and mechanisms enhances our understanding of the methanotrophic aryl transformation potential and allows for better prediction of the formation of oxidized intermediates by methanotrophic bacteria. 相似文献
6.
Studies were performed to determine if the growth of Methylomicrobium album BG8 on methanol could be enhanced through the provision of chloromethane. M. album BG8 was found to be able to oxidize chloromethane via the particulate methane monooxygenase with an apparent K(s) of 11+/-3 microM and V(max) of 15+/-0.6 nmol (min mg protein)(-1). When up to 2.6 mM chloromethane was provided with 5 mM methanol, methanotrophic growth was significantly enhanced in comparison to the absence of chloromethane, indicating that methanotrophs can utilize chloromethane to support growth, although it could not serve as a sole growth substrate. [(14)C]chloromethane was found to be oxidized to [(14)C]CO(2) as well as incorporated into biomass. These results indicate that reactions previously thought to be cometabolic may actually provide some benefit to methanotrophs and that these cells can use multiple compounds to enhance growth. 相似文献
7.
The rate and products of trichloroethylene (TCE) oxidation by Methylomicrobium album BG8 expressing membrane-associated methane monooxygenase (pMMO) were determined using 14C radiotracer techniques. [(14)C]TCE was degraded at a rate of 1.24 nmol (min mg protein)(-1) with the initial production of glyoxylate and then formate. Radiolabeled CO(2) was also found after incubating M. album BG8 for 5 h with [(14)C]TCE. Experiments with purified pMMO from Methylococcus capsulatus Bath showed that TCE could be mineralized to CO(2) by pMMO. Oxygen uptake studies verified that M. album BG8 could oxidize glyoxylate and that pMMO was responsible for the oxidation based on acetylene inactivation studies. Here we propose a pathway of TCE oxidation by pMMO-expressing cells in which TCE is first converted to TCE-epoxide. The epoxide then spontaneously undergoes HCl elimination to form glyoxylate which can be further oxidized by pMMO to formate and CO(2). 相似文献
8.
The intact phospholipid profiles (IPPs) of seven species of methanotrophs from all three physiological groups, type I, II and X, were determined using liquid chromatography/electrospray ionization/mass spectrometry. In these methanotrophs, two major classes of phospholipids were found, phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) as well as its derivatives phosphatidylmethylethanolamine (PME) and phosphatidyldimethylethanolamine (PDME). Specifically, the type I methanotrophs, Methylomonas methanica, Methylomonas rubra and Methylomicrobium album BG8 were characterized by PE and PG phospholipids with predominantly C16:1 fatty acids. The type II methanotrophs, Methylosinus trichosporium OB3b and CSC1 were characterized by phospholipids of PG, PME and PDME with predominantly C18:1 fatty acids. Methylococcus capsulatus Bath, a representative of type X methanotrophs, contained mostly PE (89% of the total phospholipids). Finally, the IPPs of a recently isolated acidophilic methanotroph, Methylocella palustris, showed it had a preponderance of PME phospholipids with 18:1 fatty acids (94% of total). Principal component analysis showed these methanotrophs could be clearly distinguished based on phospholipid profiles. Results from this study suggest that IPP can be very useful in bacterial chemotaxonomy. 相似文献
9.
Methane and Trichloroethylene Degradation by Methylosinus trichosporium OB3b Expressing Particulate Methane Monooxygenase 下载免费PDF全文
Whole-cell assays of methane and trichloroethylene (TCE) consumption have been performed on Methylosinus trichosporium OB3b expressing particulate methane monooxygenase (pMMO). From these assays it is apparent that varying the growth concentration of copper causes a change in the kinetics of methane and TCE degradation. For M. trichosporium OB3b, increasing the copper growth concentration from 2.5 to 20 μM caused the maximal degradation rate of methane (Vmax) to decrease from 300 to 82 nmol of methane/min/mg of protein. The methane concentration at half the maximal degradation rate (Ks) also decreased from 62 to 8.3 μM. The pseudo-first-order rate constant for methane, Vmax/Ks, doubled from 4.9 × 10−3 to 9.9 × 10−3 liters/min/mg of protein, however, as the growth concentration of copper increased from 2.5 to 20 μM. TCE degradation by M. trichosporium OB3b was also examined with varying copper and formate concentrations. M. trichosporium OB3b grown with 2.5 μM copper was unable to degrade TCE in both the absence and presence of an exogenous source of reducing equivalents in the form of formate. Cells grown with 20 μM copper, however, were able to degrade TCE regardless of whether formate was provided. Without formate the Vmax for TCE was 2.5 nmol/min/mg of protein, while providing formate increased the Vmax to 4.1 nmol/min/mg of protein. The affinity for TCE also increased with increasing copper, as seen by a change in Ks from 36 to 7.9 μM. Vmax/Ks for TCE degradation by pMMO also increased from 6.9 × 10−5 to 5.2 × 10−4 liters/min/mg of protein with the addition of formate. From these whole-cell studies it is apparent that the amount of copper available is critical in determining the oxidation of substrates in methanotrophs that are expressing only pMMO. 相似文献
10.
Louise Kuhn Grace M. Aldrovandi Moses Sinkala Chipepo Kankasa Katherine Semrau Prisca Kasonde Mwiya Mwiya Wei-Yann Tsai Donald M. Thea for the Zambia Exclusive Breastfeeding Study 《PloS one》2009,4(6)