The impact of environmental perturbation (e.g., nitrogenous fertilizers) on the dynamics of methane fluxes from soils and wetland systems is poorly understood. Results of fertilizer studies are often contradictory, even within similar ecosystems. In the present study the hypothesis of whether these contradictory results may be explained by the composition of the methane-consuming microbial community and hence whether methanotrophic diversity affects methane fluxes was investigated. To this end, rice field and forest soils were incubated in microcosms and supplemented with different nitrogenous fertilizers and methane concentrations. By labeling the methane with 13 C, diversity and function could be coupled by analyses of phospholipid-derived fatty acids (PLFA) extracted from the soils at different time points during incubation. In both rice field and forest soils, the activity as well as the growth rate of methane-consuming bacteria was affected differentially. For type I methanotrophs, fertilizer application stimulated the consumption of methane and the subsequent growth, while type II methanotrophs were generally inhibited. Terminal restriction fragment length polymorphism analyses of the pmoA gene supported the PLFA results. Multivariate analyses of stable-isotope-probing PLFA profiles indicated that in forest and rice field soils, Methylocystis (type II) species were affected by fertilization. The type I methanotrophs active in forest soils (Methylomicrobium/Methylosarcina related) differed from the active species in rice field soils (Methylobacter/Methylomonas related). Our results provide a case example showing that microbial community structure indeed matters, especially when assessing and predicting the impact of environmental change on biodiversity loss and ecosystem functioning.The loss of biodiversity from ecosystems and the potential consequences in terms of ecosystem functioning and stability have been central issues for environmental sciences in the last decade (35). Microbial communities comprise much of Earth's biodiversity and have a critical role in ecosystem functioning (42, 43) by collectively determining the biogeochemical processes that regulate the Earth system. Nevertheless, microorganisms have not been considered in the ongoing debate about global biodiversity loss and global change.This neglect is probably due to the huge diversity and associated functional redundancy within microbial communities (42), which make it unlikely that losing a single bacterial species will result in altered ecosystem functioning. Changes in microbial community composition in concordance with changes in the functions that the microorganisms catalyze have been observed for specific groups of low diversity catalyzing a very narrow range of biogeochemical functions, such as ammonia-oxidizing bacteria (23,44). However, in these and other cases separate community members could not be linked to the functions they catalyze, and therefore a direct link between diversity and biogeochemical functioning cannot be made. ...

Temperature change affects methane consumption in soil. However, there is no information on possible temperature control of methanotrophic bacterial populations. Therefore, we studied CH(4) consumption and populations of methanotrophs in an upland forest soil and a rice field soil incubated at different temperatures between 5 and 45 degrees C for up to 40 days. Potential methane consumption was measured at 4% CH(4). The temporal progress of CH(4) consumption indicated growth of methanotrophs. Both soils showed maximum CH(4) consumption at 25-35 degrees C, but no activity at >40 degrees C. In forest soil CH(4) was also consumed at 5 degrees C, but in rice soil only at 15 degrees C. Methanotroph populations were assessed by terminal restriction fragment length polymorphism (T-RFLP) targeting particulate methane monooxygenase (pmoA) genes. Eight T-RFs with relative abundance >1% were retrieved from both forest and rice soil. The individual T-RFs were tentatively assigned to different methanotrophic populations (e.g. Methylococcus/Methylocaldum, Methylomicrobium, Methylobacter, Methylocystis/Methylosinus) according to published sequence data. Two T-RFs were assigned to ammonium monooxygenase (amoA) gene sequences. Statistical tests showed that temperature affected the relative abundance of most T-RFs. Furthermore, the relative abundance of individual T-RFs differed between the two soils, and also exhibited different temperature dependence. We conclude that temperature can be an important factor regulating the community composition of methanotrophs in soil.

This review addresses the perspectives of Azolla as a multifaceted aquatic resource to ensure ecosystem sustainability. Nitrogen fixing potential of cyanobacterial symbiont varies between 30 and 60 kg N ha(-1) which designates Azolla as an important biological N source for agriculture and animal industry. Azolla exhibits high bioremediation potential for Cd, Cr, Cu, and Zn. Azolla mitigates greenhouse gas emission from agriculture. In flooded rice ecosystem, Azolla dual cropping decreased CH4 emission by 40 % than did urea alone and also stimulated CH4 oxidation. This review highlighted integrated approach using Azolla that offers enormous public health, environmental, and cost benefits.

Zinc oxide (ZnO) nanoparticles have attracted significant interest in a number of applications ranging from electronics to biomedical sciences due to their large exaction binding energy (60 meV) and wide bandgap of 3.37 eV. In the present study, we report the low-cost bacterium based "eco-friendly" efficient synthesis of ZnO nanoparticles by using the zinc-tolerant bacteria Serratia nematodiphila. The physicochemical characterization of ZnO nanoparticles was performed by employing UV-vis spectroscopy, XRD, TEM, DLS, Zeta potential, and Raman spectroscopy. The antimicrobial and antifungal studies were investigated at different concentrations using the agar well-diffusion method, whereby the microbial growth rate decreases with the increase in nanoparticle concentration. Further, photocatalytic performance studies were conducted by taking methyl orange (MO) as a reference dye.

A laboratory incubation experiment was conducted with uranium-contaminated subsurface sediment to assess the geochemical and microbial community response to ethanol amendment. A classical sequence of terminal electron-accepting processes (TEAPs) was observed in ethanol-amended slurries, with NO3- reduction, Fe(III) reduction, SO4(2-) reduction, and CH4 production proceeding in sequence until all of the added 13C-ethanol (9 mM) was consumed. Approximately 60% of the U(VI) content of the sediment was reduced during the period of Fe(III) reduction. No additional U(VI) reduction took place during the sulfate-reducing and methanogenic phases of the experiment Only gradual reduction of NO3-, and no reduction of U(VI), took place in ethanol-free slurries. Stimulation of additional Fe(III) or SO4(2-) reduction in the ethanol-amended slurries failed to promote further U(VI) reduction. Reverse transcribed 16S rRNA clone libraries revealed major increases in the abundance of organisms related to Dechloromonas, Geobacter, and Herbaspirillum in the ethanol-amended slurries. Phospholipid fatty acids (PLFAs) indicative of Geobacter showed a distinct increase in the amended slurries, and analysis of PLFA 13C/12C ratios confirmed the incorporation of ethanol into these PLFAs. A increase in the abundance of 13C-labeled PLFAs indicative of Desulfobacter, Desulfotomaculum, and Desulfovibrio took place during the brief period of sulfate reduction that followed the Fe(III) reduction phase. Our results show that major redox processes in ethanol-amended sediments can be reliably interpreted in terms of standard conceptual models of TEAPs in sediments. However, the redox speciation of uranium is complex and cannot be explained based on simplified thermodynamic considerations.