Diversity Of Methanotrophic Bacteria Research Articles

Activity and abundance of methanotrophic bacteria in a northern mountainous gradient of wetlands.

Methane uptake and diversity of methanotrophic bacteria was investigated across six hydrologically connectedwetlands in a mountainous forest landscape upstream of lake Langtjern, southern Norway. From floodplain through shrubs, forest and sedges to aSphagnum covered site, growing season CH4 production was insufficiently consumed to balance release into the atmosphere. Emission increased by soil moisture ranging 0.6-6.8mg CH4 m-2 h-1 . Top soils of all sites consumed CH4 including at the lowest 78 ppmv CH4 supplied, thus potentially oxidizing 17-51 nmol CH4 g-1 dw h-1 , with highest Vmax 440 nmol g-1 dw h-1 under Sphagnum and lowest Km 559 nM under hummocked Carex. Nine genera and several less understood type I and type II methanotrophs were detected bythe key functional gene pmoA involved in methane oxidation. Microarray signal intensities from all sites revealed Methylococcus, the affiliated Lake Washington cluster, Methylocaldum, a Japanese rice cluster, Methylosinus, Methylocystis and the affiliated Peat264 cluster. Notably enriched by site was a floodplain Methylomonas and a Methylocapsa-affiliated watershed cluster in the Sphagnum site. The climate sensitive water table was shown to be a strong controlling factor highlighting its link with the CH4 cycle in elevated wetlands.

Abundance, activity and diversity of methanotrophic bacteria in the Elbe Estuary and southern North Sea

Shelf sea areas are the primary oceanic source for methane release, the most abundant hydrocarbon in the atmosphere. As such, the southern North Sea’s methane concentration is mainly determined by river runoff and tidal marshes. Within such a highly variable temperate estuary, this study is the first to reveal detailed information on the in situ activity, abundance and community structure of methane oxidizing bacteria along a transect from the marine environment near Helgoland island to the riverine harbor of Hamburg, Germany. The in situ methane oxidation rate was determined with a radio tracer, and methane concentration with the head-space method. Abundance and diversity of the methanotrophic bacterial community in the water column was assessed with quantitative polymerase chain reaction for the particulate methane monooxygenase and monooxygenase intergenic spacer analysis. Median abundances ranged from 2.8 × 104 cells l−1 in the marine environment to 7.5 × 105 cells l−1 in the riverine environment. Except for salinity, no conclusive linear correlation between any environmental parameter and the abundance of methanotrophs could be determined. Relating activity with abundance of methanotrophs showed that about 70% of the population is inactive, especially in the coastal and marine environment. This study found distinct operational taxonomic unit (OTU) community compositions among the 3 environmental categories (river, coast, marine). Several identified OTUs have been reported previously and imply a wide geographic occurrence. Overall, we propose that salinity is the most important driver of differing communities in the riverine, coastal and marine environment.

Activity and Diversity of Methanotrophic Bacteria at Methane Seeps in Eastern Lake Constance Sediments

The activity and community structure of aerobic methanotrophic communities were investigated at methane seeps (pockmarks) in the littoral and profundal zones of an oligotrophic freshwater lake (Lake Constance, Germany). Measurements of potential methane oxidation rates showed that sediments inside littoral pockmarks are hot spots of methane oxidation. Potential methane oxidation rates at littoral pockmark sites exceeded the rates of the surrounding sediment by 2 orders of magnitude. Terminal restriction fragment length polymorphism (T-RFLP) analysis of the pmoA gene revealed major differences in the methanotrophic community composition between littoral pockmarks and the surrounding sediments. Clone library analysis confirmed that one distinct Methylobacter-related group dominates the community at littoral pockmarks. In profundal sediments, the differences between pockmarks and surrounding sediments were found to be less pronounced.

Stable Isotope Probing Analysis of the Diversity and Activity of Methanotrophic Bacteria in Soils from the Canadian High Arctic

The melting of permafrost and its potential impact on CH(4) emissions are major concerns in the context of global warming. Methanotrophic bacteria have the capacity to mitigate CH(4) emissions from melting permafrost. Here, we used quantitative PCR (qPCR), stable isotope probing (SIP) of DNA, denaturing gradient gel electrophoresis (DGGE) fingerprinting, and sequencing of the 16S rRNA and pmoA genes to study the activity and diversity of methanotrophic bacteria in active-layer soils from Ellesmere Island in the Canadian high Arctic. Results showed that most of the soils had the capacity to oxidize CH(4) at 4 degrees C and at room temperature (RT), but the oxidation rates were greater at RT than at 4 degrees C and were significantly enhanced by nutrient amendment. The DGGE banding patterns associated with active methanotrophic bacterial populations were also different depending on the temperature of incubation and the addition of nutrients. Sequencing of the 16S rRNA and pmoA genes indicated a low diversity of the active methanotrophic bacteria, with all methanotroph 16S rRNA and pmoA gene sequences being related to type I methanotrophs from Methylobacter and Methylosarcina. The dominance of type I methanotrophs over type II methanotrophs in the native soil samples was confirmed by qPCR of the 16S rRNA gene with primers specific for these two groups of bacteria. The 16S rRNA and pmoA gene sequences related to those of Methylobacter tundripaludum were found in all soils, regardless of the incubation conditions, and they might therefore play a role in CH(4) degradation in situ. This work is providing new information supporting the potential importance of Methylobacter spp. in Arctic soils found in previous studies and contributes to the limited body of knowledge on methanotrophic activity and diversity in this extreme environment.

Diversity and Dynamics of Methanotrophs within an Experimental Landfill Cover Soil

Three experimental biocovers were installed during the summer of 2006 at the St‐Nicéphore landfill in Québec (Canada). The main objectives of the experimental program were to assess the efficiency of these biocovers in reducing CH4 emissions and to monitor the evolution in space and time of the dynamics and diversity of methanotrophic bacteria that may be responsible for CH4 abatement. Dynamics of methanotroph populations derived from most probable number (MPN) counts exhibited different steps (lag, growth, and collapse phases), with mean abundances decreasing somewhat with depth. Methanotroph diversity, as assessed by denaturing gradient gel electrophoresis showed changes over time in the community structure. These changes were dependent on the sampling depth and only Type I methanotrophs belonging essentially to the genus Methylobacter were retrieved from our samples. Given the youthful character of the system under study, together with the reported behavior of this functional group of methanotrophs, it was concluded that Type I methanotrophs forming the community structure might reflect pioneer species with a potentially high growth rate (r‐strategists) that become numerically dominant reducing the evenness of species distribution. These results contribute to the generally limited body of knowledge on methanotroph diversity in landfill cover soils.

POTENTIAL ACTIVITY AND DIVERSITY OF METHANOTROPHIC BACTERIA IN FOREST SOIL, PEAT, AND SEDIMENTS FROM A HYDROELECTRIC RESERVOIR (ROBERT-BOURASSA) AND LAKES IN THE CANADIAN TAIGA

The potential activity and diversity of methanotrophic bacteria in samples from forest soil, peat, and sediment from a hydroelectric reservoir (Robert–Bourassa) and lakes located in the sub-arctic taiga were studied. Incubation experiments with soil slurries, methanotrophic bacterial counts, and direct PCR amplification of genes specific to methanotrophic bacteria were carried out on soil and sediment samples from three locations (nonflooded, periodically flooded, and flooded) from the reservoir. Sediments from three lakes located near the reservoir were also sampled to compare with nearby unperturbed aquatic systems. Only the uppermost part (5–10 cm) of soils and sediments was analyzed. Regardless of the incubation temperature, potential methane (CH4) oxidation rates were lower (0.028–0.066 6mol CH4 g j1 soil d j1 )i n nonflooded forest soil compared to lacustrine sediments that exhibited potential oxidation rates generally close to those observed in periodically flooded or flooded forest soil (0.04–0.14 6mol CH4 g j 1 soil d j1 ), but far below the range of values (0.20–0.58 6mol CH4 g j 1 soil d j1 ) recorded in peat systems. Samples from flooded forest soil and peat had higher CH4 uptake activity, but this could not be related to a greater number of methanotrophic bacteria (pmoA probe-positive colonies). Analysis of genes specific to methanotrophic bacteria revealed a low diversity in the methanotrophic community, with the genus Methylocystis being dominant. Overall, samples of flooded soil and peat with higher CH4 production rates also had higher rates of CH4 oxidation by methanotrophic bacteria. Flooding also seems to modify the resilience of the methanotrophic community to temperature fluctuations, an important consideration for future studies. (Soil Science 2006;171:127–137)

Diversity of Methanotrophic Bacteria in Tropical Upland Soils under Different Land Uses

Three upland soils from Thailand, a natural forest, a 16-year-old reforested site, and an agricultural field, were studied with regard to methane uptake and the community composition of methanotrophic bacteria (MB). The methane uptake rates were similar to rates described previously for forest and farmland soils of the temperate zone. The rates were lower at the agricultural site than at the native forest and reforested sites. The sites also differed in the MB community composition, which was characterized by denaturing gradient gel electrophoresis (DGGE) of pmoA gene fragments (coding for a subunit of particulate methane monooxygenase) that were PCR amplified from total soil DNA extracts. Cluster analysis based on the DGGE banding patterns indicated that the MB communities at the forested and reforested sites were similar to each other but different from that at the farmland site. Sequence analysis of excised DGGE bands indicated that Methylobacter spp. and Methylocystis spp. were present. Sequences of the "forest soil cluster" or "upland soil cluster alpha," which is postulated to represent organisms involved in atmospheric methane consumption in diverse soils, were detected only in samples from the native forest and reforested sites. Additional sequences that may represent uncultivated groups of MB in the Gammaproteobacteria were also detected.

Diversity of the Particulate Methane Monooxygenase Gene in Methanotrophic Samples from Different Rice Field Soils in China and the Philippines

Methanotrophic bacteria play a crucial role in regulating the emission of CH4 from rice fields into the atmosphere. We investigated the CH4 oxidation activity together with the diversity of methanotrophic bacteria in ten rice field soils from different geographic locations. Upon incubation of aerated soil slurries under 7% CH4, rates of CH4 oxidation increased after a lag phase of 1-4 days and reached values of 3-10 micromol d(-1) g-dw(-1) soil. The methanotrophic community was assayed by retrieval of the pmoA gene which encodes the a subunit of the particulate methane monooxygenase. After extraction of DNA from actively CH4-oxidizing soil samples and PCR-amplification of the pmoA, the community was analyzed by Denaturant Gradient Gel Electrophoresis (DGGE) and Terminal Restriction Fragment Length Polymorphism (T-RFLP). DGGE bands were excised, the pmoA re-amplified, sequenced and the encoded amino acid sequence comparatively analyzed by phylogenetic treeing. The analyses allowed the detection of pmoA sequences related to the following methanotrophic genera: the type-I methanotrophs Methylobacter, Methylomicrobium, Methylococcus and Methylocaldum, and the type-II methanotrophs Methylocystis and Methylosinus. T-RFLP analysis detected a similar diversity, but type-II pmoA more frequently than DGGE. All soils but one contained type-II in addition to type-I methanotrophs. Type-I Methylomonas was not detected at all. Different combinations of methanotrophic genera were detected in the different soils. However, there was no obvious geographic pattern of the distribution of methanotrophs.