Frog virus 3 prevalence in tadpole populations inhabiting cattle-access and non-access wetlands in Tennessee, USA.
(33/354)
Ranaviruses have been associated with most of the reported larval anuran die-offs in the United States. It is hypothesized that anthropogenically induced stress may increase pathogen prevalence in amphibian populations by compromising immunity. Cattle use of wetlands may stress resident tadpole populations by reducing water quality. We isolated a Ranavirus from green frog Rana clamitans (n = 80) and American bullfrog R. catesbeiana (n = 104) tadpoles collected at 5 cattle-access and 3 non-access wetlands on the Cumberland Plateau, Tennessee, USA. Sequencing confirmed Frog virus 3 (FV3); therefore, we compared its prevalence between tadpole populations inhabiting cattle-access and non-access wetlands, and among 3 seasons (winter, summer, and autumn) in 2005. We found FV3 in both tadpole species and cattle land-use types; however, prevalence of FV3 was greater in green frog tadpoles residing in cattle-access wetlands compared to those in non-access wetlands. No difference in FV3 prevalence was detected between cattle land uses for American bullfrog tadpoles. A seasonal trend in FV3 prevalence also existed, with prevalence greater in autumn and winter than in summer for both species. In addition, we found that FV3 prevalence decreased significantly as Gosner stage increased in American bullfrog tadpoles. No trend was detected between FV3 prevalence and developmental stage for green frog tadpoles. Our results suggest that cattle use of wetlands may increase prevalence of FV3 in Rana tadpoles, although this effect may depend on species, season, and tadpole developmental stage. (+info)
Schlesneria paludicola gen. nov., sp. nov., the first acidophilic member of the order Planctomycetales, from Sphagnum-dominated boreal wetlands.
(34/354)
Three strains of budding, ellipsoid-shaped and rosette-forming bacteria were isolated from acidic Sphagnum-dominated boreal wetlands of northern Russia and were designated strains MPL7T, MOB77 and SB2. The presence of crateriform pits and numerous fibrillar appendages on the cell surface and an unusual spur-like projection on one pole of the cell indicated a planctomycete morphotype. These isolates are moderately acidophilic, mesophilic organisms capable of growth at pH values between 4.2 and 7.5 (with an optimum at pH 5.0-6.2) and at temperatures between 4 and 32 degrees C (optimum 15-26 degrees C). The major fatty acids are C16:0 and C16:1omega7c; the major quinone is MK-6. The G+C content of the DNA is 54.4-56.5 mol%. Strains MPL7T, MOB77 and SB2 possess nearly identical 16S rRNA gene sequences and belong to the planctomycete lineage defined by the genus Planctomyces, being most closely related to Planctomyces limnophilus DSM 3776T (86.9-87.1% sequence similarity). However, strain MPL7T showed only 28% DNA-DNA hybridization with P. limnophilus DSM 3776T. Compared with currently described members of the genus Planctomyces, the isolates from northern wetlands do not form long and distinctive stalks, have greater tolerance of acidic conditions and low temperatures, are more sensitive to NaCl, lack pigmentation and degrade a wider range of biopolymers. The data therefore suggest that strains MPL7T, MOB77 and SB2 represent a novel genus and species, for which the name Schlesneria paludicola gen. nov., sp. nov., is proposed. Strain MPL7T (=ATCC BAA-1393T=VKM B-2452T) is the type strain of Schlesneria paludicola. (+info)
The flow generated by an active olfactory system of the red swamp crayfish.
(35/354)
Crayfish are nocturnal animals that mainly rely on their chemoreceptors to locate food. On a crayfish scale, chemical stimuli received from a distant source are dispersed by an ambient flow rather than molecular diffusion. When the flow is weak or absent, food searching can be facilitated by currents generated by the animal itself. Crayfish employ their anterior fan organs to produce a variety of flow patterns. Here we study the flow generated by Procambarus clarkii in response to odour stimulation. We found that while searching for food the crayfish generates one or two outward jets. These jets induce an inflow that draws odour to the crayfish's anterior chemoreceptors. We quantified velocity fields in the inflow region using Particle Image Velocimetry. The results show that the inflow velocity decreases proportionally to the inverse distance from the animal so that it takes about 100 s for an odour plume to reach the animal's chemoreceptors from a distance of 10 cm. We compare the inflow generated by live crayfish with that produced by a mechanical model. The model consists of two nozzles and an inlet and provides two jets and a sink so that the overall mass flux is zero. Use of the model enabled us to analyze the inflow at various jet parameters. We show that variation of directions and relative intensities of the jets allows the direction of odour attraction to be changed. These results provide a rationale for biomimetic robot design. We discuss sensitivity and efficiency of such a robot. (+info)
Quantifying microbial utilization of petroleum hydrocarbons in salt marsh sediments by using the 13C content of bacterial rRNA.
(36/354)
Natural remediation of oil spills is catalyzed by complex microbial consortia. Here we took a whole-community approach to investigate bacterial incorporation of petroleum hydrocarbons from a simulated oil spill. We utilized the natural difference in carbon isotopic abundance between a salt marsh ecosystem supported by the 13C-enriched C4 grass Spartina alterniflora and 13C-depleted petroleum to monitor changes in the 13C content of biomass. Magnetic bead capture methods for selective recovery of bacterial RNA were used to monitor the 13C content of bacterial biomass during a 2-week experiment. The data show that by the end of the experiment, up to 26% of bacterial biomass was derived from consumption of the freshly spilled oil. The results contrast with the inertness of a nearby relict spill, which occurred in 1969 in West Falmouth, MA. Sequences of 16S rRNA genes from our experimental samples also were consistent with previous reports suggesting the importance of Gamma- and Deltaproteobacteria and Firmicutes in the remineralization of hydrocarbons. The magnetic bead capture approach makes it possible to quantify uptake of petroleum hydrocarbons by microbes in situ. Although employed here at the domain level, RNA capture procedures can be highly specific. The same strategy could be used with genus-level specificity, something which is not currently possible using the 13C content of biomarker lipids. (+info)
Uliginosibacterium gangwonense gen. nov., sp. nov., isolated from a wetland, Yongneup, in Korea.
(37/354)
Diversity of the nitrite reductase gene nirS in the sediment of a free-water surface constructed wetland.
(40/354)
The diversity of the nitrite reductase gene nirS was studied in the bulk sediment of a free-water surface constructed wetland (FWS-CW) located next to the Empuriabrava wastewater treatment plant (WWTP), in Castello d'Empuries (Girona, NE Spain). The study period extended from the inception of the treatment wetland, in June 1998, until March 1999 and comprised periods of relatively high nitrate and ammonium concentrations at the influent and low nitrate-removal efficiencies. To evaluate nirS diversity, partial gene sequences were obtained by cloning of the respective PCR products. Rarefaction curves based on DOTUR analyses of the deduced amino-acid sequences predicted a greater diversity of nirS genes in samples containing higher ammonium concentrations. Estimated Shannon-Weaver indices of the four cloned samples showed a positive relationship with the N-NH4 +/N-NO3 - ratios measured at the FWS-CW inlet. Identities between the deduced amino-acid sequences and those previously deposited in public databases ranged from 72 to 97%. Phylogenetic analysis based on these deduced sequences grouped 165 nirS clones in seven main clusters according to high similarity indices. Up to 60% of the clones clustered together in a highly homogeneous group with little homologies to any sequence retrieved from cultured representatives. Moreover, prevailing environmental conditions appeared to select for particular denitrifying populations, e.g., with respect to ammonium load and nitrogen removal efficiencies. This observation is of particular interest for the management of treatment wetlands, in which only slight variations in the theoretical denitrification potential of the system can occur. (+info)