Comparative summer dynamics of surface cyanobacterial communities in two connected lakes from the west of Ireland.

The eutrophication of lakes is typically associated with high biomass proliferations of potentially toxic cyanobacteria. At a regional level, the sustainable management of water resources necessitates an approach that recognises the interconnectivity of multiple water systems within river catchments. This study examined the dynamics in summer diversity of planktonic cyanobacterial communities and microcystin toxin concentrations in two inter-connected lakes from the west of Ireland prone to nutrient enrichment. DGGE analysis of 16S rRNA gene amplicons of genotype-I cyanobacteria (typically spherical) showed changes in the communities of both Lough Corrib and Ballyquirke Lough throughout the summer, and identified cyanobacterial genotypes both unique and shared to both lakes. Microcystin concentrations, estimated via the protein phosphatase 2A inhibition assay, were greater in August than in July and June in both lakes. This was concomitant to the increased occurrence of Microcystis as evidenced by DGGE band excision and subsequent sequencing and BLAST analysis. RFLP analysis of PCR amplified mcy-A/E genes clustered together the August samples of both lakes, highlighting a potential change in microcystin producers across the two lakes. Finally, the multiple factor analysis of the combined environmental data set for the two lakes highlighted the expected pattern opposing greater water temperature and chlorophyll concentration against macronutrient concentrations, but also indicated a negative relationship between microcystin concentration and cyanobacterial diversity, possibly underlining allelopathic interactions. Despite some element of connectivity, the dissimilarity in the composition of the cyanobacterial assemblages and the timing of community change in the two lakes likely were a reflexion of niche differences determined by meteorologically-forced variation in physico-chemical parameters in the two water bodies.

Nutrient, metal and microbial loss in surface runoff following treated sludge and dairy cattle slurry application to an Irish grassland soil.

Treated municipal sewage sludge ("biosolids") and dairy cattle slurry (DCS) may be applied to agricultural land as an organic fertiliser. This study investigates losses of nutrients in runoff water (nitrogen (N) and phosphorus (P)), metals (copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr)), and microbial indicators of pollution (total and faecal coliforms) arising from the land application of four types of treated biosolids and DCS to field micro-plots at three time intervals (24, 48, 360 h) after application. Losses from biosolids-amended plots or DCS-amended plots followed a general trend of highest losses occurring during the first rainfall event and reduced losses in the subsequent events. However, with the exception of total and faecal coliforms and some metals (Ni, Cu), the greatest losses were from the DCS-amended plots. For example, average losses over the three rainfall events for dissolved reactive phosphorus and ammonium-nitrogen from DCS-amended plots were 5 and 11.2 mg L(-1), respectively, which were in excess of the losses from the biosolids plots. When compared with slurry treatments, for the parameters monitored biosolids generally do not pose a greater risk in terms of losses along the runoff pathway. This finding has important policy implications, as it shows that concern related to the reuse of biosolids as a soil fertiliser, mainly related to contaminant losses upon land application, may be unfounded.

Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability.

We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar "stealth baryon" dark matter candidate, arising from a dark SU(4) confining gauge theory-"stealth dark matter." In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest "baryon" states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m(B)(6), suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.

Two-color gauge theory with novel infrared behavior.

Using lattice simulations, we study the infrared behavior of a particularly interesting SU(2) gauge theory, with six massless Dirac fermions in the fundamental representation. We compute the running gauge coupling derived nonperturbatively from the Schrödinger functional of the theory, finding no evidence for an infrared fixed point up through gauge couplings g(2) of order 20. This implies that the theory either is governed in the infrared by a fixed point of considerable strength, unseen so far in nonsupersymmetric gauge theories, or breaks its global chiral symmetries producing a large number of composite Nambu-Goldstone bosons relative to the number of underlying degrees of freedom. Thus either of these phases exhibits novel behavior.

Parity doubling and the S parameter below the conformal window.

We describe a lattice simulation of the masses and decay constants of the lowest-lying vector and axial resonances, and the electroweak S parameter, in an SU(3) gauge theory with N(f)=2 and 6 fermions in the fundamental representation. The spectrum becomes more parity doubled and the S parameter per electroweak doublet decreases when N(f) is increased from 2 to 6, motivating study of these trends as N(f) is increased further, toward the critical value for transition from confinement to infrared conformality.

Enrichment of acetogenic bacteria in high rate anaerobic reactors under mesophilic and thermophilic conditions.

The objective of the current study was to expand the knowledge of the role of acetogenic Bacteria in high rate anaerobic digesters. To this end, acetogens were enriched by supplying a variety of acetogenic growth supportive substrates to two laboratory scale high rate upflow anaerobic sludge bed (UASB) reactors operated at 37 degrees C (R1) and 55 degrees C (R2). The reactors were initially fed a glucose/acetate influent. Having achieved high operational performance and granular sludge development and activity, both reactors were changed to homoacetogenic bacterial substrates on day 373 of the trial. The reactors were initially fed with sodium vanillate as a sole substrate. Although % COD removal indicated that the 55 degrees C reactor out performed the 37 degrees C reactor, effluent acetate levels from R2 were generally higher than from R1, reaching values as high as 5023 mg l(-1). Homoacetogenic activity in both reactors was confirmed on day 419 by specific acetogenic activity (SAA) measurement, with higher values obtained for R2 than R1. Sodium formate was introduced as sole substrate to both reactors on day 464. It was found that formate supported acetogenic activity at both temperatures. By the end of the trial, no specific methanogenic activity (SMA) was observed against acetate and propionate indicating that the methane produced was solely by hydrogenotrophic Archaea. Higher SMA and SAA values against H(2)/CO(2) suggested development of a formate utilising acetogenic population growing in syntrophy with hydrogenotrophic methanogens. Throughout the formate trial, the mesophilic reactor performed better overall than the thermophilic reactor.

Toward TeV conformality.

We study the chiral properties of an SU(3) gauge theory with N{f} massless Dirac fermions in the fundamental representation when N{f} is increased from 2 to 6. For N{f}=2, our lattice simulations lead to a value of psi psi/F{3}, where F is the Nambu-Goldstone-boson decay constant and psi psi is the chiral condensate, which agrees with the measured QCD value. For N{f}=6, this ratio shows significant enhancement, presaging an even larger enhancement anticipated as N{f} increases further, toward the critical value for transition from confinement to infrared conformality.

Nucleon axial charge in full lattice QCD.

The nucleon axial charge is calculated as a function of the pion mass in full QCD. Using domain wall valence quarks and improved staggered sea quarks, we present the first calculation with pion masses as light as 354 MeV and volumes as large as (3.5 fm)3. We show that finite volume effects are small for our volumes and that a constrained fit based on finite volume chiral perturbation theory agrees with experiment within 7% statistical errors.

The effect of levofloxacin concentration on the development and maintenance of antibiotic-resistant clones of Escherichia coli in chemostat culture.

A levofloxacin-sensitive strain of Escherichia coli (broth MIC: 0.0625 mg x l(-1)) was grown in carbon-limited chemostat culture for 316 h (D=0.294 h(-1)). Hyperresistant strains isolated after 58 and 91 generations of culture retained a 16- to 47-fold increase in tolerance to levofloxacin during antibiotic-free serial batch and continuous culture (20 generations, glucose-limited, D=0.2 h(-1)). Isolates differed from the original strain in their maximum growth rates in the presence and absence of subinhibitory levels of levofloxacin, protein-banding profiles, and resistance to a range of antibiotics. Competition between resistant isolates and the original sensitive strain was studied in glucose-limited chemostat cultures (D=0.2 h(-1)). At levofloxacin concentrations less than 0.03 mg x l(-1), the sensitive strain outcompeted resistant isolates and displaced them from the culture, whereas the reverse was true at higher concentrations. These results have clinical and environmental implications for those administering levofloxacin.

Plasmid instability in an industrial strain of Bacillus subtilis grown in chemostat culture.

A pUB110-derived plasmid/Bacillus subtilis host combination was segregationally unstable when grown in chemostat culture with complex or minimal medium and under starch, glucose or magnesium limitation. The kinetics of plasmid loss were described in terms of the difference in growth rates between plasmid-containing and plasmid-free cells (d mu) and the rate at which plasmid-free cells were generated from plasmid-containing cells (R). Loss of plasmid-containing cells from the population was d mu dominated. Changes in medium composition and the nature of growth limitation caused variations in both d mu and R. The plasmid was most stable in glucose-limited chemostat cultures with minimal medium and least stable under starch limitation with complex medium. R and d mu were smaller for cultures in complex media than those in minimal media. Limitation by starch induced expression of the plasmid-encoded HT alpha amylase gene and was associated with increased values of R and d mu. Magnesium limitation in minimal medium caused a significant increase in d mu and a decrease in R.

The metabolism of benzo(a)pyrene by the lungs of asbestos exposed rats.

A group of Fischer F344 rats were exposed to an aerosol of crocidolite asbestos for 36 d. Short-term organ cultures were established from the lungs of these animals and from a similar control group. The ability of these cultures to metabolise benzo(a)pyrene to water-soluble and ether-soluble forms was measured. Crocidolite treatment reduced the lungs ability to produce both types of metabolite although only the reduction in water-soluble forms was significant. DNA binding increased in cultures from treated rats, though this was not statistically significant. The possible relationship of these results to asbestos pathogenesis is discussed.

Asbestos affects the in vitro uptake and detoxification of aromatic compounds.

A number of mineral dusts were tested for their ability to catalyze the transformation of benzo(a)pyrene from the microcrystalline state into lipid solution. The findings of Lakowicz and his co-workers, that fibrous dusts were more active than nonfibrous dusts, were confirmed. Macromolecular binding metabolites of BaP were formed in A549 cells to a similar extent whether the BaP was added in solution or adsorbed to fibers; however, the level of water-soluble metabolites was lower in cultures treated with adsorbed hydrocarbon. It was found that asbestos can also inhibit the accumulation of 1-naphthyl glucuronide in cultures treated with 1-naphthol. The significance of this in asbestos pathogenesis is briefly discussed.

Study of the cell-transforming ability of amosite and crocidolite asbestos and the ability to induce changes in the metabolism and macromolecular binding of benzo(a)pyrene in C3H10T1/2 cells.

The cell transforming ability of asbestos dusts was investigated using C3H10T1/2 murine fibroblasts. In a series of experiments, crocidolite and amosite caused no increase in the number of transformed colonies over that seen in cultures from untreated cells. The dusts were, however, capable of augmenting the oncogenic effect of benzo(a)pyrene. This synergistic effect was evident when fibers and chemicals were added to cultures as simple mixtures and when benzo(a)pyrene was adsorbed to the surface of fibers. Asbestos dust did not, however, appear to exert its oncogenic enhancing effect by modifying the metabolism of benzo(a)pyrene in C3H10T1/2 cells.

The influence of asbestos dust on the oncogenic transformation of C3H10T 1/2 cells.

The cell transforming ability of asbestos dust was investigated using C3H10T 1/2 murine fibroblasts. In a series of experiments both crocidolite and amosite caused no increase in the number of transformed foci over that seen in cultures from untreated cells. The dusts, were, however, capable of augmenting the oncogenic effect of benzo[a]pyrene (BP). This putative synergistic effect was evident when fibres and chemicals were added to cultures as simple mixtures and when BP was adsorbed to the surface of the fibres.