Bacterial bioclusters relate to hydrochemistry in New Zealand groundwater.

Groundwater is a major source of New Zealand's water supply and supports base flows in rivers. Microbial communities in groundwater ecosystems mediate biogeochemical processes, and it is therefore crucial to understand microbial diversity in these ecosystems. We analysed bacterial assemblages from 35 New Zealand groundwater monitoring sites with varying hydrogeochemical conditions across the country. Proteobacteria was the most abundant phylum, and Variovorax represented the most common taxon. Pseudomonas, Burkholderia, Acidovorax, Janthinobacterium, Polaromonas and Caulobacter were the other common taxa. There was no Operational Taxonomic Unit (OTU) that was found in every one of the 35 samples. Here, we introduce a framework that has potential utility for groundwater ecosystem management, where the samples with similar microbial communities are grouped together into 'bioclusters'. Metabolic inferences derived from the taxonomic data were used to predict the oxygen requirements, metabolic potential and bacterial energy sources of each biocluster. Groundwater chemistry explains 59% of the variation in the relative abundance of all OTUs, with NO3-N, pH, DO, NH4-N, Fe, Br and SO4 displaying the strongest relationships to bioclusters. We propose that the biocluster framework, coupled with metabolic inferences derived from the taxonomic data, may have application outside New Zealand for on-going monitoring of the health of groundwater ecosystems.

Arsenate-ferrihydrite systems from minutes to months: a macroscopic and ir spectroscopic study of an elusive equilibrium.

Sorption by ferrihydrite is an important control on As(V) concentrations in many oxic aquatic systems. There are significant discrepancies in reported sorption constants (log(KAs)), which presents a problem for quantifying and understanding this important system. A review of reported ferrihydrite-As(V) sorption studies indicated a positive correlation between reaction time used in the experiments and the log(KAs) values derived from the data. In this paper, we study the kinetics of As(V) sorption over ≈3000 h in nine systems with varying pH and As(V)/Fe. Ferrihydrite was stable in all systems containing As(V), and the [As(V)] in solution decreased linearly as a function of log(t) (termed Elovich kinetics) over the full 3000 h in most systems. A stable [As(V)] was only observed in systems with low As(V)/Fe and low pH. Apparent As(V) sorption constants were derived from the data at specific time intervals using the diffuse layer model and equations describing log(KAs) values as a function of time provide a way to describe this elusive equilibrium. IR spectra support the hypothesis that slow interparticle diffusion is responsible for the slow approach to equilibrium. This work resolves discrepancies in previous studies of As(V)-ferrihydrite and provides equations to allow for system appropriate log(KAs) values to be used.

Influence of pH and natural organic matter on zinc biosorption in a model lignocellulosic biofuel biorefinery effluent.

The effect of dissolved natural organic matter (NOM) and pH on microbial biosorption of Zn was evaluated in a model lignocellulosic biofuel refinery effluent rich in NOM. Batch culture experiments conducted with two model microorganisms (yeast, Candida tropicalis; bacteria Novosphingobium nitrogenifigens Y88(T)), showed an inhibitory effect of NOM, and an optimum pH for Zn removal at 7.5-8.0. Membrane bioreactors with mixed autochthonous organisms were operated at pH 6.5 and pH 8.0 to better simulate real-world remediation scenarios. More Zn was removed at the high (91%) than at the low (26%) pH, presumably because the higher pH freed negatively-charged functional groups on the cellular biomass for passive Zn binding. Manipulating the pH of bioreactors can significantly improve metal removal in NOM rich wastewater. Such reactors could maintain water quality for closed-cycle biorefineries, leading to reduced water consumption, and a more sustainable biofuel.

National survey of molecular bacterial diversity of New Zealand groundwater: relationships between biodiversity, groundwater chemistry and aquifer characteristics.

Groundwater is a vital component of rural and urban water supplies in New Zealand. Although extensive monitoring of chemical and physical properties is conducted due to the high demand for this valuable resource, current information on its bacterial content is limited. However, bacteria provide an immense contribution to drive the biogeochemical processes in the groundwater ecosystem as in any other ecosystem. Therefore, a proper understanding of bacterial diversity is crucial to assess the effectiveness of groundwater management policies. In this study, we investigated the bacterial community structure in NZ groundwater at a national scale using the terminal restriction fragment length polymorphism (T-RFLP) molecular profiling tool and determined the relationships between bacterial diversity and groundwater chemistry, geological parameters and human impact. Considerable bacterial diversity was present and the community structures were strongly related to groundwater chemistry, and in particular to redox potential and human impact, reflecting their potential influence on determination of bacterial diversity. Further, the mean residence time of groundwater also showed relationships with bacterial community structure. These novel findings pertaining to community composition and its relationships with environmental parameters will provide a strong foundation for qualitative exploration of the bacterial diversity in NZ groundwater in relation to sustainable management of this valuable resource.

Dynamic groundwater monitoring networks: a manageable method for reviewing sampling frequency.

Optimization of a water quality network through a change in sampling frequency is the only way to increase cost-efficiency without any reduction in the robustness of the data. Existing techniques define optimal sampling frequency based on analysis of historical data from the monitoring network under investigation. Their application to a large network comprised of many sites and many monitored parameters is both technical and challenging. This paper presents a simple non-parametric method for reviewing sampling frequency that is consistent with highly censored environmental data and oriented towards reduction of sampling frequency as a cost-saving measure. Based on simple descriptive statistics, the method is applicable to large networks with long time series and many monitored parameters. The method also provides metrics for interpretation of newly collected data, which enables identification of sites for which a future change in sampling frequency may be necessary, ensuring that the monitoring network is both current and adaptive. Application of this method to the New Zealand National Groundwater Monitoring Programme indicates that reduction of sampling frequency at any site would result in a significant loss of information. This paper also discusses the potential for reducing analysis frequency as an alternative to reduction of sampling frequency.

Microbial life in Champagne Pool, a geothermal spring in Waiotapu, New Zealand.

Surveys of Champagne Pool, one of New Zealand's largest terrestrial hot springs and rich in arsenic ions and compounds, have been restricted to geological and geochemical descriptions, and a few microbiological studies applying culture-independent methods. In the current investigation, a combination of culture and culture-independent approaches were chosen to determine microbial density and diversity in Champagne Pool. Recovered total DNA and adenosine 5'-triphosphate (ATP) content of spring water revealed relatively low values compared to other geothermal springs within New Zealand and are in good agreement with low cell numbers of 5.6 +/- 0.5 x 10(6) cells/ml obtained for Champagne Pool water samples by 4',6-diamidino-2-phenylindole (DAPI) staining. Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA (small-subunit ribosomal nucleic acid) gene clone library analyses of environmental DNA indicated the abundance of Sulfurihydrogenibium, Sulfolobus, and Thermofilum-like populations in Champagne Pool. From these results, media were selected to target the enrichment of hydrogen-oxidizing and sulfur-dependent microorganisms. Three isolates were successfully obtained having 16S rRNA gene sequences with similarities of approximately 98% to Thermoanaerobacter tengcongensis, 94% to Sulfurihydrogenibium azorense, and 99% to Thermococcus waiotapuensis, respectively.

Acid-base titrations of functional groups on the surface of the thermophilic bacterium Anoxybacillus flavithermus: comparing a chemical equilibrium model with ATR-IR spectroscopic data.

Acid-base functional groups at the surface of Anoxybacillus flavithermus (AF) were assigned from the modeling of batch titration data of bacterial suspensions and compared with those determined from in situ infrared spectroscopic titration analysis. The computer program FITMOD was used to generate a two-site Donnan model (site 1: pKa = 3.26, wet concn = 2.46 x 10(-4) mol g(-1); site 2: pKa = 6.12, wet concn = 6.55 x 10(-5) mol g(-1)), which was able to describe data for whole exponential phase cells from both batch acid-base titrations at 0.01 M ionic strength and electrophoretic mobility measurements over a range of different pH values and ionic strengths. In agreement with information on the composition of bacterial cell walls and a considerable body of modeling literature, site 1 of the model was assigned to carboxyl groups, and site 2 was assigned to amino groups. pH difference IR spectra acquired by in situ attenuated total reflection infrared (ATR-IR) spectroscopy confirmed the presence of carboxyl groups. The spectra appear to show a carboxyl pKa in the 3.3-4.0 range. Further peaks were assigned to phosphodiester groups, which deprotonated at slightly lower pH. The presence of amino groups could not be confirmed or discounted by IR spectroscopy, but a positively charged group corresponding to site 2 was implicated by electrophoretic mobility data. Carboxyl group speciation over a pH range of 2.3-10.3 at two different ionic strengths was further compared to modeling predictions. While model predictions were strongly influenced by the ionic strength change, pH difference IR data showed no significant change. This meant that modeling predictions agreed reasonably well with the IR data for 0.5 M ionic strength but not for 0.01 M ionic strength.

Cadmium ion biosorption by the thermophilic bacteria Geobacillus stearothermophilus and G. thermocatenulatus.

This study reports surface complexation models (SCMs) for quantifying metal ion adsorption by thermophilic microorganisms. In initial cadmium ion toxicity tests, members of the genus Geobacillus displayed the highest tolerance to CdCl2 (as high as 400 to 3,200 microM). The thermophilic, gram-positive bacteria Geobacillus stearothermophilus and G. thermocatenulatus were selected for further electrophoretic mobility, potentiometric titration, and Cd2+ adsorption experiments to characterize Cd2+ complexation by functional groups within and on the cell wall. Distinct one-site SCMs described the extent of cadmium ion adsorption by both studied Geobacillus sp. strains over a range of pH values and metal/bacteria concentration ratios. The results indicate that a functional group with a deprotonation constant pK value of approximately 3.8 accounts for 66% and 80% of all titratable sites for G. thermocatenulatus and G. stearothermophilus, respectively, and is dominant in Cd2+ adsorption reactions. The results suggest a different type of functional group may be involved in cadmium biosorption for both thermophilic strains investigated here, compared to previous reports for mesophilic bacteria.

Hg(II) adsorption by bacteria: a surface complexation model and its application to shallow acidic lakes and wetlands in Kejimkujik National Park, Nova Scotia, Canada.

The fate and environmental threat posed by mercury in aquatic systems is controlled, in part, bythe transport of Hg(II) from oxic to anoxic zones in lakes and its subsequent transformation to organic mercury. The transport of Hg(II) in aquatic systems can be affected by its partitioning between the dissolved and particulate phases. In this study, batch experiments were performed to quantify Hg(II) adsorption to Bacillus subtilis as bacteria-to-metal ratio, pH, chloride concentration, growth phase, and reaction time were independently varied. The laboratory data were well described by a surface complexation model (SCM) considering the adsorption of neutral Hg(II) hydroxide and chloride complexes by specific functional groups on the bacterial surface. To evaluate its applicability to complex aquatic systems, the SCM was used to predict the distributions of Hg(II) in 36 shallow acidic lakes and wetlands in Kejimkujik National Park, Nova Scotia, Canada. The lab-derived SCM provided a statistically accurate (r2 = 0.615, P < 0.01) fit to the field data when it was expanded to consider Hg(II) complexation by dissolved organic matter. Inclusion of Hg(II)-mineral adsorption reactions did not improve the fit of the model. The quality of fit provided by the expanded SCM suggested that the major assumptions implicit in applying a lab-derived model to the field were justifiable. Our study has demonstrated that SCMs are powerful tools for dynamic prediction of the sorption of environmental contaminants to biocolloids at the regional scale.