Long-term adaptation of methanol-fed thermophilic (55 °C) sulfate-reducing reactors to NaCl

A laboratory-scale upflow anaerobic sludge bed (UASB) reactor was operated during 273 days at increasing NaCl concentrations (0.5–12.5 g NaCl l^–1) to assess whether the stepwise addition of the salt NaCl results in the acclimation of that sludge. The 6.5-l thermophilic (55 °C), sulfidogenic [a chemical oxygen demand (COD) to SO₄^2– ratio of 0.5] UASB reactor operated at an organic loading rate of 5 g COD l^–1 day^–1, a hydraulic retention time of 10 h and was fed with methanol as the sole electron donor. The results show that the adaptation of the thermophilic, sulfidogenic methanol-degrading biomass to a high osmolarity environment is unlikely to occur. Sulfide was the main mineralization product from methanol degradation, regardless of the NaCl concentration added to the influent. However, sulfide production in the reactor steadily decreased after the addition of 7.5 g NaCl l^–1, whereas acetate production was stimulated at that influent NaCl concentration. Batch tests performed with sludge harvested from the UASB reactor when operating at different influent salinities confirmed that acetate is the main metabolic product at NaCl concentrations higher than 12.5 g l^–1. The apparent order of NaCl toxicity towards the different trophic groups was found to be: sulfate-reducing bacteria > methane-producing archaea > acetogenic bacteria.     

Metal chelate affinity precipitation of RNA and purification of plasmid DNA

The affinity of metal chelates for amino acids, such as histidine, is widely used in purifying proteins, most notably through six-histidine `tails'. We have found that metal affinity interactions can also be applied to separation of single-stranded nucleic acids through interactions involving exposed purines. Here we describe a metal affinity precipitation method to resolve RNA from linear and plasmid DNA. A copper-charged copolymer of N-isopropyl acrylamide (NIPAM) and vinyl imidazole (VI) is used to purify plasmid from an alkaline lysate of E. coli. The NIPAM units confer reversible solubility on the copolymer while the imidazole chelates metal ions in a manner accessible to interaction with soluble ligands. RNA was separated from the plasmid by precipitation along with the polymer in the presence of 800 mM NaCl. Bound RNA could be recovered by elution with imidazole and separated from copolymer by a second precipitation step. RNA binding showed a strong dependence on temperature and on the type of buffer used.     

Advances in biotreatment of acid mine drainage and biorecovery of metals: 1. Metal precipitation for recovery and recycle

Acid mine drainage (AMD), an acidic metal-bearingwastewater, poses a severe pollution problem attributedto post mining activities. The metals usuallyencountered in AMD and considered of concern for riskassessment are arsenic, cadmium, iron, lead, manganese,zinc, copper and sulfate. The pollution generated byabandoned mining activities in the area of Butte, Montanahas resulted in the designation of the Silver Bow Creek–ButteArea as the largest Superfund (National Priorities List) sitein the U.S. This paper reports the results of bench-scalestudies conducted to develop a resource recovery basedremediation process for the clean up of the Berkeley Pit.The process utilizes selective, sequential precipitation (SSP)of metals as hydroxides and sulfides, such as copper, zinc,aluminum, iron and manganese, from the Berkeley Pit AMDfor their removal from the water in a form suitable foradditional processing into marketable precipitates and pigments.The metal biorecovery and recycle process is based on completeseparation of the biological sulfate reduction step and themetal precipitation step. Hydrogen sulfide produced in the SRBbioreactor systems is used in the precipitation step to forminsoluble metal sulfides. The average metal recoveries usingthe SSP process were as follows: aluminum (as hydroxide) 99.8%,cadmium (as sulfide) 99.7%, cobalt (as sulfide) 99.1% copper(as sulfide) 99.8%, ferrous iron (sulfide) 97.1%, manganese(as sulfide) 87.4%, nickel (as sulfide) 47.8%, and zinc (as sulfide)100%. The average precipitate purity for metals, copper sulfide,ferric hydroxide, zinc sulfide, aluminum hydroxide and manganesesulfide were: 92.4, 81.5, 97.8, 95.6 , 92.1 and 75.0%, respectively.The final produced water contained only calcium and magnesiumand both sulfate and sulfide concentrations were below usablewater limits. Water quality of this agriculturally usable watermet the EPA's gold standard criterion.     

A simple and effective separation and purification procedure for DNA fragments using Dodecyltrimethylammonium bromide

In this work we describe a simple two step separation procedure for the separation and purification of short DNA fragments. The first step involves precipitating the DNA using the cationic surfactant dodecyltrimethylammonium bromide. Dodecyltrimethylammonium bromide, unlike cetyltrimethylammonium bromide will not precipitate DNA before complexation is complete thus providing a high purity DNA. The second step involves dissolution of the DNA-dodecyltrimethylammonium complex in 75% ethanol, followed by precipitation of the Sodium-DNA salt, by titrating in a salt solution. This method is particularly suited to purification of short fragments as it does not require high salt concentrations in the ethanol precipitation step, which can be damaging for short DNA. The ability of dodecyltrimethylammonium bromide to remove ethidium bromide from intercalation sites on the DNA is also discussed     

One step purification of peanut phospholipase D by precipitation with alginate

A simple titrimetric assay with soybean lecithin has been used for screening phospholipase D activity from some plant sources, viz. peanut, wheat germ, cabbage and carrot. The enzyme from peanut has been purified by binding to alginate which is a water soluble polymer. The purification consisted of co-precipitation of enzyme with alginate upon addition of 0.06 M Ca⁺⁺. The enzyme was eluted from the polymer using 0.2 M sodium chloride. The activity recovery was 61% with 34 fold purification.     

Climate and the U.S. distribution of C4 grass subfamilies and decarboxylation variants of C4 photosynthesis

I compared the C(4) grass flora and climatic records for 32 sites in the United States. Consistent with previous studies, I found that the proportion of the grass flora that uses the NADP malic enzyme (NADP-ME) variant of C(4) photosynthesis greatly increases with increasing annual precipitation, while the proportion using the NAD malic enzyme (NAD-ME) variant (and also the less common phosphoenolpyruvate carboxykinase [PCK] variant) decreases. However the association of grass subfamilies with annual precipitation was even stronger than for the C(4) decarboxylation variants. Analysis of the patterns of distribution by partial correlation analysis showed that the correlations between the frequency of various C(4) types and rainfall were solely due to the association of the C(4) types with particular grass subfamilies. In contrast, there was a strong correlation of the frequency of the different subfamilies with annual precipitation that was independent of the influence of the different C(4) variants. It therefore appears that other, as yet unidentified, characteristics that differ among grass subfamilies may be responsible for their differences in distribution across natural precipitation gradients.     

Riding the sulfur cycle--metabolism of sulfonates and sulfate esters in gram-negative bacteria

Sulfonates and sulfate esters are widespread in nature, and make up over 95% of the sulfur content of most aerobic soils. Many microorganisms can use sulfonates and sulfate esters as a source of sulfur for growth, even when they are unable to metabolize the carbon skeleton of the compounds. In these organisms, expression of sulfatases and sulfonatases is repressed in the presence of sulfate, in a process mediated by the LysR-type regulator protein CysB, and the corresponding genes therefore constitute an extension of the cys regulon. Additional regulator proteins required for sulfonate desulfonation have been identified in Escherichia coli (the Cbl protein) and Pseudomonas putida (the AsfR protein). Desulfonation of aromatic and aliphatic sulfonates as sulfur sources by aerobic bacteria is oxygen-dependent, carried out by the alpha-ketoglutarate-dependent taurine dioxygenase, or by one of several FMNH(2)-dependent monooxygenases. Desulfurization of condensed thiophenes is also FMNH(2)-dependent, both in the rhodococci and in two Gram-negative species. Bacterial utilization of aromatic sulfate esters is catalyzed by arylsulfatases, most of which are related to human lysosomal sulfatases and contain an active-site formylglycine group that is generated post-translationally. Sulfate-regulated alkylsulfatases, by contrast, are less well characterized. Our increasing knowledge of the sulfur-regulated metabolism of organosulfur compounds suggests applications in practical fields such as biodesulfurization, bioremediation, and optimization of crop sulfur nutrition.     

Contrasting long-term alpine and subalpine precipitation trends in a mid-latitude North American mountain system,Colorado Front Range,USA

Background: Long-term climate trends in mountain systems often vary strongly with elevation.

Aims: To evaluate elevation dependence in long-term precipitation trends in subalpine forest and alpine tundra zones of a mid-continental, mid-latitude North American mountain system and to relate such dependence to atmospheric circulation patterns.

Methods: We contrasted 59-year (1952–2010) precipitation records of two high-elevation climate stations on Niwot Ridge, Colorado Front Range, Rocky Mountains, USA. The sites, one in forest (3022 m a.s.l.) and the other in alpine tundra (3739 m), are closely located (within 7 km horizontally, ca. 700 m vertically), but differ with respect to proximity to the mountain-system crest (the Continental Divide).

Results: The sites exhibited significant differences in annual and seasonal precipitation trends, which depended strongly on their elevation and distance from the Continental Divide. Annual precipitation increased by 60 mm (+6%) per decade at the alpine site, with no significant change at the subalpine site. Seasonally, trends at the alpine site were dominated by increases in winter, which we suggest resulted from an increase in orographically generated precipitation over the Divide, driven by upper-air (700 hPa) north-westerly flow. Such a change was not evident at the subalpine site, which is less affected by orographic precipitation on north-westerly flow.

Conclusions: Elevation dependence in precipitation trends appears to have arisen from a change in upper-air flow from predominantly south-westerly to north-westerly. Dependence of precipitation trends on topographic position and season has complex implications for the ecology and hydrology of Niwot Ridge and adjacent watersheds, involving interactions among physical processes (e.g. snowpack dynamics) and biotic responses (e.g. in phenologies and ecosystem productivity).     

Plant invasions differentially affected by diversity and dominant species in native‐ and exotic‐dominated grasslands

Plant invasions are an increasingly serious global concern, especially as the climate changes. Here, we explored how plant invasions differed between native‐ and novel exotic‐dominated grasslands with experimental addition of summer precipitation in Texas in 2009. Exotic species greened up earlier than natives by an average of 18 days. This was associated with a lower invasion rate early in the growing season compared to native communities. However, invasion rate did not differ significantly between native and exotic communities across all sampling times. The predictors of invasion rate differed between native and exotic communities, with invasion being negatively influenced by species richness in natives and by dominant species in exotics. Interestingly, plant invasions matched the bimodal pattern of precipitation in Temple, Texas, and did not respond to the pulse of precipitation during the summer. Our results suggest that we will need to take different approaches in understanding of invasion between native and exotic grasslands. Moreover, with anticipated increasing variability in precipitation under global climate change, plant invasions may be constrained in their response if the precipitation pulses fall outside the normal growing period of invaders.     

Selective removal of keratan sulfate in chondroitin sulfate samples by sequential precipitation with ethanol

Keratan sulfate (KS) is present as a contaminant in chondroitin sulfate (CS) mainly extracted from shark cartilage. We report a selective removal procedure of KS in CS samples by means of sequential precipitation with ethanol. Purified shark CS containing approximately 10% to 15% KS was subjected to a precipitation procedure in the presence of increasing percentages of saturated ethanol. In contrast to other solvents, 1.0 volume of ethanol was able to selectively purify CS, with a purity of approximately 100%, from KS. The current selective and simple procedure appears to be a reliable industrial preparation of CS devoid of large amounts of the residual KS.