Bacteria Respond Stronger Than Fungi Across a Steep Wood Ash-Driven pH Gradient

Soil pH is probably the most important variable explaining bacterial richness and community composition locally as well as globally. In contrast, pH effects on fungi appear to be less pronounced, but also less studied. Here we analyze the community responses of bacteria and fungi in parallel over a local extreme pH gradient ranging from 4 to 8. We established the pH gradient by applying strongly alkaline wood ash in dosages of 0, 3, 9, 15, 30, and 90 t ha–1 to replicated plots in a Picea abies plantation and assessed bacterial and fungal community composition using high throughput amplicon sequencing 1 year after ash application. At the same time, the experiment investigated if returning wood ash to plantation forests pose any immediate threats for the microbial communities. Among the measured environmental parameters, pH was by far the major driver of the microbial communities, however, bacterial and fungal communities responded differently to the pH increment. Whereas both bacterial and fungal communities showed directional changes correlated with the wood ash-induced increase in pH, the bacterial community displayed large changes at wood ash dosages of 9 and 15 t ha–1 while only higher dosages (>30 t ha–1) significantly changed the fungal community. The results confirm that fungi are less sensitive to pH changes than bacteria but also that fertilizing plantation forests with wood ash, viewed through the lens of microbial community changes, is a safe management at standard dosages (typically 3 t ha–1).

The Proton in Biochemistry: Impacts on Bioenergetics, Biophysical Chemistry, and Bioorganic Chemistry

The proton is the smallest atomic particle, and in aqueous solution it is the smallest hydrated ion, having only two waters in its first hydration shell. In this article we survey key aspects of the proton in chemistry and biochemistry, starting with the definitions of pH and pKa and their application inside biological cells. This includes an exploration of pH in nanoscale spaces, distinguishing between bulk and interfacial phases. We survey the Eigen and Zundel models of the structure of the hydrated proton, and how these can be used to explain: a) the behavior of protons at the water-hydrophobic interface, and b) the extraordinarily high mobility of protons in bulk water via Grotthuss hopping, and inside proteins via proton wires. Lastly, we survey key aspects of the effect of proton concentration and proton transfer on biochemical reactions including ligand binding and enzyme catalysis, as well as pH effects on biochemical thermodynamics, including the Chemiosmotic Theory. We find, for example, that the spontaneity of ATP hydrolysis at pH ≥ 7 is not due to any inherent property of ATP (or ADP or phosphate), but rather to the low concentration of H+. Additionally, we show that acidification due to fermentation does not derive from the organic acid waste products, but rather from the proton produced by ATP hydrolysis.

Thresholds of acidification impacts on macroinvertebrates adapted to seasonally acidified tropical streams: potential responses to extreme drought-driven pH declines

Background Drought-driven acidification events of increasing frequency and severity are expected as a consequence of climate change, and these events may expose macroinvertebrate taxa to increased acidification beyond their tolerance levels. Recent work in lowland Costa Rica has shown that poorly-buffered tropical streams exhibit natural seasonal variation in pH, with extremely low levels (<4.5) after extreme dry seasons). Our goal was to determine the threshold of pH effects on survival of three tropical stream macroinvertebrate taxa. Methods We conducted laboratory mesocosm experiments to determine acidification effects (using diluted HCl) on three focal macroinvertebrate taxa collected from a poorly-buffered stream at La Selva Biological Station: (1) mayfly naiads (Ephemeroptera: Leptophlebiidae: Traverella holzenthali), (2) adult shrimp (Decapoda: Palaemonidae: Macrobrachium olfersii), and (3) larval midges (Diptera: Chironomidae). We also compared the effect of pH on survival and growth rates of larval midges from a poorly-buffered (pH 4.3–6.9) vs. a naturally well-buffered (pH 5.1–6.9) stream. Results/Discussion Mayfly and shrimp survival decreased between pH 4.0 and 3.5, overlapping with the range of lowest pH levels (3.6–4.0) recorded during a previous extreme El Niño Southern Oscillation event in 1998 and suggesting that increasingly extreme acidification events induced by climate change may negatively affect their survival. In contrast, survival of larval midges was unaffected by pH regimes at/above 3.5, indicating tolerance to pH levels experienced in poorly-buffered stream during seasonal acidification, which has presumably occurred over millennia. These findings highlight the potential importance of historical pH regimes in structuring macroinvertebrate communities. These results are relevant not only to lowland Neotropical streams, but also signal the need for further research in lotic ecosystems worldwide where drought-driven pH declines have been documented or are probable in the future.

Preparation, Characterization and Analytical Studies of novel Azo dyes and Diazo dyes

The amino {4-hydroxy-3-[(E)-{4-[(5-methylisoxazol-3-yl) sulfamoyl] phenyl} diazenyl] phenyl} acetic acid (1) and the amino {4-hydroxy-3,5-bis[(E)-{4-[(5-methylisoxazol-3-yl) sulfamoyl] phenyl} diazenyl] phenyl} acetic acid (2) were Prepared. The resulting azo and diazo dyes were then characterized using m.p., IR, UV-visible, mass spectrum and 1H-NMR spectrum. Analytical studies were carried on the azo dye (1) and the diazo dye (2). The best solubility of (1) and (2) was in methanol and ethyl acetate respectively, with no deviation from the linear relationship in each dye, which is due to the fact that the effect of the dielectric constant is the main factor that can control the shift of the absorption beaks. Though, the pH effects of (1) and (2) in a range of buffer solution were showed one and two isopiestic points respectively. Calculation of the ionization (pKa) and the protonation (pKp) constants by using the half height method was associated to the nitrogen atom and the OH-groups respectively. The pKp1, pKa1 and pKa2 were also intended. But, the value of the pKp2 was absent in the azo dye (1) and seems to be equal to 2.5 in the diazo dye (2). These results were indicated the suggested ionization scheme in acidic and basic medium of each dye. Furthermore, the dyes with different concentrations have harmless, nontoxic and no haemolysis effects.