Mercury alters the bacterial community structure and diversity in soil even at concentrations lower than the guideline values

This study evaluated the effect of inorganic mercury (Hg) on bacterial community and diversity in different soils. Three soils—neutral, alkaline and acidic—were spiked with six different concentrations of Hg ranging from 0 to 200 mg kg⁻¹ and aged for 90 days. At the end of the ageing period, 18 samples from three different soils were investigated for bacterial community structure and soil physicochemical properties. Illumina MiSeq-based 16s ribosomal RNA (rRNA) amplicon sequencing revealed the alteration in the bacterial community between un-spiked control soils and Hg-spiked soils. Among the bacterial groups, Actinobacteria (22.65%) were the most abundant phyla in all samples followed by Proteobacteria (21.95%), Bacteroidetes (4.15%), Firmicutes (2.9%) and Acidobacteria (2.04%). However, the largest group showing increased abundance with higher Hg doses was the unclassified group (45.86%), followed by Proteobacteria. Mercury had a considerable negative impact on key soil functional bacteria such as ammonium oxidizers and nitrifiers. Canonical correspondence analysis (CCA) indicated that among the measured soil properties, Hg had a major influence on bacterial community structure. Furthermore, nonlinear regression analysis confirmed that Hg significantly decreased soil bacterial alpha diversity in lower organic carbon containing neutral and alkaline soils, whereas in acidic soil with higher organic carbon there was no significant correlation. EC₂₀ values obtained by a nonlinear regression analysis indicated that Hg significantly decreased soil bacterial diversity in concentrations lower than several guideline values.

     

Bioremediation of mercury: not properly exploited in contaminated soils!

Applied Microbiology and Biotechnology - Contamination of land and water caused by heavy metal mercury (Hg) poses a serious threat to biota worldwide. The seriousness of toxicity of this neurotoxin...     

Triazole-fused sugars from nitroalkene-containing C-glycosides by a tandem 1,3-dipolar cycloaddition and intramolecular Michael addition

A synthetic method to triazole-fused sugars by treatment of nitroalkene-containing C-glycosides with sodium azide is described. Initial experiments conducted at room temperature gave only the 1,3-dipolar cycloaddition products. However, at elevated reaction temperature the tandem β-elimination/cycloaddition/Michael addition yielded 1,5-disubstituted triazole-fused sugars.     

Purification and biological characterization of a halophilic thermostable protease from <Emphasis Type="Italic">Haloferax lucentensis</Emphasis> VKMM 007

An extremely halophilic archaeon Haloferax lucentensis VKMM 007, isolated from a solar saltern, was found to produce a protease. This extracellular enzyme consisted of a single polypeptide chain of 57.8 kDa as determined by SDS–PAGE and was purified by a combination of ultrafiltration, bacitracin–Sepharose affinity chromatography and Sephadex G-100 gel filtration. The purified protein was stable in a wide range of temperatures (20–70°C), NaCl concentrations (0.85–5.13 M) and pH (5.0–9.0) with maximal activity observed at 60°C, 4.3 M NaCl and pH 8.0. Proteolytic activity was enhanced by Ca²⁺, K⁺, Mg²⁺, Na⁺, and Fe²⁺ ions and the protein was classified as a trypsin-like serine protease. Further assays indicated highest degree of specificity when hemoglobin was used as an enzyme substrate. Most importantly, the proteolytic activity remained stable or only marginally inhibited in the presence of various polar and non-polar solvents, surfactants and reducing agents thus emphasizing the biotechnological potential of this novel halophilic protease.     

Purification and characterization of a novel plant-type carbonic anhydrase from Bacillus subtilis

Carbonic anhydrase enzyme, one of the fastest known enzymes, remains largely unexplored in prokaryotes when compared to its mammalian counterparts despite its ubiquity. In this study, the enzyme has been purified from Bacillus subtilis SA3 using sequential Sephadex G-75 chromatography, DEAE cellulose chromatography, and sepharose-4B-L-tyrosinesulphanilamide affinity chromatography and characterized to provide additional insights into its properties. The apparent molecular mass of carbonic anhydrase obtained by SDS-PAGE was found to be approximately 37 kDa. Isoelectric focusing of the purified enzyme revealed an isoelectric point (pI) of around 6.1 when compared with marker. The presence of metal ions such as Zn²⁺, Co²⁺, Cu²⁺, Fe³⁺, Mg²⁺, and anion SO₄⁻ increased enzyme activity while strong inhibition was observed in the presence of Hg²⁺, Cl⁻, HCO₃⁻, and metal chelator EDTA. The optimum pH and temperature for the enzyme were found to be 8.3 and 37°C, respectively. Enzyme kinetics with p-nitrophenyl acetate as substrate at pH 8.3 and 37°C determined the V_max and K_m values of the enzyme to be 714.28 μmol/mg protein/min and 9.09 mM, respectively. The K_i value for acetazolamide was 0.22 mM, compared to 0.099 mM for sulphanilamide. The results from N-terminal amino acid sequencing imply the purified protein is a putative beta-carbonic anhydrase with close similarities to CAs from plants, microorganisms.     

Synthetic studies of neoclerodane diterpenes from Salvia divinorum: selective modification of the furan ring

A synthetic sequence has been developed to selectively functionalize the furan ring of the natural product salvinorin A (2a). The synthetic routes described convert the furan ring in 2a into an N-sulfonylpyrrole, oxazole or an oxadiazole. In addition, a procedure has been found to remove the furan skeleton completely. Biological results indicate that replacement of the furan ring with an N-sulfonylpyrrole leads to reduced affinity and efficacy at kappa opioid receptors.     

Substituent activity relationship studies on new azolo benzoxazepinyl oxazolidinones

In an effort to discover potent antibacterials based on the entropically favored 'bioactive conformation' approach, a series of novel tricyclic molecules mimicking the conformationally constrained structure of Linezolid is reported. Based on the initial tricyclic molecule 1, the benzazepine derivative 2 was designed where the tricyclic structure had more flexibility around C-N bond compared to 1. While, the molecule 2 was less active, the molecule 3 showed promising antibacterial activity presumably after having obtained rigidity due to pyrrole ring. The syntheses, SAR studies, and evaluation of 3 as a lead compound are reported.     

Familiarity with Own Population’s Appearance Influences Facial Preferences

Previous studies have found that individuals from rural areas in Malaysia and in El Salvador prefer heavier women than individuals from urban areas. Several explanations have been proposed to explain these differences in weight preferences but no study has explored familiarity as a possible explanation. We therefore sought to investigate participants’ face preferences while also examining the facial characteristics of the actual participants. Our results showed that participants from rural areas preferred heavier-looking female faces than participants from urban areas. We also found that the female faces from the rural areas were rated as looking heavier than the female faces from the urban areas. Our findings are consistent with the hypothesis that familiarity may be contributing to the differences found in face preferences between rural and urban areas given that people from rural and urban areas are exposed to different faces.