Extensive use of chromium (Cr) and arsenic (As) based preservatives from the leather tanning industry in Pakistan has had a deleterious effect on the soils surrounding production facilities. Bacteria have been shown to be an active component in the geochemical cycling of both Cr and As, but it is unknown how these compounds affect microbial community composition or the prevalence and form of metal resistance. Therefore, we sought to understand the effects that long-term exposure to As and Cr had on the diversity and structure of soil microbial communities. Soils from three spatially isolated tanning facilities in the Punjab province of Pakistan were analyzed. The structure, diversity and abundance of microbial 16S rRNA genes were highly influenced by the concentration and presence of hexavalent chromium (Cr (VI)) and arsenic. When compared to control soils, contaminated soils were dominated by Proteobacteria while Actinobacteria and Acidobacteria (which are generally abundant in pristine soils) were minor components of the bacterial community. Shifts in community composition were significant and revealed that Cr (VI)-containing soils were more similar to each other than to As contaminated soils lacking Cr (VI). Diversity of the arsenic resistance genes, arsB and ACR3 were also determined. Results showed that ACR3 becomes less diverse as arsenic concentrations increase with a single OTU dominating at the highest concentration. Chronic exposure to either Cr or As not only alters the composition of the soil bacterial community in general, but affects the arsenic resistant individuals in different ways.

Aims: The aim of this study was to investigate the potential of bacterial strains of Bacillus, Pseudomonas, Escherichia, Micrococcus and Staphylococcus genera associated with wild herbaceous flora to enhance endogenous indole-3-acetic acid (IAA) content and growth of Triticum aestivum var. Inqalab-91. Methods and Results: Gas chromatography and mass spectrometric (GC–MS) analysis revealed that bacterial strains produced 0·6–8·22 μg IAA ml⁻¹ in the presence of L-tryptophan. Plant microbe experiments showed a significant positive correlation between auxin production by bacterial strains and endogenous IAA content of T. aestivum for GC–MS (r = 0·618; P = 0.05) and colorimetric analysis (r = 0·693; P = 0.01). Similarly, highly significant positive correlation for shoot length (r = 0·627; P = 0.01) and shoot fresh weight (r = 0·626; P = 0.01) was observed with auxin production under axenic conditions. Bacterial inoculations also enhanced shoot length (up to 29·16%), number of tillers (up to 97·35%), spike length (up to 25·20%) and seed weight (up to 13·70%) at final harvest. Conclusions: Bacterial strains have the ability to increase the endogenous IAA content and growth of T. aestivum var. Inqalab-91. Significance and Impact of the Study: Microbial strains of wild herbaceous flora can be effectively used to enhance the growth and yield of agronomically important crops.

Small circular single-stranded DNA satellites, termed DNAβ, have recently been found associated with some geminivirus infections. The DNA β associated with Cotton leaf curl virus is responsible for symptom expression of a devastating disease in Pakistan. Mutagenesis of DNA β revealed that the complementary-sense open reading frame (ORF) βC1 is required for inducing disease symptoms in Nicotiana tabacum. An ORF present on the virion-sense strand βV1 appeared to have no role in pathogenesis. Tobacco plants transformed with a βC1 ORF under the control of the Cauliflower mosaic virus 35S promoter or with a dimeric DNA β exhibited severe disease-like phenotypes, while plants transformed with a mutated version of βC1 appeared normal. Northern blot analysis of RNA from the transgenic plants, using strand-specific probes, identified a single complementary-sense transcript. The transcript carries the full βC1 ORF encoding a 118-amino acid product. It maps to the DNA β at nucleotide position 186 to 563 and contains a polyadenylation signal 18 nt upstream of the stop codon. A TATA box is located 43 nt upstream of the start codon. Our results indicate that βC1 protein is responsible for DNA β-induced disease symptoms.