Draft Genome Sequence of the Nitrogen-Fixing Endophyte Azoarcus communis SWub3

Here we report a draft genome sequence of Azoarcus communis SWub3, a nitrogen-fixing bacterium isolated from root tissues of Kallar grass in Pakistan.

Grass filtration in parallel with VFCW technology for community wastewater treatment through the king's initiative nature-by-nature process

The 15-year research is aimed to apply the Vertical Flow Constructed Wetland (VFCW) technology along with growing Star, Kallar, Coast couch grasses for community wastewater treatment as obtained from Phetchaburi municipal after anaerobic digesting inside the 18.5 km High-density Polyethylene (HDPE) pipe. The results found that pH value did not evidently show any change of influent to effluent among grass species but drastic change due to treatment efficiency in Biological Oxygen Demand (BOD), Total Kjeldahl Nitrogen (TKD), Total Phosphorus (TP), and Total Potassium (TK) due to supporting rapidly growing of Star, Kallar, and Coast couch grasses, and also some parts of organic forms to escape from the VFCW technical units as volatile gaseous chemicals; and precipitating down to the VFCW technical unit beds as sludge. The Star and Coast couch grasses showed higher potential in community wastewater treatment efficiency than Kallar grass but treating power were not different in wide ranges. Besides, the heavy metals (Pb, Cd, Hg as example) were contaminated in both treated wastewater and sludge (sediment). However, the influent and effluent as inflow and outflow of VFCW technical units found very low contamination but three grasses (Star, Kallar, and Coast couch) showed their eligibility in treating heavy metals, especially when their age at 45-day growth as the same findings of treating BOD, TKN, TP, and TK according to meet highest treatment efficiency at age of 45 days. In other words, the harvesting age at 45 days was not only reached the maximum treatment efficiency as well as maximum grass biomass but also kept away from heavy contamination.

An Endoglucanase Is Involved in Infection of Rice Roots by the Not-Cellulose-Metabolizing Endophyte Azoarcus Sp. Strain BH72

The nitrogen-fixing endophyte Azoarcus sp. strain BH72 infects roots of Kallar grass and rice inter- and intra-cellularly and can spread systemically into shoots without causing symptoms of plant disease. Although cellulose or its breakdown products do not support growth, this strain expresses an endoglucanase, which might be involved in infection. Sequence analysis of eglA places the secreted 34-kDa protein into the glycosyl hydrolases family 5, with highest relatedness (40% identity) to endoglucanases of the phytopathogenic bacteria Xanthomonas campestris and Ralstonia solanacearum. Transcriptional regulation studied by eglA:: gusA fusion was not significantly affected by cellulose or its breakdown products or by microaerobiosis. Strongest induction (threefold) was obtained in bacteria grown in close vicinity to rice roots. Visible sites of expression were the emergence points of lateral roots and root tips, which are the primary regions of ingress into the root. To study the role in endophytic colonization, eglA was inactivated by transposon mutagenesis. Systemic spreading of the eglA mutant and of a pilAB mutant into the rice shoot could no longer be detected by polymerase chain reaction. Microscopic inspection of infection revealed that the intracellular colonization of root epidermis cells was significantly reduced in the eglA-mutant BHE6 compared with the wild type and partially restored in the complementation mutant BHRE2 expressing eglA. This provides evidence that Azoarcus sp. endoglucanase is an important determinant for successful endophytic colonization of rice roots, suggesting an active bacterial colonization process.

Amelioration of a saline sodic soil through cultivation of a salt-tolerant grass Leptochloa fusca

Reclamation of saline lands seems difficult for climatic and economic reasons, but cultivation of salt-tolerant plants is an approach to increasing productivity and improvement of salt-affected wastelands. A five-year field study was conducted to evaluate the effects of growing a salt-tolerant species Leptochloa fusca (L.) Kunth (kallar grass) on chemical properties of a saline sodic soil irrigated with poor quality groundwater. Soil salinity, sodicity and pH decreased exponentially by growing kallar grass as a result of leaching of salts from surface (0–20 cm) to lower depths (>100 cm). Concentrations of soluble cations (Na+, K+, Ca2+ and Mg2+) and anions (Cl−, SO42− and HCO3−) were reduced through to greater soil depths. A significant decline in soil pH was attributed to release of CO2 by grass roots and solublization of CaCO3. Both soil salinity and soil pH were significantly correlated with Na+, Ca2+, Mg2+, K+, Cl−, HCO3− and sodium adsorption ratio (SAR). Significant correlations were found between soluble cations (Na+, Ca2+ and K+), soluble anions (Cl−, SO42− and HCO3−) and the SAR. In contrast, there were negative correlations between soil organic matter content and all chemical properties. The ameliorative effects on the soil chemical environment were pronounced after three years of growing kallar grass. Cultivation of kallar grass enhanced leaching and interactions among soil chemical properties and thus restored soil fertility. The soil maintained the improved characteristics with further growth of the grass up to five years suggesting that growing salt-tolerant plants is a sustainable approach to biological amelioration of saline wastelands.