Dynamism of PGPR in bioremediation and plant growth promotion in heavy metal contaminated soil.

Heavy metal contamination, particularly of cultivable lands, is a matter of concern. Bioremediation helps in reversing such contamination to certain extent. Here, we report isolation, polyphasic identification and the role of siderophore producing rhizobacteria Alcaligenes feacalis RZS2 and Pseudomonas aeruginosa RZS3 in bioremediation of heavy metal contaminated soil and plant growth promotion activity in such contaminated soil. Siderophore produced by A. feacalis RZS2 and P. aeruginosa RZS3 strains chelated various heavy metal ions like MnCl2.4H2O, NiCl2.6H2O, ZnCl2, CuCl2 and CoCl2 other than FeCl3.6H2O at batch scale. Their bioremediation potential was superior over the chemical ion chelators like EDTA and citric acid. These isolates also promoted growth of wheat and peanut seeds sown in heavy metal contaminated soil. Effective root colonizing ability of these isolates was observed in wheat and peanut plants.

Statistical-based optimization and scale-up of siderophore production process on laboratory bioreactor.

We report the enhanced production of siderophore in succinate medium by applying two-stage statistical approach, i.e., Plackett-Burman design and response surface methodology (RSM) using central composite design (CCD). In the first stage of optimization, out of 11 variable components of succinate medium, succinic acid, pH and temperature were found as significant components that influenced the siderophore production in Pseudomonas aeruginosa RZS9. The second stage of RSM using CCD consisted of optimizing the concentrations of the variables. Here, 0.49 g/100 ml concentration of succinic acid, pH 7.08 and temperature of 27.80 °C yielded the maximum (68.41 %) siderophore units. All the significant components exhibited quadratic effect on siderophore production. The F value of 28.63, multiple correlation coefficient (R 2) of 0.9626, percent coefficient of variation of 8.81 values indicated that the model was significant and that the experimental data was satisfactorily adjusted to the quadratic model. During validation of these experiments, 6.10 % increase in siderophore yield was obtained. Scale-up of this protocol optimized at shake  flask level up to 5 L-capacity reactor further enhanced the siderophore yield. We claim it to be the first report on statistical optimization of siderophore production by P. aeruginosa RZS9.

Stenotrophomonas sp. RZS 7, a novel PHB degrader isolated from plastic contaminated soil in Shahada, Maharashtra, Western India.

This paper reports an isolation and identification of novel poly-ß-hydroxybutyrate (PHB) degrading bacterium Stenotrophomonas sp. RZS 7 and studies on its extracellular PHB degrading depolymerase enzyme. The bacterium isolated from soil samples of plastic contaminated sites of municipal area in Shahada, Maharashtra, Western India. It was identified as Stenotrophomonas sp. RZS 7 based on polyphasic approach. The bacterium grew well in minimal salt medium (MSM) and produced a zone (4.2 mm) of PHB hydrolysis on MSM containing PHB as the only source of nutrient. An optimum yield of enzyme was obtained on the fifth day of incubation at 37 °C and at pH 6.0. Further increase in enzyme production was recorded with Ca2+ ions, while other metal ions like Fe2+ (1 mM) and chemical viz. mercaptoethanol severally affected the production of enzyme.

Open lung biopsy for diffuse infiltrative lung disease.

The purpose of this study was to determine the most appropriate site of biopsy in patients with diffuse infiltrative lung disease (DILD). Twenty patients were evaluated. During open lung biopsy, a representative region (inflamed and least fibrotic) of the radiographically most involved lobe was identified and a biopsy done. A second biopsy specimen was obtained from an adjacent accessible lobe. The biopsy specimen from each lobe was processed separately, and a descriptive histologic report was generated for each of the two lobes. Tissue was cultured for bacteria, fungi, and mycobacteria. In 17 patients, the second biopsy site had fewer roentgenographic abnormalities than the radiographically most involved lobe. In 3 patients, the number of radiographic abnormalities was equal in all lobes. The same pathologic diagnosis was reached by histologic examination of the two biopsy specimens in 8 of 10 patients with acute DILD and in 10 of 10 patients with chronic DILD. In 2 patients, the biopsy specimen from the radiographically most involved lobe showed pathologic features not seen in the other specimen. Cultures from both biopsy specimens were grown separately in 6 patients. Fungi (n = 2) and bacteria (n = 1) were isolated from the radiographically most involved lobe (n = 2) or from the lobe of initial lung infiltration (n = 1) in 3 patients. When biopsy specimens are obtained from a representative region of the radiographically most involved lobe in patients with DILD, biopsy of other lobes is unnecessary.