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The present study demonstrates the metal toxicity ameliorating and growth promoting abilities of three different bacterial isolates when applied to rice as host plant. The three bacterial strains included a cadmium resistant Ochrobactrum sp., a lead resistant Bacillus sp. and an arsenic resistant Bacillus sp. designated as CdSP9, PbSP6, and AsSP9, respectively. When these isolates were used as inocula applied to metal-treated rice plants of variety Satabdi, the germination percentage, relative root elongation (RRE), amylase and protease activities were increased. The toxic effect of metal was reduced in presence of these bacteria. The overall biomass and root/shoot ratio were also enhanced by bacterial inoculation. Hydroponic studies showed that the superoxide dismutase (SOD) activity and malondialdehyde (MDA) level, which had been increased in the presence of metal stress in rice roots, were lowered by the bacterial inoculation. In addition, all three strains were 1-aminocyclopropane-1-carboxylate (ACC) deaminase and catalase positive, whereas siderophore producing ability was lacking in PbSP6. However, both PbSP6 and AsSP9 were protease positive and could hydrolyse starch. The data indicate that these bacteria have promise for bioremediation as well as for plant growth promotion.

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The goal was to investigate the cellulase enzyme production ability of bacterial strain C1 isolated from cow dung and identified as Bacillus sp. on the basis of 16 S rDNA sequence homology. The effects of different carbon sources like Carboxymethyl cellulose (CMC), avicel, starch, maltose, sucrose, glucose, fructose, galactose and lactose on cellulase production at varying environmental parameters of incubation period (2-10 days), temperature (35-55°C), and pH (6.0-8.5) were examined. The CMC was the best carbon source for cellulase production followed by lactose in this bacterial strain. The maximum enzyme production was achieved at a temperature of 50°C by Bacillus sp. with pH of 7.0 on the 8th day of growth. The nitrogen source NH 4 NO 3 at 0.175% was optimum for cellulase production by this bacterium. A putative mutant (C1M 26 ) was screened from wild C1 strain after mutagenesis with N-methyl-N 0 -nitro-N-nitrosoguanidine (NTG) as a mutagenic agent. The mutant C1M 26 produced a larger amount of cellulase in comparison to wild type C1 strain. ª 2014 Production and hosting by Elsevier B.V. on behalf of King Saud University.

Phosphorus is a primary macronutrient required for normal plant health, metabolism and survival. It is present in soil in compound insoluble form for which plant cannot uptake it directly from the soil. Some phosphate solubilizing bacteria possess some important enzymes for phosphate solubilization as well as mineralization. Alkaline (or basic) phosphatase (EC 3.1.3.1) is a type of zinc containing dimeric hydrolase enzyme responsible for removing the phosphate groups from various kinds of molecules including nucleotides, proteins, and alkaloids. Unlike acid phosphatases alkaline phosphatases are most effective in an alkaline environment. Alkaline phosphatases (ALPs) are of immense importance in various agricultural industries including dairy industries for testing successful pasteurization process. In this present study, Pseudomonas aeruginosa phosphatase was selected for a detailed computational investigation to exploit its physicochemical characteristics, structural properties including 3D model, model quality analysis, phylogenetic assessment and functional analysis using a number of available standard bioinformatics tools. The protein having average molecular weight about 51 kDa, was found thermostable and alkaline in nature belonging to metalloenzyme superfamily. Specifically, the thermostable behavior of the protein is suitable for the dairy industry. Moreover, this theoretical overview will help researchers to get an idea about the predicted protein structure and it may also help to design genetically engineered phosphate solubilizing bacteria by designing specific primers.

Cadmium (Cd) phytotoxicity in agricultural land is a major global concern now-a-days resulting in very poor yield. Plant growth-promoting rhizobacteria (PGPR)-mediated bioremediation is one of the convenient strategies for detoxification of Cd from the soil and for plant growth promotion under Cd stress. The selected strain K5 was identified as Klebsiella pneumoniae based on MALDI-TOF MS ribosomal protein and 16S rDNA sequence-based homology. The strain possessed several PGP traits viz. IAA production (3413 μg/mL), phosphate solubilization (80.25 ppm), ACC deaminase activity (40 ng α-ketobutyrate/mg protein/h), N fixation ability (1.84 μg N fixed/h), etc. and has the highest Cd resistance (4000 μg/mL) among Cd-resistant PGPR so far reported. This strain efficiently accumulated Cd and remained viable under Cd stress as confirmed by AAS-TEM-EDX analysis and viability test, respectively. The significant (p < 0.05) positive effect of the strain was reflected in various plant growth parameters like increased seed germination (50 to 90%), root length (5-fold), shoot length (about 2-fold), root fresh weight (> 2-fold), and shoot fresh weight (1.23-fold) under Cd stress compared with uninoculated set. Moreover, the positive impact of this strain on antioxidant enzyme activity (CAT, MDA, SOD) and several other biochemical parameters (proline, α-amylase, protease, total sugar, total protein, chlorophyll content) were also measured that favors plant growth promotion under Cd stress. Besides, the K5 strain also decreased stress-ethylene level under Cd stress and reduction of Cd accumulation in seedling (> 1.5-fold) was conducive to alleviate Cd phytotoxicity. Hence, K. pneumoniae strain K5 can be used as a phytostimulating and Cd-bioremediating biofertilizer for sustainable agriculture in heavy metal-contaminated sites.