Although plant growth-promoting rhizobacteria (PGPR) have been reported to influence plant growth, yield and nutrient uptake by an array of mechanisms, the specific traits by which PGPR promote plant growth, yield and nutrient uptake were limited to the expression of one or more of the traits expressed at a given environment of plant-microbe interaction. We selected nine different isolates of PGPR from a pool of 233 rhizobacterial isolates obtained from the peanut rhizosphere on the basis of ACC-deaminase activity. The nine isolates were selected, initially, on the basis of germinating seed bioassay in which the root length of the seedling was enhanced significantly over the untreated control. All the nine isolates were identified as Pseudomonas spp. Four of these isolates, viz. PGPR1, PGPR2, PGPR4 and PGPR7 (all fluorescent pseudomonads), were the best in producing siderophore and indole acetic acid (IAA). In addition to IAA and siderophore-producing attributes, Pseudomonas fluorescens PGPR1 also possessed the characters like tri-calcium phosphate solubilization, ammonification and inhibited Aspergillus niger and A. flavus in vitro. P. fluorescens PGPR2 differed from PGPR1 in the sense that it did not show ammonification. In addition to the traits exhibited by PGPR1, PGPR4 showed strong in vitro inhibition to Sclerotium rolfsii. The performances of these selected plant growth-promoting rhizobacterial isolates were repeatedly evaluated for 3 years in pot and field trials. Seed inoculation of these three isolates, viz. PGPR1, PGPR2 and PGPR4, resulted in a significantly higher pod yield than the control, in pots, during rainy and post-rainy seasons. The contents of nitrogen and phosphorus in soil, shoot and kernel were also enhanced significantly in treatments inoculated with these rhizobacterial isolates in pots during both the seasons. In the field trials, however, there was wide variation in the performance of the PGPR isolates in enhancing the growth and yield of peanut in different years. Plant growth-promoting fluorescent pseudomonad isolates, viz. PGPR1, PGPR2 and PGPR4, significantly enhanced pod yield (23-26%, 24-28% and 18-24%, respectively), haulm yield and nodule dry weight over the control in 3 years. Other attributes like root length, pod number, 100-kernel mass, shelling out-turn and nodule number were also enhanced. Seed bacterization with plant growth-promoting P. fluorescens isolates, viz. PGPR1, PGPR2 and PGPR4, suppressed the soil-borne fungal diseases like collar rot of peanut caused by A. niger and PGPR4 also suppressed stem rot caused by S. rolfsii. Studies on the growth patterns of PGPR isolates utilizing the seed leachate as the sole source of C and N indicated that PGPR4 isolate was the best in utilizing the seed leachate of peanut, cultivar JL24. Studies on the rhizosphere competence of the PGPR isolates, evaluated on the basis of spontaneous rifampicin resistance, indicated that PGPR7 was the best rhizoplane colonizer and PGPR1 was the best rhizosphere colonizer. Although the presence o...

A plant growth-promoting isolate of a fluorescent Pseudomonas sp. EM85 and two bacilli isolates MR-11(2) and MRF, isolated from maize rhizosphere, were found strongly antagonistic to Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina, causal agents of foot rots and wilting, collar rots/stalk rots and root rots and wilting, and charcoal rots of maize, respectively. Pseudomonas sp. EM85 produced antifungal antibiotics (Afa+), siderophore (Sid+), HCN (HCN+) and fluorescent pigments (Flu+) besides exhibiting plant growth promoting traits like nitrogen fixation, phosphate solubilization, and production of organic acids and IAA. While MR-11(2) produced siderophore (Sid+), antibiotics (Afa+) and antifungal volatiles (Afv+), MRF exhibited the production of antifungal antibiotics (Afa+) and siderophores (Sid+). Bacillus spp. MRF was also found to produce organic acids and IAA, solubilized tri-calcium phosphate and fixed nitrogen from the atmosphere. All three isolates suppressed the diseases caused by Fusarium moniliforme, Fusarium graminearum and Macrophomina phaseolina in vitro. A Tn5:: lacZ induced isogenic mutant of the fluorescent Pseudomonas EM85, M23, along with the two bacilli were evaluated for in situ disease suppression of maize. Results indicated that combined application of the two bacilli significantly (P = 0.05) reduced the Macrophomina-induced charcoal rots of maize by 56.04%. Treatments with the MRF isolate of Bacillus spp. and Tn5:: lacZ mutant (M23) of fluorescent Pseudomonas sp. EM85 significantly reduced collar rots, root and foot rots, and wilting of maize caused by Fusarium moniliforme and F. graminearum (P = 0.05) compared to all other treatments. All these isolates were found very efficient in colonizing the rhizotic zones of maize after inoculation. Evaluation of the population dynamics of the fluorescent Pseudomonas sp. EM85 using the Tn5:: lacZ marker and of the Bacillus spp. MRF and MR-11(2) using an antibiotic resistance marker revealed that all the three isolates could proliferate successfully in the rhizosphere, rhizoplane and endorhizosphere of maize, both at 30 and 60 days after seeding. Four antifungal compounds from fluorescent Pseudomonas sp. EM85, one from Bacillus sp. MR-11(2) and three from Bacillus sp. MRF were isolated, purified and tested in vitro and in thin layer chromatography bioassays. All these compounds inhibited R. solani, M. phaseolina, F. moniliforme, F. graminearum and F. solani strongly. Results indicated that antifungal antibiotics and/or fluorescent pigment of fluorescent Pseudomonas sp. EM85, and antifungal antibiotics of the bacilli along with the successful colonization of all the isolates might be involved in the biological suppression of the maize root diseases.

This study investigated the expression and localization of APin (which was previously identified and cloned from a rat odontoblast cDNA library), during ameloblast differentiation in rat incisors, by using in situ hybridization and immunohistochemistry. The subcellular localization of APin varied during ameloblast differentiation, but was stage-specific. APin mRNA was not expressed in pre-ameloblasts, was weakly expressed in secretory ameloblasts, and was strongly expressed in maturation-stage ameloblasts as well as in the junctional epithelium attached to the enamel of erupted molars. In the maturation-stage ameloblasts, APin protein was conspicuous in the supranuclear area (Golgi complex) of smooth-ended ameloblasts as well as in both the supranuclear area and the ruffle end of ruffle-ended ameloblasts. During ameloblast-lineage cell culture, APin was expressed at a low level in the early stages of culture, but at a high level in the late stage of culture, which was equivalent to the maturation stage. APin protein was efficiently secreted from transfected cells in culture. Furthermore, its overexpression and inactivation caused an increase and decrease in matrix metalloproteinase-20 (MMP-20) and tuftelin expression, respectively. These findings indicate a functional role for APin in the mineralization and maturation of enamel that is mediated by the expression of MMP-20 and tuftelin.

The diversity of culturable, aerobic and heterotrophic Bacillus and Bacillus-derived genera (BBDG) was investigated in various extreme environments (including thermal springs, cold deserts, mangroves, salt lakes, arid regions, salt pans and acidic soils) of India. Heat treatment followed by enrichment in different media led to a total of 893 bacterial isolates. Amplified ribosomal DNA restriction analysis (ARDRA) using three restriction enzymes AluI, MspI and HaeIII led to the clustering of these isolates into 12-74 groups for the different sites at 75 % similarity index, adding up to 559 groups. Phylogenetic analysis based on 16S rRNA gene sequencing led to the identification of 392 bacilli, grouped in two families, Bacillaceae (89.03 %) and Paenibacillaceae (10.97 %), and included 13 different genera with 75 distinct species. It was found that among the thirteen genera, nine (Bacillus, Halobacillus, Lysinibacillus, Oceanobacillus, Pontibacillus, Salinibacill us, Sedimini bacillus, Thalassobacillus and Virgibacillus) belonged to Bacillaceae and four (Ammoniphilus, Aneurinibacillus, Brevibacillus and Paenibacillus) belonged to Paenibacillaceae. Novel isolates tolerant to low and high pH and temperature, salt and low moisture were identified. The major outcome of the present investigation was the identification of niche-specific species and also the ubiquitous presence of selected species of BBDG, which illustrate the diversity and pervasive nature of BBDG in extreme environments.

Archaea are unique microorganisms that are present in ecological niches of high temperature, pH and salinity. A total of 157 archaea were obtained from thirteen sediment, water and rhizospheric soil samples collected from Rann of Kutch, Gujarat, India. With an aim to screen phosphate solubilizing archaea, a new medium was designed as Haloarchaea P Solubilization (HPS) medium. The medium supported the growth and P solubilization activity of archaea. Employing the HPS medium, twenty isolates showed the P-solubilization. Phosphate solubilizing archaea were identified as seventeen distinct species of eleven genera namely Haloarcula, Halobacterium, Halococcus, Haloferax, Halolamina, Halosarcina, Halostagnicola, Haloterrigena, Natrialba, Natrinema and Natronoarchaeum. Natrinema sp. strain IARI-WRAB2 was identified as the most efficient P-solubilizer (134.61 mg/L) followed by Halococcus hamelinensis strain IARI-SNS2 (112.56 mg/L). HPLC analysis detected seven different kinds of organic acids, namely: gluconic acid, citric acid, formic acid, fumaric acid succinic acid, propionic acid and tartaric acid from the cultures of these isolates. These phosphate solubilizing halophilic archaea may play a role in P nutrition to vegetation growing in these hypersaline soils. This is the first report for these haloarchaea to solubilize considerable amount of P by production of organic acids and lowering of pH.