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Plant growth promoting rhizobacteria are known to improve plant performance by developing healthy and productive interactions with the host plants. These associations may be symbiotic or asymbiotic depending upon the genetic potential of the resident microbe and promiscuity of the host. Present study describes the potential of two Serratia spp. strains for promotion of plant growth in homologous as well as non-homologous hosts. The strains KPS-10 and KPS-14; native to potato rhizosphere belong to genus Serratia based on 16S rRNA gene sequences (accession no. LN831934 and LN831937 respectively) and contain multiple plant growth promoting properties along-with the production of quorum sensing acyl homoserine lactone (AHL) molecules. Both Serratia spp. strains showed solubilization of inorganic tri-calcium phosphate while KPS-14 also exhibited phytase activity (1.98 10 -10 kcat). KPS-10 showed higher P-solubilization activity (128.5 μg/mL), IAA production (8.84 μg/mL), antifungal activity and also showed the production of two organic acids i.e., gluconic acid and lactic acid. Both strains produced three common AHLs: C6-HSL, 3oxo-C10-HSL, 3oxo-C12-HSL while some strain-specific AHLs (3OH-C5-HSL, 3OH-C6-HSL, C10-HSL specific to KPS-10 and 3OH-C6-HSL, C8-HSL, 3oxo-C9-HSL, 3OH-C9-HSL specific to KPS-14). Strains showed roots and rhizosphere colonization of potato and other non-homologous hosts up to one month. In planta AHLs-detection confirmed a likely role of AHLs during seedling growth and development where both extracted AHLs or bacteria inoculated roots showed extensive root hair. A significant increase in root/shoot lengths, root/ shoot fresh weights, root/shoot dry weights was observed by inoculation in different hosts. PGP-characteristics along with the AHLs-production signify the potential of both strains as candidate for the development of bio-inoculum for potato crop in specific and other crops in general. This inoculum will not only reduce the input of chemical fertilizer to the environment but also improve soil quality and plant growth., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Bacterial plasmids carry genes that code for additional traits such as osmoregulation, CO 2 fixation, antibiotic and heavy metal resistance, root nodulation and nitrogen fixation. The main objective of the current study was to identify plasmid-conferring osmoregulatory genes in bacteria isolated from rhizospheric and non-rhizospheric soils of halophytes (Salsola stocksii and Atriplex amnicola). More than 55% of halophilic bacteria from the rhizosphere and 70% from non-rhizospheric soils were able to grow at 3 M salt concentrations. All the strains showed optimum growth at 1.5-3.0 M NaCl. Bacterial strains from the Salsola rhizosphere showed maximum (31%) plasmid elimination during curing experiments as compared to bacterial strains from the Atriplex rhizosphere and non-rhizospheric soils. Two plasmid cured strains Bacillus HL2HP6 and Oceanobacillus HL2RP7 lost their ability to grow in halophilic medium, but they grew well on LB medium. The plasmid cured strains also showed a change in sensitivity to specific antibiotics. These plasmids were isolated and transformed into E. coli strains and growth response of wild-type and transformed E. coli strains was compared at 1.5-4 M NaCl concentrations. Chromosomal DNA and plasmids from Bacillus filamentosus HL2HP6 were sequenced by using high throughput sequencing approach. Results of functional analysis of plasmid sequences showed different proteins and enzymes involved in osmoregulation of bacteria, such as trehalose, ectoine synthetase, porins, proline, alanine, inorganic ion transporters, dehydrogenases and peptidases. Our results suggested that plasmid conferring osmoregulatory genes play a vital role to maintain internal osmotic balance of bacterial cells and these genes can be used to develop salt tolerant transgenic crops., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Biofertilizers are usually carrier-based inoculants containing beneficial microorganisms. Incorporation of microorganisms in carrier material enables easy-handling, long-term storage and high effectiveness of biofertilizers. Objective of the present study was to assess enriched biogas sludge and soil as biofertilizer carriers on growth and yield of wheat. Six phosphate solubilizing strains were used in this study. Three phosphate solubilizing strains, 77-NS2 (Bacillus endophyticus), 77-CS-S1 (Bacillus sphaericus) and 77-NS5 (Enterobacter aerogenes) were isolated from the rhizosphere of sugarcane, two strains, PSB5 (Bacillus safensis) and PSB12 (Bacillus megaterium) from the rhizosphere of wheat and one halophilic phosphate solubilizing strain AT2RP3 (Virgibacillus sp.) from the rhizosphere of Atriplex amnicola, were used as bioinoculants. Phosphate solubilization ability of these strains was checked in vitro in Pikovskaya medium, containing rock phosphate (RP) as insoluble P source, individually supplemented with three different carbon sources, i.e., glucose, sucrose and maltose. Maximum phosphate solubilization; 305.6μg/ml, 217.2μg/ml and 148.1μg/ml was observed in Bacillus strain PSB12 in Pikovskaya medium containing sucrose, maltose and glucose respectively. A field experiment and pot experiments in climate control room were conducted to study the effects of biogas sludge and enriched soil based phosphorous biofertilizers on growth of wheat. Bacillus strain PSB12 significantly increased root and shoot dry weights and lengths using biogas sludge as carrier material in climate control room experiments. While in field conditions, significant increase in root and shoot dry weights, lengths and seed weights was seen by PSB12 and PSB5 (Bacillus) and Enterobacter strain 77-NS5 using biogas sludge as carrier. PSB12 also significantly increased both root and shoot dry weights and lengths in field conditions when used as enriched soil based inoculum. These results indicated that bacterial isolates having plant beneficial traits such as P solubilization are more promising candidates as biofertilizer when used with carrier materials., (Copyright © 2017 Elsevier GmbH. All rights reserved.)