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Diversity of culturable methylotrophic bacteria in different genotypes of groundnut and their potential for plant growth promotion.

ABSTRACT: This study aimed at documenting the culturable methylotrophic bacterial diversity across different groundnut genotypes and evaluating their effect on the growth of groundnut. 80 methylotrophic bacterial isolates were obtained from the phyllosphere of 15 groundnut genotypes collected from Tamil Nadu, India. The bacterial isolates were identified through sequencing of the 16S rDNA and were tested for their plant growth-promoting properties. Groundnut seeds were inoculated with methylotrophic bacteria and their effect on growth was evaluated via in vitro and pot experiments. Molecular identification revealed that the isolates belonged to 30 different species. A higher diversity of methylotrophic bacteria at genus and species level was found in groundnut genotype TMV2. Shannon diversity index was the highest in genotype TMV7, followed by VRI2 and TMV2. Similarly, geographical location also influenced the diversity of methylotrophic bacteria. In vitro seed germination assay revealed that methylotrophic isolates enhanced root growth and improved formation of root hair. The radicle length of treated seeds ranged from 2.7 to 8.4 cm. A higher shoot length was observed in the plants from seeds treated with Methylobacterium radiotolerans VRI8-A4 (27.3 cm), followed by Pseudomonas psychrotolerans TMV13-A1 (26.3 cm) and Bacillus aryabhattai K-CO3-3 (23 cm). The findings of this study strongly suggest that beneficial methylotrophic bacteria associated with the phyllosphere of groundnut play a major role in regulating plant growth.

SUBMITTER: Krishnamoorthy R

PROVIDER: S-EPMC5971017 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Diversity of culturable methylotrophic bacteria in different genotypes of groundnut and their potential for plant growth promotion.

Krishnamoorthy R R Kwon Soon-Wo SW Kumutha K K Senthilkumar M M Ahmed S S Sa Tongmin T Anandham R R

3 Biotech 20180526 6

This study aimed at documenting the culturable methylotrophic bacterial diversity across different groundnut genotypes and evaluating their effect on the growth of groundnut. 80 methylotrophic bacterial isolates were obtained from the phyllosphere of 15 groundnut genotypes collected from Tamil Nadu, India. The bacterial isolates were identified through sequencing of the 16S rDNA and were tested for their plant growth-promoting properties. Groundnut seeds were inoculated with methylotrophic bacte ...[more]

PMID: 29868313

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Project description:BackgroundA diverse community of microbes naturally exists on the phylloplane, the surface of leaves. It is one of the most prevalent microbial habitats on earth and bacteria are the most abundant members, living in communities that are highly dynamic. Today, one of the key challenges for microbiologists is to develop strategies to culture the vast diversity of microorganisms that have been detected in metagenomic surveys.ResultsWe isolated bacteria from the phylloplane of Hedera helix (common ivy), a widespread evergreen, using five growth media: Luria-Bertani (LB), LB01, yeast extract-mannitol (YMA), yeast extract-flour (YFlour), and YEx. We also included a comparison with the uncultured phylloplane, which we showed to be dominated by Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. Inter-sample (beta) diversity shifted from LB and LB01 containing the highest amount of resources to YEx, YMA, and YFlour which are more selective. All growth media equally favoured Actinobacteria and Gammaproteobacteria, whereas Bacteroidetes could only be found on LB01, YEx, and YMA. LB and LB01 favoured Firmicutes and YFlour was most selective for Betaproteobacteria. At the genus level, LB favoured the growth of Bacillus and Stenotrophomonas, while YFlour was most selective for Burkholderia and Curtobacterium. The in vitro plant growth promotion (PGP) profile of 200 isolates obtained in this study indicates that previously uncultured bacteria from the phylloplane may have potential applications in phytoremediation and other plant-based biotechnologies.ConclusionsThis study gives first insights into the total bacterial community of the H. helix phylloplane, including an evaluation of its culturability using five different growth media. We further provide a collection of 200 bacterial isolates underrepresented in current databases, including the characterization of PGP profiles. Here we highlight the potential of simple strategies to obtain higher microbial diversity from environmental samples and the use of high-throughput sequencing to guide isolate selection from a variety of growth media.

Project description:Plant growth-promoting rhizobacteria (PGPR) can produce hormone-like substances, promote plant nutrient uptake, enhance plant resistance, inhibit the growth of pathogenic bacteria, and induce plant resistance to biotic and abiotic stresses. Bacillus is one of the most studied genera that promote plant root development. Since its discovery in 2009, B. aryabhattai has shown promising properties such as promoting plant growth and improving crop yield. However, the mechanisms of B. aryabhattai promoting plant growth remain to be investigated. In this study, the chromosome of B. aryabhattai strain LAD and five plasmids within the cell were sequenced and annotated. The genome, with a length of 5,194,589 bp and 38.12% GC content, contains 5,288 putative protein-coding genes, 39 rRNA, and 112 tRNA. The length of the five plasmids ranged from 116,519 to 212,484 bp, and a total of 810 putative protein-coding genes, 4 rRNA, and 32 tRNA were predicted in the plasmids. Functional annotation of the predicted genes revealed numerous genes associated with indole-3 acetic acid (IAA) and exopolysaccharides (EPSs) biosynthesis, membrane transport, nitrogen cycle metabolism, signal transduction, cell mobility, stress response, and antibiotic resistance on the genome which benefits the plants. Genes of carbohydrate-active enzymes were detected in both the genome and plasmids suggesting that LAD has the capacity of synthesizing saccharides and utilizing organic materials like root exudates. LAD can utilize different carbon sources of varied carbon chain length, i.e., methanol, acetate, glycerol, glucose, sucrose, and starch for growth and temperature adaptation suggesting a high versatility of LAD for thriving in fluctuating environments. LAD produced the most EPSs with sucrose as sole carbon source, and high concentration of IAA was produced when the maize plant was cultivated with LAD, which may enhance plant growth. LAD significantly stimulated the development of the maize root. The genome-based information and experimental evidence demonstrated that LAD with diverse metabolic capabilities and positive interactions with plants has tremendous potential for adaptation to the dynamic soil environments and promoting plant growth.

Project description:Sierra Mixe maize is a geographically remote landrace variety grown on nitrogen-deficient fields in Oaxaca, Mexico that meets its nutritional requirements without synthetic fertilizer by associating with free-living diazotrophs comprising the microbiota of its aerial root mucilage. We selected nearly 500 diazotrophic (N2-fixing) bacteria isolated from Sierra Mixe maize mucilage and sequenced their genomes. Comparative genomic analysis demonstrated that isolates represented diverse genera and composed three major diazotrophic groups based on nitrogen fixation gene content. In addition to nitrogen fixation, we examined deamination of 1-amino-1-cyclopropanecarboxylic acid, biosynthesis of indole-3-acetic acid, and phosphate solubilization as alternative mechanisms of direct plant growth promotion (PGP). Genome mining showed that isolates of all diazotrophic groups possessed marker genes for multiple mechanisms of direct plant growth promotion (PGP). Implementing in vitro assays corroborated isolate genotypes by measuring each isolate's potential to confer the targeted PGP traits and revealed phenotypic variation among isolates based on diazotrophic group assignment. Investigating the ability of mucilage diazotrophs to confer PGP by direct inoculation of clonally propagated potato plants in planta led to the identification of 16 bio-stimulant candidates. Conducting nitrogen-stress greenhouse experiments demonstrated that potato inoculation with a synthetic community of bio-stimulant candidates, as well as with its individual components, resulted in PGP phenotypes. We further demonstrated that one diazotrophic isolate conferred PGP to a conventional maize variety under nitrogen-stress in the greenhouse. These results indicate that, while many diazotrophic isolates from Sierra Mixe maize possessed genotypes and in vitro phenotypes for targeted PGP traits, a subset of these organisms promoted the growth of potato and conventional maize, potentially through the use of multiple promotion mechanisms.

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Diversity of culturable methylotrophic bacteria in different genotypes of groundnut and their potential for plant growth promotion.

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Diversity of culturable methylotrophic bacteria in different genotypes of groundnut and their potential for plant growth promotion.

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