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Author

Manoharan Shankar

Other affiliations: VIT University, University of Kansas
Bio: Manoharan Shankar is an academic researcher from Madurai Kamaraj University. The author has contributed to research in topics: Pseudomonas putida & Enterobacter cloacae. The author has an hindex of 9, co-authored 20 publications receiving 239 citations. Previous affiliations of Manoharan Shankar include VIT University & University of Kansas.

Papers
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Journal ArticleDOI
TL;DR: Enterobacter cloacae GS1 colonized rice roots and significantly improved the fresh weight, root length, shoot length, and nitrogen content in inoculated rice seedlings as compared to uninoculated controls.
Abstract: Enterobacter cloacae GS1 was isolated by in-planta enrichment of a rice rhizoplane bacterial community. It displayed strong seed adherence ability (2.5 × 105 cfu/seed) and colonized rice roots reaching up to 1.65 × 109 cfu/g of fresh root weight in a gnotobiotic root colonization system. E. cloacae GS1 was motile, able to solubilize tricalcium phosphate, and produced indole acetic acid like substances (15 μg/ml). As an introduced bioinoculant in non-sterile soil, E. cloacae GS1 colonized rice roots and significantly improved the fresh weight, root length, shoot length, and nitrogen content in inoculated rice seedlings as compared to uninoculated controls. This isolate was tagged with green fluorescent protein and various stages of root colonization in gnotobiotic hydroponic environment and non-sterile soil environment were followed by fluorescence microscopy. Owing to its effective root colonizing ability and growth promoting potential, Enterobacter cloacae GS1 is a promising symbiotic bioinoculant for rice. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

58 citations

Journal ArticleDOI
28 May 2015-PLOS ONE
TL;DR: A putative role of the LiaSR system in heat shock responses of S. mutans is suggested using a new 25-bp conserved motif essential for LiaR binding based on sequence analysis and DNA binding studies.
Abstract: The LiaSR two-component signal transduction system regulates cellular responses to several environmental stresses, including those that induce cell envelope damages Downstream regulons of the LiaSR system have been implicated in tolerance to acid, antibiotics and detergents In the dental pathogen Streptococcus mutans, the LiaSR system is necessary for tolerance against acid, antibiotics, and cell wall damaging stresses during growth in the oral cavity To understand the molecular mechanisms by which LiaSR regulates gene expression, we created a mutant LiaR in which the conserved aspartic acid residue (the phosphorylation site), was changed to alanine residue (D58A) As expected, the LiaR-D58A variant was unable to acquire the phosphate group and bind to target promoters We also noted that the predicted LiaR-binding motif upstream of the lia operon does not appear to be well conserved Consistent with this observation, we found that LiaR was unable to bind to the promoter region of lia; however, we showed that LiaR was able to bind to the promoters of SMU753, SMU2084 and SMU1727 Based on sequence analysis and DNA binding studies we proposed a new 25-bp conserved motif essential for LiaR binding Introducing alterations at fully conserved positions in the 25-bp motif affected LiaR binding, and the binding was dependent on the combination of positions that were altered By scanning the S mutans genome for the occurrence of the newly defined LiaR binding motif, we identified the promoter of hrcA (encoding a key regulator of the heat shock response) that contains a LiaR binding motif, and we showed that hrcA is negatively regulated by the LiaSR system Taken together our results suggest a putative role of the LiaSR system in heat shock responses of S mutans

27 citations

Journal ArticleDOI
TL;DR: For the first time, the microbial production of a chromanone derivative with antifungal activity is reported, which makes P. aeruginosa PGPR2 a suitable strain for biocontrol.
Abstract: Pseudomonas aeruginosa PGPR2 was found to protect mungbean plants from charcoal rot disease caused by Macrophomina phaseolina. Secondary metabolites from the culture supernatant of P. aeruginosa PGPR2 were extracted with ethyl acetate and the antifungal compound was purified by preparative HPLC using reverse phase chromatography. The purified compound showed antifungal activity against M. phaseolina and other phytopathogenic fungi (Fusarium sp., Rhizoctonia sp. Alternaria sp., and Aspergillus sp.). The structure of the purified compound was determined using (1)H, (13)C, 2D NMR spectra and liquid chromatography-mass spectrometry (LC-MS). Spectral data suggest that the antifungal compound is 3,4-dihydroxy-N-methyl-4-(4-oxochroman-2-yl)butanamide, with the chemical formula C14H17NO5 and a molecular mass of 279. Though chemically synthesized chromanone derivatives have been shown to have antifungal activity, we report for the first time, the microbial production of a chromanone derivative with antifungal activity. This ability of P. aeruginosa PGPR2 makes it a suitable strain for biocontrol.

20 citations

Journal Article
TL;DR: By virtue of its early production time, thermostability and effective antifungal ability, the protease purified and characterized from P. aeruginosa PGPR2 has several potential applications as fungicidal agents in agriculture.
Abstract: A new antagonistic bacterial strain PGPR2 was isolated from the mungbean rhizosphere and documented for the production of hydrolytic enzymes with antifungal activity. Based on the phylogenetic analysis of the 16S rRNA gene sequence and phenotyping, this strain was identified as Pseudomonas aeruginosa. Maximum protease activity (235 U/mL) was obtained at 24 h of fermentation. The protease was purified to homogeneity in three steps: ammonium sulphate precipitation, anion exchange chromatography on DEAE- cellulose resin and gel filtration chromatography using P6 column. The purified enzyme had a molecular weight of similar to 33 kDa. The purified protease exhibited maximum activity at pH 6.0 and retained 80% of activity in a pH range of 5.0 - 9.0. Proteolytic activity was maximum in a temperature range of 40-70 degrees C. However, the enzyme was stable at 40 degrees C for 60 mm. Among the metals tested, Mg2+ enhanced the protease activity. Internal amino acid sequence of the protease obtained by MALDI -ToF and subsequent Mascot database search showed maximum similarity to the HtpX protease of P. aeruginosa strain-PA7. Thus, by virtue of its early production time, thermostability and effective antifungal ability, the protease purified and characterized from P. aeruginosa PGPR2 has several potential applications as fungicidal agents in agriculture.

16 citations


Cited by
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01 Jun 2012
TL;DR: SPAdes as mentioned in this paper is a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler and on popular assemblers Velvet and SoapDeNovo (for multicell data).
Abstract: The lion's share of bacteria in various environments cannot be cloned in the laboratory and thus cannot be sequenced using existing technologies. A major goal of single-cell genomics is to complement gene-centric metagenomic data with whole-genome assemblies of uncultivated organisms. Assembly of single-cell data is challenging because of highly non-uniform read coverage as well as elevated levels of sequencing errors and chimeric reads. We describe SPAdes, a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler (specialized for single-cell data) and on popular assemblers Velvet and SoapDeNovo (for multicell data). SPAdes generates single-cell assemblies, providing information about genomes of uncultivatable bacteria that vastly exceeds what may be obtained via traditional metagenomics studies. SPAdes is available online ( http://bioinf.spbau.ru/spades ). It is distributed as open source software.

10,124 citations

Journal Article
TL;DR: This volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of the instrument and its ancillary tools are simply and well presented.
Abstract: I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

3,197 citations

Journal ArticleDOI
TL;DR: The state of the art for LAB stress behavior is presented, and the stress defense mechanisms that have been reported to date are concentrated on, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope.
Abstract: Lactic acid bacteria (LAB) are important starter, commensal, or pathogenic microorganisms. The stress physiology of LAB has been studied in depth for over 2 decades, fueled mostly by the technological implications of LAB robustness in the food industry. Survival of probiotic LAB in the host and the potential relatedness of LAB virulence to their stress resilience have intensified interest in the field. Thus, a wealth of information concerning stress responses exists today for strains as diverse as starter (e.g., Lactococcus lactis), probiotic (e.g., several Lactobacillus spp.), and pathogenic (e.g., Enterococcus and Streptococcus spp.) LAB. Here we present the state of the art for LAB stress behavior. We describe the multitude of stresses that LAB are confronted with, and we present the experimental context used to study the stress responses of LAB, focusing on adaptation, habituation, and cross-protection as well as on self-induced multistress resistance in stationary phase, biofilms, and dormancy. We also consider stress responses at the population and single-cell levels. Subsequently, we concentrate on the stress defense mechanisms that have been reported to date, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope. Stress-induced responses of probiotic LAB and commensal/pathogenic LAB are highlighted separately due to the complexity of the peculiar multistress conditions to which these bacteria are subjected in their hosts. Induction of prophages under environmental stresses is then discussed. Finally, we present systems-based strategies to characterize the "stressome" of LAB and to engineer new food-related and probiotic LAB with improved stress tolerance.

398 citations

Journal ArticleDOI
31 Oct 2012-PLOS ONE
TL;DR: Crop cultivation provides critical ecosystem services in arid lands with the plant root system acting as a “resource island” able to attract and select microbial communities endowed with multiple PGP traits that sustain plant development under water limiting conditions.
Abstract: Background Traditional agro-systems in arid areas are a bulwark for preserving soil stability and fertility, in the sight of “reverse desertification”. Nevertheless, the impact of desert farming practices on the diversity and abundance of the plant associated microbiome is poorly characterized, including its functional role in supporting plant development under drought stress.

393 citations

Journal ArticleDOI
TL;DR: It is argued that although making direct linkage of genomes to global phenomena is a significant challenge, many connections at intermediate scales are viable with integrated application of new systems biology approaches and powerful analytical and modelling techniques.

348 citations