MAJOR RESEARCH ACCOMPLISHMENT:
Demonstration of abundant bacterial colonization in the peri-space between cell wall and plasma membrane in banana, and revelation of cytoplasmic peri-space as a niche for endophytic bacteria;
Description of ''Cytobacts' and 'Peribacts, the intracellular colonizing endophytic bacteria TECHNOLOGIES DEVELOPED:
Micropropagation technology for (i) papaya, (ii) triploid seedless watermelon, (iii) grapes and (iv) chrysanthemum;
Sachet technique for the small-scale acclimatization of micropropagated plants of different crops;
Diagnostics for the detection of covert and endophytic bacteria in tissue cultures; METHODOLOGIES:
Spotting-and-tilt-spreading (SATS) as a simple and efficient method for bacterial cfu estimation over spread plating;
Use of cotton with high hydrophilicity for Bacillus spore surveillance over foam, nylon, or polyester swabs and high spore recovery efficiency;
Optimization of seedling root-injury-inoculation technique for the screening of tomato against Ralstonia solanacearum at seedling stage;
Development of single-plate-serial-dilution-spotting (SP-SDS) as an assured tool for bacterial cfu estimation; CONCEPTS:
Role of leaf in promotion of adventitious rooting; Identification and cloning of genes involved in regulation of rooting in stem cuttings
Identification of covert and unsuspecting association of diverse bacteria as the cause for the decline in the performance or degeneration of micropropagated cultures
Cleansing the established in vitro cultures from covert microbial contaminants through a combination of surface disinfection, antibiotic challenge followed by recurrent tissue indexing
Identification of normally unsuspected routes of microbial entry in plant tissue cultures including deep seated endophytes, alcohol resistant bacteria and autoclaving defying spore-formers, and identification of 90% ethanol as a universally adoptable better bacteri/sporicidal level of alcohol
Establishing the ubiquitous and integral association of endophytes with plant tissue in no-cultivable form through molecular and microscopic techniques
Isolation and characterization of a series of bacterial endophytes from different plant hosts including field grown plants and in vitro stocks;
Elucidation of the chances of bacterial cell injury due to the inoculum spreader during spread plating and development of a simple spotting-and-tilt-spreading (SATS) to maximize CFU and to avoid CFU inconsistencies during bacterial sampling.
- Thomas, P., Sekhar, A.C., and Shaik, S.P. 2017. High taxonomic diversity of cultivation-recalcitrant endophytic bacteria in grapevine field shoots, their in vitro introduction, and unsuspected persistence. Planta 246: 879-898.
- Thomas, P., Sekhar AC. 2017. Cultivation versus molecular analysis of banana (Musa sp.) shoot-tip tissue reveals enormous diversity of normally uncultivable endophytic bacteria. Microbial Ecology 73: 885-899
- Thomas, P., Agrawal, M. and Bharathkumar, C.B., 2017. Use of Plant Preservative Mixture™ for establishing in vitro cultures from field plants: Experience with papaya reveals several PPM™ tolerant endophytic bacteria. Plant Cell Reports 36: 1717–1730
- Thomas, P. 2017. Potential Applications of Endophytic Microorganisms in Agriculture. Asian Biotechnology and Development Review 19: 3-23
- Thomas, P., Sekhar AC. 2016. Effects due to rhizospheric soil application of an antagonistic bacterial endophyte on native bacterial community and its survival in soil: A case study with Pseudomonas aeruginosa from banana. Frontiers in Microbiology 7: 493.
- Thomas, P. and Upreti, R. 2016. Evaluation of tomato seedling root-associated bacterial endophytes towards organic seedling production. Organic Agriculture 6: 89-98
- Thomas, P, Sekhar, A.C., Upreti, R., Mujawar, M.M., Pasha, S.S. 2015. Optimization of single plate-serial dilution spotting (SP-SDS) with sample anchoring as an assured method for bacterial and yeast cfu enumeration and single colony isolation from diverse samples. Biotechnology Reports 8: 45-55
- Upreti, R. and Thomas, P. 2015. Root-associated bacterial endophytes from Ralstonia solanacearum resistant and susceptible tomato cultivars and their pathogen antagonistic effects. Frontiers in Microbiology 6: 255
- Thomas, P., Sadashiva, A.T., Upreti, R. and Mujawar, M. M. 2015. Direct delivery of inoculum to shoot tissue interferes with genotypic resistance to Ralstonia solanacearum in tomato seedlings. Journal of Phytopathology 163: 320-323
- Thomas, P., Sekhar, A. C., Mujawar, M. M. 2014. Vulnerability of Bacillus spores and of related genera to physical impaction injury with particular reference to spread-plating. Journal of Applied Microbiology 117: 1358-1372
- Thomas, P. and Upreti, R. 2014. Significant Effects due to peptone in Kelman medium on colony characteristics and virulence of Ralstonia solanacearum in tomato. The Open Microbiology Journal 8: 95-113
- Thomas, P., Sekhar, A.C. 2014. Live cell imaging reveals extensive intracellular cytoplasmic colonization of banana genotypes by normally non-cultivable endophytic bacteria. AoB PLANTS 6: plu002; doi: 10.1093/aobpla/plu002.
- Thomas, P., Mujawar, M. M., Sekhar, A. C. and Upreti, R. 2014. Physical impaction injury effects on bacterial cells during spread-plating influenced by cell characteristics of the organisms. Journal of Applied Microbiology 116, 911-922.
- Thomas, P., Mujawar, M. M., Upreti, R., Sekhar, A. C. 2013. Improved recovery of Bacillus spores from nonporous surfaces with cotton swabs over foam, nylon, or polyester, and the role of hydrophilicity of cotton in governing the recovery efficiency. Applied and Environmental Microbiology. 79: 381-384.
- Thomas, P., Reddy, M. K. 2013. Microscopic elucidation of abundant endophytic bacteria colonizing the cell wall – plasma membrane peri-space in the shoot-tip tissue of banana. AoB PLANTS 5: plt011 doi: 10.1093/aobpla/plt011.
- Thomas, P., Sekhar, AC., Mujawar, MM. 2012. Non-recovery of varying proportions of viable bacteria during spread-plating governed by the extent of spreader usage and proposal for an alternate spotting-spreading approach to maximize the CFU. Journal of Applied Microbiology 113: 339-350
- Thomas, P. 2012. Long-term survival of Bacillus spores in alcohol and identification of 90% ethanol as relatively more spori/bactericidal. Current Microbiology 64: 130-139
- Thomas, P. 2011. Intense association of non-culturable endophytic bacteria with antibiotic-cleansed in vitro watermelon and their activation in degenerating cultures. Plant Cell Reports 30: 2313-2325
- Thomas, P., Gopalakrishnan, C., Krishnareddy, M. 2011. Soft-rot inciting Pectobacterium carotovorum (syn. Erwinia carotovora) is unlikely to be transmitted as a latent pathogen in micropropagated banana Plant Cell Tissue Organ Culture. 105:423–429.
- Thomas, P. and Kumari, S. 2010. Inconspicuous endophytic bacteria mimicking latex exudates in shoot-tip cultures of papaya. Scientia Horticulturae124: 469-474
- Thomas, P., Soly, T. A. 2009. Endophytic bacteria associated with growing shoot tips of banana (Musa sp.) cv. Grand Naine and the affinity of endophytes to the host. Microbial Ecology. 58: 952-964
- Thomas P, Swarna GK, Patil P, Rawal, RD. 2008. Ubiquitous presence of normally non-cultivable endophytic bacteria in field shoot-tips of banana and their gradual activation to quiescent cultivable form in tissue cultures. Plant Cell Tissue and Organ Culture 93:39-54
- Thomas P, Swarna GK, Roy PK, Patil, P. 2008. Identification of cultivable and originally non-culturable endophytic bacteria isolated from shoot tip cultures of banana cv. Grand Naine. Plant Cell Tissue Organ Culture 93:55-63
- Thomas, P., Kumari, S., Swarna, G.K., Prakash, D.P., Dinesh, M.R. 2007. Ubiquitous presence of fastidious endophytic bacteria in field shoots and index-negative apparently clean shoot-tip cultures of papaya. Plant Cell Reports 26: 1491-1499
- Thomas, P., Kumari, S., Swarna, G.K., Gowda, T.K.S. 2007. Papaya shoot tip associated endophytic bacteria isolated from in vitro cultures and host-endophyte interaction in vitro and in vivo. Canadian Journal of Microbiology 53: 380-390
- Thomas, P. 2006. Isolation of an ethanol-tolerant endospore-forming Gram-negative Brevibacillus sp as a covert contaminant in grape tissue cultures. Journal of Applied Microbiology 101: 764-774
- Thomas, P., Prabhakara, B. S., and Pitchaimuthu, M. 2006. Cleansing the long-term micropropagated triploid watermelon cultures from covert bacteria and field testing the plants for clonal fidelity and fertility during the 7-10 year period in vitro. Plant Cell Tissue and Organ Culture 85: 317-329
- Thomas, P. 2004. Isolation of Bacillus pumilus from in vitro grapes as a long-term alcohol-surviving and rhizogenesis inducing covert endophyte. Journal of Applied Microbiology 97: 114-123
- Thomas, P. 2004. In vitro decline in plant cultures: Detection of a legion of covert bacteria as the cause for degeneration of long-term micropropagated triploid watermelon cultures. Plant Cell Tissue and Organ Culture 77: 173-179
- Thomas, P. 2004. A three-step screening procedure for the detection of covert and endophytic bacteria in plant tissue cultures. Current Science 87: 67-72
- Thomas, P. and Schiefelbein, J. W. 2004. Roles of leaf in regulation of root and shoot growth from single node softwood cuttings of grape (Vitis vinifera). Annals of Applied Biology 144: 27-37.
- Thomas, P., Lee, M. M. and Schiefelbein, J. W. 2003. Molecular identification of proline-rich protein genes induced during root formation in grape (Vitis.) stem cuttings. Plant, Cell and Environment 26: 1497-1504
- Thomas, P. and Schiefelbein, J. W. 2002. Cloning and characterization of an actin depolymerizing factor gene from grape (Vitis vinifera L.) expressed during rooting in stem cuttings. Plant Science 162: 283-288
- Thomas, P., Mythili, J. B. and Shivashankara, K. S. 2000. Effects of photo-oxidative loss of Fe-EDTA and of higher iron supply on chlorophyll content, growth and propagation rate in triploid watermelon cultures. In Vitro Cellular Development Biology- Plant 36: 537-542
- Thomas, P. 2000. Microcutting leaf area, weight and position on the stock shoot influence root vigour, shoot growth and incidence of shoot tip necrosis in grape plantlets in vitro. Plant Cell Tissue and Organ Culture 61: 189-198
- Thomas, P., Mythili, J. B. and Shivashankara, K. S. 2000. Explant, medium and vessel aeration affect the incidence of hyperhydricity and recovery of normal plantlets in triploid watermelon. Journal of Horticultural Science and Biotechnology 75: 19-25
- Thomas P. 1999. Somatic embryogenesis and plantlet regeneration from nucellus tissue of monoembryonic mango. Journal of Horticultural Science and Biotechnology 74:135-139
- Thomas, P. 1998. Contribution of leaf lamina of grape nodal microcuttings to rooting, root vigour and plantlet growth in vitro. Journal of Plant Physiology, 153: 727-732
- Thomas, P. and Ravindra, M. B. 1997. Shoot tip culture in mango: Influence of genotype, medium, explant factors, season and decontamination treatments on phenolic exudation, explant survival and axenic culture establishment. The Journal of Horticultural Science, 72: 713-722.
- Thomas, P. and Warren, G. S. 1994. Relationship between cell growth and viral antigen content of cultures of Nicotiana tabacum inoculated with tobacco mosaic virus. Journal of Experimental Botany. 45: 987-994
Fellow, National Academy of Agricultural Sciences, New Delhi (from 1st Jan. 2011);
Fellow, National Academy of Biological Sciences (NABS), Chennai (from June 2012);
Dr. B. P. Pal Outstanding Scientists Award- 2015 by the National Academy of Biological Sciences (NABS), Chennai (Aug. 2016)
Shri. Hari Krishna Shasri Memorial Award (2011) from IARI, New Delhi in Feb. 2012 for research contributions in the area of Molecular Profiling and Endophytic Microbiology;
Shri. Giridhari Lal Chadha Memorial Gold Medal (2010), from Horticultural Society of India New Delhi;
DBT Overseas Associateship (Short-term) Award (2006-07); 6 months (March-Sept. 2007). Availed at the Flinders University, Adelaide, Australia;
Sukumar Basu Memorial Award (1999-2000) conferred by IARI, New Delhi in Feb. 2002 for research contributions in the area of Horticultural Biotechnology;
DBT, Overseas Long term Associateship (Long-term) Award (1999-2000) availed at the University of Michigan, Ann Arbor, USA (1½ yrs);
Commonwealth Post-Doctoral Fellowship awarded during 1989-90 for advanced research at the University of Sheffield, Sheffield, U. K. (1+ year) 1989-1990);
Young Scientist Award at Kerala Science Congress 1990
Best Poster Award from Horticultural Society of India, New Delhi;
Fellow: Horticultural Society of India, New Delhi (From Nov. 2010)
Member/Fellow, Plant Tissue Culture Association of India (PTCA-I), New Delhi (From Feb 2004)