Research Groups

Plant Biology: Insect Resistance

Staff Research Scientist: Nirupama Banerjee

Group Leader: Raj K. Bhatnagar

Group Members

Research Interests

Bacterial pathogenesis, Insecticidal toxins, Mycobacterial dormancy, stringent response.

Description of Research

The broad focus of the research is to understand host-pathogen interactions in bacterial infections. We are currently working on two bacterial systems, an insect pathogenic bacterium Xenorhabdus nematophila and the human pathogen Mycobacterium tuberculosis.
X. nematophila is an insect larval pathogen that resides as a symbiont in the gut of a soil nematode. The bacterial secretome containing a wide spectrum of biologically active molecules is the major focus of our research. We are specifically interested in identifying novel insecticidal and microbicidal molecules, to study their biology and mode of action in the respective host.
The bacterium also produces a variety of antibiotics constituting the microbicidal arsenal of this highly prolific soil bacterium. We have isolated a gene pair encoding antimicrobial bacteriocin protein, active against both Gram positive and negative microbes. Presently we are working out the secretion pathway of the bacteriocin.
Mycobacterium tuberculosis has emerged as a successful pathogen infecting millions of people worldwide. Its ability to survive and replicate in the host macrophages is critical to establishment of infection. Research is focused on understanding the role of toxin-antitoxin (TA) modules in controlling the cell cycle of this intracellular pathogen. A large number of TA loci have been identified in the Mycobacterial genome. To unravel the significance of TA modules in the biology of Mycobacterial infection a systematic analysis is necessary. Our objective is to study the TA modules in response to nutrient deprivation that leads to stringent response and trigger dormancy in the bacilli.
The unique chemistry of the Mycobacterial cell wall is largely responsible for inherent resistance of the bacterium against various antibiotics, cell-wall active agents and osmotic changes. It also helps Mycobacterium to endure stressful conditions encountered in the host. The cell wall of pathogenic Mycobacteria are known to contain Polyglutamine, forming a capsule like layer associated with the peptidoglycan. We are currently studying the role of polyglutamine in providing M. tuberculosis resistance against various in vivo and in vitro antimicrobial agents, which may have important implications towards drug development.

Recent publications

Kant, S., Kapoor, R., Banerjee, N. 2009. Identification of a catabolite responsive element necessary for regulation of cry4A gene of Bacillus thuringiensis israelensis. J. Bacteriol. 191, 4687-4692

Joshi, M.C., Sharma, A., Kant, S., Birah, A., Gupta, G.P.,  Khan, S.R., Bhatnagar, R., Banerjee, N. 2008. An insecticidal GroEL protein with chitin binding activity from Xenorhabdus nematophila. J. Biol. Chem. 283, 28287-28296

Singh, J., Banerjee, N. 2008. Transcriptional analysis and functional characterization of a gene pair encoding iron regulated xenocin and immunity proteins of Xenorhabdus nematophila. J. Bacteriol. 190, 3877-3885

Chandra, H., Khandelwal, P., Khattri, A., Banerjee, N. 2008. Type 1 fimbriae of insecticidal bacterium Xenorhabdus nematophila is necessary for growth and colonization of its symbiotic host nematode Steinernema carpocapsiae. Environ. Microbiol. 10, 1285-1295

Banerjee, J., Singh, J., Joshi, M.C., Ghosh, S., Banerjee, N. 2006. The cytotoxic fimbrial structural subunit of Xenorhabdus nematophila is a pore-forming toxin. J.  Bacteriol. 188, 22