Saswati Biswas, MA, PhD
Research Assistant Professor
Microbiology, Molecular Genetics and Immunology
M.Sc., Physics, Banaras Hindu University, India
Ph.D., Microbiology, University of Kansas Medical Center
Senior Scientist, University of Kansas Medical Center
have a longstanding interest in various antimicrobials targeted against bacteria. In an earlier study, I have identified and characterized one efflux pump of quaternary compounds (published in Antimicrobial Agents and Chemotherapy). In the past ten years, I have been involved in understanding the survival and resistance mechanism in streptococci against a lantibiotic antimicrobial named Smb. So far, we characterized the Smb’s immunity protein and discovered the first lantibiotic receptor (articles published in J. Bact). We also showed the specificity of a protease, SepM, which cleaves a signaling peptide to control lantibiotic Smb production and secretion (published in J. Bact). My long-term goal is to use lantibiotics to eliminate specific organisms of interest without altering the composition of microbiota. We have recently made an interesting observation that the presence of a motif is necessary in the Smb’s receptor on the target for killing. We are also studying lantibiotic Smb to increase its efficacy and modulate its specificity so that we can direct it against any chosen target. I have over 15 years of experience in handling both naturally competent and noncompetent streptococci. I am thoroughly trained in molecular microbiology, protein chemistry, and genomics research.
In addition to studies related to lantibiotics, I have also initiated studies related to Lactobacillus rhamnosus, which is a firmicute often found in the oral cavity. A L. rhamnosus strain (LGG) originally isolated from the gastrointestinal tract is widely used as a probiotic organism since it has many beneficial traits including immuno-modulatory activity. We have isolated and characterized a L. rhamnosus strain (LRB) from a healthy baby-tooth that has naturally fallen out. We first determined the complete genome sequence of LRB to understand its suitability as a probiotic strain since L. rhamnosus is known to undergo genome rearrangement frequently. We found that LRB is closely related to the widely used LGG strain. We found that LRB showed good bactericidal activity against most oral streptococci and against Klebsiella pneumonia, an ESKAPE pathogen. We also assessed its ability to survive in the gut environment. Interestingly this strain showed resistance against low pH but low tolerance against bile salt. However, this strain can efficiently tolerate other stresses that are frequently encountered in the oral cavity. Surprisingly, we also found a deletion in the ribosomal protein L4; this deletion differentially affects the resistance against various antibiotics including macrolides. Currently, we are exploring the possibility for using LRB as a vaccine delivery vehicle (oral) to control various illnesses.