Dr. Sunil Saroj
Stress is a universal phenomenon which spares none of the life forms; the humans experience it, the animals experience it and even the bacteria residing within us experience it. However, every individual has differential coping mechanisms; which shapes the overall interactions and outcomes. Under stress, bacteria evolve survival strategies; humans develop personalities. Somewhere between these differential responses lies much of my scientific curiosity.
I have been increasingly fascinated by the fact that bacteria are far more dynamic than we often give them credit for. They constantly sense changes around them, exchange signals, alter their metabolism, and adapt surprisingly fast to conditions that should ideally limit their survival.
As my research evolved, so did the questions that interested me. Early on, I worked on understanding bacterial virulence and the genetic determinants that influence pathogenicity. Understanding metabolites such as polyamines in bacterial physiology. This gradually expanded into studies on CRISPR systems and their association with bacterial virulence and evolution. Around the same time, I also became increasingly interested in antimicrobial resistance and the remarkable ability of pathogens to continuously remodel themselves under selective pressure. Another phase of my research involved exploring host-associated and beneficial microbial systems, including Lactobacillus. Working with both pathogenic and beneficial bacteria gave me a very different perspective on host–microbe interactions. The phenomenon became increasing clear that bacterial behaviour need to be studied in context of their social life. The context matters; the changes in host metabolites, host immune responses, neighbouring microbes and the available nutrients, they all shape the microbial behaviour.
Over time, these quest of knowledge which seems separate now converge into into what now forms the broader theme of the Laboratory for Bacterial Communication at the Symbiosis School of Biological Sciences (SSBS). Questions related to polyamines, metabolic adaptation, oxidative stress responses, interspecies signaling, quorum sensing, and adaptive antimicrobial resistance all eventually pointed toward the same larger idea; “bacteria are constantly sensing, responding, and communicating”.
Postdoctoral experience at the Chiba University (Japan), Emory University (USA), and Stockholm University (Sweden) exposed me to different ways of thinking about infection biology, microbial adaptation, and host responses. Returning to India through the Ramalingaswami Re-entry Fellowship was an important turning point in my academic journey. It provided me the opportunity to establish an independent research program and pursue questions connecting bacterial communication, stress adaptation, host–pathogen interactions, and antimicrobial resistance within a broader translational context.
We strive to understand the factors that contribute to the transition of a pathogen from asymptomatic persistence to symptomatic disease. A large part of our research is to underandand how pathogens react to oxidative stress, antibiotics, bile, nutrient limitation, and host-derived signaling molecules, and link it with the adaptive responses that influence virulence, persistence, and antimicrobial resistance.
Over the years, the laboratory has worked on pathogens such as Neisseria meningitidis, Acinetobacter baumannii, Klebsiella pneumoniae, and Streptococcus pyogenes. Working with these organisms has taught me that bacteria rarely behave the way we expect them to. Some experiments work exactly as planned, but many do not. In fact, some of the most interesting observations in the laboratory have started from results we initially thought were wrong; a strain behaving strangely, a phenotype refusing to fit the hypothesis, or an experiment giving completely opposite trends on different days. Over time, we have probably become more interested in the physiological uncertainties than perfectly clean datasets.
The central idea behind the Laboratory for Bacterial Communication remains fairly simple. Bacteria are constantly interacting with the host, with the environment, and with each other. The more we understand these interactions, the better we may understand not only infectious diseases and antimicrobial resistance, but also adaptation.