Microbiology and Cell Biology

Department website: http://mcbl.iisc.ernet.in/


A cell is never idle. The information necessary for its function is contained within the nucleus, in its genes. Genes are made of DNA, a long molecule made of repeating units which is passed on from one generation to the next. When a gene is expressed - turned on, in other words - information from genes is transferred to ribonucleic acid (RNA), through a process called transcription. When a protein is the desired end product, a type of RNA called messenger RNA (mRNA) is produced, which is made into protein by special units called ribosomes in a process called translation.

These and a variety of other processes, in human beings and other organisms, are the focus of the Department of Microbiology and Cell Biology. Cells, their component parts, their life cycle and how they interact with the environment, are the main focus of research. Research work in the department spans almost all kingdoms of life: from viruses and bacteria to plants and mice. The Department has contributed significantly to the understanding of microbes that cause diseases, like Mycobacterium tuberculosis, the causative agent of tuberculosis.

Ajitkumar has been working on the mechanisms of cell division, especially the proteins used, the genes involved and their expression, and the regulation of cell division. To study bacterial cell division, the lab uses Mycobacterium tuberculosisMycobacterium smegmatis (a harmless bacterium considered to be a surrogate for the deadly M. tuberculosis) and Escherichia coli, which is found commonly in the human intestines

How Mycobacterium tuberculosis and its relatives cause infections is the focus of K N Balaji’s lab. Only 10% of people infected with Mycobacterium tuberculosis go on to develop an active infection. Others have a latent infection, which may get reactivated at a later stage. This reactivation is more common in patients whose immunity is suppressed, like those with AIDS. The lab is investigating the interaction between mycobacteria and their host.

S Vijaya’s group works on the genetics of Mycobacterium tuberculosis, and the development of better vaccines for the disease. They also work on the Japanese encephalitis virus, which causes encephalitis and is carried between hosts by mosquitoes. Amit Singh works on a different stage of the Mycobacterium tuberculosis infection cycle: how to track the bacterium during the course of an infection. He also works on HIV infection, and possible anti-oxidant based therapy for AIDS.

Some viruses are extremely simple in structure, and cannot carry out protein synthesis on their own. After infecting a host, they cheat the host cell’s machinery to make virus proteins. Saumitra Das works on the mechanism by which viruses get this done. He has been working on the hepatitis C virus, and trying to figure out which stage of the virus attack is best for designing antivirals.

C Durga Rao works on how gene expression is regulated after a protein is formed. He is also interested in the molecular biology of viruses - rotavirus, which causes acute gastroenteritis in babies and enteroviruses, which include the viruses causing polio, meningitis and foot-and-mouth disease.

Restriction enzymes are proteins that can cleave DNA at specific points to make smaller fragments. Bacteria use these enzymes to protect themselves from foreign DNA introduced into bacteria by some viruses. At the same time, bacteria need to protect their own DNA, which may contain these specific stretches of DNA that the restriction enzymes recognise. They modify their own DNA by adding a few molecules to throw the restriction endonuclease off. V Nagaraja and his group have been investigating these enzymes, especially one called Kpn1. The lab also works on regulation of transcription. Often, because of various reasons, DNA in the cell gets coiled up - that is, it changes its topology. V Nagaraja’s lab has been working on several enzymes involved in interconverting the topology of DNA as targets for antibacterials.

S S Indi uses his expertise with the electron microscope, which can magnify objects up to 10 million times, to figure out molecular structures. He has been working on the structure of tiny Copper nanoparticles, and on two neurological diseases Parkinson’s and Alzheimer’s disease. During the process of gene expression, the messenger RNAs formed are regulated by small RNAs called micro RNAs. The mechanism of how they regulate mRNA function is the focus of Saibal Chatterjee’s lab.

We have all heard of the dangers of improperly cooked poultry and fish dishes - deadly bugs belonging to the group Salmonella could hop on and devastate our unsuspecting guts. One particularly severe member of the group is Salmonella typhimurium, which causes food poisoning (and gastro-enteritis) in humans and other mammals. Dipshikha Chakravortty's lab has been looking at all aspects of the infection - how the bacteria enters a host, how it evades detection by host cells, and the effect of medical intervention.

Think of a plant, and green leaves and beautiful flowers immediately come to mind. How does a mass of undifferentiated cells become a pointed leaf or a spindly petal? Utpal Nath and his lab have been working on this puzzle, using a small relative of cabbage called Arabidopsis as a model system. They also work on the set of genes that come together to determine when a plant flowers.  

Dr Usha Vijayaraghavan's lab uses plant systems to understand the factors regulating transcription. Last year, the lab found that the master regulator of gene expression in rice (OsMADS1) regulates the development of stem tips into flowering stalks, through an intricate pathway involving transcription factors and hormones.

Umesh Varshney’s protein synthesis group works on how the process is initiated and how cellular components are recycled. Using the bacteria Escherichia coli, they showed that a special type of RNA that initiates protein synthesis in bacteria is actually a lot more flexible than previously thought - this means, bacteria have a lot more in their arsenal while reacting to stressful conditions. Another group works on DNA repair - the processes that spot and correct errors caused by internal processes and the environment like UV light in the genome.

Glioblastoma is the commonest form of aggressive brain tumour in humans, involving the star shaped astrocytes that make the “glue” that holds the brain together. Kumar Somasundaram’s lab has come up with another marker to track the early stages of this tumour, to help identify patients as being at low or high risk. They also investigated changes in the cancer cells when treated with temozolomide, a chemotherapeutic drug used to treat glioblastomas, shedding more light on its mode of action.

DNA in our cells exist in an elegantly structured form imparted upon it by many proteins, major among them being histones. Histones are also a target for chemical modifications, which occur as a part of normal physiological processes to regulate gene expression. A class of these modifications can be removed by a group of proteins called Sirtuins. Ravi Sundaresan’s lab works on Sirtuins and studies their role inheart failure as well as in metabolic diseases such as diabetes. His group aims to unravel new functions of Sirtuins to better our health.