For a bacterial infection to linger after antibiotic treatment only a small handful of bacteria need to remain.
What is different about these cells from the ones that were easily killed? How do these differences arise?
These are especially important questions with respect to Mycobacterium tuberculosis, the causative agent of tuberculosis. TB kills more people each year than any other pathogen. Part of the reason for Mtb’s success as a pathogen is that it can exhibit a tremendous amount of variability even in a genetically identical population of pathogen cells. This diversity allows the pathogen to survive the stresses imposed by the host and by antibiotics used to treat TB.
Our lab uses a variety of techniques: from parallel transposon sequencing to super-resolution microscopy to discover the strategies mycobacteria use to grow and survive. We hope what we learn will be helpful in designing new tuberculosis therapeutics designed to kill the infection faster and more completely.
Current projects in the lab include
1 – Uncovering the molecular mechanisms of cell-division mediated heterogeneity
We have recently discovered that a single protein in mycobacteria, called LamA, can generate variability every time a cell divides. It does so by establishing asymmetric polar growth and division. We are interested in understanding the molecular basis of this process. LamA has no homologs in other organisms, but it is conserved throughout mycobacteria. We are using a variety of genetic, molecular, and cellular techniques to understand how LamA functions as a member of the mycobacterial division complex.
2 – Discovering other drivers of heterogeneity
We think LamA may be the ‘tip of the iceberg’ as deleting it does not collapse all the heterogeneity we and others observe. We initially found LamA using a fluorescent reporter that predicted survival to the first-line TB drug, rifampin. Thus, we are working on developing other fluorescent reporter strategies that are relevant for survival in different conditions to find additional drivers of heterogeneity.
3 – Characterizing the role of novel cell growth and division factors
Mycobacteria use growth and division to vary the behavior of single cells at a very high frequency. However, the details of cell growth and division in mycobacteria are not well understood. We do know that the mechanisms must be fundamentally different in mycobacteria compared to model rod-shaped bacteria. That’s because mycobacteria insert new cell wall material at their poles rather than side walls and are missing many obvious homologs of known growth and division factors. In addition, nearly half of the mycobacterial genome encodes proteins of unknown function. Our lab is currently characterizing the function of several proteins-of-unknown function that we think may be involved in cell growth or division.