Collaborations

Rich Losick - Fruiting Body Formation by Bacillus subtilis

All of our work on Bacillus subtilis biofilms has been done in collaboration with the Losick Laboratory of Harvard University.

Abraham Minsky - DNA Protection Mechanisms

Aerobic organisms have evolved many mechanisms to cope with oxidative damage to their DNA. Dps is unique in that it affords protection to DNA from oxidative damage. The structure of Dps, which is homologous to the iron cages of ferritin, suggests that Dps sequesters iron atoms that are found in the vicinity of the DNA. In this way hydrogen peroxide cannot react with iron and therefore no hydroxyl radicals form near the DNA. The iron sequestering properties and DNA binding properties of Dps are currently being investigated. This project is a collaboration with Abraham Minsky of the Weizmann Institute in Rehovot, Israel.

Subramony Mahadevan - Population Dynamics in Stationary Phase (GASP)

When nutrients are plentiful and conditions are propitious for growth most bacteria grow exponentially. However, due to the usual limited availability of nutrients, exponential growth periods tend to be short-lived and bacteria must cope with prolonged periods of starvation. Most bacteria respond to starvation by developing increased resistance to environmental stresses. However, if starvation continues for very long what ensues is anything but stationary. Prolonged starvation inevitably leads to heterogeneous populations with some cells dying while others survive. Most importantly, the survivors in starving populations are not just cells identical to the initial strain but rather the progeny of mutant subpopulations that have a Growth Advantage in Stationary Phase (referred to as mutants that can express a GASP phenotype).

From these observations emerges the hypothesis that underlies much of the research in this project: In some instances starving bacterial populations can both survive and evolve by repeated takeovers of GASP mutants under conditions when essential nutrients are provided predominantly by the dead cells. This hypothesis makes many predictions and raises many questions.

Currently, we are studying the mutations that can confer a GASP phenotype. We are also exploring the evolutionary consequences of repeated cycles of GASP takeovers during extremely long periods of incubation in stationary phase.

This project is a collaboration with Professor Subramony Mahadevan from the Indian Institute of Science in Bangalore, India.

Relevant publications:

Zambrano, M.M., D.A. Siegele, M. Almirón, A. Tormo and R. Kolter. 1993. Microbial competition: Escherichia coli mutants that take over stationary phase cultures. Science 259:1757-1760.

Zambrano, M.M. and R. Kolter. 1996. GASPing for life in stationary phase. Cell 86:181-184.

Finkel, S. and R. Kolter. 1999. Evolution of microbial diversity during stationary phase. Proc. Natl. Acad. Sci. 96:4023-4027.

Zinser, E.R. and R. Kolter. 1999. Mutations Enhancing Amino Acid Catabolism Confer a Growth Advantage in Stationary Phase. J. Bacteriol. 181:5800-5807.