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NIAID Grantees Study How Bacteria Communicate and Compete

Scientists at the University of California, Santa Barbara recently studied a bacterial toxin delivery system used by different strains of bacteria to chemically communicate with one another and compete for the same ecological niche. The results of this NIAID-funded study were published in the journal Nature in November 2010.

The researchers had previously discovered a phenomenon known as contact-dependent growth inhibition (CDI) taking place in one strain of Escherichia coli, in which the growth of other E. coli strains was inhibited upon cell-to-cell contact. They further explored this inhibition in the new study and found CDI taking place in several species of bacteria.

In addition, the researchers found high variability in the genetic sequences that code for CDI. This implies that a variety of toxic activities can take place. For example, a comparison of the activities of those regions in E. coli, another type of bacteria called Burkholderia, and the plant pathogen Dickeya dadantii showed different mechanisms of growth inhibition. The investigators also found that bacteria without these coding regions were unable to compete with wild-type bacteria, both in the lab and in animals.

“Sometimes, there are multiple strains of a single species of bacteria in a small ecological area,” explained Rona Hirschberg, Ph.D., chief of NIAID’s Regional Centers, Translational Research, and Biodefense Training Section. “In this competition between bacterial ‘first cousins,’ some strains may be more pathogenic to humans than others, and the outcome of that competition may have implications for human disease.”

In future studies, the researchers plan to further investigate how CDI works at the molecular level. They will also examine broader issues relating to its significance and implications.


Aoki SK, Diner EJ, de Roodenbeke Ct’K, Burgess BR, Poole SJ, Braaten BA, Jones AM, Webb JS, Hayes CS, Cotter PA, Low DA. (2010). A widespread family of polymorphic contact-dependent toxin delivery systems in bacteria. Nature. 468(7322): 439-442. DOI: 10.1038/nature09490.​

Last Updated December 06, 2010

Last Reviewed December 06, 2010