Lethal protein produced in response to competition between sibling bacterial colonies

Avraham Be'er*, Gil Ariel, Oren Kalisman, Yael Helman, Alexandra Sirota-Madi, H. P. Zhang, E. L. Florin, Shelley M. Payne, Eshel Ben-Jacob, Harry L. Swinney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Sibling Paenibacillus dendritiformis bacterial colonies grown on low-nutrient agar medium mutually inhibit growth through secretion of a lethal factor. Analysis of secretions reveals the presence of subtilisin (a protease) and a 12 kDa protein, termed sibling lethal factor (Slf). Purified subtilisin promotes the growth and expansion of P. dendritiformis colonies, whereas Slf is lethal and lyses P. dendritiformis cells in culture. Slf is encoded by a gene belonging to a large family of bacterial genes of unknown function, and the gene is predicted to encode a protein of approximately 20 kDa, termed dendritiformis sibling bacteriocin. The 20 kDa recombinant protein was produced and found to be inactive, but exposure to subtilisin resulted in cleavage to the active, 12 kDa form. The experimental results, combined with mathematical modeling, show that subtilisin serves to regulate growth of the colony. Below a threshold concentration, subtilisin promotes colony growth and expansion. However, once it exceeds a threshold, as occurs at the interface between competing colonies, Slf is then secreted into the medium to rapidly reduce cell density by lysis of the bacterial cells. The presence of genes encoding homologs of dendritiformis sibling bacteriocin in other bacterial species suggests that this mechanism for self-regulation of colony growth might not be limited to P. dendritiformis.

Original languageAmerican English
Pages (from-to)6258-6263
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - 6 Apr 2010
Externally publishedYes


  • Bacterial competition
  • Bacterial growth inhibition
  • Growth regulation
  • Paenibacillus dendritiformis
  • Subtilisin


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