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Abstract
The advantages of living in a regulated bacterial system include greater access to nutrient sources, enhanced protection and establishment of environmental niches. Cell growth and regulation within bacterial systems is partially mediated by diffusible autoinducers. When populations reach high cell densities in closed systems, the increase in concentration of autoinducer results in an overall change in cellular activity. Autoinducer 2 (AI-2), an acyl homoserine lactone, is an example of a signaling molecule that functions in both interspecies and intraspecies communication. Vibrio harveyi was the first bacteria in which AI-2 activity was observed, as the genes impacted by AI-2 regulate bioluminescence. The luminescence emitted by V. harveyi provides a system often exploited for bioassays in order to assess autoinducer activity. AI-2 was used to induce a low cell density culture of Escherichia coli B23, previously shown to be capable of induction, to behave in a similar fashion to a high-density cell population. It was found that AI-2 did not affect growth rate but it did enhance the extent of growth. Analysis of protein abundance in young cultures upon exposure to AI-2 was performed in order to compare protein profiles between young and old cultures. Comparison of young cultures treated with AI-2 revealed points of similarity with old cultures that were not present in young cultures grown in the absence of AI-2.