The effect of changing environmental conditions with the use of Sephadex beads on the growth of an Escherichia coli strain able to use quorum sensing (AB1157) by limiting availability of autoinducers

Abstract

Bacteria communicate by releasing molecules that accumulate in dense populations. This process is known as quorum sensing, and is involved in regulating a variety of cellular processes including growth. Escherichia coli strain AB1157 cells can produce homoserine lactone (HSL) autoinducer molecules, which participate in quorum sensing. The E. coli strain DH5 α can not produce the autoinducer molecules, and were used as a negative control. We attempted to determine the effect on growth of making the autoinducers unavailable to the cells by adding Sephadex beads to the media. We also experimented with changing the carbon source by supplementing the media with glucose or glycerol. Both OD readings and spread plate counts were used to monitor the growth of the various 600 cultures. The pH was also monitored to detect whether fluctuations that may affect growth had occurred. The results from the two trials were inconclusive. It appears as though Sephadex may have a deleterious effect on cell growth, irrespective of the quorum sensing capacity of the cells. Fluctuations in the pH of the cultures would have also affected growth, which may have confounded our interpretation of the results. Further experimentation is required to obtain a distinct correlation between inhibition of autoinducers and growth.