Aim: The aim of this study was to investigate the role of quorum sensing in Bacillus anthracis growth and toxin production. Methods and Results: A microwell plate culture method was developed to simulate the normal UK-licensed anthrax vaccine production run. Once established, sterile supernatant additions from a previous B. anthracis culture were made, and reductions in lag phase and early stimulation of the anthrax toxin component protective antigen (PA) were monitored using ELISA. The addition of the quorum-sensing inhibitor, fur-1, prolonged the lag phase and impeded PA production. Spin filters of various sizes were used to identify the molecular weight fraction of the sterile supernatant responsible for the autoinducer effect. A weight fraction between 5 and 10 kDa was responsible for the autoinducer effect; however, further identification using mass spectroscopy proved inconclusive. Conclusions: Quorum sensing mediated by the autoinducer two molecule plays a significant role in both B. anthracis growth and toxin production. Significance and Impact of the study: While genomic analysis has eluded to the importance of LuxS and quorum sensing in anthrax, this is the first analysis using a production strain of B. anthracis and a quorum-sensing inhibitor to monitor the effect on growth and toxin production. This gives insights into anthrax pathogenicity and vaccine manufacture.