Which of the following is not true about "quorum sensing" in bacteria?
A. Quorum sensing is the regulation of gene expression in response to fluctuations in cell-population density.
B. Bacteria that use quorum sensing constantly produce and secrete certain signaling molecules called autoinducers or pheromones that increase in concentration as a function of cell density. As the population grows and the concentration of the inducer passes a threshold, a positive feedback loop is formed, causing more inducer to be synthesized, leading to further gene expression to control many of their physiological activities.
C. Pseudomonas aeruginosa uses quorum sensing to coordinate the formation of biofilms, i.e. it grows within a host without harming it until it reaches a certain concentration, then it begins aggressively growing and leading to disease.
D. Escherichia coli does not have the quorum sensing mechanism.
Answer: D
In E. coli, cell division is also partially regulated by the quorum sensing mechanism, as are many gram positive and gram negative organisms.
References
1. Prof Bonnie Bassler, Princeton University
2. Rosenberg E. Microbial ecology and infectious disease. American Society for Microbiology, 1999.