ORIGINS OF INDIVIDUAL SWIMMING BEHAVIOR IN BACTERIA

Cells in a cloned population of coliform bacteria exhibit a wide range of swimming behaviors-a form of non-genetic individuality. We used co mputer models to examine the proposition that these variations are due to differences in the number of chemotaxis signaling molecules from o ne cell to the next. Simulations were run in which the concentrations of seven gene products in the chemotaxis pathway were changed either d eterministically or stochastically, with the changes derived from inde pendent normal distributions. Computer models with two adaptation mech anisms were compared with experimental results from observations on in dividuals drawn from genetically identical populations. The range of s wimming behavior predicted for cells with a standard deviation of prot ein copy number per cell of 10% of the mean was found to match closely the experimental range of the wild-type population. We also make pred ictions for the swimming behaviors of mutant strains lacking the adapt ational mechanism that can be tested experimentally.