Colonies of Bacillus cereus were grown on the surface of nutrient agar
plates. After inoculation as spread plates from serial dilutions, dia
meter and coefficients of circularity were determined from captured im
ages using a particle analysis program. Radial growth rate was strictl
y linear whilst the coefficient of circularity fell with time. Followi
ng point inoculation at the centre of the plate, colony growth was mon
itored daily and images captured, converted to absorbance and presente
d as wire frame diagrams. Successive subtraction of these images indic
ated that growth took place after about 24 hours, only at the peripher
y of the colony.