In this paper we consider a mathematical model motivated by patterned
growth of bacterial cells. The model is a system of differential equat
ions that consists of two subsystems. One is a system of ordinary diff
erential equations and the other is a reaction-diffusion system. An al
ternating-direction implicit (ADI) method is derived for numerically s
olving the system. The ADI method given here is different from the usu
al ADI schemes for parabolic equations due to the special treatment of
nonlinear reaction terms in the system. Stability and convergence of
the ADI method are proved. We apply these results to the numerical sol
ution of a problem in microbiology.