Surface Colonization Parameters from Cell Density and Distribution

Abstract

Population growth and cell adhesion can occur simultaneously during surface colonization. Consequently, it is difficult to determine whether changes in colonization rate are due primarily to growth, adhesion, or both. To solve this problem, attempts have been made to calculate the rates of growth and attachment from the characteristic cell distribution pattern formed by cells as they colonize surfaces. This approach has been used to study colonization in the chemostat, where the growth rate of planktonic cells is set by the dilution rate and compared to that of cells colonizing immersed surfaces. These studies assume that growth and attachment are the primary processes responsible for the observed distribution pattern. They also assume that the mean rates of cell growth and attachment are initially constant. The accuracy of these assumptions have been tested in a limited number of surface environments. It appears from these studies that colonization might be more accurately described by defining the cell attachment rate as a function of cell surface density and by defining the growth rate as a function of microcolony size. However, a substantial improvement in the accuracy of methods used to gather population data is necessary to define adequately these functions and determine whether they are useful. Culture studies in continuous-flow capillaries, using on-line image processing techniques, may be helpful in this respect.