A Note on the Lag-Phase in the Growth of Micro-Organisms

Ledingham and Penfold have shown that during the lag-phase of growth ofB. coliin a nutrient medium the time and bacilli are connected by an equation of the formXn=KlogYwherenandkare constants (the initial seeding = 1). It has been pointed out in this communication that there is a relationship betweennandk, and that the above equation can be put in the form The advantage of this new equation is thatKremains of the same value throughout the whole series of experiments. In the case investigated by Ledingham and Penfold the constant of unrestricted growth is approximately equal to 2K. The equation can also be put in the form whereZis the “constant” of growth at a timeX. By suitably adjustingnandathis equation can be made to represent not only the lag-phase of growth but also the logarithmic phase, and the special phase of retarded growth when theX−Ycurve is rectilinear. When cell-death occurs the bacteria usually perish at such a rate that theX−Ycurve is logarithmic; the general equation therefore also covers this case.