CORRELATION BETWEEN BRANCHING AND ELONGATION IN GERM TUBES OF STREPTOMYCES-GRANATICOLOR

With four individual germ tubes (GTs), the distinct time of birth of branches was correlated to the kinetics of GT-elongation. During the first three hours, corresponding to five doubling times, branching was suppressed. The time of birth of the first branch (t(b1)) coincided with the 5th step of the typical stepwise increase of the GT elongation rate (alpha). During this time, the quasi-exponential kinetics of alpha changed to linear kinetics, which was attained either at the 5th of 6th alpha-step. At the 5th step, the quotient of successive alpha-values had been reduced from 2 at the beginning of outgrowth to 1.2. Once the first branch had been formed, further branches appeared as clusters (additional 2, 4, and 8 branches) at D-intervals representing the doubling time of the hyphal length. The first branch appeared always in the vicinity of the spore. The average distance to the spore of 6.6-mu-m corresponded to four unit cells. At t(b1), the unbranched region located between the first branch and the tip of the GTs was 42-mu-m long. The data concerning timing and location of the first branching in GTs suggest that initiation of branching was dependent on the accumulation of envelope precursors.