Dependence of the mycelial growth pattern on the individually regulated cell cycle in Streptomyces granaticolor

Abstract

The growth behaviour of Streptomyces granaticolor E T H 7437 was studied by the microculture technique. The kinetics of growth and branching were recorded and, since elongation was found t o be restricted to apical elongation sites (e-sites), the rate of elongation per site (a) was determined as well. The mycelia grew exponentially. Initially the growth was dependent on a of the germ tube, but after the start of branching, growth paralleled the exponential increase of the number of branches while a attained a constant average value.Further, for liquid grown mycelia showing about the same growth kinetics the cellular structure was determined after cell wall staining. Three types of cells could be distinguished: apical branchless cells (20y0), non-apical branchless cells (20%) and non-apical cells with one branch each (60%). Since both the apical and the branched cells possessed an e-site, 80% of the cells must have been growing a t the time of sampling.Combining detailed data obtained from both the alive and the stained mycelia a model was elaborated, which may reflect the events taking place on the cellular level during mycelial growth. The model is based on the assumption that each cell behaves as a n independent unity with respect to its cell cycle. But, in contrast to the behaviour of single cell bacteria, in mycelia the two daughter cells formed upon division are neither equivalent nor uniform. Here, the sister cells differ in length, shape and posssession of a n e-site. Only one of the daughter cells receives the e-site of the mother cell, while the other starts its own cell cycle by generating a new e-site a t the cylindrical part of its envelope. Regarding the length of sister cells the degree of heterogeneity increases with the age of the corresponding region of the mycelium, and eventually some cells lose the ability t o generate an e-site, i. e. to grow.With this model the kinetic and structural peculiarities of the mycelial growth of Streptomyces granaticolor can be explained.Studying the growth behaviour of some unrelated actinomycetes strains ( SCHUH- MANN and BERGTER 1976, KRETSCHMER 1978,1981 it has become evident that niycelial growth underlies common rules. Unlimited mycelial growth is characterized by two features: exponential increase of the total length parallel to the number of branches, and elongation being restricted to elongation sites (e-sites) (BEGG and DONACHIE 1977) situated at each hyphal tip.The exponential increase of mycelial length ( SCHUHMANN and BERGTER 1976, KRETSCHMER 1978, 1981) resp. of the biomass (HILLIGER and RIESENBERG 1976)indicates that the cytoplasm is exponentially synthesized equally throughout the whole mycelium. Indeed, with Streptomyces hygroscopicus growing in a chemostat it was demonstrated autoradiographically that protein synthesis is not restricted to the hyphal tips, and that the portion of mycelial regions with high synthetic activity rises with increasing growth rate (RIESENBERG and BERGTER 1979). Also, pulse labelling the D N A of s. hygroscopicus, s. gr...

Time-Lapse Microscopy of Streptomyces coelicolor Growth and Sporulation

“…Following germination, hyphal extension occurred at a rate of ϳ20 m h Ϫ1 and FtsZ-EGFP rings were laid down ϳ56 m behind the growing tip. Streptomyces granaticolor lays down septa 28 m from the hyphal tip (17), and as septum formation is dependent on the initial formation of a ring of FtsZ (26), it appears that either there is some variability in the frequency of septum formation between these two species or cultivation conditions affect septal frequency. It was thought that the subapical daughter compartment created a new extension site through branching (14) and this new apical cell was eventually partitioned from the subapical cell by a new septum.…”

Cell division and DNA segregation inStreptomyces: how to build a septum in the middle of nowhere?

“…In contrast, during vegetative growth cell division results in the formation of hyphal cross‐walls, which are widely spaced, and delimit adjacent elongated compartments that each contain multiple copies of the genome. Studies of Streptomyces granaticolor suggested initiation of division at the middle of the growing apical cell when it reaches a certain length (Kretschmer, 1982). However, considerable variation is seen in the frequency and spacing of vegetative septa in Streptomyces hyphae, both between different species and within a single species between different growth conditions.…”

Growth and development of Frankia spp. strain CcI3 at the single-hypha level in liquid culture

“…We find in this study that, although very slow, the growth kinetics of Frankia sp. strain CcI3 resembled that of other filamentous actinomycetes in having an exponential increase in total mycelium length and arithmetic or pseudolinear increase in individual hyphae (Kretschmer 1978(Kretschmer , 1982Allan and Prosser 1983). Moreover, the interbranch distances of strain CcI3 were similar to those described in Streptomyces coelicolor A3(2) (Allan and Prosser 1983).…”