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Septation behaviour of the apical cell in Streptomyces granaticolor mycelia
Author(s) -
Kretschmer S.
Publication year - 1989
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620290906
Subject(s) - hypha , cell division , chemostat , elongation , mycelium , apical cell , biology , growth rate , cell wall , biophysics , cell , chemistry , botany , biochemistry , genetics , bacteria , materials science , geometry , mathematics , ultimate tensile strength , metallurgy
The septation behaviour of the apical hyphal cell, which solely brings about hyphal elongation, was studied using mycelia grown at different specific growth rates (μ) (chemostat and batch cultures). After cell wall staining it was found that both the apical cell ( c 1) and the adjacent subapical cell ( c 2) were generally unbranched. Thus, their length ( L ) could be easily determined. As the growth rate decreased, Lc 1 as well as Lc 2 decreased, but cells smaller than 5 μm were not observed, even at extremely slow rates of growth (μ = 0.06 h −1 ). The largest cells were observed in rich media, where Lc 1 attained 4l μm. Since Lc 2 represented the length of one of the new‐born daughter cells of c 1, the distribution curves of Lc 2 were used to look for regularity of septation. Especially at slow rates of growth, the curves indicated that in c 1 septation did not occur randomly. By using Lc 2 the interdivision time T of c 1 was calculated. At fast rates of growth it was identical to the earlier determined replication time C , indicating that in mature hyphae septation was coupled to the rounds of DNA replication. Lc 1 and Lc 2 were used to calculate the length of c 1 at birth and at the start of septation. It was found that upon septation the appearing daughter cells were differently sized. Depending on the growth rate, the apically situated daughter cell was 1.37 to 1.81 times larger than the subapical daughter ( c 2). Based on the functional heterogeneity of the sister cells a hypothesis was invented, which could explain the asymmetric septation pattern. It involves the existence of a period S between the determination of the septum site at median position and the actual process of septum formation. The duration of S was calculated, and its correlation to the T and C values at the corresponding growth rates was discussed. Two mechanisms could be distinguished, which were responsible for the immense increase of Lc 1 at fast rates of growth.