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Increase of nucleoid size with increasing age of hyphal region in vegetative mycelia of Streptomyces granaticolor
Author(s) -
Kretschmer Sigrid,
Kummer Christel
Publication year - 1987
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.3620270104
Subject(s) - nucleoid , hypha , biology , mycelium , dna , cell division , silver stain , biophysics , microbiology and biotechnology , biochemistry , escherichia coli , botany , cell , gene
In mycelia of Streptomyces granaticolor grown in liquid cultures the distribution of DNA was surveyed by staining and autoradiographic methods. The frequency of stained nucleoids was rather similar in young and old hyphal regions. However, the size of the nucleoids increased with the age of a hyphal region. The degree of heterogeneity in nucleoid size was particularly high during slow growth. In the autoradiograms silver grains ( 3 H‐thymidine label) were also heterogeneously distributed along the hyphae. Calculation of the average number of silver grains per nucleoid revealed that the amount of DNA per nucleoid was 1.6 times higher in the more distant subapical regions than within the 35 μm long apical region. From a chase experiment it became obvious that the DNA segregated in a normal manner only within the apical region. When the chase lasted for one doubling time, the frequency of silver grains was reduced to 50% only within the about 30 μm long apical region. The label incorporated subapieally remained almost constant, therefore, indicating a lack of normal segregation. Only about 10% of the label was lost by branching. The lack of segregation of sister nucleoids after repeated rounds of replication was found to be responsible for the increase of nucleoid size within subapieal hyphal regions.