Cell reproduction and morphological changes in Mycoplasma capricolum.
The cell reproduction of Mycoplasma capricolum was studied. The velocity of DNA replication fork progression was about 6 kb/min, which is 10 times slower than that of Escherichia coli. The time required for one round of DNA replication accorded with the doubling time. The origin/terminus ratio was 2.0. M. capricolum cell morphology was classified into two types, rod and branched. In the ordinary-growth phase, the rod cells accounted for about 90% of the total population, with branched cells comprising the remaining 10%. The proportion of branched cells increased to 90% following inhibition of DNA replication by nucleoside starvation. An increase in the proportion of branched cells was induced by transfer of a temperature-sensitive mutant deficient in DNA replication to the restrictive temperature. The rod cells had a regular structure, a fixed cell length, and constrictions in the center. The DNA contents of individual rod cells were distributed with a standard deviation of 0.40 of average. The branched cells had irregular structures and a wide distribution of DNA contents. Counting of viable cells revealed that the cells ceased division upon cell type conversion; however, branched cells maintained a reproductive capacity. A model for the reproduction process is proposed.
Seto
S
S
Department of Biology, Faculty of Science, Osaka City University, Osaka, Japan.
Miyata
M
M
D001426:Bacterial Proteins / Q000032:analysis; D004261:DNA Replication; D004269:DNA, Bacterial / Q000032:analysis; D007700:Kinetics; D009174:Mycoplasma / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D013696:Temperature
D001426:Bacterial Proteins; D004269:DNA, Bacterial