CELL DIVISION AFTER INHIBITION OF DNA AND PROTEIN SYNTHESIS IN NEISSERIA MENINGITIDIS

A comparison has been undertaken between a transformable ( cp +) and a non transformable ( cp ‐ ) variant of the Neisseria meningitidis Strain M1. Previous evidence indicates that these variants have different origin and direction of replication. Hydroxyurea inhibition resulted in 41 per cent and 43 per cent increase in colony‐forming units in exponentially growing cultures of the cp + and the cp ‐ variants respectively. Chloramphenicol exhibited a concentration effect. At 2.5 μg/ml, exponential increase in colony‐forming units stopped, but the number increased with 73 per cent in the cp + variant and with 45 per cent in the cp ‐ one. Concentrations above 10–15 μg/ml permitted no significant residual division. The rate of increase in absorbancy was reduced by hydroxyurea and chloramphenicol, but there was no significant difference between the two variants. The findings have been discussed in relation to the age distribution function for bacterial chromosomes in an exponential population. The results support the hypothesis that there are two kinds of proteins involved in cell division. The synthesis of one of these is inhibited by low concentrations of chloramphenicol, and seems to be triggered by the replication of a distinct region or locus on the chromosome. This region is probably located close to or at the origin (or terminus) for the chromosome of the cp ‐ variant, whereas it is distant from that for the cp + one.