Earlier onset of EB production in a C. muridarum Pgp4-deficient strain. Progeny assay analysis of L929 cells infected with C. trachomatis (A) or C. muridarum (B) strains at 4-h time intervals is shown. The number of infectious progeny, as measured in a secondary infection, are reported as inclusion-forming units. For each time point and strain, the results are the average from 3 experiments, with error bars showing standard deviation. Statistically significant differences are indicated by asterisks (*, P < 0.05).