Control of the Chlamydial Developmental Cycle by a Plasmid-Encoded Protein
An important step in the developmental cycle of the pathogenic bacterium Chlamydia is the conversion from a replicating to an infectious form inside a host cell. Zhang et al. (e00793-19) provide new insights into how the timing of this conversion is controlled through EUO, a regulator of late gene expression. Using in vitro approaches and infection with deletion strains, they showed that a plasmid-encoded protein, Pgp4, modulates the ability of EUO to repress late genes and could alter the timing of conversion. These findings suggest that the plasmid may have a role in controlling the developmental cycle in Chlamydia.
Transcription Termination Checkpoints Do Not Limit Plasmid Transfer from Pheromone-Induced Enterococcus faecalis
Enterococcal pheromone-inducible conjugation functions efficiently in vitro and in host environments. However, in experiments where single rounds of transfer are measured, only about 1 to 10% of highly induced donor populations can transfer, even in dense, mixed cultures with excess recipients. Erickson et al. (e00685-19) used the hybridization chain reaction and fluorescent reporters to visualize both induction of multiple pCF10 conjugation genes and mating at the single-cell level. They found that all donors induced for expression of 5′ conjugation genes also produced transcripts from 3′ genes. Thus, failure of donors to transfer does not result from incomplete transcription of conjugation genes.
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