Transcriptome dynamics ofPseudomonas aeruginosaduring transition from replication-uncoupled to -coupled growth

Abstract

In bacteria, either chromosome duplication is coupled to cell division with only one replication round per cell cycle or DNA is replicated faster than the cells divide thus both processes are uncoupled. Here, we show that the opportunistic pathogen Pseudomonas aeruginosa switches from fast uncoupled to sustained coupled growth when cultivated under standard laboratory conditions. The transition was characterized by fast-paced, sequential changes in transcriptional activity along the ori-ter axis of the chromosome reflecting adaptation to the metabolic needs during both growth phases. Quorum sensing (QS) activity was highest at the onset of the coupled growth phase during which only a quarter of the cells keeps replicating. RNA sequencing of subpopulations of these cultures sorted based on their DNA content, revealed a strong gene dosage effect as well as specific expression patterns for replicating and non-replicating cells. Expression of flagella and mexE, involved in multi drug efflux was restricted to cells that did not replicate, while those that did showed a high activity of the cell division locus and recombination genes. A possible role of QS in the formation of these subpopulations upon switching to coupled growth could be a subject of further research.