GENOMIC STRATEGIES TO RATIONALLY REPROGRAM BACTERIAL GROWTH

SOLER BISTUE A

Virtual

Congreso; Congreso SAIB SAMiGe 2020; 2020

SAIB y SAMiGe

The genetic basis of bacterial growth rate (GR) remains elusive. Bioinformatic studies link genome structure to growth: a higher number of rRNA operons (rrn) and a greater proximity of the transcription and translation genes to the replication origin (oriC) correlate with faster growth. We aim at testing these observations experimentally using slow and fast-growing bacteria. Vibrio cholerae, the causative agent of cholera disease, divides every 17 minutes. We systematically relocated S10-spc-α (S10), the main ribosomal protein locus, and rpoBC, encoding the RNA polymerase core, to different genomic locations. Their relocation far from oriC resulted in a reduction of GR, fitness and infectivity due to replication-dependent lower dosage. This effect was also observed in absence of multi-fork replication, suggesting that genomic position is relevant in slow-growing bacteria. Surprisingly, S10 location didn?t influence translation but altered macromolecular crowding of the cytoplasm. In this line, S10 relocation displayed stronger phenotypic effects than rpoBC repositionning. In parallel, we study the physiology of Bradyrhizobium as slow-growing model. We performed the first time-lapse microscopy of this bacterium uncovering its extreme asymmetric division. Bradyrhizobia isolates bear 2 or 1 rrn. The former showed shorter lag phase, faster GR, higher fitness and larger cell size. To prove causation we are currently altering rrn ploidy within each strain. Overall, these studies will be useful to set up strategies to reprogram the growth of bacteria of biotechnological interest or to reduce the GR of fast growing pathogens to rationally generate attenuated strains.