Hacking bacterial growth: genomic strategies to reprogram generation time.

LETICIA LAROTONDA; IAN MEDICI; DIDIER MAZEL; COMERCI, D; ELIAS MONGIARDINI; ALFONSO SOLER BISTUE

Copenhagen

Conferencia; Major ideas in quantitative microbial physiology: Past, Present and Future.; 2022

University of Copenhagen, UCSD and Novo Nordisk Foundation

Growth rate (GR) varies widely among bacterial species. The genetic factors shaping GR are still an open question. However, the growing genomic database and comparative genomics studies, offer some clues. Some observations coming from Bioinformatics link genome structure to growth. Bacteria bearing a high number of ribosomal operons (rrn) display higher GRs reflected in shorter generation times (GT). Also, 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. These physiological effects could not be compensated by suppressor mutations after 1000 generations of evolution. In parallel, we study the physiology of Bradyrhizobium as slow-growing bacterial model, well known for its symbiotic interaction with plants. Bradyrhizobia bear 2 or 1 rrn. The former showed shorter lag phase, faster GR, higher fitness and larger cell size. To prove causation we are deleted one out of 2 rrn in Bradyrhizobium japonicum E109. As expected rrn deletion was accompanied by a GT increase. However we noticed that the strongest phenotype was an enlargement of lag phase. Meanwhile, experimental evolution approach applied at both bacterial models allowed an reduces GT. 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.