Genomic relocation of genes implicated in the flow of genetic information impact bacterial growth and fitness.

BELEN BORDIGNON; LETICIA LAROTONDA; ALFONSO SOLER BISTUE; DIEGO COMERCI

Buenos Aires

Congreso; Congreso Argentino de Microbiología 2019 (CAM2019); 2019

Asociación Argentina de Microbiología (AAM)-Sociedad Argentina de Microbiología General (SAMiGe))

Growth rate (GR) is a key parameter of bacterial physiology widely varying among microorganisms. However, the genetic basis of GR is still unclear. In fast-growing bacteria, the genes encoding ribosomal protein genes (RP) and RNA polymerase (RNAP) are close to the origin of replication (oriC). During exponential growth, fast growers perform multi-fork replication. As a consequence, genes near oriC benefit of higher dosage during this growth phase. Thus, such positional bias can be a strategy to maximize the expression of transcription and translation machineries. Since most of these observations come from bioinformatic studies, we aimed at experimentally testing these correlations in a fast-growing bacterium. We used Vibrio cholerae as experimental model. Its genome can be widely modified by natural transformation coupled to recombineering techniques based on lambdoid phage recombination tools. As model loci we studied S10-spc-α (S10) which codes most of RP and rpoBC encoding the core of the sole bacterial RNAP. Using the aforementioned tools we altered the genomic location of these strategic loci. Previous evidence attributed more predictive power of GR to RNAP position. We relocated these loci at increasing distances of the oriC. Our results show that the relocation of both loci far for the oriC led to lower GR and fitness. The relocation of S10 caused a stronger effect. Close relocation displayed no phenotype indicating that relocation process per se was not detrimental. Trough time-lapse microscopy we checked that differences in GR are due to the relocation of the locus and not to viability loss or death of a subpopulation. Also, the parameter of UFC/OD was invariable between the strains suggesting that the relocalization of the locus doesn´t alter the cell viability. In future works, we seek to push Vibrio cholera growth to its lower limit. This in turn, could be a potential strategy to obtain attenuated strains that could be potental candidates for a nwe cholera vaccine.