La relación entre la posición del locus s10-spc-alpha, la tasa de crecimiento y la capacidad de infección de Vibrio cholerae ayuda a comprender la organización genómica de la bacteria.

SOLER BISTUE, ALFONSO

Mar del Plata

Congreso; X Congreso de Microbiologia General; 2014

SAMIGE

Comparative genomics revealed a conserved trend in genome organization of fast-growing bacteria: position of ribosomal and RNA polymerase genes are biased towards the origin of replication (oriC). It has been speculated that this bias would allow increased gene dosage during exponential phase. Experimental evidence is scarce though. In bacteria, a single locusS10-spc-α (S10) encodes half of ribosomal protein genes. Vibrio cholerae, a bichromosomal fast-growing pathogen, was tested for precise relocation of this highly conserved locus. S10 repositioning was achieved using lamboid phage recombinases through transient excision followed by targeted reintegration. A set of isogenic mutants where S10 was moved next to its original position, to the middle of the replichore, to the terminal region of Chromosome 1 and to the secondary chromosome was obtained. Analysis of growth kinetics and time-lapse microscopy experiments showed that, in fast-growing conditions, the further away S10 was moved the lower growth rate (GR) was obtained. Interestingly, this phenotype correlated with a reduction of S10-dosage and S10 mRNA abundance. Importantly, upon the returning the locus to its original position GR is recovered. Although S10 could be easily moved to several positions within the genome, infection tests on the model organismDrosophila melanogaster showed that mutants are highly impaired in host invasion. This fact suggests that, in nature, strong selective pressure drove this locus nearoriC. Overall, our results support the idea that fitness advantage of positional bias is to provide higher dose during fast growth. S10 positioning plays a key role linking genome structure with cell physiology as it is involved in growth global control and in host invasion that may have a role in the ecological success of V.cholerae.