EXPLORING THE INFLUENCE OF RIBOSOMAL RNA PLOIDY ON ΑPROTEOBACTERIAL PHYSIOLOGY AND HOST INTERACTIONS: AN OPEN QUESTION

WADE, NAZARENA; ROMANI, ALEXIS; MEDICI, IAN; COMERCI, DIEGO J.; MARCHESINI, MARÍA INÉS; SOLER BISTUÉ, ALFONSO

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General; 2023

Even though it's a well-studied topic, the genetic factors shaping the maximum growth rateof a microorganism remain an open question. Various bioinformatic studies suggest that thequantity and proximity of rrn to the replication origin correlate to observed generation times. Most experimental work on this subject has been developed in classical model bacteria (e.g.Escherichia coli). Due to their symbiotic or pathogenic interactions with eukaryoticorganisms, α-Proteobacteria are economically relevant models to approach this subject.Bacteria of the Brucella genus are pathogens responsible for brucellosis, a zoonotic diseasethat causes significant economic losses. The aim of this work is to investigate the role ofploidy and genomic location of rrn in cellular physiology and the ability to interact with hostorganisms. Clean deletions of each of the three rrn were performed in Brucella suis 1330to generate single and double mutants for different rrn. Automated growth curves wereemployed to calculate doubling time and lag phase duration. Antibiotic protection assayswere conducted on the macrophage cell line J774.A1and CFU were counted at variouspost-infection time points. Considering that bacteria of the Brucella genus exhibit genomehomologies exceeding 98%, these constructs were used to replicate the experiments inBrucella abortus 2308 and Brucella melitensis. For Brucella suis, the deletion of a singlerRNA gene wouldn't impact growth rate negatively but would affect host interaction.However, the most significant effects were observed in double mutants, where growth andpathogenesis were strongly affected. Surprisingly, for Brucella abortus and Brucellamelitensis, single mutants exhibited significant differences in both growth parameters andpathogenesis. In conclusion, these experiments show the importance of rrn ploidy inmodulating growth and host interaction in Brucella genus. Overall, we were able to obtain astrain with identical gene content but different infection capacity.