Analíse do papel do fator sigma C na resposta de Corynebacterium pseudotuberculosis a diferentes condições de estresse ambiental

Abstract

Corynebacterium pseudotuberculosis is a Gram-positive bacterium, which causes caseous lymphadenitis in sheep and goats. To cause a successful infection, this facultative intracellular pathogen needs to respond efficiently to the changes in the extracellular environment, being able to survive faced with the harsh conditions found in the host organism. One of the main mechanisms used by pathogenic bacteria to achieve this goal is the transient activation of specific genes in response to extracellular environmental stresses by alternative sigma factors of RNA polimerase. After the sequencing of the genome of C. pseudotuberculosis by Rede Genoma de Minas Gerais e Rede Paraense de Gen?ica e Prote?ica, it was identified seven alternative sigma factors in this bacterium, the sigma factors B, C, D, E, H, K and M. Between these, the sigma factor C stands out, which has been linked to virulence in Mycobacterium tuberculosis, and whose gene is located in a pathogenicity island in C. pseudotuberculosis. In this context, our research group has been studying the role of the alternative sigma factors of C. pseudotuberculosis in response to different stress conditions in vitro and in virulence of the bacterium. In this work, we constructed a strain of C. pseudotuberculosis deficient for the sigma factor C, using a suicide plasmid, and evaluated the resistance of this strain to oxidative, acid, osmotic and heat stresses in vitro, by comparing the differences in relative growth and relative viability of bacteria exposed to stress conditions in relation to bacteria grown under normal conditions, between the successive times of exposure of 1002 wild strain and the strain mutant for the sigma factor C for each stress generator agent. There was no significant difference in the susceptibility of the strain mutant for the sigma factor C for the acid stress in relation to the 1002 wild strain. However, it was found that this strain is significantly more susceptible to oxidative, osmotic and heat stresses than the 1002 wild strain, showing that the sigma factor C should play an important role for the bacteriums response to this stress conditions, and possibly, for its survival in the environment and in the host and for its virulence.