Nutritional Virulence: The Role Of Serine During The Infection Of Brucella

REVORA V; MARCHESINI M.I; COMERCI D. J

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias. LIII Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB).; 2017

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Upon invasion of host cell, the ability to survive in the harsh intracellular milieu is crucial for many pathogenic bacteria as is the case of Brucella. How pathogens adapt their metabolism to the mew nutritional conditions encounter in the intracellular environment has been one of the most underestimated aspects of bacterial pathogenesis. Recently, those mechanisms and strategies and how they affects the virulence traits of pathogenic bacteria began to be considered.In this work we study SerB (BAB1_1410), a phosposerine phosphatase involved in the last step of synthesis of serine from 3-phosphoglycerate (3PG). We demonstrated that recombinant SerB has optimal phosphoserine phosphatase activity at pH of 7 with a strong preference for Mg2+ over Mn2+. To analyze the importance of serine in the biology of Brucella, we constructed clean-deletion mutants of serB in Brucella suis and Brucella abortus and tested their ability to grow in both complex (TSB) and defined media (GW). Deletion of serB affected the ability of Brucella to grow in GW and this defect was reverted by supplementing the medium with serine, indicating that both SeB and the synthesis of serine is required under this growth conditions. To assess whether SerB is necessary during the intracellular stages of Brucella, in vitro infection of J774 macrophage-like cells and epithelial HeLa cells were assayed. In both models, B. abortus serB and B. suis serB were unable to sustain intracellular replication. As it was observed in the axenic culture, supplementation of the cell culture medium with serine was capable to revert the defect, indicating that synthesis of serine is necessary to sustain intracellular infection. Serine supplementation was effective during the first phase of infection when Brucella remains arrested in G1 in a non-replicative vacuole. Once Brucella resume the S phase and the replicative vacuole is formed, serine supplementation was unable to revert the intracellular growth defect. Mice infection demonstrated that SerB mutants are attenuated thus confirming the cell culture infection assays. Taken together these results indicate that serine plays a central role during Brucella infection.