How does Bordetella bronchiseptica respond to a lethal condition found within the host?

FINGERMANN M. HOZBOR D.; GAILLARD ME,; BOTTERO D.; FERNÁNDEZ J.; GRAIEB A.; ROBERTS R.; SIST. F.; HOZBOR D.

Pilar, Bs. As; Argentina

Congreso; 1st Annual Iberoamerican Proteomics Congress; 2007

How does Bordetella bronchiseptica respond to a lethal condition found within the host?Matías Fingermann, María Emilia Gaillard , Daniela Bottero, Julieta Fernandez, Augusto Leandro Graieb, Roy Martin, Sisti Federico Bernardo, Hozbor Daniela FlaviaBordetella bronchiseptica is a gram-negative bacterium that causes respiratory tract infections in different mammals including humans, characterized by a chronic period. Although first considered to be an extracellular pathogen, several reports have already demonstrated that B. bronchiseptica can survive in professional phagocytes. However, the specific properties of this pathogen leading to resistance against the otherwise bactericidal conditions encountered inside the phagosomal enviroment (i.e. reactive oxygen metabolites, acidification to a pH below 5.0 and reléase of lysosomal hydrolases) have been scarcely characterized. In this work we studied the responses of B. bronchiseptica 9.73 strain to acidic pH.  Viability of this strain was not significantly decreased at a pH as low as 4.5, but it did at pH 4.0. To investígate whether B. bronchiseptica may be endowed with an acid-tolerance response (ATR), we determined its survival rate either previously exposed or not to acidic pH. A slight difference in survival was observed when bacteria were preincubated at pH 5.5. Interestingly, phase variation regulated by the BvgAS two-component system influenced acid tolerance in our experiments.Membrane proteomes of avirulent B. bronchiseptica exposed to mild acidic (pH 5.5) and non-acidic growing conditions were compared to analyze whether protein changes occurred during the observed pH adaptation. Membrane proteins were separated by two-dimensional (2D) gel electrophoresis and analyzed by Matrix-assisted láser desorption ionization time of flight (MALDI-TOF). Wild-type and pH-adapted B. bronchiseptica membranes displayed similar spot diversity, approximately 8 % of proteins identified from purifíed membrane fractions being observed as differentially expressed. Most differentially expressed proteins were up-regulated in the pH-adapted strain. Baseu on puiative identifications, a significant proportion of these up-regulated proteins were involved with transport and metabolism. Overall, the results suggested that membrane-associated proteins are either being synthesized in lower quantities or not properly incorporated into the cell membrane of the non-adapted strain.Address: calles 47 y 115    La Plata   Buenos Aires   Argentina 1900Institución:E-mail: hozbor@biol.unlp.edu.ar