Acid tolerance response of Bordetella bronchiseptica in avirulent phase

FINGERMAN M; HOZBOR D

MICROBIOLOGICAL RESEARCH

ELSEVIER GMBH

Año: 2015 vol. 181 p. 52 - 60

0944-5013

Bordetella bronchiseptica is a Gram-negative bacterium responsible for respiratory diseases in many mam-malian hosts, including humans. This pathogen has been shown as able to persist inside the host cells,even in the phagosomes that are acidified to pH 4.5?5.0 after bacterial infection. Here we evaluated theresistance of B. bronchiseptica to survive under acidic conditions. In particular we analyzed the bacterialcapacity to develop the mechanism known as acid tolerance response (ATR). Our studies were mainlyfocused on the avirulent phase of the bacteria since this phenotypic phase was reported to be moreresistant to environmental stress conditions than the virulent phase. Results from B. bronchiseptica invirulent phase were also included for comparison purposes. In fact, for B. bronchiseptica 9.73 bacteria invirulent phase we observed that the viability of bacteria does not decrease significantly when grown atpH as low as 4.5, but it is affected when the pH of the medium was equal to or less than 4.0. After acid-adaptation at pH 5.5 for several hours, the survival rate of B. bronchiseptica 9.73 at lethal pH 4.0 for 6 h wasincreased. Interestingly, the avirulent phase mediated by the two-component BvgAS system conferredfurther resistance to lethal acid challenge and a marked increase in the magnitude of the expressed ATR.The ATR for this avirulent phase seems to be associated with changes in LPS and surface protein profiles.2D-gel electrophoresis revealed at least 25 polypeptides differentially expressed, 17 of which were onlyexpressed or over-expressed under acid conditions. Using MALDI-TOF mass spectrometry, 10 of thesedifferentially expressed polypeptides were identified.