The Bvg accessory factor (Baf) enhances pertussis toxin expression in Escherichia coli and is essential for Bordetella pertussis viability

Pertussis toxin expression in the Gram-negative respiratory pathogen, Borde tella pertussis, is regulated by the BvgAS two-component system. Previous s tudies suggested that an additional gene encoding a Bvg accessory factor (B af) was required, along with BvgAS, for expression of a ptx-lacZ fusion in Escherichia coli grown in rich medium. However, other studies showed that B vgAS is sufficient for ptx-lacZ expression in minimal medium. Here we show that Baf acts with BvgAS to further increase ptx-lacZ expression in E. coli grown in minimal media and this is concomitant with a two-fold increase in BvgA protein levels. Gene replacement experiments show that baf is essenti al for viability of B. pertussis, suggesting that Baf affects the expressio n of other genes in addition to ptx. (C) 2000 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights reserved .