Evolution towards Virulence in a Burkholderia Two-Component System

Abstract

Infections caused by members of the Burkholderia cepacia complex (BCC) are a serious concern for patients with cystic fibrosis (CF) as these bacteria are often resistant to many antibiotics. During long-term infection of CF patients with BCC, mutations in genes encoding the FixLJ system often become prevalent, suggesting that these changes may benefit the bacteria during infection.

Small-molecule activators of a bacterial signaling pathway inhibit virulence

“…This approach was based on our previous work that found mutations within the fixL gene leading to lower FixLJ pathway activity were selected for during chronic infection in people with CF (30,31) and correlated with periods of decline in lung function in people with CF. (34) These findings lead us to the hypothesis that a small molecule activating the FixLJ pathway could make Burkholderia less pathogenic, in a way coaxing the bacteria back to its soil existence where FixLJ activity is high.…”

“…The ability of BFA compounds to inhibit the uptake of and/or intracellular survival of Burkholderia into THP-1-dervived macrophages was determined using published protocols. (33,34) Human THP-1 monocytes were differentiated into macrophages by seeding 1 mL into 24well plates at 7.5x10 5 cells/mL with 200 nM phorbol 12-myristate 13-acetate (PMA). Log-phase…”

“…Our recent work showed that otherwise isogenic BCC constructs carrying evolved (late) fixL sequence variants are more virulent than constructs carrying ancestral (early) fixL sequence variants. (34) Interestingly, bacteria carrying these evolved fixL sequence variants have lower levels of FixLJ pathway activity, demonstrating that high levels of FixLJ pathway activity are detrimental to virulence. (34) These findings led us to the hypothesis that small-molecule activators of the Burkholderia FixLJ pathway could make the bacteria less virulent.…”

“…(34) Interestingly, bacteria carrying these evolved fixL sequence variants have lower levels of FixLJ pathway activity, demonstrating that high levels of FixLJ pathway activity are detrimental to virulence. (34) These findings led us to the hypothesis that small-molecule activators of the Burkholderia FixLJ pathway could make the bacteria less virulent. In the current study, we describe a high-throughput screen that identified 11 novel activators of the Burkholderia FixLJ pathway.…”

Heme-Based Gas Sensors in Nature and Their Chemical and Biotechnological Applications

“…FixL or analogs have been found in other microorganisms, such as Caulobacter crescentus [65], Brucella abortus [66], Chlamydomonas reinhardtii [67] and Burkholderia cepacia [68,69]. This latter bacterium is part of a class of pathogens causing concerns in cystic fibrosis patients.…”