Stress-based identification and classification of antibacterial agents: second-generation Escherichia coli reporter strains and optimization of detection

Dual Effects of MLS Antibiotics

The macrolide-lincosamide-streptogramin (MLS) antibiotics are an important group of translation inhibitors that act on the 50S ribosome. We show that, at subinhibitory concentrations, members of the MLS group modulate specific groups of bacterial promoters, as detected by screening a library of promoter-luxCDABE reporter clones of Salmonella enterica serovar Typhimurium. The patterns of transcription permit identification of classes of promoters having differential responses to antibiotics of related structure and mode-of-action; studies of antibiotic synergy or antagonism showed that eukaryotic translation inhibitors may act on the 50S ribosome. The mechanism of transcriptional modulation is not known but may involve bacterial stress responses and/or the disturbance and subsequent compensation of metabolic networks as a result of subtle interference with ribosome function. Transcriptional patterns detected with promoter-lux clones provide a novel approach to antibiotic discovery and mode-of-action studies.

Identification of antibiotic stress-inducible promoters: a systematic approach to novel pathway-specific reporter assays for antibacterial drug discovery

As present antibiotics therapy becomes increasingly ineffectual, new technologies are required to identify and develop novel classes of antibacterial agents. An attractive alternative to the classical target-based approach is the use of promoter-inducible reporter assays for high-throughput screening. The wide usage of these assays is, however, limited by the small number of specifically responding promoters that are known at present. This work describes a novel approach for identifying genetic regulators that are suitable for the design of pathway-specific assays. The basis for the proposed strategy is a large set of antibiotics-triggered expression profiles ("Reference Compendium"). Pattern recognition algorithms applied to the expression data pinpoint the relevant transcription-factor-binding sites in whole-genome sequences. Using this technique, we constructed a fatty-acid-pathway-specific reporter assay that is based on a novel stress-inducible promoter. In a proof-of-principle experiment, this assay was shown to enable screening for new small-molecule inhibitors of bacterial growth.