P060

1:Royal Veterinary College, University of London; 2:UK Health Security Agency; 3:Birkbeck, University of London

Efflux pumps play a significant role in both intrinsic and acquired drug resistance in M. tuberculosis. These transport proteins actively extrude a wide range of compounds and are important for many regular cellular processes, often facilitating resistance to antimicrobial agents incidentally. Studying the regulation, structure, and substrate specificity of efflux pumps expands our understanding of M. tuberculosis physiology while informing novel therapeutic strategies, such as efflux pump inhibition. The aims of this project are to further our knowledge of the functions of mycobacterial efflux pumps and to investigate the transcriptional regulation of these export proteins. In many bacterial species, transcription factors in the TetR family of regulators (TFRs) commonly control efflux pump expression. In this study, an M. tuberculosis TFR, Rv1255c, hypothesised to regulate an efflux pump gene, tap, was recombinantly produced in E. coli. Binding assays revealed Rv1255c does not regulate tap, but instead binds to a regulatory motif in the promoter region of the adjacent orientated gene rv1256c (cyp130) and does so as a protein homodimer. In addition to work with the regulator, the physiological role of the Tap efflux pump is also being explored. The impact of CRISPRi-mediated silencing of tap on growth and the genome wide transcriptional response was measured. While there was no impact on growth, expression analysis found changes to lipid metabolism genes that could indicate a novel role for Tap.