FasR Regulates Fatty Acid Biosynthesis and Is Essential for Virulence of Mycobacterium tuberculosis

Enhanced analysis of the genomic diversity of Mycobacterium bovis in Great Britain to aid control of bovine tuberculosis

Bovine tuberculosis (bTB) is an endemic disease in Great Britain (GB) that affects mainly cattle but also other livestock and wild mammal species, leading to significant economic and social impact. Traditional genotyping of Mycobacterium bovis (M. bovis) isolates, which cause bTB, had been used routinely since the late 1990s as the main resource of genetic information in GB to describe their population and to understand their epidemiology. Since 2017, whole-genome sequencing (WGS) has been implemented on M. bovis isolates collected during routine surveillance. In this study, we analysed genome sequences from 3,052 M. bovis isolates from across GB to characterise their diversity and population structure in more detail. Our findings show that the M. bovis population in GB, based on WGS, is more diverse than previously indicated by traditional genotyping and can be divided into seven major clades, with one of them subdivided further into 29 clades that differ from each other by at least 70 single-nucleotide polymorphisms (SNPs). Based on the observed phylogenetic structure, we present a SNP-based classification system that replaces the genotype scheme that had been used until recently in GB. The predicted function and associated processes of the genes harbouring these SNPs are discussed with potential implications for phenotypic/functional differences between the identified clades. At the local scale, we show that WGS provides greater discriminatory power and that it can reveal the origin of infection and associated risk pathways even in areas of high bTB prevalence. The difficulty in determining transmission pathways due to the limited discrimination of isolates by traditional typing methods has compromised bTB control, as without such information it is harder to determine the relative efficacy of potential intervention measures. This study demonstrates that the higher resolution provided by WGS data can improve determination of infection sources and transmission pathways, provide important insights that will inform and shape bTB control policies in GB, as well as improve farm specific advice on interventions that are likely to be effective.

Differential expression of genes associated with lipid import, β-oxidation and lactate oxidation induced by Mycobacterium tuberculosis curli pili in broth culture compared to intracellular bacilli within THP-1 macrophages

Introduction. The adhesin, Mycobacterium tuberculosis curli pili (MTP), assists the pathogen in attachment, invasion and disease progression. Previously, this adhesin was demonstrated to contribute to the pathogen's cell wall functions and fatty acid metabolism and affects total metabolite abundance in central carbon metabolism and fatty acid metabolism of the host. The accumulation/depletion of metabolites is reliant on the gene expression of proteins involved in the import, transport and breakdown of substrates.Gap statement. MTP has not been investigated in relation to genes involved in import/transport/breakdown of substrates.Aim. This study aimed to investigate the possible regulatory role of MTP in modulating metabolic changes of the pathogen in different microenvironments.Methods. Ribonucleic acid was harvested from bacterial broth cultures of adhesin-proficient and adhesin-deficient M. tuberculosis. These strains were also used to infect differentiated THP-1 macrophages for 4 h prior to isolation of intracellular bacteria, RNA extraction and reverse transcription real-time quantitative PCR. The expression levels of selected genes involved in fatty acid transport (lucA, mce1D, mceG, Rv2799, Rv0966c and omamB), β-oxidation (fadA5 and fadB), lactate oxidation (lldD1 and lldD2) and gluconeogenic carbon flow (pckA) were analysed by absolute quantification.Results. The gene expression levels of lucA, mce1D and pckA were significantly lower, and those of Rv2799, Rv0966c, mceG, fadA5 and lldD2 were significantly higher in the adhesin-proficient cultured bacterial strains relative to the Δmtp strain. The intracellular adhesin-proficient bacteria displayed significantly higher gene expression levels of Rv2799 and significantly lower gene expression levels of Rv0966c, fadA5, lldD1 and pckA relative to the Δmtp strain. Interestingly, during early infection, the intracellular Δmtp displayed significantly increased expression of omamB, mceG, fadB, lldD1 and lldD2 relative to the broth culture. This trend was inverted in the WT models.Conclusion. MTP are significantly associated with the regulation of genes involved in lipid transport, β-oxidation and lactate oxidation.