The pncA gene mutations of Mycobacterium tuberculosis in multidrug-resistant tuberculosis

HigA2 (Rv2021c) Is a Transcriptional Regulator with Multiple Regulatory Targets in Mycobacterium tuberculosis

Toxin-antitoxin (TA) systems are the major mechanism for persister formation in Mycobacterium tuberculosis (Mtb). Previous studies found that HigBA2 (Rv2022c-Rv2021c), a predicted type II TA system of Mtb, could be activated for transcription in response to multiple stresses such as anti-tuberculosis drugs, nutrient starvation, endure hypoxia, acidic pH, etc. In this study, we determined the binding site of HigA2 (Rv2021c), which is located in the coding region of the upstream gene higB2 (Rv2022c), and the conserved recognition motif of HigA2 was characterized via oligonucleotide mutation. Eight binding sites of HigA2 were further found in the Mtb genome according to the conserved motif. RT-PCR showed that HigA2 can regulate the transcription level of all eight of these genes and three adjacent downstream genes. DNA pull-down experiments showed that twelve functional regulators sense external regulatory signals and may regulate the transcription of the HigBA2 system. Of these, Rv0903c, Rv0744c, Rv0474, Rv3124, Rv2603c, and Rv3583c may be involved in the regulation of external stress signals. In general, we identified the downstream target genes and possible upstream regulatory genes of HigA2, which paved the way for the illustration of the persistence establishment mechanism in Mtb.

Screening of Microbial Fermentation Products for Anti-M. tuberculosis Activity

Simple Summary

M. tuberculosis (M.tb) is the main pathogen of tuberculosis (TB). The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) M.tb has brought new challenges to the treatment of TB. Therefore, finding new materials for the development of natural anti-TB drugs is crucial to the prevention and treatment of TB. In order to discover new anti-TB drug materials, we isolated microorganisms from the soil and tested the anti-M.tb activity of their fermentation products. The results showed that the four fermentation products had anti-M.tb activities in vitro and in intracellular bacteria. The qPCR results showed that the four fermentation products down-regulated some growth-essential gene expression of M.tb. Thus, we speculated that the fermentation product may exert its anti-M.tb effect by down-regulating the expression of the essential genes of M.tb.

Abstract

Tuberculosis (TB), caused by M. tuberculosis (M.tb), is the leading infectious cause of mortality worldwide. The emergence of drug-resistant M.tb has made the control of TB more difficult. In our study, we investigated the ability of microorganism fermentation products from the soil to inhibit M.tb. We successfully identified four fermentation products (Micromonospora chokoriensis, Micromonospora purpureochromogenes, Micromonospora profundi, Streptomyces flavofungini) that inhibited the growth of M.tb in vitro and in intracellular bacteria at 25 μg/mL MIC. Importantly, the fermentation products decreased some essential gene expression levels for M.tb growth. Our data provide the possibility that microbial fermentation products have potential development value for anti-M.tb drugs.