Multidrug resistance, strong side effects, and compliance problems in TB chemotherapy mandate new ways to kill Mycobacterium tuberculosis (Mtb). Here we show that deletion of the gene encoding homoserine transacetylase (metA) inactivates methionine and S-adenosylmethionine (SAM) biosynthesis in Mtb and renders this pathogen exquisitely sensitive to killing in immunocompetent or immunocompromised mice, leading to rapid clearance from host tissues. Mtb ΔmetA is unable to proliferate in primary human macrophages, and in vitro starvation leads to extraordinarily rapid killing with no appearance of suppressor mutants. Cell death of Mtb ΔmetA is faster than that of other auxotrophic mutants (i.e., tryptophan, pantothenate, leucine, biotin), suggesting a particularly potent mechanism of killing. Time-course metabolomics showed complete depletion of intracellular methionine and SAM. SAM depletion was consistent with a significant decrease in methylation at the DNA level (measured by single-molecule real-time sequencing) and with the induction of several essential methyltransferases involved in biotin and menaquinone biosynthesis, both of which are vital biological processes and validated targets of antimycobacterial drugs. Mtb ΔmetA could be partially rescued by biotin supplementation, confirming a multitarget cell death mechanism. The work presented here uncovers a previously unidentified vulnerability of Mtb-the incapacity to scavenge intermediates of SAM and methionine biosynthesis from the host. This vulnerability unveils an entirely new drug target space with the promise of rapid killing of the tubercle bacillus by a new mechanism of action.host-pathogen interaction | bactericidal auxotrophy | amino acid biosynthesis | metabolism U nderstanding the metabolic interactions between an invading microbe and its host is becoming a new cornerstone of host-pathogen research (1-3). Many intracellular pathogens modulate the host response to satisfy their nutritional needs and as a result have become auxotrophic for several essential amino acids and cofactors (4-6). Mycobacterium tuberculosis (Mtb), arguably the most deadly bacterial pathogen in the world (7), adopted a different strategy. This ultra-slow-growing bacterium is prototrophic for all essential cofactors and amino acids, suggesting that it either dwells in host compartments where such metabolites are unavailable or actively chooses this autarkic lifestyle to retain metabolic flexibility and remain invisible to the host. Indeed, much of Mtb's long-term success as a human pathogen is ascribed to its extraordinary stealth in the face of host immunity (8, 9); Mtb's ability to evade detection by the host might explain why devising an efficient vaccine has failed thus far and why drug therapy is difficult. Therefore, understanding Mtb's in vivo metabolic requirements could help in the development of much-needed new strategies for antimycobacterial therapy.Methionine and S-adenosylmethionine (SAM) are essential metabolites that have gained considerable scientific attenti...

A major constraint for developing new anti-tuberculosis drugs is the limited number of validated targets that allow eradication of persistent infections. Here, we uncover a vulnerable component of Mycobacterium tuberculosis (Mtb) persistence metabolism, the aspartate pathway. Rapid death of threonine and homoserine auxotrophs points to a distinct susceptibility of Mtb to inhibition of this pathway. Combinatorial metabolomic and transcriptomic analysis reveals that inability to produce threonine leads to deregulation of aspartate kinase, causing flux imbalance and lysine and DAP accumulation. Mtb’s adaptive response to this metabolic stress involves a relief valve-like mechanism combining lysine export and catabolism via aminoadipate. We present evidence that inhibition of the aspartate pathway at different branch-point enzymes leads to clearance of chronic infections. Together these findings demonstrate that the aspartate pathway in Mtb relies on a combination of metabolic control mechanisms, is required for persistence, and represents a target space for anti-tuberculosis drug development.

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Coevolution of pathogens and host has led to many metabolic strategies employed by intracellular pathogens to deal with the immune response and the scarcity of food during infection. Simply put, bacterial pathogens are just looking for food. As a consequence, the host has developed strategies to limit nutrients for the bacterium by containment of the intruder in a pathogen-containing vacuole and/or by actively depleting nutrients from the intracellular space, a process called nutritional immunity. Since metabolism is a prerequisite for virulence, such pathways could potentially be good targets for antimicrobial therapies. In this chapter, we review the current knowledge about the in vivo diet of Mycobacterium tuberculosis, with a focus on amino acid and cofactors, discuss evidence for the bacilli’s nutritionally independent lifestyle in the host, and evaluate strategies for new chemotherapeutic interventions.

SUMMARY AT A GLANCEN-benzylpiperazine (BZP) is a popular recreational party drug. There is a potential for acute kidney injury, and this needs to be considered when any individual presents with symptoms of recreational drug overdose with 3,4-methylenedioxymethamphetamine (MDMA) and/or BZP components. ABSTRACT:N-benzylpiperazine (BZP) is the active ingredient in recreational 'party' pills with a stimulant, euphoric mechanism of action akin to that of 3,4-methylenedioxymethamphetamine (MDMA or ecstasy). Many people (ab)use BZP-based party pills usually without any significant toxic effects. However, nephrotoxicity secondary to hyperthermia and rhabdomyolysis has been reported. Another serious renal-related side-effect is hyponatraemia with acute cerebral oedema. There is also evidence that these agents may have a specific toxic effect producing acute kidney injury. Thus, acute kidney injury either direct or secondary to the effects of BZP or MDMA need to be considered when any individual presents with symptoms of a recreational party drug overdose.