Aspartate aminotransferase Rv3722c governs aspartate-dependent nitrogen metabolism in Mycobacterium tuberculosis.

Gene rv3722c of Mycobacterium tuberculosis is essential for in vitro growth, and encodes a putative pyridoxal phosphate-binding protein of unknown function. Here we use metabolomic, genetic and structural approaches to show that Rv3722c is the primary aspartate aminotransferase of M. tuberculosis, and mediates an essential but underrecognized role in metabolism: nitrogen distribution. Rv3722c deficiency leads to virulence attenuation in macrophages and mice. Our results identify aspartate biosynthesis and nitrogen distribution as potential species-selective drug targets in M. tuberculosis.

Itaconyl-CoA forms a stable biradical in methylmalonyl-CoA mutase and derails its activity and repair.

Itaconate is an immunometabolite with both anti-inflammatory and bactericidal effects. Its coenzyme A (CoA) derivative, itaconyl-CoA, inhibits B12-dependent methylmalonyl-CoA mutase (MCM) by an unknown mechanism. We demonstrate that itaconyl-CoA is a suicide inactivator of human and Mycobacterium tuberculosis MCM, which forms a markedly air-stable biradical adduct with the 5'-deoxyadenosyl moiety of the B12 coenzyme. Termination of the catalytic cycle in this way impairs communication between MCM and its auxiliary repair proteins. Crystallography and spectroscopy of the inhibited enzyme are consistent with a metal-centered cobalt radical ~6 angstroms away from the tertiary carbon-centered radical and suggest a means of controlling radical trajectories during MCM catalysis. Mycobacterial MCM thus joins enzymes in the glyoxylate shunt and the methylcitrate cycle as targets of itaconate in pathogen propionate metabolism.

Mycobacterium tuberculosis releases an antacid that remodels phagosomes.

Mycobacterium tuberculosis (Mtb) is the world's most deadly pathogen. Unlike less virulent mycobacteria, Mtb produces 1-tuberculosinyladenosine (1-TbAd), an unusual terpene nucleoside of unknown function. In the present study 1-TbAd has been shown to be a naturally evolved phagolysosome disruptor. 1-TbAd is highly prevalent among patient-derived Mtb strains, where it is among the most abundant lipids produced. Synthesis of TbAd analogs and their testing in cells demonstrate that their biological action is dependent on lipid linkage to the 1-position of adenosine, which creates a strong conjugate base. Furthermore, C20 lipid moieties confer passage through membranes. 1-TbAd selectively accumulates in acidic compartments, where it neutralizes the pH and swells lysosomes, obliterating their multilamellar structure. During macrophage infection, a 1-TbAd biosynthesis gene (Rv3378c) confers marked phagosomal swelling and intraphagosomal inclusions, demonstrating an essential role in regulating the Mtb cellular microenvironment. Although macrophages kill intracellular bacteria through phagosome acidification, Mtb coats itself abundantly with antacid.

Incidence of Viremia With DNA Viruses in Oncology Patients With Febrile Neutropenia.

BACKGROUND: Although febrile neutropenia (FN) is one of the most common adverse events produced by chemotherapy, its microbiological etiology is determined for only 15% to 30% of cases. OBJECTIVES: We investigated the rate of viremia with common DNA viruses in patients with FN. STUDY DESIGN: From June 2012 to April 2014, 72 blood samples from 24 patients receiving chemotherapy, who experienced FN episodes, were examined for the presence of herpes viruses and other DNA viruses. We used real-time polymerase chain reaction assays to detect herpes simplex virus type 1 and 2, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, human herpes virus types 6 and 7, BK virus and human parvovirus B19 (B19). RESULTS: Viruses were identified in 14 of 72 samples (19.4%). The detected etiological agents were BK virus (5 episodes), human herpes virus type 6 (4 episodes), B19 (4 episodes), Epstein-Barr virus (2 episodes), and cytomegalovirus (1 episode). CONCLUSIONS: Our results indicate that viral infections are common causes in patients with FN. Therefore, viruses may be responsible for FN in a large proportion of patients in whom a causative microorganism could not be identified, and this viral etiology may explain their poor response to antibiotic therapy.