Mycolicibacterium baixiangningiae sp. nov. and Mycolicibacterium mengxianglii sp. nov., two new rapidly growing mycobacterial species

Four bacterial strains (LJ126T/S18 and Z-34T/S20) recovered from faecal samples of Tibetan antelopes on the Qinghai–Tibet Plateau of China were analysed using a polyphasic approach. All four isolates were aerobic, short rod-shaped, non-motile, Gram-stain-positive, acid-fast and fast-growing. Phylogenetic analyses based upon 16S rRNA and whole-genome sequences showed that the two pair of strains formed two distinct branches within the evolutionary radiation of the genus Mycolicibacterium . Strains LJ126T/S18 and Z-34T/S20 were most closely related to Mycolicibacterium austroafricanum CCUG 37667T, Mycobacterium aurum NCTC 10437T, Mycobacterium pyrenivorans DSM 44605T, Mycobacterium monacense JCM 15658T, Mycolicibacterium sarraceniae JCM 30395T, Mycolicibacterium tokaiense JCM 6373T and Mycobacterium murale JCM 13392T, but readily distinguished from the known species by a combination of chemotaxonomic and phenotypic features and by low average nucleotide identity values (74.4–84.9 %). Consequently, the two strain pairs are considered to represent different novel species of Mycolicibacterium for which the names Mycolicibacterium baixiangningiae sp. nov. and Mycolicibacterium mengxianglii sp. nov. are proposed, with LJ126T (=CGMCC 1.1992T=KCTC 49535T) and Z-34T (=CGMCC 1.1993T=DSM 106172T) as the respective type strains.

Synthesis, structural characterization and antimycobacterial evaluation of several halogenated non-nitro benzothiazinones

Abstract8-Nitro-1,3-benzothiazin-4-ones (BTZs), with BTZ043 and PBTZ169 as the most advanced compounds, represent a new class of potent antitubercular agents, which irreversibly inhibit decaprenylphosphoryl-β-d-ribose-2′-epimerase (DprE1), an enzyme crucial for cell wall synthesis in the pathogen Mycobacterium tuberculosis. Synthesis, structural characterization and in vitro testing against Mycobacterium aurum DSM 43999 and M. tuberculosis H37Rv of halogenated 2-(4-ethoxycarbonylpiperazin-1-yl)-1,3-benzothiazin-4-ones lacking a nitro group are reported. X-ray crystallography reveals that the structure of the BTZ scaffold can significantly deviate from planarity. In contrast to recent reports, the results of the present study indicate that further investigation of halogenated non-nitro BTZs for antitubercular activity is less than a promising approach.

Weighted Gene Co-Expression Network Analysis Identifies Key Modules and Hub Genes Associated with Mycobacterial Infection of Human Macrophages

Tuberculosis (TB) is still a leading cause of death worldwide. Treatments remain unsatisfactory due to an incomplete understanding of the underlying host–pathogen interactions during infection. In the present study, weighted gene co-expression network analysis (WGCNA) was conducted to identify key macrophage modules and hub genes associated with mycobacterial infection. WGCNA was performed combining our own transcriptomic results using Mycobacterium aurum-infected human monocytic macrophages (THP1) with publicly accessible datasets obtained from three types of macrophages infected with seven different mycobacterial strains in various one-to-one combinations. A hierarchical clustering tree of 11,533 genes was built from 198 samples, and 47 distinct modules were revealed. We identified a module, consisting of 226 genes, which represented the common response of host macrophages to different mycobacterial infections that showed significant enrichment in innate immune stimulation, bacterial pattern recognition, and leukocyte chemotaxis. Moreover, by network analysis applied to the 74 genes with the best correlation with mycobacteria infection, we identified the top 10 hub-connecting genes: NAMPT, IRAK2, SOCS3, PTGS2, CCL20, IL1B, ZC3H12A, ABTB2, GFPT2, and ELOVL7. Interestingly, apart from the well-known Toll-like receptor and inflammation-associated genes, other genes may serve as novel TB diagnosis markers and potential therapeutic targets.

Antimicrobial and Efflux Pump Inhibitory Activity of Carvotacetones from Sphaeranthus africanus Against Mycobacteria

Carvotacetones (1–7) isolated from Sphaeranthus africanus were screened for their antimycobacterial and efflux pump (EP) inhibitory potential against the mycobacterial model strains Mycobacterium smegmatis mc2 155, Mycobacterium aurum ATCC 23366, and Mycobacterium bovis BCG ATCC 35734. The minimum inhibitory concentrations (MICs) of the carvotacetones were detected through high-throughput spot culture growth inhibition (HT-SPOTi) and microbroth dilution assays. In order to assess the potential of the compounds 1 and 6 to accumulate ethidium bromide (EtBr) in M. smegmatis and M. aurum, a microtiter plate-based fluorometric assay was used to determine efflux activity. Compounds 1 and 6 were analyzed for their modulating effects on the MIC of EtBr and the antibiotic rifampicin (RIF) against M. smegmatis. Carvotacetones 1 and 6 had potent antibacterial effects on M. aurum and M. bovis BCG (MIC ≤ 31.25 mg/L) and could successfully enhance EtBr activity against M. smegmatis. Compound 1 appeared as the most efficient agent for impairing the efflux mechanism in M. smegmatis. Both compounds 1 and 6 were highly effective against M. aurum and M. bovis BCG. In particular, compound 1 was identified as a valuable candidate for inhibiting mycobacterial efflux mechanisms and as a promising adjuvant in the therapy of tuberculosis or other non-tubercular mycobacterial infections.

Fitness Cost and Compensatory Evolution in Levofloxacin-Resistant Mycobacterium aurum

ABSTRACT We isolated spontaneous levofloxacin-resistant strains of Mycobacterium aurum to study the fitness cost and compensatory evolution of fluoroquinolone resistance in mycobacteria. Five of six mutant strains with substantial growth defects showed restored fitness after being serially passaged for 18 growth cycles, along with increased cellular ATP level. Whole-genome sequencing identified putative compensatory mutations in the glgC gene that restored the fitness of the resistant strains, presumably by altering the bacterial energy metabolism.

Synthesis and Biological Evaluation of a Novel C8-Pyrrolobenzodiazepine (PBD) Adenosine Conjugate. A Study on the Role of the PBD Ring in the Biological Activity of PBD-Conjugates

Here we sought to evaluate the contribution of the PBD unit to the biological activity of PBD-conjugates and, to this end, an adenosine nucleoside was attached to the PBD A-ring C8 position. A convergent approach was successfully adopted for the synthesis of a novel C8-linked pyrrolo(2,1-c)(1,4)benzodiazepine(PBD)-adenosine(ADN) hybrid. The PBD and adenosine (ADN) moieties were synthesized separately and then linked through a pentynyl linker. To our knowledge, this is the first report of a PBD connected to a nucleoside. Surprisingly, the compound showed no cytotoxicity against murine cells and was inactive against Mycobacterium aurum and M. bovis strains and did not bind to guanine-containing DNA sequences, as shown by DNase I footprinting experiments. Molecular dynamics simulations revealed that the PBD–ADN conjugate was poorly accommodated in the DNA minor groove of two DNA sequences containing the AGA-PBD binding motif, with the adenosine moiety of the ligand preventing the covalent binding of the PBD unit to the guanine amino group of the DNA duplex. These interesting findings shed further light on the ability of the substituents attached at the C8 position of PBDs to affect and modulate the biological and biophysical properties of PBD hybrids.

LYCOPENE PRODUCTION IN MYCOBACTERIUM SMEGMATIS BY EXPRESSION OF CRT GENES FROM MYCOBACTERIUM AURUM AND PROTECTIVE EFFECT OF LYCOPENE IN VIVO AND IN VITRO AGAINST UV RADIATION

Objective: The aim of the present study was to express in Mycobacterium smegmatis the clustered mycobacterial genes coding for lycopene synthesis and to investigate the protective properties of lycopene against ultraviolet (UV) irradiation.Methods: The genes, which encode the biogenesis of lycopene in Mycobacterium aurum A+, were introduced into Mycobacterium smegmatis by electroporation. The pigments produced were analyzed by thin layer chromatography, and the absorption spectra were determined. A survival test using UV irradiations was also performed.Results: The transformed Mycobacterium smegmatis were found to synthesize lycopene with important yield (1.41± 3.09 mg/g) and was more resistant to ultraviolet irradiation than non-pigmented strain (p<0.01). Furthermore, cells of M. smegmatis not transformed but coated with lycopene are more resistant to UV than those uncoated (p<0.01).Conclusion: M. smegmatis can form orange colonies on agar plates when it is transformed with the lycopene genes, and the transformants produces 1.41 mg/g (dry weight) of this carotene. Our findings strongly suggest that lycopene has antioxidant activities and prevent the lethal action of UV irradiation on bacterial cells in vivo and in vitro, and deserves further studies considering the amelioration of the production.