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Mycothiol (MSH) is the major low-molecular-mass thiol in mycobacteria and is associated with the protection of Mycobacterium tuberculosis from toxic oxidants and antibiotics. The biosynthesis of MSH is a multistep process, with the enzymatic reaction designated MshC being the ligase step in MSH production. A targeted disruption of the native mshC gene in M. tuberculosis Erdman produced no viable clones possessing either a disrupted mshC gene or reduced levels of MSH. However, when a second copy of the mshC gene was incorporated into the chromosome prior to the targeted disruption, multiple clones having the native gene disrupted and the second copy of mshC intact were obtained. These clones produced normal levels of MSH. These results demonstrate that the mshC gene and, more generally, the production of MSH are essential for the growth of M. tuberculosis Erdman under laboratory conditions.

The ligase activity of the mycothiol biosynthesis enzyme MshC consists of two proteins of different sizes coded by the cys52. The enzymes catalyze ATP-dependent ligation of L-cysteine with 1D-myo-inosityl 2-amino-2-deoxy-alpha-D-glucopyranoside. The cys52 gene, implicated in the synthesis of cysteinyl-tRNA synthetases, also codes for the ATP-dependent L-cysteine: 1D-myo-inosityl 2-amino-2-deoxy-alpha-D-glucopyranoside ligase.

Lantibiotics are lanthionine ring containing natural products that belong to the class of ribosomally synthesized and posttranslationally modified peptides (RiPPs). Recent expansion in the availability of microbial genome data and in silico analysis tools have accelerated the discovery of these promising alternatives to antibiotics. Following the genome‐mining approach, a biosynthetic gene cluster for a putative two‐component lantibiotic, roseocin, was identified in the genome of an Actinomycete, Streptomyces roseosporus NRRL 11379. Posttranslationally modified lanthipeptides of this cluster were obtained by heterologous expression of the genes in Escherichia coli, and were in vitro reconstituted to their bioactive form by exploiting commercial proteases like endoproteinase GluC, and proteinase K. The two peptides displayed synergistic antimicrobial activity against Gram‐positive bacteria including the WHO high‐priority pathogens, MRSA and VRE. Structural characterization confirmed the installation of four (methyl)lanthionine rings with an indispensable disulfide bond in the α‐peptide, and six (methyl)lanthionine rings in the β‐peptide, by a single promiscuous lanthionine synthetase, RosM. Roseocin is the first two‐component lantibiotic from a non‐Firmicute, with extensive lanthionine bridging. [ABSTRACT FROM AUTHOR]

A nanocellulose (NC)-based cross-linked adsorbent has been employed herein for the removal of dye pollutants (e.g., methylene blue) from the textile industry. The synthesized hydrogel was optimized to achieve the best concentrations of the adsorbent constituents, i.e., 1.55% guar gum, 1.46% NC, and 0.84% borax for achieving the maximum swelling index (SI, 3741.42%) and higher adsorption capacity ( q e , 24.05 mg g -1 ). 98.8% of dye q e was achieved at optimal conditions of pH 8 within 30 min at 30 °C. Adsorption isotherms and kinetics investigations showed good correlation with the Freundlich adsorption isotherm model ( R 2 > 0.9889; Δ G ° = -4.71; Δ H ° = -12.30; Δ S ° = -0.025) as well as the pseudo-second-order kinetics model, indicating multilayered and intricate adsorption mechanisms for dye removal. The study of thermodynamic parameters confirmed the exothermic nature of the adsorption process. The adsorption-desorption study of the resulting hydrogel exhibited 64.58% dye removal efficiency even after 4 consecutive cycles of reuse. Further, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction analysis revealed the surface morphology, functional moieties, thermal behavior, and crystallinity pattern of the hydrogel. Rheological analysis demonstrated pseudoplastic flow and improved mechanical behavior for the hydrogel. The current study found that the synthesized adsorbent with a higher SI and q e has a noticeable potential for the removal of dye pollutants from wastewater., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Covering: up to June 2020Ribosomally-synthesized and post-translationally modified peptides (RiPPs) are a large group of natural products. A community-driven review in 2013 described the emerging commonalities in the biosynthesis of RiPPs and the opportunities they offered for bioengineering and genome mining. Since then, the field has seen tremendous advances in understanding of the mechanisms by which nature assembles these compounds, in engineering their biosynthetic machinery for a wide range of applications, and in the discovery of entirely new RiPP families using bioinformatic tools developed specifically for this compound class. The First International Conference on RiPPs was held in 2019, and the meeting participants assembled the current review describing new developments since 2013. The review discusses the new classes of RiPPs that have been discovered, the advances in our understanding of the installation of both primary and secondary post-translational modifications, and the mechanisms by which the enzymes recognize the leader peptides in their substrates. In addition, genome mining tools used for RiPP discovery are discussed as well as various strategies for RiPP engineering. An outlook section presents directions for future research.