Genetic and Chemical Diversity of Edible Mushroom Pleurotus Species

The genus Pleurotus is one of the most widely cultivated and edible mushrooms with various cultivators. Three molecular characteristics were used to evaluate the genetic diversity of 132 tested samples. Phylogenetic analysis showed five clades for tested samples of the genus Pleurotus by the combined ITS and LSU sequences with strong bootstraps and Bayesian posterior probability supports. A total of 94 polymorphic fragments ranging from 10 to 100 bp were observed by using an intersimple sequence repeat (ISSR) marker. The DNA fragment pattern showed that P. ostreatus cultivator (strain P9) was clearly distinguished from wild strain based on their clear banding profiles produced. DNA GC content of the genus Pleurotus varied from 55.6 mol% to 43.3 mol%. Their chemical composition was also determined, including sugar, amino acid, polar lipid, mycolic acid, quinone, and fatty acid, which presented some high homogeneity. Most of the tested samples contained mycolic acid; glucose and arabinose as the main sugars; aspartic acid, arginine, lysine, tyrosine, and alanine as the main amino acids; and C16:0, C18:0, C18:2cis-9,12, anteiso-C14:0, and summed feature 8 as the main fatty acids. In addition, their polar lipid profiles were investigated for the first time, which significantly varied among Pleurotus species. The genus Pleurotus contained menaquinone-6 as the sole respiratory quinone, which showed a significant difference with that of its closely related genera. These results of this study demonstrated that the combined method above could efficiently differentiate each Pleurotus species and thus be considered an efficient tool for surveying the genetic diversity of the genus Pleurotus.

Phylogenomic Reappraisal of Fatty Acid Biosynthesis, Mycolic Acid Biosynthesis and Clinical Relevance Among Members of the Genus Corynebacterium

The genus Corynebacterium encompasses many species of biotechnological, medical or veterinary significance. An important characteristic of this genus is the presence of mycolic acids in their cell envelopes, which form the basis of a protective outer membrane (mycomembrane). Mycolic acids in the cell envelope of Mycobacterium tuberculosis have been associated with virulence. In this study, we have analysed the genomes of 140 corynebacterial strains, including representatives of 126 different species. More than 50% of these strains were isolated from clinical material from humans or animals, highlighting the true scale of pathogenic potential within the genus. Phylogenomically, these species are very diverse and have been organised into 19 groups and 30 singleton strains. We find that a substantial number of corynebacteria lack FAS-I, i.e., have no capability for de novo fatty acid biosynthesis and must obtain fatty acids from their habitat; this appears to explain the well-known lipophilic phenotype of some species. In most species, key genes associated with the condensation and maturation of mycolic acids are present, consistent with the reports of mycolic acids in their species descriptions. Conversely, species reported to lack mycolic acids lacked these key genes. Interestingly, Corynebacterium ciconiae, which is reported to lack mycolic acids, appears to possess all genes required for mycolic acid biosynthesis. We suggest that although a mycolic acid-based mycomembrane is widely considered to be the target for interventions by the immune system and chemotherapeutics, the structure is not essential in corynebacteria and is not a prerequisite for pathogenicity or colonisation of animal hosts.

Nocardia acididurans sp. nov., an acid-tolerant actinobacterium isolated from bio-fertilizer of Musa species

A novel acid-tolerant actinobacterium (strain LPG 2T), which formed fragmented substrate mycelia, was isolated from bio-fertiliser of Musa spp. collected from Lampang Province, Thailand. Its morphological and chemotaxonomic properties, e.g., the presence of mycolic acid and MK-8 (H4ω-cycl) in the cells, showed that strain LPG 2T was a member of the genus Nocardia . 16S rRNA gene sequence analysis revealed that this strain was closely related to Nocardia otitidiscaviarum NBRC 14405T (98.7 %). The low average nucleotide identity–blast and digital DNA–DNA hybridization values (<78.6 and <24.0 %, respectively), and several phenotypic differences between strain LPG 2T and its related Nocardia type strains, indicated that the strain merits classification as representing a novel species of the genus Nocardia , for which we propose the name Nocardia acididurans sp. nov. The type strain is LPG 2T (=TBRC 11242T=NBRC 114293T).

2Receptor Specific Ligand conjugated Nanocarriers: an Effective Strategy for Targeted Therapy of Tuberculosis

: Tuberculosis (TB) is an ancient chronic disease caused by the bacillus Mycobacterium tuberculosis, which has affected mankind for more than 4,000 years. Compliance with the standard conventional treatment can assure recovery from tuberculosis, but emergence of drug resistant strains pose a great challenge for effective management of tuberculosis. The process of discovery and development of new therapeutic entities with better specificity and efficacy is unpredictable and time consuming. Hence, delivery of pre-existing drugs with improved targetability is the need of the hour. Enhanced delivery and targetability can ascertain improved bioavailability, reduced toxicity, decreased frequency of dosing and therefore better patient compliance. Nanoformulations are being explored for effective delivery of therapeutic agents, however optimum specificity is not guaranteed. In order to achieve specificity, ligands specific to receptors or cellular components of macrophage and Mycobacteria can be conjugatedto nanocarriers. This approach can improve localization of existing drug molecules at the intramacrophageal site where the parasites reside, improve targeting to the unique cell wall structure of Mycobacterium or improve adhesion to epithelial surface of intestine or alveolar tissue (lectins). Present review focuses on the investigation of various ligands like Mannose, Mycolic acid, Lectin, Aptamers etc. installed nanocarriers that are being envisaged for targeting antitubercular drugs.

Fragment-Based Ligand Discovery Applied to the Mycolic Acid Methyltransferase Hma (MmaA4) from Mycobacterium tuberculosis: A Crystallographic and Molecular Modelling Study

The mycolic acid biosynthetic pathway represents a promising source of pharmacological targets in the fight against tuberculosis. In Mycobacterium tuberculosis, mycolic acids are subject to specific chemical modifications introduced by a set of eight S-adenosylmethionine dependent methyltransferases. Among these, Hma (MmaA4) is responsible for the introduction of oxygenated modifications. Crystallographic screening of a library of fragments allowed the identification of seven ligands of Hma. Two mutually exclusive binding modes were identified, depending on the conformation of residues 147–154. These residues are disordered in apo-Hma but fold upon binding of the S-adenosylmethionine (SAM) cofactor as well as of analogues, resulting in the formation of the short η1-helix. One of the observed conformations would be incompatible with the presence of the cofactor, suggesting that allosteric inhibitors could be designed against Hma. Chimeric compounds were designed by fusing some of the bound fragments, and the relative binding affinities of initial fragments and evolved compounds were investigated using molecular dynamics simulation and generalised Born and Poisson–Boltzmann calculations coupled to the surface area continuum solvation method. Molecular dynamics simulations were also performed on apo-Hma to assess the structural plasticity of the unliganded protein. Our results indicate a significant improvement in the binding properties of the designed compounds, suggesting that they could be further optimised to inhibit Hma activity.

Actinomadura graeca sp. nov.: A novel producer of the macrocyclic antibiotic zelkovamycin

As part of a screening programme for antibiotic-producing bacteria, a novel Actinomadura species was discovered from a soil sample collected in Santorini, Greece. Preliminary 16S rRNA gene sequence comparisons highlighted Actinomadura macra as the most similar characterised species. However, whole-genome sequencing revealed an average nucleotide identity (ANI) value of 89% with A. macra, the highest among related species. Further phenotypic and chemotaxonomic analyses confirmed that the isolate represents a previously uncharacterised species in the genus Actinomadura, for which the name Actinomadura graeca sp. nov. is proposed (type strain 32-07T). The G+C content of A. graeca 32–07 is 72.36%. The cell wall contains DL-diaminopimelic acid, intracellular sugars are glucose, ribose and galactose, the predominant menaquinone is MK-9(H6), the major cellular lipid is phosphatidylinositol and fatty acids consist mainly of hexadecanoic acid. No mycolic acid was detected. Furthermore, A. graeca 32–07 has been confirmed as a novel producer of the non-ribosomal peptide antibiotic zelkovamycin and we report herein a provisional description of the unique biosynthetic gene cluster.

Intimate relationships among soil bacteria: actinomycetes and mycolic acid-containing bacteria

Co-culture is an efficient strategy for natural product discovery. We have used mycolic acid-containing bacteria (MACB) Tsukamurella pumonis TP-B0596 to induce secondary metabolism by actinomycetes and have found several natural products. We also observed that MACB attached to the mycelium of Streptomyces lividans forming coaggregates during combined-culture. This stimulated interest in the interactions among actinomycetes and MACB, and we found that soil isolated cultures contained a mixture of actinomycetes and MACB. Our previously observed interactions were the result of selective screening and combination of bacteria in the lab, which warranted investigation of the existence of these interactions in the natural soil environment. Therefore, in this paper, we report the interaction between a co-isolated natural pair of actinomycetes and MACB in terms of morphology and metabolic changes. A natural pair of actinomycetes and MACB co-aggregated in liquid culture and showed metabolic changes. Interestingly, co-aggregated actinomycetes and MACB were re-isolated from soil with no obvious morphological colony differences from the colony of a single strain. The results demonstrate that there is a stochastic chance of picking colonies containing co-aggregated actinomycetes and MACB, which suggests that the pair can exist in co-aggregate form in the soil environment and interact with each other.

Mechanism of Action, Resistance, Synergism, and Clinical Implications of Delamanid Against Multidrug-Resistant Mycobacterium tuberculosis

Multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis (MTB) remain a primary global threat to the end of tuberculosis (TB) era. Delamanid (DLM) is a nitro-dihydro-imidazooxazole derivative utilized to treat MDR-TB. DLM has distinct mechanism of action, inhibiting methoxy- and keto-mycolic acid (MA) synthesis through the F420 coenzyme mycobacteria system and generating nitrous oxide. While DLM resistance among MTB strains is uncommon, there are increasing reports in Asia and Europe, and such resistance will prolong the treatment courses of patients infected with MDR-TB. In this review, we address the antimycobacterial properties of DLM, report the global prevalence of DLM resistance, discuss the synergism of DLM with other anti-TB drugs, and evaluate the documented clinical trials to provide new insights into the clinical use of this antibiotic.