Molecular basis for dual functions in pilus assembly modulated by the lid of a pilus-specific sortase.

The biphasic assembly of Gram-positive pili begins with the covalent polymerization of distinct pilins catalyzed by a pilus-specific sortase, followed by the cell wall anchoring of the resulting polymers mediated by the housekeeping sortase. In Actinomyces oris, the pilus-specific sortase SrtC2 not only polymerizes FimA pilins to assemble type 2 fimbriae with CafA at the tip, but it can also act as the anchoring sortase, linking both FimA polymers and SrtC1-catalyzed FimP polymers (type 1 fimbriae) to peptidoglycan when the housekeeping sortase SrtA is inactive. To date, the structure-function determinants governing the unique substrate specificity and dual enzymatic activity of SrtC2 have not been illuminated. Here, we present the crystal structure of SrtC2 solved to 2.10-Å resolution. SrtC2 harbors a canonical sortase fold and a lid typical for class C sortases and additional features specific to SrtC2. Structural, biochemical, and mutational analyses of SrtC2 reveal that the extended lid of SrtC2 modulates its dual activity. Specifically, we demonstrate that the polymerizing activity of SrtC2 is still maintained by alanine-substitution, partial deletion, and replacement of the SrtC2 lid with the SrtC1 lid. Strikingly, pilus incorporation of CafA is significantly reduced by these mutations, leading to compromised polymicrobial interactions mediated by CafA. In a srtA mutant, the partial deletion of the SrtC2 lid reduces surface anchoring of FimP polymers, and the lid-swapping mutation enhances this process, while both mutations diminish surface anchoring of FimA pili. Evidently, the extended lid of SrtC2 enables the enzyme the cell wall-anchoring activity in a substrate-selective fashion.

Pullenvalenes A-D: Nitric Oxide-Mediated Transcriptional Activation (NOMETA) Enables Discovery of Triterpene Aminoglycosides from Australian Termite Nest-Derived Fungi.

We report on the use of nitric oxide-mediated transcriptional activation (NOMETA) as an innovative means to detect and access new classes of microbial natural products encoded within silent biosynthetic gene clusters. A small library of termite nest- and mangrove-derived fungi and actinomyces was subjected to cultivation profiling using a miniaturized 24-well format approach (MATRIX) in the presence and absence of nitric oxide, with the resulting metabolomes subjected to comparative chemical analysis using UPLC-DAD and GNPS molecular networking. This strategy prompted study of Talaromyces sp. CMB-TN6F and Coccidiodes sp. CMB-TN39F, leading to discovery of the triterpene glycoside pullenvalenes A-D (1-4), featuring an unprecedented triterpene carbon skeleton and rare 6-O-methyl-N-acetyl-d-glucosaminyl glycoside residues. Structure elucidation of 1-4 was achieved by a combination of detailed spectroscopic analysis, chemical degradation, derivatization and synthesis, and biosynthetic considerations.

Tongue-Coating Microbial and Metabolic Characteristics in Halitosis.

Halitosis is a common oral condition, which leads to social embarrassment and affects quality of life. Cumulative evidence has suggested the association of tongue-coating microbiome with the development of intraoral halitosis. The dynamic variations of tongue-coating microbiota and metabolites in halitosis have not been fully elucidated. Therefore, the present study aimed to determine the tongue-coating microbial and metabolic characteristics in halitosis subjects without other oral diseases using metagenomics and metabolomics analysis. The participants underwent oral examination, halitosis assessment, and tongue-coating sample collection for the microbiome and metabolome analysis. It was found that the microbiota richness and diversity were significantly elevated in the halitosis group. Furthermore, species from Actinomyces, Prevotella, Veillonella, and Solobacterium were significantly more abundant in the halitosis group. However, the Rothia and Streptococcus species exhibited opposite tendencies. Eleven Kyoto Encyclopedia of Genes and Genomes pathways were significantly enriched in the halitosis tongue coatings, including cysteine and methionine metabolism. Functional genes related to sulfur, indole, skatole, and cadaverine metabolic processes (such as serA, metH, metK and dsrAB) were identified to be more abundant in the halitosis samples. The metabolome analysis revealed that indole-3-acetic, ornithine, and L-tryptophan were significantly elevated in the halitosis samples. Furthermore, it was observed that the values of volatile sulfur compounds and indole-3-acetic abundances were positively correlated. The multiomics analysis identified the metagenomic and metabolomic characteristics to differentiate halitosis from healthy individuals using the least absolute shrinkage and selection operator logistic regression and random forest classifier. A total of 19 species and 39 metabolites were identified as features in halitosis patients, which included indole-3-acetic acid, Bacillus altitudinis, Candidatus Saccharibacteria, and Actinomyces species. In conclusion, an evident shift in microbiome and metabolome characteristics was observed in the halitosis tongue coating, which may have a potential etiological significance and provide novel insights into the mechanism for halitosis.

Screening biosurfactant-producing actinomycetes: Identification of Streptomyces sp. RP1 as a potent species for bioremediation.

This study aimed to isolate biosurfactant-producing and hydrocarbon-degrading actinomycetes from different soils using glycerol-asparagine and starch-casein media with an antifungal agent. The glycerol-asparagine agar exhibited the highest number of actinomycetes, with a white, low-opacity medium supporting pigment production and high growth. Biosurfactant analyses, such as drop collapse, oil displacement, emulsification, tributyrin agar test, and surface tension measurement, were conducted. Out of 25 positive isolates, seven could utilize both olive oil and black oil for biosurfactant production, and only isolate RP1 could produce biosurfactant when grown in constrained conditions with black oil as the sole carbon source and inducer, demonstrating in situ bioremediation potential. Isolate RP1 from oil-spilled garden soil is Gram-staining-positive with a distinct earthy odor, melanin formation, and white filamentous colonies. It has a molecular size of ~621 bp and 100% sequence similarity to many Streptomyces spp. Morphological, biochemical, and 16 S rRNA analysis confirmed it as Streptomyces sp. RP1, showing positive results in all screenings, including high emulsification activity against kerosene (27.2%) and engine oil (95.8%), oil displacement efficiency against crude oil (7.45 cm), and a significant reduction in surface tension (56.7 dynes/cm). Streptomyces sp. RP1 can utilize citrate as a carbon source, tolerate sodium chloride, resist lysozyme, degrade petroleum hydrocarbons, and produce biosurfactant at 37°C in a 15 mL medium culture, indicating great potential for bioremediation and various downstream industrial applications with optimization.

Aerobic Denitrification Promoting by Actinomycetes Coculture: Investigating Performance, Carbon Source Metabolic Characteristic, and Raw Water Restoration.

The coculture theory that promotes denitrification relies on effectively utilizing the resources of low-efficiency denitrification microbes. Here, the strains Streptomyces sp. PYX97 and Streptomyces sp. TSJ96 were isolated and showed lower denitrification capacity when cultured individually. However, the coculture of strains PYX97 and TSJ96 enhanced nitrogen removal (removed 96.40% of total nitrogen) and organic carbon reduction (removed 92.13% of dissolved organic carbon) under aerobic conditions. Nitrogen balance analysis indicated that coculturing enhanced the efficiency of nitrate converted into gaseous nitrogen reaching 70.42%. Meanwhile, the coculturing promoted the cell metabolism capacity and carbon source metabolic activity. The coculture strains PYX97 and TSJ96 thrived in conditions of C/N = 10, alkalescence, and 150 rpm shaking speed. The coculturing reduced total nitrogen and CODMn in the raw water treatment by 83.32 and 84.21%, respectively. During this treatment, the cell metabolic activity and cell density increased in the coculture strains PYX97 and TSJ96 reactor. Moreover, the coculture strains could utilize aromatic protein and soluble microbial products during aerobic denitrification processes in raw water treatment. This study suggests that coculturing inefficient actinomycete strains could be a promising approach for treating polluted water bodies.

Advances in the biosynthesis of cyclodipeptide type natural products derived from actinomycetes / 生物工程学报

Cyclodipeptide (CDP) composed of two amino acids is the simplest cyclic peptide. These two amino acids form a typical diketopiperazine (DKP) ring by linking each other with peptide bonds. This characteristic stable ring skeleton is the foundation of CDP to display extensive and excellent bioactivities, which is beneficial for CDPs' pharmaceutical research and development. The natural CDP products are well isolated from actinomycetes. These bacteria can synthesize DKP backbones with nonribosomal peptide synthetase (NRPS) or cyclodipeptide synthase (CDPS). Moreover, actinomycetes could produce a variety of CDPs through different enzymatic modification. The presence of these abundant and diversified catalysis indicates that actinomycetes are promising microbial resource for exploring CDPs. This review summarized the pathways for DKP backbones biosynthesis and their post-modification mechanism in actinomycetes. The aim of this review was to accelerate the genome mining of CDPs and their isolation, purification and structure identification, and to facilitate revealing the biosynthesis mechanism of novel CDPs as well as their synthetic biology design.

Actinomicetos con actividad anti-candida aisladas de hormigas cortadoras de hojas Atta cephalotes (Formicidae: Myrmicinae: Attini) / Actinomyces with anti-candida activity isolated from leaf-cutting ants Atta cephalotes (Formicidae: Myrmicinae: Attini)

RESUMEN Objetivos. Aislar, seleccionar e identificar actinomicetos asociados a hormigas cortadoras de hojas Atta cephalotes (Linnaeus, 1758), que presenten mayor actividad anti-Candida. Materiales y métodos. Estudio transversal realizado en hormigas recolectadas de una localidad de Huánuco, Perú, a partir de las cuales se aislaron cepas de actinomicetos que fueron evaluadas mediante pruebas in vitro para determinar su capacidad antagonista frente a especies de Candida. Los actinomicetos de mayor antagonismo fueron seleccionados y cultivados en agitación, luego se obtuvieron los metabolitos extracelulares con solventes orgánicos y finalmente se evaluaron los extractos crudos para determinar cuantitativamente la concentración mínima inhibitoria (CMI). Resultados. Se logró aislar 30 actinomicetos, de los cuales el 47 % presentaron actividad antagonista a Candida albicans (C. albicans) ATCC 7516, el 43 % a Candida parapsilosis ATCC 7307, el 37% a Candida tropicalis ATCC 7206 y C. albicans ATCC 10231 y el 30% a C. albicans ATCC 98028. Extractos orgánicos de las cepas HAA-16 y HAA-17 presentaron marcada actividad anti-Candida; siendo el extracto de acetato de etilo de la cepa HAA17 el de mejor rendimiento por tener mayor espectro de actividad y presentar una CMI de 3,25 mg/ml frente a C. albicans ATCC 7516 y Candida parapsilosis ATCC 7307. Los actinomicetos seleccionados se identificaron mediante técnicas moleculares como miembros del género Streptomyces. Conclusiones. Los actinomicetos asociados a Atta cephalotes son excelentes productores de compuestos bioactivos, capaces de inhibir el crecimiento de levaduras patógenas del género Candida y con potencial aplicación en el desarrollo de nuevos productos naturales de interés biomédico.

ABSTRACT Objectives. To isolate, select and identify actinomyces associated to leaf-cutting ants Atta cephalotes (Linnaeus, 1758), that present a greater anti-Candida activity. Materials and Methods. Cross-sectional study made with ants collected at a location in Huánuco, Peru, from which strands of actinomyces were isolated and later evaluated by in vitro testing in order to determine its antagonistic capacity against species of Candida. The actinomyces with greater antagonism were selected and cultured by agitation, then the reliable extracellular metabolites were obtained with organic solvents, and finally the crude extracts were evaluated to determine quantitatively the minimum inhibiting concentration (MIC). Results. Thirty (30) actinomyces were isolated, of which 47% exhibited antagonistic activity against Candida albicans (C. albicans) ATCC 7516, 43% to Candida parapsilosis ATCC 7307, 37% to Candida tropicalis ATCC 7206 and C. albicans ATCC 10231, and 30% to C. albicans ATCC 98028. Organic extracts of the HAA-16 and HAA-17 strands exhibited noticeable anti-Candida activity, being the ethyl acetate extract of the HAA-17 strand the one with the highest performance thanks to a wider activity spectrum of MIC 3.25 mg/mL against C. albicans ATCC 7516 and Candida parapsilosis ATCC 7307. The selected actinomyces were identified by means of molecular techniques as members of the Streptomyces genus. Conclusions. Actinomyces associated to Atta cephalotes are excellent producers of bioactive compounds, being able to inhibit the growth of pathogenic mold of the Candida genus and with potential for application in the development of new natural products for the biomedical field.

Manchas dentárias extrínsecas pretas: revisäo de literatura / Extrinsic dental black stain

O objetivo deste trabalho foi discutir, através de uma revisäo da literatura, as manchas dentárias extrínsecas pretas, elucidando o que säo e por quê removê-las. Sugestöes quanto à natureza química dos pigmentos pretos foram feitas e mostraram que este é um sal férrico, produzido pela bactéria. Prevotella melaninogênica