Antiarthritic potential of ethanolic extract of Ixora coccinea leaves on complete Freund's adjuvant-induced arthritis in animal model.

CONTEXT: Ixora coccinea leaves possess antioxidant, anti-inflammatory, antinociceptive, antimutagenic, and gastroprotective properties. On this background, its antiarthritic potential was evaluated. AIMS: The objective is to evaluate the effect of Ethanolic extract of Ixora coccinea leaves (EEICL) on complete Freund's adjuvant-induced arthritis in rats. SETTINGS AND STUDY DESIGN: PG research laboratory, Pharmacology Department, MKCG Medical College, Berhampur, Odisha. SUBJECTS AND METHODS: Thirty-six Wistar albino rats were randomly distributed into sixgroups (n = 6) as follows: Gr 1 (normal control)-DW p.o, Gr-2 (disease control [DC] - Tween 80 p.o), Gr-3 (piroxicam 0.9 mg/kg p.o), Gr-4 (EEICL-1 g/kg, p.o, Gr 4-EEICL-1.5 g/kg p.o, Gr 5-ED50 (0.82 g/kg) + piroxicam (0.45 mg/kg) p.o. After induction of arthritis, drugs, and vehicles were administered daily from 5th to 25th day. On 0, 5th, 10th, 15th, and 25th day, parameters like body weight, rotarod fall time, paw volume displacement, and arthritis index were measured. On the last day, Erythrocyte sedimentation rate (ESR), tissue malondialdehyde (MDA), and histopathological analysis were done. STATISTICAL ANALYSIS USED: Analysis of parametric data was done by one-way ANOVA and nonparametric data by Kruskal-Wallis test using graph pad prism 7.0. P < 0.05 was considered statistically significant. RESULTS: EEICL (1.5 mg/kg) showed anti-arthritic effect compared with DC. Rotarod fall-off time 137.5 ± 2.5 sec and body weight (139 ± 12.74 g) were increased significantly. The percentage inhibition of paw volume was increased(52%) whereas arthritic score(0.33), ESR(3.51mm/hr), synovial tissue MDA level (0.62±0.13µmol/gm) and Mankin score(2) were reduced significantly as compared to disease control. CONCLUSIONS: EEICL has anti-arthritic potential in rat model.

Evaluation of Azido 3-Deoxy-d-manno-oct-2-ulosonic Acid (Kdo) Analogues for Click Chemistry-Mediated Metabolic Labeling of Myxococcus xanthus DZ2 Lipopolysaccharide.

Metabolic labeling paired with click chemistry is a powerful approach for selectively imaging the surfaces of diverse bacteria. Herein, we explored the feasibility of labeling the lipopolysaccharide (LPS) of Myxococcus xanthus-a Gram-negative predatory social bacterium known to display complex outer membrane (OM) dynamics-via growth in the presence of distinct azido (-N3) analogues of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo). Determination of the LPS carbohydrate structure from strain DZ2 revealed the presence of one Kdo sugar in the core oligosaccharide, modified with phosphoethanolamine. The production of 8-azido-8-deoxy-Kdo (8-N3-Kdo) was then greatly improved over previous reports via optimization of the synthesis of its 5-azido-5-deoxy-d-arabinose precursor to yield gram amounts. The novel analogue 7-azido-7-deoxy-Kdo (7-N3-Kdo) was also synthesized, with both analogues capable of undergoing in vitro strain-promoted azide-alkyne cycloaddition (SPAAC) "click" chemistry reactions. Slower and faster growth of M. xanthus was displayed in the presence of 8-N3-Kdo and 7-N3-Kdo (respectively) compared to untreated cells, with differences also seen for single-cell gliding motility and type IV pilus-dependent swarm community expansion. While the surfaces of 8-N3-Kdo-grown cells were fluorescently labeled following treatment with dibenzocyclooctyne-linked fluorophores, the surfaces of 7-N3-Kdo-grown cells could not undergo fluorescent tagging. Activity analysis of the KdsB enzyme required to activate Kdo prior to its integration into nascent LPS molecules revealed that while 8-N3-Kdo is indeed a substrate of the enzyme, 7-N3-Kdo is not. Though a lack of M. xanthus cell aggregation was shown to expedite growth in liquid culture, 7-N3-Kdo-grown cells did not manifest differences in intrinsic clumping relative to untreated cells, suggesting that 7-N3-Kdo may instead be catabolized by the cells. Ultimately, these data provide important insights into the synthesis and cellular processing of valuable metabolic labels and establish a basis for the elucidation of fundamental principles of OM dynamism in live bacterial cells.

Bacterial Outer Membrane Polysaccharide Export (OPX) Proteins Occupy Three Structural Classes with Selective ß-Barrel Porin Requirements for Polymer Secretion.

Secretion of high-molecular-weight polysaccharides across the bacterial envelope is ubiquitous, as it enhances prokaryotic survival in (a)biotic settings. Such polymers are often assembled by Wzx/Wzy- or ABC transporter-dependent schemes implicating outer membrane (OM) polysaccharide export (OPX) proteins in cell-surface polymer translocation. In the social predatory bacterium Myxococcus xanthus, the exopolysaccharide (EPS) pathway WzaX, major spore coat (MASC) pathway WzaS, and biosurfactant polysaccharide (BPS) pathway WzaB were herein found to be truncated OPX homologues of Escherichia coli Wza lacking OM-spanning α-helices. Comparative genomics across all bacteria (>91,000 OPX proteins identified and analyzed), complemented with cryo-electron tomography cell-envelope analyses, revealed such "truncated" WzaX/S/B architecture to be the most common among three defined OPX-protein structural classes independent of periplasm thickness. Fold recognition and deep learning revealed the conserved M. xanthus proteins MXAN_7418/3226/1916 (encoded beside wzaX/S/B, respectively) to be integral OM ß-barrels, with structural homology to the poly-N-acetyl-d-glucosamine synthase-dependent pathway porin PgaA. Such bacterial porins were identified near numerous genes for all three OPX protein classes. Interior MXAN_7418/3226/1916 ß-barrel electrostatics were found to match properties of their associated polymers. With MXAN_3226 essential for MASC export, and MXAN_7418 herein shown to mediate EPS translocation, we have designated this new secretion machinery component "Wzp" (i.e., Wz porin), with the final step of M. xanthus EPS/MASC/BPS secretion across the OM now proposed to be mediated by WzpX/S/B (i.e., MXAN_7418/3226/1916). Importantly, these data support a novel and widespread secretion paradigm for polysaccharide biosynthesis pathways in which those containing OPX components that cannot span the OM instead utilize ß-barrel porins to mediate polysaccharide transport across the OM. IMPORTANCE Diverse bacteria assemble and secrete polysaccharides that alter their physiologies through modulation of motility, biofilm formation, and host immune system evasion. Most such pathways require outer membrane (OM) polysaccharide export (OPX) proteins for sugar-polymer transport to the cell surface. In the prototypic Escherichia coli Group-1-capsule biosynthesis system, eight copies of this canonical OPX protein cross the OM with an α-helix, forming a polysaccharide-export pore. Herein, we instead reveal that most OPX proteins across all bacteria lack this α-helix, raising questions as to the manner by which most secreted polysaccharides actually exit cells. In the model developmental bacterium Myxococcus xanthus, we show this process to depend on OPX-coupled OM-spanning ß-barrel porins, with similar porins encoded near numerous OPX genes in diverse bacteria. Knowledge of the terminal polysaccharide secretion step will enable development of antimicrobial compounds targeted to blocking polymer export from outside the cell, thus bypassing any requirements for antimicrobial compound uptake by the cell.

Harmonizing Prokaryotic Nomenclature: Fixing the Fuss over Phylum Name Flipping.

Lloyd and Tahon recently criticized proposed bacterial phylum nomenclature changes (K.G. Lloyd, G. Tahon, Nat Rev Microbiol 20:123-124, 2022, https://doi.org/10.1038/s41579-022-00684-2) precipitated by the International Committee on Systematics of Prokaryotes (ICSP)'s official recognition of phylum nomenclature rules. Here, we extend the critique. While we applaud bringing consistency to phylum names, we prognosticate what this minute but momentous change entails for the future of microbial nomenclature and how this will sow confusion among researchers. Several pitfalls of the proposed ICSP framework-based nomenclature are also detailed, including (i) improper type genus name and suffix usage, (ii) loss of Bacteria/Archaea distinctions, (iii) disruption of major phylum name prefixes, and (iv) absence of organism name prevalidation. Finally, we suggest new names for the key bacterial phyla Proteobacteria (Proteobacteriota), Firmicutes (Firmicuteota), Actinobacteria (Actinobacteriota), and Tenericutes (Tenericuteota), while keeping the archaeal phylum names Crenarchaeota, Thaumarchaeota, and Euryarchaeota. Together, these changes will help researchers attain chaos-free uniform nomenclature.