Abstract Antibiotic resistance has progressively increased over time, thus necessitating the discovery of sustainable, novel antimicrobials. Ammonia producing bacteria (APB) are predominant organisms occupying many niches in the rumens of cattle and soil. The objective of this study was to discover target phyto-phenolic compounds (PPCs) that can act as replacements for existing antimicrobials, as well as at what concentration ranges may be optimal for inhibition of APB growth. In recognition of this discovery, producers may have alternative antimicrobial compounds for use in managing APB and common silage spoilage organisms. To shed light on this matter, inhibitory concentrations (IC) and ammonia assays were implemented. ICs analyzed the inhibitory action of six structurally similar PPCs: thymol, eugenol, carvacrol, hydro-cinnamic acid (H-CA), trans-cinnamic acid (T-CA), and phloroglucinol. Five APB (SR, MD1, F, BG1, and B14) were exposed to five concentrations of phytochemicals via a 10% v/v serial dilution: 10, 1, 0.1, 0.01, 0.001 mM. Following serial dilution, the bacteria were incubated ~24h at 39°C in a water bath, and visually inspected for growth. Ammonia assays utilized the least, fully inhibitory concentration of each phytochemical identified via the inhibitory concentration experiments. Ammonia concentrations were determined using the phenolic acid/hypochlorite method. All protocols utilized anaerobic sterile technique. All experiments were repeated in triplicate and significant results (P < 0.05) were determined using a one-way ANOVA with Tukey’s post hoc test utilizing OriginPro statistical software. Inhibition results revealed that eugenol, thymol, and carvacrol were successful in inhibiting bacterial growth at a concentration range of 10 mM to 1 mM. However, phloroglucinol was not fully inhibitory at any concentration tested against any bacteria. Eugenol, thymol, carvacrol were fully inhibitory at either 10 mM or 1 mM for all organisms tested except BG1, where it was only inhibitory at 10 mM. Ammonia analyses determined that eugenol and carvacrol greatly reduced ammonia production for all species tested except for B14, a generalist, which had no measurable changes in ammonia for any of the treatments including control. Thymol reduced ammonia production for MD1, BG1, and SR. Additionally, H-CA and T-CA decreased ammonia production of SR compared with control but not as much as eugenol or carvacrol. Results suggested that the growth of APB was generally inhibited by the greatest concentrations of PPCs (10 mM to 1 mM) tested here. Additionally, phloroglucinol did not inhibit bacterial growth therefore it was not included in the ammonia analyses. Eugenol and carvacrol significantly reduced ammonia production in all organisms, therefore indicating possible antimicrobial candidates to be further investigated. In comparison with carvacrol and eugenol, T-CA and H-CA made a modest to negligible reduction in ammonia. Phyto-phenolic compounds that were successful in inhibiting bacterial growth and reducing ammonia production demonstrate several promising target antimicrobials.

Amino-acid-fermenting bacteria are wasteful organisms within the rumens of beef cattle that remove dietary amino nitrogen by producing ammonia, which is then excreted renally. There are currently no on-label uses for the control of this microbial guild, but off-label use of broad-spectrum antimicrobials has shown efficacy, which contributes to antimicrobial resistance. Plant-derived antimicrobials supplemented into the diets of cattle may offer worthwhile alternatives. This study sought to investigate the role of cannabidiol (CBD) as a terpenophenolic antimicrobial. Ex vivo cell suspensions were harvested from the rumen fluid of Angus × Holstein steers in non-selective media with amino acid substrates. The suspensions were treated with five concentrations of CBD (860 μg mL−1–0.086 μg mL−1) and incubated (24 h), after which ammonia production and viable number of cells per substrate and treatment were measured. The data demonstrated a ~10–15 mM reduction in ammonia produced at the highest concentration of CBD and negligible changes in the viable number of amino-acid-fermenting bacteria. CBD does not appear to be a biologically or economically viable terpenophenolic candidate for the control of amino acid fermentation in beef cattle.

Amino acid-fermenting Clostridia have undesirable effects in agricultural systems, which can be mitigated by antibiotics, but resistance necessitates alternatives. Here, we demonstrate the efficacy of cannabidiol on growth and ammonia inhibition of five agriculturally relevant Clostridia: Clostridium sporogenes, Peptostreptococcus spp., Clostridioides difficile, Acetoanaerobium sticklandii, and Clostridium aminophilum.

Clostridioides difficile is a clinically and agriculturally important organism with diverse metabolic capabilities. Commercially available media types to cultivate C. difficile typically include multiple growth substrates and often selective agents. Under these conditions, it is difficult to determine what the bacteria utilized and which products are derived from which substrates. These experiments compared a commercial broth (Reinforced Clostridium Medium/RCM) to simpler, defined, carbonate-based media types influenced by Robert Hungate. Peptides (tryptone peptone), amino acids (casamino acids), and/or glucose were added to evaluate the growth of C. difficile strains 9689, BAA-1870, and 43597, and the metabolism of the type strain 9689. C. difficile grew to the greatest optical density in the rich RCM broth but produced less ammonia than the tryptone-containing media types. C. difficile utilized all glucose in RCM and T+G media in addition to performing amino acid fermentations, though the volatile fatty acids produced were not necessarily consistent across media type. When cultured in CAA-containing media, 9689 performed very little metabolism and did not grow regardless of supplementation with glucose. These data demonstrated that C. difficile could metabolize substrates and grow in defined, anaerobic, and carbonate-buffered media. Hungate-style media appear to be an acceptable choice for reliable culturing of C. difficile.

Objectives: This study aimed to elucidate mechanistic explanation(s) for compositional changes to enteric microbiota by determining the impacts of continuous nicotine/cotinine exposure on representative gastrointestinal bacteria and how these alterations impact innate immune cell plasticity.Methods: In vitro cultures of the gastrointestinal bacteria (Bacteroides fragilis 25285, Prevotella bryantii B14, and Acetoanaerobium sticklandii SR) were continuously exposed to nicotine or cotinine. Supernatant samples were collected for fermentation acid analysis. Vesicles were collected and analyzed for physiological changes in number, size, and total protein cargo. Cultured macrophages were stimulated to a tolerogenic phenotype, exposed to control or altered (nicotine or cotinine - exposed) vesicles, and inflammatory plasticity assessed via inflammatory cytokine production.Results: Nicotine/cotinine exposure differentially affected metabolism of all bacteria tested in a Gram (nicotine) and concentration-dependent (cotinine) manner. Physiological studies demonstrated changes in vesiculation number and protein cargo following nicotine/cotinine exposures. Continuous exposure to 1 mu M nicotine and 10 mu M cotinine concentrations reduced total protein cargo of Gram (-) - 25285 and B14 vesicles, while cotinine generally increased total protein in Gram (+) -SR vesicles. We found that theses physiological changes to the vesicles of 25285 and SR formed under nicotine and cotinine, respectively, challenged the plasticity of tolerogenic macrophages. Tolerogenic macrophages exposed to vesicles from 1 mu M nicotine, and 5 or 10 mu\M cotinine cultures produced significantly less IL-12p70, TNF alpha, or KC/GRO, regardless of macrophage exposure to nicotine/ cotinine.Conclusions: Nicotine/cotinine exposure differentially alters bacterial metabolism and vesicle physiology, ultimately impacting the inflammatory response of tolerogenic macrophages.

Nicotine is a highly addictive compound present in tobacco, which causes the release of dopamine in different regions of the brain. Recent studies have shown that astrocytes express nicotinic acetylcholine receptors (nAChRs) and mediate calcium signaling. In this study, we examine the morphological and functional adaptations of astrocytes due to nicotine exposure. Utilizing a combination of fluorescence and atomic force microscopy, we show that nicotine-treated astrocytes exhibit time-dependent remodeling in the number and length of both proximal and fine processes. Blocking nAChR activity with an antagonist completely abolishes nicotine's influence on astrocyte morphology indicating that nicotine's action is mediated by these receptors. Functional studies show that 24-hr nicotine treatment induces higher levels of calcium activity in both the cell soma and the processes with a more substantial change observed in the processes. Nicotine does not induce reactive astrocytosis even at high concentrations (10 μM) as determined by cytokine release and glial fibrillary acidic protein expression. We designed tissue clearing experiments to test whether morphological changes occur in vivo using astrocyte specific Aldh1l1-tdTomato knock in mice. We find that nicotine induces a change in the volume of astrocytes in the prefrontal cortex, CA1 of the hippocampus, and the substantia nigra. These results indicate that nicotine directly alters the functional and morphological properties of astrocytes potentially contributing to the underlying mechanism of nicotine abuse.

Current research indicates that changes in gut microbiota can impact the host, but it is not always clear how dietary and environmental factors alter gut microbiota. One potential factor is antimicrobial activity of compounds ingested by the host. The goal of this study was to determine the antimicrobial activity of common plant secondary metabolites against pure cultures of paired, structurally and phylogenetically distinct gastrointestinal bacteria of human or bovine origin: Prevotella bryantii B(1)4, Bacteroides fragilis 25285, Acetoanaerobium (Clostridium) sticklandii SR and Clostridioides difficile 9689. When growth media were amended with individual phytochemicals (the alkaloids: berberine, capsaicin, nicotine, piperine and quinine and the phenolic: curcumin), growth of each species was inhibited to varying degrees at the three greatest concentrations tested (0.10-10.00 mg mL(-1)). The viable cell numbers of all the cultures were reduced, >= 4-logs, by berberine at concentrations >= 1.00 mg mL(-1). Quinine performed similarly to berberine for B 1 4, 25285, and SR at the same concentrations. The other phytochemicals were inhibitory, but not as much as quinine or berberine. Nicotine had activity against all four species (>= 2-log reduction in viable cell number at 10.00 mg mL(-1)), but had stronger activity against the Gram-positive bacteria, SR and 9689, (>= 4-log reductions at 10.00 mg mL(-1)). In conclusion, the phytochemicals had varying spectra of antimicrobial activity. These results are consistent with the hypothesis that ingested phytochemicals have the ability to differentially impact gut microbiota through antimicrobial activity. (C) 2019 Published by Elsevier Ltd.