Interplay between particle size and microbial ecology in the gut microbiome.

Physical particles can serve as critical abiotic factors that structure the ecology of microbial communities. For non-human vertebrate gut microbiomes, fecal particle size (FPS) has been known to be shaped by chewing efficiency and diet. However, little is known about what drives FPS in the human gut. Here, we analyzed FPS by laser diffraction across a total of 76 individuals and found FPS to be strongly individualized. Surprisingly, a behavioral intervention with 41 volunteers designed to increase chewing efficiency did not impact FPS. Dietary patterns could also not be associated with FPS. Instead, we found evidence that mammalian and human gut microbiomes shaped FPS. Fecal samples from germ-free and antibiotic-treated mice exhibited increased FPS relative to colonized mice. In humans, markers of longer transit time were correlated with smaller FPS. Gut microbiota diversity and composition were also associated with FPS. Finally, ex vivo culture experiments using human fecal microbiota from distinct donors showed that differences in microbiota community composition can drive variation in particle size. Together, our results support an ecological model in which the human gut microbiome plays a key role in reducing the size of food particles during digestion, and that the microbiomes of individuals vary in this capacity. These new insights also suggest FPS in humans to be governed by processes beyond those found in other mammals and emphasize the importance of gut microbiota in shaping their own abiotic environment.

A pilot study of fecal pH and redox as functional markers in the premature infant gut microbiome.

The infant gut microbiome is a crucial factor in health and development. In preterm infants, altered gut microbiome composition and function have been linked to serious neonatal complications such as necrotizing enterocolitis and sepsis, which can lead to long-term disability. Although many studies have described links between microbiome composition and disease risk, there is a need for biomarkers to identify infants at risk of these complications in practice. In this pilot study, we obtained stool samples from preterm infant participants longitudinally during the first postnatal months, and measured pH and redox, as well as SCFA content and microbiome composition by 16S rRNA gene amplicon sequencing. These outcomes were compared to clinical data to better understand the role of pH and redox in infant gut microbiome development and overall health, and to assess the potential utility of pH and redox as biomarkers. We found that infants born earlier or exposed to antibiotics exhibited increased fecal pH, and that redox potential increased with postnatal age. These differences may be linked to changes in SCFA content, which was correlated with pH and increased with age. Microbiome composition was also related to birth weight, age, pH, and redox. Our findings suggest that pH and redox may serve as biomarkers of metabolic state in the preterm infant gut.

Fecal pH and redox as functional markers in the premature infant gut microbiome.

The infant gut microbiome is a crucial factor in health and development. In preterm infants, altered gut microbiome composition and function have been linked to serious neonatal complications such as necrotizing enterocolitis and sepsis, which can lead to long-term disability. Although many studies have described links between microbiome composition and disease risk, there is a need for biomarkers to identify infants at risk of these complications in practice. In this study, we obtained stool samples from preterm infant participants longitudinally during the first postnatal months, and measured pH and redox, as well as SCFA content and microbiome composition by 16S rRNA gene amplicon sequencing. These outcomes were compared to clinical data to better understand the role of pH and redox in infant gut microbiome development and overall health, and to assess the potential utility of pH and redox as biomarkers. We found that infants born earlier or exposed to antibiotics exhibited increased fecal pH, and that redox potential increased with postnatal age. These differences may be linked to changes in SCFA content, which was correlated with pH and increased with age. Microbiome composition was also related to birth weight, age, pH, and redox. Our findings suggest that pH and redox may serve as biomarkers of metabolic state in the preterm infant gut.

Ecological memory of prior nutrient exposure in the human gut microbiome.

Many ecosystems have been shown to retain a memory of past conditions, which in turn affects how they respond to future stimuli. In microbial ecosystems, community disturbance has been associated with lasting impacts on microbiome structure. However, whether microbial communities alter their response to repeated stimulus remains incompletely understood. Using the human gut microbiome as a model, we show that bacterial communities retain an "ecological memory" of past carbohydrate exposures. Memory of the prebiotic inulin was encoded within a day of supplementation among a cohort of human study participants. Using in vitro gut microbial models, we demonstrated that the strength of ecological memory scales with nutrient dose and persists for days. We found evidence that memory is seeded by transcriptional changes among primary degraders of inulin within hours of nutrient exposure, and that subsequent changes in the activity and abundance of these taxa are sufficient to enhance overall community nutrient metabolism. We also observed that ecological memory of one carbohydrate species impacts microbiome response to other carbohydrates, and that an individual's habitual exposure to dietary fiber was associated with their gut microbiome's efficiency at digesting inulin. Together, these findings suggest that the human gut microbiome's metabolic potential reflects dietary exposures over preceding days and changes within hours of exposure to a novel nutrient. The dynamics of this ecological memory also highlight the potential for intra-individual microbiome variation to affect the design and interpretation of interventions involving the gut microbiome.

Modulation of microbial community dynamics by spatial partitioning.

Microbial communities inhabit spatial architectures that divide a global environment into isolated or semi-isolated local environments, which leads to the partitioning of a microbial community into a collection of local communities. Despite its ubiquity and great interest in related processes, how and to what extent spatial partitioning affects the structures and dynamics of microbial communities are poorly understood. Using modeling and quantitative experiments with simple and complex microbial communities, we demonstrate that spatial partitioning modulates the community dynamics by altering the local interaction types and global interaction strength. Partitioning promotes the persistence of populations with negative interactions but suppresses those with positive interactions. For a community consisting of populations with both positive and negative interactions, an intermediate level of partitioning maximizes the overall diversity of the community. Our results reveal a general mechanism underlying the maintenance of microbial diversity and have implications for natural and engineered communities.

Introducing the Microbes and Social Equity Working Group: Considering the Microbial Components of Social, Environmental, and Health Justice.

Humans are inextricably linked to each other and our natural world, and microorganisms lie at the nexus of those interactions. Microorganisms form genetically flexible, taxonomically diverse, and biochemically rich communities, i.e., microbiomes that are integral to the health and development of macroorganisms, societies, and ecosystems. Yet engagement with beneficial microbiomes is dictated by access to public resources, such as nutritious food, clean water and air, safe shelter, social interactions, and effective medicine. In this way, microbiomes have sociopolitical contexts that must be considered. The Microbes and Social Equity (MSE) Working Group connects microbiology with social equity research, education, policy, and practice to understand the interplay of microorganisms, individuals, societies, and ecosystems. Here, we outline opportunities for integrating microbiology and social equity work through broadening education and training; diversifying research topics, methods, and perspectives; and advocating for evidence-based public policy that supports sustainable, equitable, and microbial wealth for all.

Synthesis and SAR studies of novel benzodiazepinedione-based inhibitors of Clostridium difficile (C. difficile) toxin B (TcdB).

Synthesis and structure-activity relationships (SAR) of a novel series of benzodiazepinedione-based inhibitors of Clostridium difficile toxin B (TcdB) are described. Compounds demonstrating low nanomolar affinity for TcdB, and which possess improved stability in mouse plasma vs. earlier compounds from this series, have been identified. Optimized compound 11d demonstrates a good pharmacokinetic (PK) profile in mouse and hamster and is efficacious in a hamster survival model of Clostridium difficile infection.

Treatment of Clostridium difficile Infection with a Small-Molecule Inhibitor of Toxin UDP-Glucose Hydrolysis Activity.

Clostridium difficile infection (CDI) is the leading cause of hospital-acquired infectious diarrhea, with significant morbidity, mortality, and associated health care costs. The major risk factor for CDI is antimicrobial therapy, which disrupts the normal gut microbiota and allows C. difficile to flourish. Treatment of CDI with antimicrobials is generally effective in the short term, but recurrent infections are frequent and problematic, indicating that improved treatment options are necessary. Symptoms of disease are largely due to two homologous toxins, TcdA and TcdB, which are glucosyltransferases that inhibit host Rho GTPases. As the normal gut microbiota is an important component of resistance to CDI, our goal was to develop an effective nonantimicrobial therapy. Here, we report a highly potent small-molecule inhibitor (VB-82252) of TcdA and TcdB. This compound inhibits the UDP-glucose hydrolysis activity of TcdB and protects cells from intoxication after challenge with either toxin. Oral dosing of the inhibitor prevented inflammation in a murine intrarectal toxin challenge model. In a murine model of recurrent CDI, the inhibitor reduced weight loss and gut inflammation during acute disease and did not cause the recurrent disease that was observed with vancomycin treatment. Lastly, the inhibitor demonstrated efficacy similar to that of vancomycin in a hamster disease model. Overall, these results demonstrate that small-molecule inhibition of C. difficile toxin UDP-glucose hydrolysis activity is a promising nonantimicrobial approach to the treatment of CDI.

Identification and initial optimization of inhibitors of Clostridium difficile (C. difficile) toxin B (TcdB).

The discovery, synthesis and preliminary structure-activity relationship (SAR) of a novel class of inhibitors of Clostridium difficile (C. difficile) toxin B (TcdB) is described. A high throughput screening (HTS) campaign resulted in the identification of moderately active screening hits 1-5 the most potent of which was compound 1 (IC50 = 0.77 µM). In silico docking of an early analog offered suggestions for structural modification which resulted in the design and synthesis of highly potent analogs 13j(IC50 = 1 nM) and 13 l(IC50 = 7 nM) which were chosen as leads for further optimization.

Synthesis and SAR studies of novel 2-(6-aminomethylaryl-2-aryl-4-oxo-quinazolin-3(4H)-yl)acetamide vasopressin V1b receptor antagonists.

Synthesis and structure-activity relationships (SAR) of a novel series of vasopressin V(1b) antagonists are described. 2-(6-Aminomethylaryl-2-aryl-4-oxo-quinazolin-3(4H)-yl)acetamide have been identified with low nanomolar affinity for the V(1b) receptor and good selectivity with respect to related receptors V(1a), V(2) and OT. Optimised compound 16 shows a good pharmacokinetic profile and activity in a mechanistic model of HPA dysfunction.

Synthesis and SAR studies of novel 2-(4-oxo-2-aryl-quinazolin-3(4H)-yl)acetamide vasopressin V1b receptor antagonists.

Synthesis and structure-activity relationships (SAR) of a novel series of vasopressin V(1b) (V(3)) antagonists are described. 2-(4-Oxo-2-aryl-quinazolin-3(4H)-yl)acetamides have been identified with low nanomolar affinity for the V(1b) receptor and good selectivity with respect to related receptors V(1a), V(2) and oxytocin (OT). Optimised compound 12j demonstrates a good pharmacokinetic profile and activity in a mechanistic model of HPA dysfunction.

Identification and optimization of novel 2-(4-oxo-2-aryl-quinazolin-3(4H)-yl)acetamide vasopressin V3 (V1b) receptor antagonists.

The discovery, synthesis, and preliminary structure-activity relationship (SAR) of a novel class of vasopressin V3 (V1b) receptor antagonists is described. Compound 1, identified by high throughput screening of a diverse, three million-member compound collection, prepared using ECLiPS technology, had good activity in a V3 binding assay (IC50=0.20 microM), but less than desirable physicochemical properties. Optimization of compound 1 yielded potent analogs 19 (IC50=0.31 microM) and 24 (IC50=0.12 microM) with improved drug-like characteristics.

Identification and hit-to-lead optimization of a novel class of CB1 antagonists.

The discovery, synthesis and preliminary structure-activity relationships (SARs) of a novel class of CB1 antagonists is described. Initial optimization of benzimidazole-based screening hit 4 led to the identification of 'inverted' indole-based lead compound 18c with improved properties versus compound 4 including reduced AlogP, improved microsomal stability and improved aqueous solubility. Compound 18c demonstrates in vivo CB1 antagonist efficacy (CB1 agonist induced hypothermia model) and is orally bioavailable in rat.

2-Benzimidazolyl-9-(chroman-4-yl)-purinone derivatives as JAK3 inhibitors.

A novel class of Janus tyrosine kinase 3 (JAK3) inhibitors based on a 2-benzimidazoylpurinone core structure is described. Through substitution of the benzimidazoyl moiety and optimization of the N-9 substituent of the purinone, compound 24 was identified incorporating a chroman-based functional group. Compound 24 shows excellent kinase activity, good oral bioavailability and demonstrates efficacy in an acute mechanistic mouse model through inhibition of interleukin-2 (IL-2) induced interferon-gamma (INF-gamma) production.

Synthesis and initial evaluation of novel, non-peptidic antagonists of the alpha(v)-integrins alpha(v)beta(3) and alpha(v)beta(5).

The discovery, synthesis and preliminary SAR of a novel class of non-peptidic antagonists of the alpha(v)-integrins alpha(v)beta(3) and alpha(v)beta(5) is described. High-throughput screening of an extensive series of ECLiPStrade mark compound libraries led to the identification of compound 1 as a dual inhibitor of the alpha(v)-integrins alpha(v)beta(3) and alpha(v)beta(5). Optimization of compound 1 involving, in part, introduction of two novel constraints led to the discovery of compounds 15a and 15b with reduced PSA and much improved potency for both the alpha(v)beta(3) and alpha(v)beta(5) integrins. Compounds 15a and 15b were shown to have promising activity in functional cellular assays and compound 15a also exhibited a promising Caco-2 permeability profile.

The discovery of orally active triaminotriazine aniline amides as inhibitors of p38 MAP kinase.

A new structural class of triaminotriazine aniline amides possessing potent p38 enzyme activity has been discovered. The initial hit (compound 1a) was identified through screening the Pharmacopeia ECLiPS compound collection. SAR modification led to the identification of a short acting triaminotriazine aniline methoxyamide (compound 1m) possessing in vitro and in vivo oral activity in animal models of acute and chronic inflammatory disease. An X-ray crystal structure of compound 1m in this class, cocrystallized with unactivated p38 alpha protein, indicates that these compounds bind to the ATP binding pocket and possess key H-bonding interactions within a deeper cleft. Hydrogen bonding between one of the triazine nitrogens and the backbone NH of the Met109 residue occurs through a water molecule. The methoxyamide NH and carbonyl oxygen are within H-bonding distance of Glu71 and Asp168.