Publications in peer reviewed journals
Lifestyle and horizontal gene transfer-mediated evolution of Mucispirillum schaedleri, a core member of the murine gut microbiota2017 - mSystems, 2: e00171-16
Mucispirillum schaedleri is an abundant inhabitant of the intestinal mucus layer of rodents and other animals and has been suggested to be a pathobiont, a commensal that plays a role in disease. In order to gain insights into its lifestyle, we analyzed the genome and transcriptome of M. schaedleri ASF 457 and performed physiological experiments to test traits predicted by its genome. Although described as a mucus inhabitant, M. schaedleri has limited capacity for degrading host-derived mucosal glycans and other complex polysaccharides. Additionally, M. schaedleri reduces nitrate and expresses systems for scavenging oxygen and reactive oxygen species in vivo, which may account for its localization close to the mucosal tissue and expansion during inflammation. Also of note, M. schaedleri harbors a type VI secretion system and putative effector proteins and can modify gene expression in mucosal tissue, suggesting intimate interactions with its host and a possible role in inflammation. The M. schaedleri genome has been shaped by extensive horizontal gene transfer, primarily from intestinal Epsilon- and Deltaproteobacteria, indicating that horizontal gene transfer has played a key role in defining its niche in the gut ecosystem.
Hidden potential: Diet-driven changes in redox level shape the rumen microbiome2017 - Environmental Microbiology, 1: 19-20
The unexpected versatility of the cellulosome2017 - Environmental Microbiology, 1: 13-14
Microbial nutrient niches in the gut2017 - Environ. Microbiol., in press
The composition and function of the mammalian gut microbiota has been the subject of much research in recent years, but the principles underlying the assembly and structure of this complex community remain incompletely understood. Processes that shape the gut microbiota are thought to be mostly niche-driven, with environmental factors such as the composition of available nutrients largely determining whether or not an organism can establish. The concept that the nutrient landscape dictates which organisms can successfully colonize and persist in the gut was first proposed in Rolf Freter's nutrient niche theory. In a situation where nutrients are perfectly mixed and there is balanced microbial growth, Freter postulated that an organism can only survive if it is able to utilize one or a few limiting nutrients more efficiently than its competitors. Recent experimental work indicates, however, that nutrients in the gut vary in space and time. We propose that in such a scenario, Freter's nutrient niche theory must be expanded to account for the co-existence of microorganisms utilizing the same nutrients but in distinct sites or at different times, and that metabolic flexibility and mixed-substrate utilization are common strategies for survival in the face of ever-present nutrient fluctuations.
A 12-week intervention with nonivamide, a TRPV1 agonist, prevents a dietary-induced body fat gain and increases peripheral serotonin in moderately overweight subjects2017 - Mol Nutr Food Res, in press
A bolus administration of 0.15 mg nonivamide has previously been demonstrated to reduce energy intake in moderately overweight men. This 12-week intervention investigated whether a daily consumption of nonivamide in a protein-based product formulation promotes a reduction in body weight in healthy overweight subjects, and affects outcome measures associated with mechanisms regulating food intake, e.g. plasma concentrations of an-/orexigenic hormones, energy substrates as well as changes in fecal microbiota .
Nineteen overweight subjects were randomly assigned to either a control (C) or a nonivamide group (NV). Changes in the body composition and plasma concentrations of satiating hormones were determined at fasting and 15, 30, 60, 90 and 120 min after a glucose load. Participants were instructed to consume 0.15 mg nonivamide per day in 450 mL of a milk shake additionally to their habitual diet. After treatment, a group difference in body fat mass change (- 0.61 ± 0.36 % in NV and + 1.36 ± 0.38 % in C), and an increase in postprandial plasma serotonin were demonstrated. Plasma metabolome and fecal microbiome read outs were not affected.
A daily intake of 0.15 mg nonivamide helps to support to maintain a healthy body composition. Nonivamide, a less-pungent capsaicin analog, was studied for its potential as an anti-obesity agent in a 12-week human intervention study. The body composition was determined at the beginning and in the end of intervention. Moreover, plasma concentrations of satiating hormones were measured Participants were instructed to drink the product formulation three times daily. After treatment, a group difference in body fat mass change, and an increase in postprandial plasma serotonin concentrations were determined in the nonivamide group. Thus, we suppose that a daily intake of nonivamide might help to maintain a healthy body composition. This article is protected by copyright. All rights reserved.
Stable isotope techniques for the assessment of host and microbiota response during gastrointestinal dysfunction2017 - J Pediatr Gastroenterol Nutr, 64: 8-14
The International Atomic Energy Agency convened a technical meeting on environmental enteric dysfunction (EED) in Vienna (28th – 30th October 2015; https://nucleus.iaea.org/HHW/Nutrition/EED_Technical_Meeting/index.html) to bring together international experts in the fields of EED, nutrition and stable isotope technologies. Advances in stable isotope labelling techniques open up new possibilities to improve our understanding of gastrointestinal dysfunction and the role of the microbiota in host health. In the context of EED, little is known about the role gut dysfunction may play in macro- and micronutrient bioavailability and requirements and what the consequences may be for nutritional status and linear growth. Stable isotope labelling techniques have been used to assess intestinal mucosal injury and barrier function, carbohydrate digestion and fermentation, protein derived amino acid bioavailability and requirements, micronutrient bioavailability and to track microbe-microbe and microbe-host interactions at the single cell level. The non-invasive nature of stable isotope technologies potentially allows for low-hazard, field deployable tests of gut dysfunction that are applicable across all age-groups. The purpose of this review is to assess the state-of-the-art in the use of stable isotope technologies and to provide a perspective on where these technologies can be exploited to further our understanding of gut dysfunction in EED.
Pediatric obesity is associated with an altered gut microbiota and discordant shifts in Firmicutes populations2017 - Environ. Microbiol., 1: 95-105
An altered gut microbiota has been linked to obesity in adulthood, although little is known about childhood obesity. The aim of this study was to characterize the composition of the gut microbiota in obese (n = 42) and normal-weight (n = 36) children aged 6 to 16. Using 16S rRNA gene-targeted sequencing, we evaluated taxa with differential abundance according to age- and sex-normalized body mass index (BMI z-score). Obesity was associated with an altered gut microbiota characterized by elevated levels of Firmicutes and depleted levels of Bacteroidetes. Correlation network analysis revealed that the gut microbiota of obese children also had increased correlation density and clustering of operational taxonomic units (OTUs). Members of the Bacteroidetes were generally better predictors of BMI z-score and obesity than Firmicutes, which was likely due to discordant responses of Firmicutes OTUs. In accordance with these observations, the main metabolites produced by gut bacteria, short chain fatty acids (SCFAs), were higher in obese children, suggesting elevated substrate utilisation. Multiple taxa were correlated with SCFA levels, reinforcing the tight link between the microbiota, SCFAs and obesity. Our results suggest that gut microbiota dysbiosis and elevated fermentation activity may be involved in the etiology of childhood obesity.