Acute stressor alters inter-species microbial competition for resistant starch-supplemented medium

Abstract

Gut microbiome community dynamics are maintained by complex microbe-microbe and microbe-host interactions, which can be disturbed by stress. In vivo studies on the dynamics and manipulation of those interactions are costly and slow, but can be accelerated using in vitro fermentation. Herein, in vitro fermentation was used to determine how an acute stressor, a sudden change in diet, impacts interbacterial species competition for resistant starch-supplemented medium (RSM). Fermentation vessels were seeded with fecal samples collected from 10 individuals consuming a habitual diet or U.S. military rations for 21 days. Lactobacillus spp. growth in response to RSM was attenuated following ration consumption, whereas growth of Ruminococcus bromii was enhanced. These differences were not evident in the pre-fermentation samples. Findings demonstrate how incorporating in vitro fermentation into clinical studies can increase understanding of stress-induced changes in nutrient-microbiome dynamics, and suggest that sudden changes in diet may impact inter-species competition for substrates.

Dietary vitamin K is remodeled by gut microbiota and influences community composition

“…A nutrient-rich, anaerobic fermentation medium mimicking ileal chyme, complex colonic medium (CCM), 42 was prepared and added to bioreactor reactor vessels assembled as previously described. 43 Bioreactors were kept at physiologic temperature under a constant flow of nitrogen to ensure anaerobicity, and pH was maintained at pH = 6.8 to mimic the conditions of the distal colon. Vitamin K or pre-vitamin K quinones ( 2 H 8 MD, 2 H 7 PK, 2 H 7 MK4, 2 H 7 MK9) were solubilized in Tween-80/acetone mixture, dried down under nitrogen, and then reconstituted in 5.0 mL water prior to addition to fermentation vessels.…”

Meeting report of the third annual Tri-Service Microbiome Consortium symposium

“…That work suggested that previous observations of increased intestinal permeability and inflammation in Soldiers consuming military rations in austere environments [25,26] were more likely due to environmental stressors [27] than any impact of the ration diet on the gut microbiota. Additionally, differential changes in gut microbiota community composition and genetic content following consumption of the ration diet were discovered using an in vitro gut model [5], findings which highlighted how in vitro gut models can be used to study critical nutrient-gut microbiota interactions that cannot be readily examined in vivo.…”

“…Over the 3 day symposium, 45 speakers (51% female, 13% underrepresented minority) which included 26 speakers (10 early-career) from government laboratories (Table 1), four from DoD-affiliated laboratories, twelve from academic institutions, and three from commercial companies presented on microbiome-related topics within five broad thematic areas: 1) human microbiomes; 2) transitioning products into Warfighter solutions; 3) environmental microbiomes; 4) engineering microbiomes; and 5) microbiome simulation and characterization. Additionally, 130 registered attendees (65% government, 8% DoD-affiliated, 13% academia, 14% industry) engaged with 30 poster presenters (83% government, 7% DoDaffiliated and 10% industry), and participated in mediated discussions centered on bioinformatics and Use of in vitro human gut models to extend insight into clinical study on effects of military food rations on the gut microbiota [4,5] USACEHR/ WRAIR Human microbiomes: Warfighter performance (stress, diet and the gut microbiome)…”

In Vitro Gut Microbiome Response to Carbohydrate Supplementation is Minimally Affected by a Sudden Change in Diet

“…That approach allowed inter-species competition in samples collected before and after the MRE intervention and at the same time points in a control group to be studied over the time scale of hours, which is not feasible in in vivo human studies which commonly rely on daily stool samples. Ruminococcus bromii, a keystone taxa and resistant starch degrader, increased in relative abundance during the MRE diet in the presence of RS2 while the ability of Lactobacillus to compete in presence of RS2 appeared to be reduced [7]. However, those results were limited in that only a few selected taxa were measured, the identity of which Lactobacillus species affected could not be elucidated, and differences in functional capacity of the community could not be examined nor the whole community metabolic response to RS both compositionally and functionally.…”

“…Herein we report a comprehensive genomic analysis employing both 16S rRNA gene amplicon and whole genome sequencing (WGS) of samples collected during the in vitro fermentation experiment described in Pantoja-Feliciano et al 2019 [7] to reveal in uence of a sudden change in diet on whole bacterial community composition and functional potential. To explore stress-induced microbial community responses, carbohydrate content, speci cally RS, in medium was increased ve-fold to allow the study of nutrient:microbiome interactions that cannot easily be explored in vivo [7].…”