Gut Archaeal Abundance Is Impacted by the Intake Level of Dietary Nutrients

Objectives: Archaea that produce methane gas (methanogens) are the largest component of the human gut archaeome and M. smithii is believed to be the primary methanogen. There is limited fecal metagenome data examining the association between the relative abundance of archaea (i.e. as a percentage of the total metagenomic sequences) and diet. However, studies that have quantified the archaea and concomitantly assessed dietary intake are largely lacking. We hypothesize that dietary intake of specific macro- and micronutrients are associated with abundance of human gut archaea. Methods: Subjects (n=144) were selected from a pre-existing stool sample library collected prospectively among people undergoing colonoscopy to screen for colon cancer who did not have a gastrointestinal disease. Subjects completed the 2014 Block Food Frequency Questionnaire and responses were assessed with the NutritionQuest2014 FFQ Database v3 to generate calorie and macro/micronutrient intake and normalized per 1000 kcal. Fecal DNA was isolated using a Qiagen kit. General archaea, general methanogen, haloarchaea, and M. smithii abundance were measured via qPCR as gene copy number per ng of total DNA. Results: General archaea and methanogen abundance were not correlated with any of the dietary variables measured, which included carbohydrates, sugar, protein, fat, fiber, alcohol, iron, phosphorus, magnesium, potassium, sodium, zinc, copper, and selenium. M. smithii abundance was positively associated with protein (p = 0.044, ρ = 0.168), magnesium (p = 0.028, ρ = 0.184), potassium (p = 0.023, ρ= 0.191), zinc (p = 0.030, ρ = 0.182), and copper (p = 0.022, ρ = 0.192). Haloarchaea were negatively associated with intakes of total fiber (p < 0.001, ρ= -0.306), as well as soluble (p < 0.001, ρ= -0.297) and insoluble fiber (p < 0.001, ρ = -0.291), magnesium (p = 0.021, ρ = -0.196), and potassium (p = 0.007, ρ = -0.227) intake. When assessed by tertiles of intake, abundance of haloarchaea was significantly lower in the highest tertile of fiber (p = 0.002), magnesium (p = 0.032), and potassium (p = 0.047) intake (Kruskal-Wallis). Conclusions: Within the archaeome, Haloarchaea abundance followed by M. smithii abundance are most related to nutrients intake. Additional studies are needed to examine dietary intake in conjunction with clinical variables. Funding Sources: NIH NCI University of Illinois Chicago NIH T32.