For example, the proportion of Bacteroides , a common microbe found in the microbiota, has been found to be higher in elderly individuals, 20 although other studies have shown a decreasing trend, 21–24 and other studies have demonstrated that the ratio of Bacteroides does not influence life expectancy. 24 At the group level, the proportions of Lactobacilli and Prevotella , in addition to Faecalibacterium prausnitzii , are significantly lower, 23 whereas the proportions of Actinobacteria (A
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