The 16S rRNA gene is a component of the ribosome in bacteria. It conveniently contains (a) highly conserved sections, allowing this gene sequence to be reliably found in DNA samples from any bacterial species, but also (b) regions that vary widely by species, allowing for the identification of the bacterial species of origin. Thus the 16S rRNA region of bacterial genomes can cost-effectively sequenced in bulk from any sample, and the data analyzed to produce an assessment of which bacterial species are present, and in what relative proportions. In the case of the gut microbiome, fecal samples lead to a map of the bacterial populations of the intestine.
The composition of the gut microbiome is presently thought to be influential on long term health. The relative proportions of bacterial species making up the gut microbiome change with age, for reasons that include diet and immune system dysfunction, but which are far from fully explored in detail. Nonetheless, in a world in which it costs little to gather this data, greater understanding will come in time. In recent years, the research community has demonstrated correlations between gut microbiome composition and chronological age, as well as the presence of specific age-related conditions. It seems likely based on animal studies that ways to produce lasting, calibrated restoration of a youthful balance of microbial populations can be produced from the starting point of fecal microbiota transplantation, and that this class of therapy will provide to be beneficial for all older people.
Identification of age-associated microbial changes via long-read 16S sequencing
In this study, we investigated the association between age and gut microbial composition in individuals residing in Singapore. To the best of our knowledge, this is the first full-length 16S rRNA gene assessment of the gut microbiota in a multi-ethnic country. Previous studies evaluating the effect of age on the gut microbiome primarily used a short-read 16S rRNA gene sequencing approach. The limited resolution of short-read sequencing often fails to detect bacterial changes at the species/strain level, which can affect data interpretation. In our work, we utilized the long-read sequencing approach to explore age-related gut microbiome alterations for the first time. In addition to replicating previous findings, our study unveiled several novel differentially abundant taxa and predicted functional pathways associated with age.
Despite the insignificant differences in alpha diversity and beta diversity, several differentially abundant bacterial taxa were detected among the age groups. For instance, a notable decrease in Bacteroides uniformis was observed in the gut microbiome of middle-aged individuals, while Bacteroides plebeius was significantly elevated in the old group. These findings align with multiple earlier studies, which reported contrasting findings on the abundances of Bacteroides in the gut microbiome of individuals from different age groups. Some studies documented increased levels in younger adults, while others reported higher abundances in the elderly group. Interestingly, recent investigations have also linked the differential abundance of Bacteroides to the overall health status of the study group. Collectively, these findings underscore the importance of employing sequencing techniques that provide precise taxonomic assignments down to the species/strain level, thereby facilitating a more comprehensive delineation of the gut microbiome and permitting a more accurate understanding of the microbial ecology associated with specific conditions.
In the pairwise comparison between middle-aged and old groups, we found that elderly individuals exhibited a significantly higher abundance of Klebsiella pneumoniae (as well as the Klebsiella genus) in their gut microbiome. The elevated level of K. pneumoniae in older individuals is believed to be associated with factors such as increased use of medication or inflammation linked to interleukin-6, both of which are common in older individuals. This bacterium, which is known to be a pathogen, may contribute to health issues frequently observed in this age group.
Besides replicating previous research findings, our study revealed several novel differentially abundant bacterial species that have not been previously reported. These include increased abundances of Eggerthella lenta in middle-aged participants and reduced levels of Catenibacterium mitsuokai in elderly individuals. E. lenta, a bacterium belonging to the Coriobacteriaceae family, is known as an opportunistic pathogen implicated in various conditions and infections. C. mitsuokai, on the other hand, is generally considered part of the normal human gut microbiome. Previous studies have linked C. mitsuokai with dyslipidemia and insulin resistance, and a higher abundance of the Catenibacterium genus has been associated with a potentially lower risk of frailty. Altogether, these findings suggest potential health implications related to changes in the levels of C. mitsuokai in the gut microbiome. The observed reduction of C. mitsuokai in elderly individuals of our cohort could either reflect age-related alterations in gut microbiome composition or represent a compensatory response to the health changes commonly seen in old individuals.
View the full article at FightAging
