Researchers have recently started to catalog the symbiotic microbes found in the intestines of extremely old human individuals, aiming to gain an understanding of the degree to which differences in microbial populations between individuals can influence the odds of survival in later life. The microbial environment of the gut has been shown to influence aging in various species to a great enough degree to be worthy of investigation by those scientists who seek a full understanding of how aging progresses. From a high level perspective, consider that calorie intake is one of the most influential of environmental factors when it comes to pace of aging, and the activities of microbial populations in the gut help to determine how the amount of calories consumed maps to amounts of specific molecular constituents of food passed on to the rest of the body. There are also interactions between gut microbes and the immune system that may be important, and no doubt a range of other mechanisms to consider as well.
The study of the extreme limits of human lifespan may allow a better understanding of how human beings can escape, delay, or survive the most frequent age-related causes of morbidity, a peculiarity shown by long-living individuals. Longevity is a complex trait in which genetics, environment, and stochasticity concur to determine the chance to reach 100 or more years of age. Because of its impact on human metabolism and immunology, the gut microbiome has been proposed as a possible determinant of healthy aging. Indeed, the preservation of host-microbes homeostasis can counteract inflammaging, intestinal permeability, and decline in bone and cognitive health.
Aiming at deepening our knowledge on the relationship between the gut microbiota and a long-living host, we provide for the first time the phylogenetic microbiota analysis of semi-supercentenarians, i.e., 105-109 years old, in comparison to adults, elderly, and centenarians, thus reconstructing the longest available human microbiota trajectory along aging. We highlighted the presence of a core microbiota of highly occurring, symbiotic bacterial taxa (mostly belonging to the dominant Ruminococcaceae, Lachnospiraceae, and Bacteroidaceae families), with a cumulative abundance decreasing along with age. Aging is characterized by an increasing abundance of subdominant species, as well as a rearrangement in their co-occurrence network. These features are maintained in longevity and extreme longevity, but peculiarities emerged, especially in semi-supercentenarians, describing changes that, even accommodating opportunistic and allochthonous bacteria, might possibly support health maintenance during aging, such as an enrichment and/or higher prevalence of health-associated groups (e.g., Akkermansia, Bifidobacterium, and Christensenellaceae).