A recent study has taken an in-depth look at the age-related changes that occur in the microbiome, particularly in regards to bacterial populations.
A detailed look at bacterial populations in the gut microbiome
The publication contains multiple graphs that track age-related changes to various bacterial populations in the gut. These graphs show a common trend: the abundance of these bacterial species increases with aging but then falls significantly in extreme old age. On these charts, Groups 1-5 contain various ages of children, Group 6 consists of 19- to 29-year-olds, and each following group is ten years older than the previous, with Group 14 containing 99- to 110-year-olds.
Lactobacillus includes lots of different species and are considered “friendly” bacteria that are normally found in the gut, urinary, and genital systems. They are also present in some types of fermented foods, such as yogurt and probiotics. They are a major part of the lactic acid bacteria group, which converts sugars into lactic acid. Lactobacillus has a symbiotic relationship with the human body, protecting the host against harmful invading pathogens and receiving a source of nutrients in return. As this chart shows, the population of Lactobacillus increases relative to advancing age, reaching its peak in the 79-89 age group (Group 12) but then declines rapidly beyond this.
The same was largely true of Oscillospira, as its population stayed relatively small during youth but rose rapidly in the 69-79 age group (Group 11) followed by a large decline after this. While poorly studied, these bacteria are often observed in significantly greater numbers in lean people than obese people. Oscillospira bacteria are important for breaking down dietary fiber, so more of them may be present in people who eat plant-based diets, particularly diets containing nuts . In general, it would appear that these particular bacteria are beneficial to health in old age, though there needs to be more research to ascertain exactly how.
Oxalobacter, in particular Oxalobacter formigenes, has a key role in breaking down oxalate in the gut, helping to prevent hyperoxaluria, which is characterized as an excessive urinary excretion of oxalate. Oxalate is created in the liver by amino acid catabolism and is also present in a wide array of food and drinks, such as chocolate, fruit, vegetables, tea, and coffee. An excessive concentration of oxalate passed via the urine is an important step in the development of kidney stones, so species like oxalobacter play an important role in degrading oxalate to avoid this issue. Once again, this species’ presence remains relatively low in earlier life, increasing significantly in later life then dramatically falling during advanced age.
Prevotellaceae is composed of four genera; the genus prevotella is of the greatest interest due to its role in the human gut microbiome, where bacteria of this genus help break down protein and carbohydrates in foods. The presence of Prevotella in the human gastrointestinal tract is inversely correlated with the development of Parkinson’s disease . Again, we see the pattern that this particular bacterial genus tends to increase in population towards later life then rapidly declines in advanced age.
Human gut microbiota are important for human health and have been regarded as a “forgotten organ”, whose variation is closely linked with various factors, such as host genetics, diet, pathological conditions and external environment. The diversity of human gut microbiota has been correlated with aging, which was characterized by different abundance of bacteria in various age groups. In the literature, most of the previous studies of age-related gut microbiota changes focused on individual species in the gut community with supervised methods. Here, we aimed to examine the underlying aging progression of the human gut microbial community from an unsupervised perspective.
The multivariate unsupervised analysis here revealed the existence of a continuous aging progression of human gut microbiota along with the host aging process. The identified genera associated to this aging process are meaningful for designing probiotics to maintain the gut microbiota to resemble a young age, which hopefully will lead to positive impact on human health, especially for individuals in advanced age groups.
The connection between the gut microbiome, health, and aging is becoming ever more apparent. These are only a few of the bacteria that the paper looks at, and we urge you to read the full study and the wealth of information contained within.
 Muralidharan, J., Galiè, S., Hernández-Alonso, P., Bulló, M., & Salas-Salvadó, J. (2019). Plant based fat, dietary patterns rich in vegetable fat and gut microbiota modulation. Frontiers in nutrition, 6, 157.
 Unger, M. M., Spiegel, J., Dillmann, K. U., Grundmann, D., Philippeit, H., Bürmann, J., … & Schäfer, K. H. (2016). Short chain fatty acids and gut microbiota differ between patients with Parkinson’s disease and age-matched controls. Parkinsonism & related disorders, 32, 66-72.