This study investigates how the Firmicutes/Bacteroidetes ratio in the human microbiota changes with age. The research compared the fecal microbiota of infants, adults, and the elderly. Using quantitative PCR (qPCR), the study assessed the abundance of major bacterial groups, including Clostridium leptum, Clostridium coccoides, Bacteroidetes, Bifidobacterium, Lactobacillus, and Escherichia coli. The results showed that the microbiota of infants was characterized by low bacterial counts, with high levels of C. leptum and C. coccoides, while elderly individuals had higher levels of E. coli and Bacteroidetes. The Firmicutes/Bacteroidetes ratio was found to change during different life stages, with ratios of 0.4 in infants, 10.9 in adults, and 0.6 in the elderly. The study confirmed that qPCR is a powerful technique for studying the complex fecal microbiota. It demonstrated that the fecal microbiota composition evolves throughout life, from early childhood to old age. The microbiota of infants was dominated by Bifidobacterium, while in adults and the elderly, the ratio of Firmicutes to Bacteroidetes was higher in adults. The study also found that the microbiota of the elderly showed a decrease in Bifidobacteria and Bacteroides, along with a decrease in Lactobacilli, and an increase in facultative anaerobes. The Firmicutes/Bacteroidetes ratio was significantly different between infants and adults, and between adults and the elderly, but not between infants and the elderly. The study highlights the importance of the microbiota in human health and the need for further research into its changes with age. The findings suggest that the microbiota undergoes significant changes during different life stages, and that the Firmicutes/Bacteroidetes ratio can be used as a marker for variations between different age groups.This study investigates how the Firmicutes/Bacteroidetes ratio in the human microbiota changes with age. The research compared the fecal microbiota of infants, adults, and the elderly. Using quantitative PCR (qPCR), the study assessed the abundance of major bacterial groups, including Clostridium leptum, Clostridium coccoides, Bacteroidetes, Bifidobacterium, Lactobacillus, and Escherichia coli. The results showed that the microbiota of infants was characterized by low bacterial counts, with high levels of C. leptum and C. coccoides, while elderly individuals had higher levels of E. coli and Bacteroidetes. The Firmicutes/Bacteroidetes ratio was found to change during different life stages, with ratios of 0.4 in infants, 10.9 in adults, and 0.6 in the elderly. The study confirmed that qPCR is a powerful technique for studying the complex fecal microbiota. It demonstrated that the fecal microbiota composition evolves throughout life, from early childhood to old age. The microbiota of infants was dominated by Bifidobacterium, while in adults and the elderly, the ratio of Firmicutes to Bacteroidetes was higher in adults. The study also found that the microbiota of the elderly showed a decrease in Bifidobacteria and Bacteroides, along with a decrease in Lactobacilli, and an increase in facultative anaerobes. The Firmicutes/Bacteroidetes ratio was significantly different between infants and adults, and between adults and the elderly, but not between infants and the elderly. The study highlights the importance of the microbiota in human health and the need for further research into its changes with age. The findings suggest that the microbiota undergoes significant changes during different life stages, and that the Firmicutes/Bacteroidetes ratio can be used as a marker for variations between different age groups.