The urban microbiome and the rural microbiome: Comparing communities across the industrialization spectrum
A team of international researchers funded by the French National Center of Scientific Research compared the microbiomes of 60 mother and infant pairs from rural and urban Senegal to identify features associated with industrialization.
“We find that urban mothers, who were more frequently overweight, had different gut microbiome compositions than rural mothers, showing an expansion of Lachnospiraceae and Enterobacter,” the researchers wrote in the journal Cell Press. “Urban infants, on the other hand, showed a delayed gut microbiome maturation and a higher susceptibility to infectious diseases.”
The study recruited mothers and their infants from the Fula ethnic group to eliminate the genetic confounder and evaluated gut microbiota by stool sample at two different time points—within six months of delivery and one year later after all infants had been introduced to solid foods.
A contrast in lifestyle
The individuals enrolled in the urban group resided in Senegal’s capital Dakar, where living conditions and diets contrast strongly with those of participants recruited from the Widou Thiengoli area at the edge of the Sahara Desert to the north.
While Dakar dwellers live with modern adaptations including electricity, running water, healthcare, education and a globalized diet, the rural Fulani continue to follow a nomadic pastoral lifestyle and a diet largely composed of fermented dairy products, cowpea, rice and millet.
The researchers noted the known role that gut microbiome composition plays in biological processes, including metabolism, immunity and behavior, as well as its plasticity in response to shifting lifestyle and environmental factors found in a “decidedly post-industrial” environment like that of Dakar.
“The post-industrial microbiome has drifted significantly from its pre-industrial state and several health conditions that are more common in industrialized societies such as obesity and inflammatory bowel disease are known to be linked with microbiome composition," they wrote.
The post-industrial drift
The study observed that urban Fulani mothers had less Enterococcus and Lactococcus (both found in fermented dairy foods) and an increased prevalence of Lachnospiraceae and Enterobater (associated with obesity).
Meanwhile, beta diversity between urban mothers and infants was found to be higher than between rural mothers and infants at both time points, and urban infants exhibited a lower alpha diversity at the second time point, which the researchers linked to higher rates of respiratory and dermatologic infections.
“Our results clearly show that urbanization associates with changes in gut microbiome composition in both adults and infants, although seemingly, in very different ways between the two groups,” the researcher wrote. “While urbanization associated with slowed growth of alpha diversity in infants, it seemed to slightly boost it in mothers.”
They deduced that urbanization alters the gut microbiome composition in mothers by promoting or inhibiting the growth of specific commensals by yet unknown mechanisms while delaying maturation in infants by limiting the exposure to diverse genera.
Despite the range of health and lifestyle data gathered, the study was not able to pinpoint what modern practices were responsible for the drift in the microbiome, whether related to nutrition, work, social structure, sanitization, antibiotics, parasite colonization, pollution or human density.
"We hope that continued efforts in studying the transition from pre- to post-industrial microbiomes will help produce treatments and health recommendations that prevent the emergence of non-communicable diseases as more of the world becomes industrialized," it concluded.
Source: Cell Press
“Urbanization associates with restricted gut microbiome diversity and delayed maturation in infants”
doi: doi.org/10.1016/j.isci.2023.108136
Authors: Francesco Morandini, et al.
