The more scientists investigate the microbes living inside us, the more they learn about the surprising impact of these tiny organisms on how we look, act, think, and feel. Are our health and well-being really driven by the bacteria, viruses, fungi, and protozoa that live in our intestines, in our lungs, on our skin, on our eyeballs? What a weird concept—that the bugs we lug around appear to be essential to establishing the basic nature of who we are.
The effects of the microbiome, this menagerie of microorganisms, can be profound—and can start incredibly early. In a study published last year, scientists showed that something supposedly as innate as a child’s temperament might be related to whether the bacteria in an infant’s gut are predominantly from one genus: the more Bifidobacterium bugs, the sunnier the baby.
This observation, from Anna-Katariina Aatsinki and her colleagues at the University of Turku in Finland, is based on an analysis of stool samples from 301 babies. Those with the highest proportion of Bifidobacterium organisms at two months were more likely at six months to exhibit a trait the researchers called “positive emotionality.”
