LAUSR

Unlike some subgroups of humans, bacteria live in “cultured” and highly diverse communities. About a decade ago, Sibley et al. [1] discovered that the composition of the bacterial population residing within the airways is an important determinant of lung infection severity and overall health of cystic fibrosis patients [1]. Accordingly, managing the composition of the microbial community was proposed to improve response to treatment when a given organism, such as Pseudomonas aeruginosa, becomes resistant to antibiotic therapy. Given that pulmonary infection is a primary complication of cystic fibrosis, the link between microbial diversity and a respiratory disorder was certainly obvious. Froma conceptual perspective, however, the study of O'Connor et al published in this issue of EBioMedicine stands out as it clearly demonstrates that disruption of microbial diversity within the gut has more far reaching consequences as it is capable of disrupting the brain circuits that regulate breathing [2]. Although it is nowwell established that a broad range of respiratory and non-respiratory stressors (e.g. intermittent hypoxia, neonatal maternal separation, respectively) can impart plasticity in respiratory control, the link between changes in gut bacterial population dynamics and anomalies in respiratory reflexes is, at first, far from intuitive. However, in light of the recent wave of discoveries on microbiota-gut-brain signalling, this should not come as a surprise. To respiratory physiologists, the vagus nerve and its main projection site (the nucleus of the solitary tract) convey essential sensory signals to respiratory neurons; yet, these structures also happen to be the main pathways by which the bidirectional interactions between the gut and the brain take place [3]. Linking these concepts therefore makes for a novel and compelling hypothesis, but testing it rigorously is a different story. To achieve this feat, O'Connor et al at University College Cork combined their expertise in respiratory physiology, nutrition, psychiatry, andmicrobiology to determinewhethermanipulation of gutmicrobiota