Babies born by caesarean section are more likely to have altered gut microbiota profiles that leave them susceptible to colonization by disease-causing bacteria, according to a study appearing in Nature this week. Scientists from the Wellcome Sanger Institute applied longitudinal sampling and whole-genome shotgun metagenomic analysis to 1,679 gut microbiota samples — taken at various time points just after birth and through infancy — from 596 full-term babies born in UK hospitals. Of these, 314 were delivered vaginally and 282 via c-section. The researchers found that babies delivered by c-section experienced decreased transmission of maternal commensal bacteria and a higher incidence of colonization with drug-resistant opportunistic pathogens, likely of environmental origin. Notably, 83.7 percent of babies delivered by c-section carried opportunistic pathogen species versus 49.4 percent of those delivered vaginally. The findings "highlight the critical role of the local environment in establishing the gut microbiota in very early life, and identify colonization with antimicrobial-resistance-containing opportunistic pathogens as a previously underappreciated risk factor in hospital births," the study's authors write. Genome Web has more on this study, here.
A new study has uncovered genomic evidence of the impact of human activity on Vavilovian mimicry, the process by which weeds evolve to resemble domesticated crop plants at certain life stages to avoid eradication. A team of US and Chinese scientists compared mimetic and non-mimetic populations of the Asian wild grass Echinochloa crus-galli phenotypically and through genome sequencing, and show that the weed in rice patties has evolved to copy the appearance of cultivated rice at the seedling stage. Writing in Nature Ecology & Evolution, the team also presents data showing that mimetic lines evolved from the non-mimetic population as recently as 1,000 years ago and were subject to a genetic bottleneck, and that genomic regions containing 87 putative plant architecture-related genes were under selection during the mimicry process.