A longitudinal study of perturbations on gut microbiota of Blattella germanica due to periodic antibiotic treatment

Resumen

Symbiosis is a widespread phenomenon in nature and can be defined as a close, long-term biological interaction between two or more species. Although most iconic symbiotic relationships are between eukaryotes and other eukaryotes, they have also formed symbiosis with bacteria and archaea. In this thesis we focus mainly in the symbiosis between insects, specifically the cockroach Blattella germanica and its gut microbiota. In these kinds of relationships insects usually gain the capability of feeding on poor-nutrient diets thanks to the prokaryotic metabolism, and bacteria gains protection and an easy source of nutrients from the host diet. The intestinal tract can harbor a great diversity of microorganisms that perform an even greater diversity of metabolic reactions that are not available for eukaryotes. This is the case for humans and other mammals, but also for some social insects such as termites, bees or cockroaches. Metagenomic studies on microbiota are usually focused in the state of the microbiota under some stress or different conditions such as diet changes, antibiotic intake, age differences, host genetics or treatments. But there is one factor that is usually left aside, the factor of time continuity. This is important to check the evolution of the changes and not only have a static picture of the final state. Longitudinal studies allow us to take pictures of the state of microbiota in different moments. In this thesis, we performed a longitudinal experiment with five populations of cockroaches with a duration of 105 days. Three of them were treated with the antibiotic kanamycin and the other two, were control populations. In this study we performed bioinformatic analyses in order to assess the diversity of the microbiota under antibiotic treatment pressure during time. We also checked the microbiota stability, co-occurrence, resilience, robustness, changes in the functional profile using PICRUSt2, and the effect of the antibiotic on the fitness of the cockroaches. We found that gut microbiota diversity is affected by kanamycin and that there are some taxa such as Lachnosclostridium and Parabacteroides that are especially resilient. We also found that phylogenetically similar taxa tend to have a similar response to treatment and the functional profile of the microbiota is affected by kanamycin treatment. Finally, antibiotic is not affecting the health status of the insect.