Gut microbiome alterations in the crustacean Pacifastacus leniusculus exposed to environmental concentrations of antibiotics and effects on susceptibility to bacteria challenges

Gut-associated microbiota from crustaceans is recognized as a key element for maintaining homeostasis and health in the animal. Since the richness of these microbial communities is strongly influenced by the local environment, especially in aquatic organisms, it is important to address to what extent the environmental variations can affect these communities. In the present study, we used high-throughput 16S rRNA sequencing technology to study the composition of gut-associated microbiota of crayfish Pacifastacus leniusculus maintained under controlled-laboratory conditions and crayfish from wild environments. Also, we examined if alterations of microbiota affect the host fitness, exposing crayfish to environmentally-relevant concentrations of antibiotics, and evaluating their susceptibility to bacterial diseases. As a result, we found high individual variability of bacteria abundance and composition in the intestinal microbiota of crayfish maintained under lab-conditions. Moreover, we found a significant increase in the abundance of pathogenic bacteria, including Vibrio sp. in the wild organisms exposed to antibiotics. However, when antibiotic-exposed crayfish susceptibility to bacterial infections was tested, including Vibrio species, the crayfish survived longer. This study represents the first approach for investigating the interplay between host and intestinal bacteria during antibiotic-pollution scenarios. Results herein should be considered by scientists before planning experiments under lab-conditions, especially to study environmental effects on aquatic animals' intestinal health.