WASHINGTON (Dispatches) -- An antibiotic commonly found at low concentrations in the environment can have major impacts on gut bacteria, report researchers at the University of Oregon.
The study applied three-dimensional microscopy to nearly transparent zebrafish to show how weak levels of antibiotics induce structural changes in gut bacterial communities that cause severe drops in the bacterial populations.
Zebrafish larvae are a good model for tackling the mystery, Parthasarathy said, because they share many anatomical similarities with humans and other vertebrates, and their intestinal microbes can be directly observed.
Doctoral student Brandon H. Schlomann and postdoctoral researcher Travis J. Wiles led the project, in which larvae were observed with 3D microscopy as they were exposed to concentrations of the antibiotic ciprofloxacin at levels comparable to that often found in environmental samples.
The researchers looked separately at zebrafish carrying one of two different bacterial species that are each frequently found in the zebrafish gut. Bacteria of one of the species are motile and fast-swimming. Bacteria of the other species are almost completely aggregated in dense colonies.
In the presence of the antibiotic, both types of bacteria showed dramatic changes in their behavior. The normally motile species became much slower and formed aggregates. The normally aggregated species shifted in structure to form even larger colonies, with less fragmentation.