Microbial diversity of aerobic heterotrophic bacteria inside the foregut of two tyrphophilous water beetle species (Coleoptera: Dytiscidae)

Using nutrient-rich and poor media 30 eutrophic or facultatively oligotrophic bacterial strains were isolated in a microbiological study of the aerobic, heterotrophic bacterial flora inside the foregut of the water beetle species Agabus affinis (Payk.) and Hydroporus melanarius Strm., 41 strains were isolated from the aquatic habitat of both beetles. A comparison is made between bacterial communities inside the beetles' gut and the surrounding environment. Furthermore a partial influence of the aquatic microflora on the bacterial colonization of the beetle foregut is discussed based on a numerical taxonomy study, which was carried out on the 71 isolates plus five reference strains using the simple matching similarity coefficient and the UPGMA clustering algorithm. Hints were found at the existence of elements of an autochthonous bacterial flora in the beetle foregut.