Will anomalies in the field of EPN associated-bacteria lead to a new paradigm?

Abstract

According to the prevailing monoxenic paradigm, entomopathogenic nematodes (EPNs) form specific association with endosymbiotic bacteria. However, many anomalies have been observed over the last 60 years, with bacterial taxa other than the known endosymbiont isolated in culture-based approaches or detected by next-generation sequencing. We have reconsidered the role of this EPN-associated microbiota — known as the second bacterial circle — in the life-cycle of EPNs. In this review, we present arguments supporting a role for certain taxa in the death of the insect and propose hypotheses concerning other properties of the bacteria involved in their interactions with EPNs. Should these functional hypotheses be confirmed, then the bacterial “anomalies” would no longer be regarded as such. Instead, they would form the basis for the establishment of a new paradigm, the polyxenic paradigm.