Endophytic bacteria discovered in oil body organelles of the liverworts Marchantia polymorpha and Radula complanata.

Abstract

Premise: Interactions between endophytic microbes and bryophytes have been understudied. The liverwort oil body has also remained poorly understood since its discovery, and modern studies have failed to ascertain its function and composition. Many liverwort species possess oil bodies with conspicuous granules of unknown structure. We surveyed these granular liverwort oil bodies for the presence of bacteria to improve upon the understanding of liverworts, their oil bodies, and bacterial endophytes in nonvascular land plants.

Methods: Wild-collected specimens from living samples of Marchantia polymorpha and Radula complanata were stained with SYTO-13 and RADA to determine the presence or absence of bacteria within their oil bodies. Samples stained with calcofluor white, SYTO-13, and RADA were observed with confocal fluorescent microscopy for presence of nucleic acids and bacterial peptidoglycan cell walls within oil bodies.

Results: We discovered large masses of bacteria within the oil bodies of M. polymorpha and R. complanata based on the presence of stained nucleic acids and peptidoglycans localized to the oil body "granules". Such bacteria were present in all oil bodies of the two species.

Conclusions: These newly discovered intraorganellar bacteria correspond to the previously described "granules" of oil bodies. The existence of granular oil bodies in many liverwort species implies that this endophytic association may not be isolated to species investigated here. Assessments of additional liverwort species for presence and identity of oil body bacteria are needed to understand this intriguing association in one of the oldest land plant lineages.