Three decades have passed since a few pioneers envisionedthe need to concert efforts and foster research of nitrogen-fixing root-nodule symbioses between Frankia and a widetaxonomic range of dicotyledonous plants (Torrey andTjepkema 1979). In those days, the excitement was high:the first Frankia isolates were established in pure culture;ultramicroscopic studies of root nodules and Frankia iso-lates revealed the colonial and pleomorphic organization ofthis actinobacteria; nitrogen-fixation efficiency was mea-sured and compared in both free-living and symbioticfrankiae; host specificity was addressed by cross-inocula-tion experiments; importance of actinorhizal symbioses forland reclamation was discussed and their implications forthe silvicultural and agricultural sustainability in diverseecosystems were debated (Gordon et al. 1979). Nowadays,new questions arose but the enthusiasm remains the same.In fact, while some challenging issues have been addres-sed, such as the innovative protection of nitrogenase tooxygen damage by a hopanoid lipidic multilayer wrappingFrankia vesicles, and the matchless plasticity of frankiaegenomes, other fundamental queries are yet to beanswered, namely the molecular signals that modulate ac-tinorhizal infection and Frankia—plant hosts specificityand the implementation of a reliable and efficient systemfor genetic manipulation of Frankia.The 16th International Meeting on Frankia and Ac-tinorhizal plants, held from the 5th to the 8th of Septemberof 2010 in Porto, Portugal, gathered frankiologists fromfour continents. Longtime friends and colleagues have metand some of them brought new people, eager to learn, todiscuss their data and to peek new opportunities. Franki-ologists have been working side by side with plant biolo-gists to improve our understanding of actinorhizalsymbioses. Therefore, besides the studies focused onFrankia, this meeting brought up relevant progresses onseveral aspects of actinorhizal plant biology, out of which aseries of manuscripts have been written and compiled on aspecial double issue of Functional Plant Biology (2011, vol38, issues 8 and 9). Concerning the microbial symbiont, therecent advances and the availability of several Frankiagenomes completed or on their way, prompted comparativegenomic analyses which complemented the proteomic andtranscriptomic studies, leading to an overall optimisticview of the coming years.In this issue of Archives of Microbiology, forefrontresearch in Frankia is illustrated by several papers. Startingwith a retrospective of nitrogen fixation in Actinobacteria,an important trait once thought to be exclusive of Frankiaspp. within this phylum, Gtari et al. review the sparsephysiological and biochemical studies made these last50 years and emphasize that nitrogen fixation within ac-tinobacteria is unlikely to be restricted to frankiae.Although most of these reports need to be confirmed anddirect evidence for nitrogenase activity is missing, theycertainly do constitute a starting point for further studies.