Lichens are remarkable and classic examples of symbiotic organisms that have fascinated scientists for centuries. Yet, it has only been for a couple of decades that significant advances have focused on the diversity of their green algal and/or cyanobacterial photobionts. Cyanolichens, which contain cyanobacteria as their photosynthetic partner, include up to 10% of all known lichens and, as such, studies on their cyanobionts are much rarer compared to their green algal counterparts. For the unicellular cyanobionts, i.e. cyanobacteria that do not form filaments, these studies are even scarcer. Nonetheless, these currently include at least 10 different genera in the cosmopolitan lichen order Lichinales. An international consortium (International Network of CyanoBionts; INCb) will tackle this lack of knowledge. In this article, we discuss the status of current unicellular cyanobiont research, compare the taxonomic resolution of photobionts from cyanolichens with those of green algal lichens (chlorolichens), and give a roadmap of research on how to recondition the underestimated fraction of symbiotic unicellular cyanobacteria in lichens.

Aristotle University of Thessaloniki Thessaloniki Greece

Botanical Research Institute of Texas United States

Dahlem Centre of Plant Sciences Freie Universität Berlin Berlin Germany

Department of Botany Faculty of Science University of South Bohemia České Budějovice Czech Republic

Herbarium Hamburgense Institute of Plant Science and Microbiology University of Hamburg Hamburg Germany

IES Tinajo Lanzarote Spain

Institute for Experimental Physics Freie Universität Berlin Berlin Germany

Institute of Biology University of Graz Graz Austria

Institute of Microbiology The Czech Academy of Sciences Třeboň Czech Republic

Institute of Organic Biogeochemistry in Geo Systems RWTH Aachen University Aachen Germany

Integrative Biotechnology University of Applied Sciences Kaiserslautern Pirmasens Germany

Museum of Evolution Uppsala University Uppsala Sweden

National Botanic Gardens Ireland

Palacký University Olomouc Olomouc Czech Republic

Rhineland Palatinate Technical University Kaiserslautern Landau Kaiserslautern Germany

Royal Botanic Garden Edinburgh Edinburgh UK

Swedish Museum of Natural History Sweden

Technical University Dresden Chair of Technical Biochemistry Dresden Germany

University of Goettingen SAG Goettingen Goettingen Germany

University of Nevada Las Vegas Las Vegas United States

University of Rostock Botanical Garden Rostock Germany

VNUHCM University of Science Vietnam

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