**About the Editor**

**Johannes F. Imhoff** is a retired professor of Marine Microbiology at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. He gained his Ph.D. in microbiology in 1980 at the Institute for Microbiology of the University of Bonn under the supervision of Prof. Dr. H.G. Truper. ¨ In 1993 , he was appointed as the head of the Marine Microbiology Department at the Institut fur¨ Meereskunde in Kiel (now the GEOMAR Helmholtz Centre for Ocean Research Kiel), where his main research themes dealt with marine microbial diversity with an emphasis on communities in deep-sea hot vents and in marine sponges. The introduction of appropriate molecular tools enabled studies of functional groups in microbial communities by sequence analysis of genes characteristic of photosynthesis and processes of sulfur oxidation, ammonia oxidation, and nitrate reduction. One of his major activities was establishing a research center for marine natural products, the "Kieler Wirkstoffzentrum" in 2005, of which he was founding director, and which was later transformed into the Marine Natural Product Chemistry research unit of GEOMAR. During these years, he laid the basis of large collections of marine bacteria and fungi, published the chemical structures and biological activities of numerous new compounds, and filed several patents on antitumoral active substances. He retired in 2017.

He published more than 350 papers, including chapters in several editions of "The Prokaryotes" and "Bergey´s Manual of Systematic Bacteriology". Since his first contact with microbiology in 1972, he has been fascinated by the culture of phototrophic bacteria, their ecology, diversity, and phylogeny. His studies focused on phototrophic bacteria from marine and hypersaline habitats, particularly salt and soda lakes, and their osmotic adaptation and compatible solute biosynthesis. He described more than 50 new taxa on the level of species, genus, family, and order of phototrophic and marine bacteria. A large culture collection of anoxygenic phototrophic bacteria, part of which was obtained from N. Pfennig in 1991, was maintained over the years and recently served to compile a large number of genomes of phototrophic bacteria. These data serve as a basis for studies on phylogenetic aspects, including photosynthesis.
