Practical aspects of working with actinobacteria

More than other bacteria Actinobacteria, especially the mycelium forming ones impress by their appearance, the color of the aerial mycelium, of the substrate mycelium and also of pigments that diffuse into the agar (Cross 1989; Krasil’nikov 1979; Küster 1976) and the morphology of their differentiation stages (Gottlieb 1961) which will be described in the later chapters. The aerial mycelium which makes them look like a fungus and the often three dimensional shape of the colony. The color of the aerial mycelium has been used by many groups for a first classification (Flaig and Kutzner 1960; Ettlinger et al. 1958; Shirling and Gottlieb 1966; Tresner and Backus 1963). The main classification groups are: white, grey white, cream (Streptomyces albus); yellow.-grey (Streptomyces griseus); rose, pale violet (Streptomyces fradiae, Microbispora rosea), rose-grey (Streptomyces lavendulae); pale brown, red brown (Streptomyces fragilis); pale blue, grey-blue (Streptomyces viridochromogenes); blue green (Streptomyces glaucescens, Actinomadura rubrobrunnea); pale green, green (Streptomyces prasinus, Microtetraspora viridis); pale grey, grey (Streptomyces violaceoruber, Microtetraspora glauca) (Blinov and Khokhlov 1970). By the description of the aerial mycelium color three points have to be kept in mind. The first is that the typical color is only expressed if the culture is also sporulating. Different species often sporulate on different media, so a number of agar cultures have to be prepared to get good results. The second is the diffusion of pigments from the substrate mycelium into the aerial mycelium which can have influences on the shade of the aerial mycelium. The third is the experience with many different Actinobacteria and their pigmentation, to do this grouping well. It is therefore very important to use the same media and culture conditions for all strains that will be compared. Over the years the use of the media from Shirling and Gottlieb (1966) from the “International Streptomyces Project/ISP” has been established in nearly all labs working with Actinobacteria (composition of media, see Sect. 11.2.1).