Streptomycetes are Gram-positive soil-dwelling bacteria, in appearance similar to filamentous fungi. The SsgA-like proteins or SALPs, of which streptomycetes typically have at least five paralogues... Show moreStreptomycetes are Gram-positive soil-dwelling bacteria, in appearance similar to filamentous fungi. The SsgA-like proteins or SALPs, of which streptomycetes typically have at least five paralogues, control specific steps of sporulation-specific cell division in streptomycetes. The expression level of SsgA, the best studied SALP, has a rather dramatic effect on septation and on hyphal morphology, which is not only of relevance for our understanding of (developmental) cell division but has also been succesfully applied in industrial fermentation, to improve growth and production of filamentous actinomycetes. The different regulation of ssgA transcription in different Streptomyces species, is at least one of the reasons why some strains are able to produce spores in liquid-grown mycelium, while others cannot. By far the most conserved SALP is SsgB, which is most likely is the archetypal SALP, with only SsgB orthologues occurring in all morphologically complex actinomycetes. SsgB is essential for sporulation of Streptomyces, and orthologues have a universally conserved function in actinomycete morphogenesis. Show less
