Actinomycetes (Actinobacteria)

Actinomycetes (Actinobacteria), nicknamed 'Ray fungi' for their fungus-like, mycelial pattern of growth, are in fact Gram-positive bacteria - anaerobic or facultatively anaerobic, and notable for having a high guanine-cytosine content in their DNA, and for not producing an aerial mycelium (e.g. Streptomyces). Frankia is a symbiotic actinobacterium that forms nitrogen-fixing root nodules in non-leguminous plants such as Alnus and Casuarina, and produces a multicellular sporangium. Actinomyces bovis grows in the oral cavity and causes the disease lumpy jaw. Streptomyces, a mycelium-forming genus that lives in soil, is responsible for the characteristic 'earthy odour' that rises from soil after rain (caused by the v …