Actinomycetales is an order of Actinobacteria. They are very diverse and contain a variety of subdivisions as well as yet unclassified isolates. This is mainly because some genera are very difficult to classify because of a highly niche dependend phaenotype. For example Nocardia contains several species that are first believed to be distinct species before it was proven that their difference is purely depending on their growth conditions.
Actinomycetales are Gram positive, however several species have complex cell wall structures what makes the gram staining unsuitable. Examples: Mycobacteriaceae
Several Actinomycetales are pathogen to humans or animals, plants or other cells. The most popular example of a human pathogen is the Mycobacterium tuberculosis.
Biotechnologically exploited Familiae
Some species are used in industry and pharma-research because of their properties. Streptomycetaceae have an unique cell morphology, cell cycle and a variety of antibiotics they produce were essential for todays antibiotic discoveries. Corynebacteriaceae, especially Corynebacterium glutamicum is used in biotechnology for production.