The order Pseudonocardiales

The order Pseudonocardiales is made of up a single family Pseudonocardiaceae as it now contains all the genera that belonged to the other family in the order, the Actinosynemmataceae. It also covers the suborder Pseudonocardineae which forms a distinct cluster between the Frankineae and Streptomycineae when members of the taxa are subjected to 16S rRNA gene phylogenetic analysis. The family has 26 genera Pseudonocardia, Actinoalloteichus, Actinokineospora, Actinomycetospora, Actinophytocola, Actinosynnema, Alloactinosynnema, Allokutzneria, Amycolatopsis, Crossiella, Goodfellowiella, Haloechinothrix, Kibdelosporangium, Kutzneria, Labedaea, Lechevalieria, Lentzea, Prauserella, Saccharomonospora, Saccharopolyspora, Saccharothrix, Sciscionella, Streptoalloteichus, Thermocrispum, Umezawaea, and Yuhushiella. These genera contain strains which are heterogenous in their morphological and chemotaxonomic features. In general, they are predominantly mycelial actinobacteria with 8 genera having sporangia, pseudosporangia and synnemata, and motile spores as a feature of at least one genus. There are no common chemotaxonomic features though the majority contain galactose in their cell walls and phophatidylethanolamine and the menaquinone MK9 (H₄), though the latter is absent in the type species of the family. There are 8 monophyletic genera and another 8 that contain between 2 and 5 species, with three genera Amycolatopsis (60), Pseudonocardia (47), and Saccharopolyspora (22) containing at least half the 237 species of the family. For ease of differentiating the taxa, the majority of the morphological, chemotaxonomic, and physiological traits have been placed in comprehensive tables. Like most actinobacteria, members of the family are predominantly soil dwelling chemoorganotrophs, but some metabolic diversity is reported with growth on carbon dioxide, hydrocarbons, and recalcitrant compounds. Some are halophiles but very few have been isolated from marine sources. Recently new species have been sourced as endophytes indicating that members of certain genera have adapted to living within plant hosts. There have been a few reports of strains isolated from human clinical samples indicating they are opportunistic pathogens. However, some Crossiella species have been implicated in equine placentitis. A number of genera including those with large numbers are known to produce antibiotics and other bioactive secondary metabolites, some of which have found clinical use.