Tolypocladium inflatum is an ascomycete fungus originally isolated from a Norwegiansoil sample that, under certain conditions, produces the immunosuppressantdrugciclosporin. In its sexual stage (teleomorph) it is a parasite on scarab beetles. It forms a small, compound ascocarp that arises from the cadaver of its host beetle. In its asexual stage (anamorph) it is a white mold that grows on soil. It is much more commonly found in its asexual stage and this is the stage that was originally given the name Tolypocladium inflatum.
In 1969, a soil sample containing microfungi from Norway, found by Hans Peter Frey. was brought to Switzerland from which a fungus misidentified as Trichoderma polysporum was isolated. In 1971 the Austrian mycologist, Walter Gams, re-identified the isolate as a previously unknown microfungus affiliated with the order Hypocreales. He erected the genus Tolypocladium to accommodate the isolate which he named T. inflatum Gams. The taxon is characterized by swollen phialides, sparingly branched conidiophores, and small, unicellularconidia borne in slimy heads. Canadian mycologist John Bissett re-examined the strain in 1983, finding it to match the species Pachybasium niveum, a fungus described prior to the work of Gams. According to the rules of publication priority for botanical nomenclature, Bissett proposed the combination Tolypocladium niveum. However due to the economic importance of the fungus to the pharmaceutical industry and the fact that the incorrect name had already become well-entrenched, a proposal to formally conserve the name T. inflatum against earlier names was made and accepted, establishing the correct name of the mold that produces ciclosporin as Tolypocladium inflatum.
Tolypocladium inflatum occurs most commonly in soil or leaf litter, particularly at high latitudes in cold soils. The species is characterized by spherically swollen phialides that are terminated with narrow necks bearing subglobose conidia.T. inflatum is highly tolerant of lead and has been found to dominate the mycota of lead-contaminated soils. A study conducted by Baath et al. found that 35% of the fungal isolates recovered from lead-laden soil were T. inflatum.
In 1996, Kathie Hodge of Cornell University and colleagues determined that the mold T. inflatum was the asexual state of what was then known as Cordyceps subsessilis.Cordyceps subsessilis was later moved to the genus Elaphocordyceps. However, under the ICN‘s 2011 “one fungus, one name” principle, fungi can not have different names for their anamorphic and teleomorphic stages if they are found to be the same species so Elaphocordyceps subsessilis was made a synonym of Tolypocladium inflatum.
The genome of the T. inflatum strain/isolate NRRL 8044 (ATCC 34921) was sequenced and published in 2013 by Bushley and colleagues. This was the same strain from which the ciclosporin was first isolated.