About Penicillium oxalicum
Penicillium oxalicum is a soil saprophyte and substrate generalist with a global distribution. It is offered on extended Penicillium panels primarily for taxonomic completeness; the species's principal mycotoxin (secalonic acid D) is teratogenic but is not a common modern indoor exposure concern.
Taxonomy
Penicillium section Lanata-Divaricata (modern Houbraken classification; previously placed in subgenus Furcatum in older Pitt 1979 framework)
Ecology and habitat
P. oxalicum is found in soil, on virtually every food substrate, and in indoor dust. It is among the more thermotolerant Penicillia (growth to 40 °C) and one of the broader substrate generalists in the genus.
Indoor relevance
P. oxalicum is a common indoor dust isolate but rarely the dominant species on a panel. Its mycotoxin signal (secalonic acid D) has limited modern indoor-exposure documentation. The toxin's principal characterization is in cereal-storage and historical food-contamination contexts.
Cardinal physiology
Minimum water activity for growth: Aw 0.79[2]. Growth across 5–40 °C with optimum 28–30 °C, more thermotolerant than most Penicillia.
Secondary metabolites
The principal mycotoxin is secalonic acid D, a teratogenic dimeric xanthone. The species also produces oxaline and (in some strains) roquefortine C. Secalonic acid D's indoor relevance is comparatively thin in the building-mycology literature.
Compounds documented as produced by Penicillium oxalicum (presence and quantity vary by chemotype, strain, and substrate):
DNA-based detection of a mycotoxin-producing species in household dust does not directly establish exposure to that mycotoxin at any specific concentration.
Lab availability
Some commercial dust testing labs offer this species as an extended-panel option. Specific lab coverage changes over time: check with your laboratory for current panel options.