Mesophilic · Extended-panel species

Penicillium aurantiogriseum and P. viridicatum

Cool-storage cereal colonizers and the historical Penicillium ochratoxin A route before P. verrucosum was distinguished in the 1980s.

Extended panelMesophilic · Aw ≥ 0.80

Moisture niche · where this species can grow

XerophilicAw < 0.80
MesophilicAw 0.80–0.89
HydrophilicAw ≥ 0.90
Min Aw 0.80
← Drier conditions toleratedRequires liquid water →
Minimum Aw
0.80
EPA reference (GM)
< 0.4 SE/mggroup basis · PenGrp1
Mycotoxin profile
7+ documented
Ecological role
Secondary colonizer

The < 0.4 SE/mg reference value is Meklin 2004's AHHS exclusion threshold: the paper retained species whose geometric mean was at least 2 spores per 5 mg dust (≈ 0.4 spores/mg) and eliminated the rest. This species was measured across the 1,096-home AHHS sample and characterized below that threshold, used here as a conservative ceiling on its true GM, not a percentile band. A detected value of X SE/mg implies an elevation factor of at least X ÷ 0.4 over the EPA reference, a lower bound, since the true GM is below 0.4. See the 82-species story for the math.

Note on cardinal Aw: P. aurantiogriseum 0.81; P. viridicatum 0.80 (growth), 0.83–0.86 (OTA production).

About Penicillium aurantiogriseum and P. viridicatum

Penicillium aurantiogriseum and P. viridicatum are closely related Penicillia of the series Viridicata, historically associated with the cereal-grain ochratoxin A contamination that P. verrucosum is now understood to dominate. Both names appear on Mycometrics's Top 15 Penicillium and Budget 15 panels, and we discuss them as a species complex.

Taxonomy

Penicillium subgenus Penicillium, series Viridicata. Modern taxonomy splits the original P. aurantiogriseum aggregate into several closely related species (a species complex); the Mycometrics panels treat both names as targets.

Ecology and habitat

Both species are psychrophilic Penicillia adapted to cool stored-grain environments. P. viridicatum was the principal organism implicated in cereal-grain OTA contamination in classical European mycology before molecular methods distinguished P. verrucosum from the broader P. viridicatum species concept in the 1980s. P. aurantiogriseum in modern taxonomy is a species complex that includes several closely related cool-storage Penicillia.

Indoor relevance

Indoors, both species are associated with damp grain-storage and cool indoor environments where cereal substrates are present. Their detection on a residential ERMI is uncommon outside of agricultural-adjacent or pet-food-storage contexts. Their inclusion on lab panels is mainly of historical and taxonomic interest. They cover the classical Penicillium OTA route that P. verrucosum is now understood to dominate in modern temperate-region storage.

Cardinal physiology

P. aurantiogriseum minimum Aw 0.81[2]; P. viridicatum minimum Aw ~0.80 for growth[2]. Northolt et al. 1979 reported OTA production at Aw 0.83–0.86 on strains then identified as P. viridicatum[3]. These production measurements predate the molecular distinction of P. verrucosum, so the OTA-producing strains in that study are likely what we would now call P. verrucosum rather than modern-sensu-stricto P. viridicatum. Both species grow from −2 to 30 °C with optima in the cool range (15–22 °C).

Psychrophilic; cool-storage environments.

Secondary metabolites

The species-specific metabolite profile in modern taxonomy:

  • P. aurantiogriseum: verrucosidin (a potent neurotoxin), brevianamide A, anacine (benzodiazepine), viridicatin / viridicatol (yellow quinoline pigments), and related extrolites
  • P. viridicatum: xanthomegnin and viomellein (nephrotoxic naphthoquinones), viridicatin, penicillic acid

Important taxonomic note: Older literature attributes ochratoxin A and citrinin to these species, but modern strict-sense P. aurantiogriseum and P. viridicatum do not produce these mycotoxins. Frisvad et al. established that within subgenus Penicillium, OTA is produced only by P. verrucosum and P. nordicum. The "historical Penicillium OTA route" attributed to these species reflects pre-1980s taxonomy in which the species we now call P. verrucosum was lumped with P. viridicatum.

Compounds documented as produced by Penicillium aurantiogriseum and P. viridicatum (presence and quantity vary by chemotype, strain, and substrate):

Verrucosidin (neurotoxin: P. aurantiogriseum)Viridicatin / viridicatol (P. viridicatum and P. aurantiogriseum)Xanthomegnin and viomellein (nephrotoxic naphthoquinones: P. viridicatum)Brevianamide A (P. aurantiogriseum)Anacine (P. aurantiogriseum)Penicillic acidOchratoxin A and citrinin: historical attribution only; modern sensu stricto P. aurantiogriseum and P. viridicatum do not produce these. OTA in subgenus Penicillium is now attributed exclusively to P. verrucosum and P. nordicum (Frisvad et al.).

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.

Related

Ochratoxin AHistorical Penicillium route to OTA.CitrininOften co-produced with OTA.Penicillium speciesBeyond the 36

References

  1. Meklin T, Haugland RA, Reponen T, Varma M, Lummus Z, Bernstein D, Wymer LJ, Vesper SJ. Quantitative PCR analysis of house dust can reveal abnormal mold conditions. J Environ Monit. 2004;6(7):615–620.
  2. Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.
  3. Northolt MD, van Egmond HP, Paulsch WE. Ochratoxin A production by some fungal species in relation to water activity and temperature. J Food Prot. 1979;42:485–490.
  4. Abellana M, Sanchis V, Ramos AJ. Effect of water activity and temperature on growth of three Penicillium species and Aspergillus flavus on a sponge cake analogue. Int J Food Microbiol. 2001;71(2–3):151–157.