Xerophilic

Penicillium chrysogenum

Penicillium chrysogenum (famous as the original source of penicillin) is one of the most common indoor molds worldwide, found in the majority of water-damaged buildings.

Environmental referenceXerophilic · Aw ≥ 0.78

Moisture niche · where this species can grow

XerophilicAw < 0.80
MesophilicAw 0.80–0.89
HydrophilicAw ≥ 0.90
Min Aw 0.78
← Drier conditions toleratedRequires liquid water →
Minimum Aw
0.78
EPA reference (GM)
5 SE/mg
Mycotoxin profile
2+ documented
Ecological role
Primary colonizer

About Penicillium chrysogenum

Penicillium chrysogenum (famous as the original source of penicillin) is one of the most common indoor molds worldwide, found in the majority of water-damaged buildings. As a Group 2 mold, it is present in most indoor environments to some degree and the ERMI calculation subtracts its log value from the Group 1 sum. It is a major respiratory allergen associated with asthma exacerbation, hypersensitivity pneumonitis, and chronic sinusitis.

Ecology and water requirements

Penicillium chrysogenum is classified as a primary colonizer with xerophilic adaptations: capable of germinating and growing at water activity as low as Aw 0.78[2], well below what most molds tolerate. Primary colonizers establish first in damp or even mildly humid environments, often before any visible moisture problem is apparent. Elevated Penicillium chrysogenum on an ERMI test is more often associated with long-term high humidity than with a sudden water event[3]. Common contexts include poorly ventilated areas, conditioned-vs-unconditioned boundary zones (attics, crawl spaces, unfinished basements), and dusty environments where ambient relative humidity is sufficient to support growth on settled organic material.

Mycotoxin biology

Penicillium chrysogenum produces a range of secondary metabolites with biological activity. The compounds documented in the literature for this species are listed in the chips below. Mycotoxin production is not uniform across all strains and is influenced by substrate, temperature, and water activity[4]. The same isolate may produce substantially different metabolite profiles on drywall paper versus wood versus settled dust[5]. DNA-based detection via the ERMI panel identifies species presence but does not directly measure mycotoxin presence; detection of a mycotoxin-producing species in household dust does not establish exposure to that mycotoxin at any specific concentration.

Detection in dust versus visual inspection

DNA-based detection of Penicillium chrysogenum in settled household dust (the basis of the ERMI panel[1]) integrates spore material from current and recent growth in the home, capturing exposure history over weeks to months. A positive detection in dust does not necessarily indicate currently-active growth at the time of sampling; conversely, an active growth site can produce relatively low dust spore counts if the spores are not being aerosolized (sealed wall cavities, behind vapor barriers, or under flooring). Interpretation requires considering the dust signal alongside building inspection, occupant symptom history, and the broader pattern of species detected on the panel.

Where it’s typically found

Penicillium chrysogenum is documented on the following substrates and locations:

  • Damp building materials
  • walls
  • wallpaper
  • carpet
  • mattress and floor dust; extremely common in water-damaged buildings

Mycotoxins

Compounds documented as produced by Penicillium chrysogenum (presence and quantity vary by chemotype, strain, and substrate):

Roquefortine C· some strainsGenerally few detectable metabolites on building materials

Mycotoxin production is not uniform across all strains and is influenced by substrate, temperature, and water activity. Detection of a mycotoxin-producing species in household dust does not directly establish exposure to that mycotoxin at any specific concentration.

On your ERMI report

Penicillium chrysogenum is one of the 10 EPA environmental reference species used to compute the SLG2 component of the ERMI score (sometimes labeled "Group 2" in EPA documentation). Group 2 species are commonly found in outdoor air; their levels are subtracted from the indicator-species sum, which means high outdoor-reference detections actually reduce the final ERMI. A low-level detection of Penicillium chrysogenum is common, because these species are also found in outdoor air. Our interpretation report reads its level alongside the indicator species.

Mycotoxins and extended panels

Related reference pages: the mycotoxins Penicillium chrysogenum can produce, and the extended-panel species most closely related to it:

ReferencePenicillium species overview

Related species

Penicillium brevicompactumAw ≥ 0.78 · XerophilicPenicillium corylophilumAw ≥ 0.80 · MesophilicPenicillium crustosumAw ≥ 0.83 · MesophilicPenicillium purpurogenumAw ≥ 0.83 · Mesophilic

References

  1. Vesper SJ, McKinstry C, Haugland RA, et al. Development of an Environmental Relative Moldiness Index for U.S. homes. J Occup Environ Med. 2007;49(8):829–833.
  2. Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.
  3. World Health Organization. WHO Guidelines for Indoor Air Quality: Dampness and Mould. Copenhagen: WHO Regional Office for Europe; 2009.
  4. Nielsen KF. Mycotoxin production by indoor molds. Fungal Genet Biol. 2003;39(2):103–117.
  5. Miller JD, McMullin DR. Fungal secondary metabolites as harmful indoor air contaminants: 10 years on. Appl Microbiol Biotechnol. 2014;98(24):9953–9966.