Mesophilic · Extended-panel species

Penicillium citrinum

Among the most ubiquitous Penicillia globally. Named for citrinin production; very common indoor isolate.

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/mgMeklin AHHS threshold
Mycotoxin profile
3+ 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: 0.80–0.84 typical; some isolates documented down to 0.775. Citrinin production min Aw ~0.81.

About Penicillium citrinum

Penicillium citrinum is among the most ubiquitous Penicillium species worldwide: isolated from soil, food, indoor dust, and water systems across virtually every substrate that supports fungal growth. Despite the breadth of its distribution, it is rarely the dominant species in any one sample, which makes interpreting an elevated detection a question of relative rather than absolute concern.

Taxonomy

Penicillium section Citrina (Houbraken & Samson 2011; previously placed in subgenus Furcatum series Citrina in older Pitt 1979 classification)

Ecology and habitat

The species is one of the most consistently isolated indoor Penicillia globally. It is found in soil, on virtually every food substrate, in indoor dust panels, and in drinking water systems. P. citrinum is sufficiently xerotolerant to grow on dry substrates that exclude most water-damage indicators, and sufficiently thermotolerant to persist in warm indoor environments year-round.

Indoor relevance

P. citrinum is a very common indoor isolate; its detection in dust panels typically reflects ambient indoor mycoflora rather than a specific moisture event. Documented presence in drinking water systems adds an additional reservoir worth noting. Biofilms in plumbing can harbor the species and contribute to indoor airborne spore counts via aerosolization at showers, sinks, and humidifier reservoirs.

Cardinal physiology

Minimum water activity for growth: Aw 0.80–0.84 typical[2], with some isolates growing as low as 0.775 in laboratory conditions. The species is among the more xerotolerant Penicillia. Citrinin production occurs at Aw ≥ 0.81[3]. Growth across 5–40 °C with optimum 26–30 °C.

One of the more xerotolerant Penicillia.

Secondary metabolites

The namesake metabolite is citrinin, a yellow nephrotoxic polyketide pigment. The species also produces tanzawaic acids and quinolactacins. P. citrinum's citrinin production is the original isolation context for the toxin (the species is the genus type for citrinin biosynthesis), though other Penicillia (P. verrucosum, P. expansum) and Aspergillus terreus also produce it.

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

Citrinin (namesake)Tanzawaic acidsQuinolactacins

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

CitrininNamesake nephrotoxic polyketide.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. Vaamonde G, Patriarca A, Fernández Pinto V, Comerio R, Degrossi C. Variability of aflatoxin and cyclopiazonic acid production by Aspergillus section flavi from different substrates in Argentina. Int J Food Microbiol. 2003 Nov 15;88(1):79-84.