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Penicillium aurantiogriseum
Penicillium aurantiogriseum is a species of fungus belonging to the phylum Ascomycota and the genus Penicillium. It is described to be a member of the subgenus Penicillium which are some of the most commonly occurring fungi on the planet. P. aurantiogriseum infects a variety of plants and fruits such as asparagus, strawberry and many cereals. Many species of Penicillium have a specific affinity for cereals, but isolates of P. aurantiogriseum can be found in many conditions. P. aurantiogriseum is known to produce many secondary metabolites which have significance in areas of pharmacology and toxicology, many of which belong to differing strains. These metabolites are desirable in different industries to be used as biofuel or novel therapeutics for cancer treatments. Some of these metabolites are toxic, and define the differences between P. aurantiogriseum and other related species. P. aurantiogriseum is also known to produce enzymes which can catalyze the process of meat preservation.

History and taxonomy
P. aurantiogriseum is a broad species where many related species are differentiated based on the production of certain secondary metabolites and slight changes in morphology. P. viridicatum and P. verrucosum, alongside other species, are examples of species commonly confused with P. aurantiogriseum due to their near identical metabolism and similar physiology. In addition, they are very similar in morphology. This tends to a system where slight differences characterized by their production of secondary metabolites define the differences between species. New methodologies which arose in the 1980s differentiated species within the subgenus Penicillium based on their metabolite profile, eliminating the old naming systems used by Raper and Thom in 1949. Other species within this subgenus are differentiated based on slight variances in colour in addition to metabolite profile.

Growth and morphology
P. aurantiogriseum grown on a Neutral Creatine Sucrose agar (CSA) for seven days at 25°C has a moderate colony growth (15-25mm colony diameter), expressing an acidic response and appearing brown. On Czapek yeast extract agar (CYA), colonies have a 30-37mm diameter and are white. The conidia formed are typically grey blue to dark green, and are formed in abundance. Some isolates of P. aurantiogriseum create and expunge a soluble pigment which is typically brown or red. Colonies show similar characteristics when grown on malt extract agar (MEA) media, matching colony size, shape and colour across all three media. In addition, these characteristics are very similar to the growth and morphology of P. viridicatum and P. verrucosum. In the past, P. aurantiogriseum has been confused with P. viridicatum due to their strikingly similar morphologies, but was later renamed due to slight differences in alcohol metabolism.

In its asexual state, the conidiophores of P. aurantiogriseum have slender, ampulliform phialides usually measuring 7-10μm in length. Typically the conidiophores are formed individually or in fascicles. It also has smooth walled, spherical conidia typically grown in columns, with a 3-4μm diameter. While testing the boundaries of growth conditions, it was discovered that P. aurantiogriseum can grow to some extent between -2°C and 30°C. Growth is little affected by changes in pH. Again, P. aurantiogriseum shows very similar growth and characteristics to 'P. viridicatum and P. verrucosum'' when comparing conidia.

Habitat and ecology
P. aurantiogriseum is endophytic, meaning that it lives within a plant for at least some duration of its life. It is a common foodborne fungus typically isolated from cereal grains and nuts, sometimes spoiling fruit. Even though A. alternata is a more well known barley fungus, large quantities of P. aurantiogriseum and other Penicillium have been isolated from barley. Similarly, P. aurantiogriseum is one also of the most common cereal-born Penicillium fungi. P. aurantiogriseum grows most readily on cereals during the drying period, exploiting the plant's condition to its benefit. P. aurantiogriseum has been isolated infrequently in atypical areas around the world from pears in addition to other fruits and vegetables such as strawberries and asparagus. When it does appear in these fruits, it is typically not the common or predominating fungus. P. aurantiogriseum has been isolated from spoiled grapes in regions near or surrounding the Middle Easy and near Italy on rare occasions, with Botrytis being the more common fungi to be isolated from spoiled grapes. When found in its more typical host plant, P. aurantiogriseum infrequently colonizes wheat in communities with other fungi, with little to no evidence of a symbiotic relationship with other fungi. P. aurantiogriseum is also known to have marine-derived strains.

Physiology
P. aurantiogriseum is found to have peak metabolic rates at temperatures of 24°C and at a pH of 7.0. Terpenes are produced when grown on artificial substrates, possibly due to a lack of certain nutrients. P. aurantiogriseum produces a few alcohols including 1-Propanol and 3-Octanone when grown on wheat, barley and synthetic media. Most alcohol production occurs in early stage development of P. aurantiogriseum. Since P. aurantiogriseum has so many isolates from around the world, there are many metabolites produced in each of these conditions which differ from region to region. Some P. aurantiogriseum isolates are known to be producers of the anti-cancer compound Anicequol. Some isolates are known to produce terpene derivatives in a similar manner to which they create alcohol derivatives, through small chemical changes to metabolic pathways. Some P. aurantiogriseum strains have genes which could lead to the biosynthesis of paclitaxel, an anti-cancer diterpenoid. As another alcohol derivative, P. aurantiogriseum is a producer of Quinazolin-4-one alkaloid derivatives, currently sought after as a pharmacophore and for potential anti-cancer treatments, and auranthine, an antimicrobial commonly produced in Penicillium species. When growing on cereal, P. aurantiogriseum is a producer of trace volatile metabolites, some of which are mentioned above. These compounds in high enough concentration can be toxic towards the host plant.

In addition to these pharmacological compounds, P. aurantiogriseum also produces collagenases. Many enzymes produced in P. aurantiogriseum are stable over a large range of pH, from 6.0 to 9.0. Certain metal ions such as Mg2+, Zn2+, Co2+ and Mn2+ additionally increase hydrolytic activity. Many strains of P. aurantiogriseum produce derivatives of known enzymes and compounds with modifications lending themselves to changes in pharmacokinetic effects, desirable for pharmacological work. These changes are the basis for further research into P. aurantiogriseum, as new compounds can be observed for drug production and medical use.

Pathogenicity
Mainly infecting plants, typically cereals, P. aurantiogriseum does not have a severe pathogenic capability. P. aurantiogriseum has peak metabolic rates below the internal temperatures of many mammals, yet tests have been done due to the variability present in the many isolates of P. aurantiogriseum. Prominent pathology has been discovered to be elicited after ingestion of 1g of P. aurantiogriseum in rats, attested to the trace amounts of auranthine production and other secondary metabolites which are nephrotoxic. No research has been conducted using human subjects, and pathology will vary greatly depending on the isolate and metabolites present.