FUNGI IMPERFECTI or DEUTEROMYCOTA SPORES

Cladosporium
Cladosporium spores are often found in higher concentrations in the air than any other fungal spore type. Bears copious numbers of spores on branched conidiophores. The spores usually have distinctive 'scars' at both ends where they were joined both to the spore at one end and to the conidiophore at the other. Although often single celled spores, frequently spores with a single transverse septum, or several transverse septa are seen. Their size ranges from 4 to 20 micrometres (microns) in length. Cladosporium is a mould which can be found growing on dead vegetation and textiles.

Aspergillus
Spores of some species of Aspergillus are hyaline (colourless), while some, such as the spores of Aspergillus niger are dark brown. Sources of Aspergillus are found indoors and include damp areas. Aspergillus is also found on stored cereal grains. Contributors to outdoor air include compost heaps and other areas of dead vegetation. Their size ranges from 2 to 10 micrometres (microns).

Penicillium
Is the mould used in the manufacture of 'blue' cheeses. Penicillium is common indoors on stored food, fruit, cheese, bread etc. and will proliferate in damp conditions. The spherical spores are produced in long unbranched chains of each conidiophore. These usually fragment into individual spores, although chains of spores are seen periodically on slides. When samples are freshly prepared from culture the spores are pale green, although this fades with age. Their size ranges from 3 to 5 micrometres (microns).
Although some species of Penicillium appear to reproduce solely by asexual means, some species of Penicillium are the anamorph (asexual) stage of the ascomycete genus Talaromyces.

• When using visual methods of identification Aspergillus and Penicillium spores cannot be differentiated because the spores are so visually similar and are grouped together into the Aspergillus/Penicillium group. Spores from this group are found almost all year round.

Alternaria
There are a number of very similar, related species which are usually grouped together as Alternaria. Alternaria is commonly found in samples taken in England. The spores of Alternaria are multi-celled. Developed in chains, head-to-toe, from which their name derives. Spores are multi-septate, both transverse and longitudinally. They vary in width and length according to species; usually 8 to 75 micrometers (microns) in length, some species such as A.longissima can be found with a length of up to 500 micrometres (0.5 millimetres). Alternaria which is both ubiquitous and abundant is both saprophytic and parasitic on plant material and is found on rotting vegetation as well as in damp indoor areas, such as bathrooms. Some species of Alternaria are the imperfect, asexual, anamorph spores of the ascomycete Pleospora, (see ascomycyetes).

Periconia
Is both parasitic or saprophytic on plant material.

Curvularia
Is a silver-grey to light brown mould. The spores are marked by two to four transverse septa and usually spores have one central cell larger than the others. The septa which separate this cell are usually very distinct.
The spores of Curvularia range in length from 18 to 43 micrometres (microns). The fungi Curvularia intermedia although originally classified as a fungi imperfecti is now recognized as the anamorph stage of the ascomycete Cochliobolus intermedius. Curvularia is seen in small numbers in England, although it is more common in the USA.

Drechslera/Helminthosporium
Vary in shape depending upon species. Many are long and tapering, others are relatively short. The ends are rounded and one 'scar' from the point of attachment can often be seen. Drechslera/Helminthosporium are distinctive in that the cells within the spore appear as 'eyes' or 'windows. Although some species may exceed 160 micrometres (microns) most are less than 75 micrometres (microns) in length.

Epicoccum
Is a mould that may play a more predominant role in allergy than previously thought, (Kendrick, 1990). The spores of epicoccum have a distinctive 'warty' appearance and are dark to golden brown. They are multi-septate spores. The cells are irregularly arranged to form a ball averaging 20 micrometres (microns) diameter.

Botrytis
The spores of Botrytis are teardrop or oval in shape and are hyaline (colourless). Botrytis is another mould. The hyaline mycelia appear white and it forms a fluffy mat with upright conidiophores supporting the spores, which appear pale brown to the naked eye. It is both saprophytic and parasitic and specialized species within this group cause vegetables and ornamental plant diseases.

Stemphylium
Is a saprophytic fungus (grows on non-living organic material) that is commonly found on cellulosic materials (that is, of plant origin, including livestock feed, cotton cloth, ceiling tiles, paper, etc.). Stemphylium is an example of a diurnal sporulator. An alternating light and dark cycle is required for spore development. It does not sporulate at all, or produces only a few spores when kept in total darkness and in constant light it forms sterile conidiophores. This fungus requires ultraviolet light for the production of conidiophores however, the second developmental phase, when the conidia are produced requires a dark period. Stemphylium also requires wet conditions for growth. The spores in this photograph were cultured from a sample taken from the bathroom of my Victorian house. Stemphylium spores vary in shape and size and range from 23 to 75 micrometres (microns) in length.