A STEP BEYOND

Test organisms

 

Test organisms were chosen according to set criteria. All bacteria have environmental origin and are not true pathogens. Genus Bacillus includes common airborne bacteria that can produce very tolerant cell forms called spores. Micrococcus is frequently found in air sampling because it produces pigments that protect it against the radiation of sunshine. Escherichia is another common type of bacterium, both in aquatic environments and in the human colon, serving as an indicator organism for faecal pollution. Among the fungi chosen were Penicillium and Saccharomyces chosen – the former because of its universal distribution as an actively sporulating mould, the latter as an internationally accepted yeast species for various types of testing.

micrococcus_luteus

Test organism Type of organism Strain code1 Nutrient agar2 Incubation (d)
Bacillus subtilis Gram-positive, aerobic, sporulating, rod-shaped bacterium E-97009T TYGA 2
Escherichia coli Gram-negative, facultatively anaerobic, rod-shaped bacterium ATCC 25922 TYGA 1
Micrococcus luteus Gram-positive, aerobic, pigmented, cocci-shaped bacterium E-93442T TYGA 4
Penicillium chrysogenum A common mould D-88381 MEA 5
Saccharomyces cerevisiae A common yeast B-62001 MEA 2

1 Strain codes of culture collection by ATCC (E.coli) or by VTT (other organisms)
2 TYGA = Tryptone Yeast Extract Glucose Agar, MEA = Malt Extract Agar