(de Bary) G. Arnaud (1918)
Aureobasidium pullulans is a ubiquitous black, yeast-like fungus that can be found in different environments (e.g. soil, water, air and limestone). It is well known as a naturally occurring epiphyte or endophyte of a wide range of plant species (e.g. apple, grape, cucumber, green beans, cabbage) without causing any symptoms of disease. A. pullulans has a high importance in biotechnology for the production of different enzymes, siderophores and pullulan. Furthermore, A. pullulans is used in biological control of plant diseases, especially storage diseases.
Chronic human exposure to A. pullulans via humidifiers or air conditioners can lead to hypersensitivity pneumonitis (extrinsic allergic alveolitis) or "humidifier lung". This condition is characterized acutely by dyspnea, cough, fever, chest infiltrates, and acute inflammatory reaction. The condition can also be chronic, and lymphocyte-mediated. The chronic condition is characterized radiographically by reticulonodular infiltrates in the lung, with apical sparing. The strains causing infections in humans were reclassified to A. melanogenum.
A. pullulans can be cultivated on potato dextrose agar, where it produces smooth, faint pink, yeast-like colonies covered with a slimy mass of spores. Older colonies change to black due to chlamydospore production. Primary conidia are hyaline, smooth, ellipsoidal, one-celled, and variable in shape and size; secondary conidia are smaller. Conidiophores are undifferentiated, intercalary or terminal, or arising as short lateral branches. Endoconidia are produced in an intercalary cell and released into a neighboring empty cell. Hyphae are hyaline, smooth, and thinwalled, with transverse septa. The fungus grows at 10–35 °C with optimum growth at 30 °C.
A. pullulans is notable for its phenotypic plasticity. Colony morphology may be affected by carbon source, colony age, temperature, light and substrate, with colonies ranging from homogeneous to sectored, yeast-like to filamentous growth, and from small to large. These changes, potentially influenced by epigenetic factors, and the particular developmental sequences that the colonies proceed through may be observed with the naked eye. Besides these morphological plasticity A. pullulans is also adaptable to various stressful conditions: hypersaline, acidic and alkaline, cold, and oligotrophic. Therefore, it is considered to be polyextremotolerant.
The morphology-based taxonomy of the species is complicated by the large morphological variability between strains and even within a single strain. Based on molecular analyses, four varieties of the species A. pullulans were recognised: var. pullulans from substrates with low water activity and the phyllosphere; var. melanogenum from aquatic habitats; var. subglaciale from glacial habitats; and var. namibiae, which was described on the basis of only one strain isolated from dolomitic marble in Namibia. However, when the genome sequences of these varieties became available, the differences between them were considered as too large to be accommodated in a single species. Therefore, the varieties were reclassified as new species: A. pullulans, A. melanogenum, A. subglaciale, and A. namibiae.
Due to the relatively recent redefinition of the species, most published work does not yet distinguish between the new species belonging to the previously recognised A. pullulans species complex. It is therefore not clear to what extent this knowledge is valid for A. pullulans s. str. and what should be attributed to the three new species.
- Andrews, J. H.; Spear, R. N.; Nordheim, E. V. (2002). "Population biology of Aureobasidium pullulans on apple leaf surfaces". Canadian Journal of Microbiology. 48 (6): 500–13. doi:10.1139/w02-044. PMID 12166677.
- Chi, Z; Wang, F; Chi, Z; Yue, L; Liu, G; Zhang, T (2009). "Bioproducts from Aureobasidium pullulans, a biotechnologically important yeast". Applied Microbiology and Biotechnology. 82 (5): 793–804. doi:10.1007/s00253-009-1882-2. PMID 19198830.
- Ferreira-Pinto, M. M.; Moura-Guedes, M. C.; Barreiro, M. G.; Pais, I; Santos, M. R.; Silva, M. J. (2006). "Aureobasidium pullulansas a biocontrol agent of blue mold in "Rocha" pear". Communications in agricultural and applied biological sciences. 71 (3 Pt B): 973–8. PMID 17390846.
- Zhang, D; Spadaro, D; Valente, S; Garibaldi, A; Gullino, M. L. (2012). "Cloning, characterization, expression and antifungal activity of an alkaline serine protease of Aureobasidium pullulans PL5 involved in the biological control of postharvest pathogens". International Journal of Food Microbiology. 153 (3): 453–64. doi:10.1016/j.ijfoodmicro.2011.12.016. PMID 22225984.
- Gostinčar, Cene; Ohm, Robin A; Kogej, Tina; Sonjak, Silva; Turk, Martina; Zajc, Janja; Zalar, Polona; Grube, Martin; Sun, Hui; Han, James; Sharma, Aditi; Chiniquy, Jennifer; Ngan, Chew Yee; Lipzen, Anna; Barry, Kerrie; Grigoriev, Igor V; Gunde-Cimerman, Nina (2014). "Genome sequencing of four Aureobasidium pullulans varieties: biotechnological potential, stress tolerance, and description of new species". BMC Genomics. 15 (1): 549. doi:10.1186/1471-2164-15-549. PMC 4227064. PMID 24984952.
- Slepecky, R. A.; Starmer, W. T. (2009). "Phenotypic plasticity in fungi: A review with observations on Aureobasidium pullulans". Mycologia. 101 (6): 823–32. doi:10.3852/08-197. PMID 19927747.
- Gostinčar, C.; Grube, M.; Gunde-Cimerman, N. (2011). "Evolution of Fungal Pathogens in Domestic Environments?". Fungal Biol. 115 (10): 1008–1018. doi:10.1016/j.funbio.2011.03.004. PMID 21944213.
- Zalar, P.; Gostincar, C.; De Hoog, G. S.; Ursic, V.; Sudhadham, M.; Gunde-Cimerman, N. (2008). "Redefinition of Aureobasidium pullulans and its varieties". Studies in Mycology. 61: 21–38. doi:10.3114/sim.2008.61.02. PMC 2610310. PMID 19287524.
- Themis J. Michailides. ""Above ground fungal diseases", Chapter 27" (PDF).[permanent dead link]
- Fleet, G.H. (2003). "Yeast interactions and wine flavour". Int. J. Food Microbiol. 86 (1–2): 11–22. doi:10.1016/s0168-1605(03)00245-9. PMID 12892919.
- Falconi, C.J.; Mendgen, K. (1994). "Epiphytic fungi on apple leaves and their value for control of the postharvest pathogens Botrytis cinerea, Monilinia fructigena and Penicillium expansum". Z. PflKrankh. PflSchutz. 101: 38–47.
- Webb, T.A.; Mundt, J.O. (1978). "Molds on vegetables at the time of harvest". Appl. Environ. Microbiol. 35 (4): 655–658. PMC 242901. PMID 646353.
- Simon, L.; Caye-Vaugien, C.; Bouchonneau, M. (1993). "Relation between pullulan production, morphological state and growth conditions in Aureobasidium pullulans: new observations". Journal of General Microbiology. 139 (5): 979–985. doi:10.1099/00221287-139-5-979.