The induction of mycelial development inAureobasidium pullulans (IMI 45533) by yeast extract

Abstract

Germ tube and subsequent mycelial development from yeast-like and swollen cells of Aureobasidium pullulans (IMI 45533) was induced by yeast extract in defined liquid medium. This morphogenetic transition was dependent on inoculum size; pH effects were not involved and once mycelial development was induced in the cells it continued even in the absence of yeast extract. The progeny of mycelium and future generations were unaffected by yeast extract. Cessation of germination was not due to any obvious medium changes but appeared to be partly due to the production of a germination inhibitor, which could also be produced by control cells grown in the absence of yeast extract.

The effect of exogenously-supplied nucleosides and nucleotides and the involvement of adenosine 3′:5′-cyclic monophosphate (cyclic AMP) in the yeast mycelium transition of Ceratocystis ( = Ophiostoma) ulmi

“…In A. pullulans, an organism showing some morphological similarities with C. ulmi, externally-supplied adenosine and adenosine 5'-monophosphate (AMP) induced an extensive yeast-mycelial transition although cAMP, dbcAMP, ADP and ATP did not [6]. It was thought that the promotion of mycelial growth in A. pullulans by yeast extract was largely due to the presence of nucleotides and nucleosides in yeast extract [6,21]. However, the efficiency of yeast extract as an inducer of mycelium formation in C. ulmi cannot be explained so easily in view of the reduced effects of the individual nucleosides/ nucleotides.…”

Glutathione metabolism and dimorphism in Aureobasidium pullulans

“…For example, GSH occupies a central position in the antioxidative defence system against free radicals and also takes part in complex metabolic stress responses to changes in the available carbon, nitrogen and sulphur sources including transportation of amino acids into and within the cells (PENNINCKX andELSKENS 1993, PENNINCKX 2000). In our experiments, we strove to minimise the effects of nutritional factors on the GSH metabolism of A. pullulans cells and, therefore, triggered morphological changes solely by varying the inoculum size (COOPER andGADD 1984, REESLEV et al 1991).…”

“…Inokula containing 2.5 u 10 7 , 2.0 u 10 8 and 3.5 u 10 9 cells were selected to get pure mycelial (ratio of yeast cells 1%), mixed morphology (ratio of yeast cells # 10%) and pure yeast (ratio of yeast cells ! 99%) cultures, respectively (COOPER andGADD 1984, REESLEV et al 1991). The growth of the micro-organism was characterised by monitoring glucose consumption (REESLEV et al 1991, PUSZTAHELYI et al 1997.…”

“…Importantly, growth in the yeast form is a prerequisite to the formation of extracellular polysaccharide in A. pullulans (CATLEY 1980, HEALD and KRISTIANSEN 1985, REESLEV et al 1991, REESLEV and JENSEN 1995. Key factors influencing both cell morphology and pullulan production of A. pullulans are well-defined and include pH (SEVIOUR et al 1984, HEALD andKRISTIANSEN 1985), inoculum size (COOPER andGADD, 1984, REESLEV et al 1991), yeast extract (COOPER andGADD 1984, REESLEV et al 1991), Zn 2+ ions (REESLEV et al 1993, REESLEV andJENSEN 1995) as well as nitrogen and glucose limitations (REESLEV et al 1996). In this paper, we present a comparative study on the GSH metabolisms observable in exponentially growing yeast cells and hyphae of A. pullulans, which may provide us with important new insights into the hypothesised role of GSH in controlling dimorphism in fungi.…”

Relation between pullulan production, morphological state and growth conditions in Aureobasidium pullulans: new observations

“…pullulans exists as either filamentous and/or cellular forms (blastospores, swollen cells and chlamydospores) (Luteraan, 1954;Ramos & Garcia-Acha, 1975 ;Cooper & Gadd, 1984). A few researchers (Catley, 1973(Catley, , 1980Dufresne et al, 1990) have emphasized correlations between pullulan synthesis and the production of cellfree biomass in the culture medium.…”