The antagonistic Metschnikowia andauensis produces extracellular enzymes and pulcherrimin, whose production can be promoted by the culture factors

Abstract

Biological control against microbial infections has a great potential as an alternative approach instead of fungicidal chemicals, which can cause environmental pollution. The pigment producer Metschnikowia andauensis belongs to the antagonistic yeasts, but details of the mechanism by which it inhibits growth of other microbes are less known. Our results confirmed its antagonistic capacity on other yeast species isolated from fruits or flowers and demonstrated that the antagonistic capacity was well correlated with the size of the red pigmented zone. We have isolated and characterized its red pigment, which proved to be the iron chelating pulcherrimin. Its production was possible even in the presence of 0.05 mg/ml copper sulphate, which is widely used in organic vineyards because of its antimicrobial properties. Production and localisation of the pulcherrimin strongly depended on composition of the media and other culture factors. Glucose, galactose, disaccharides and the presence of pectin or certain amino acids clearly promoted pigment production. Higher temperatures and iron concentration decreased the diameter of red pigmented zones. The effect of pH on pigment production varied depending of whether it was tested in liquid or solid media. In addition, our results suggest that other mechanisms besides the iron depletion of the culture media may contribute to the antagonistic capacity of M. andauensis.

Biological Activity of Pulcherrimin from the Meschnikowia pulcherrima Clade

“…The iron-binding molecule pulcherrimin was described a century ago, but it is still not known which genes are responsible for its production [ 17 ]. The production of pulcherrimin is strongly dependent on the composition of culture media and other culture cultivation factors [ 6 , 14 , 18 , 19 ].…”

Insight into Yeast–Mycotoxin Relations

“…That is, the same yeast species can inhibit certain microbes, while others are not inhibited under the same environmental conditions. Alternatively, growth of a given species is inhibited at a lower pH, while not at a higher pH [54,55]. The results of Giobbe are in line with this, because she found that Pichia fermentans was effective on the surface of apples, while its inhibitory capacity disappeared on peaches [62].…”

“…The relation between pigment production and antagonistic capacity is supported by the fact that the pigment-less M. pulcherrima mutants lacked antifungal activity [50,88]. Further studies have suggested that Metschnikowia species were able to produce proteases, cell wall degrading enzymes, or the cells competed for nutrients and space, and all these capacities could also contribute to their antagonistic capacity [50,52,53,55,100].…”

“…Numerous studies have investigated the interactions between yeasts and other microbes. Their data suggest that the microbial interaction is a complex process, which can be either stimulation or growth inhibition, which, in addition, is based on different mechanisms [49][50][51][52][53][54][55]. When a yeast species is able to inhibit the growth of an adjacent microorganism, a clear zone can be seen around the yeast cells on the laboratory medium (Figure 1).…”

“…When a yeast species is able to inhibit the growth of an adjacent microorganism, a clear zone can be seen around the yeast cells on the laboratory medium (Figure 1). The appearance of the inhibitory zone strongly depends on the partner microorganism and the culture factors like composition of the medium, pH, or temperature [54][55][56][57][58][59][60][61]. That is, the same yeast species can inhibit certain microbes, while others are not inhibited under the same environmental conditions.…”