Biological and metabolic effects of the association between the microalga Galdieria sulphuraria and the fungus Penicillium citrinum

Abstract

Contamination of microalgae cultures can reduce their productivity and affect the quality of biomass and valuable bioproducts. In this article, after having isolated and identified for the first time the filamentous fungus Penicillium citrinum from heterotrophic cultures of the red polyextremophilic microalga Galdieria sulphuraria, we investigated the biological and metabolic significance of this alga-fungus association. In the same medium, both organisms grow better in each other's presence than separately. Both cell density and cell size of G. sulphuraria increase in co-cultures compared to pure alga cultures. In co-cultures, despite very severe growth conditions, the load of P. citrinum increases compared to pure fungus cultures. Optical microscope images have shown physical contact between cells of P. citrinum hyphae and G. sulphuraria which, however, retain their morphology and cell wall intact. GC–MS-based metabolomics analysis of metabolites excreted in the culture medium shows that pure cultures of the fungus and alga and co-cultures of alga plus fungus can be easily differentiated based on their metabolic products. Indeed, a richer assortment of extracellular metabolites (comprising both products of primary and secondary metabolism) is a distinct feature of co-cultures compared to both pure alga and pure fungus cultures.

Insights into Co-Cultivation of Photosynthetic Microorganisms for Novel Molecule Discovery and Enhanced Production of Specialized Metabolites

“…This revealed the presence of riboflavin, lumichrome, and thiamine which promoted the growth and supported the cross-feeding of carbon and nitrogen sources, and was therefore considered responsible for the mutualistic interaction of the companion strain [121]. Also, a greater metabolic activation, of both primary and secondary metabolites, was evidenced in the co-culture of the microalga Galdieria sulphuraria and the fungus Penicillium citrinum by GC-MS-based metabolomics [122]. Moreover, genome engineering techniques, such as in vivo expression technology, can be used to identifying genetic elements related to symbiosis and activation of specialized metabolites [50].…”

Anti-Insect Properties of Penicillium Secondary Metabolites

“…Penicillium species (Eurotiomycetes, Aspergillaceae) are widespread in every environment on earth, from desert sands to Antarctica to ocean trenches [ 8 , 12 , 13 , 14 ]. Their occurrence in ecosystems is even more pervasive as a result of the ability to establish symbiotic relationships with various organisms [ 11 , 15 , 16 ]. These features of adaptability and eclecticism reflect a notable taxonomic diversity such that the current number of more than 400 species requires being continuously integrated with new findings and descriptions [ 13 ].…”

“…Of course, Penicillium spp. are particularly involved in this biological struggle, with reference to their renowned implications in the contamination of food and feed with mycotoxins, such as citrinin, ochratoxin A, patulin, and more [ 16 ].…”

Application of microalgae in wastewater: opportunity for sustainable development

“…The optimum temperature for the efficiency of the process is approximately 22 °C and discrete increases in temperature lead to proliferation of nitrifying bacteria and nitrification above microalgae assimilation (González-Camejo et al, 2020). On the other hand, high pH values affect microalgae metabolism, decreasing it (Zhang et al, 2019;Salvatore et al, 2023). The proportions and type of nutrients present in the effluent must be evaluated for each specific strain, being able to mix with other effluents or water to find a balance and better conditions for the microalgae to assimilate the components present (Umetani et al, 2023).…”