Pseudomonas aeruginosainhibitsRhizopus microsporusgermination through sequestration of free environmental iron

Abstract

Rhizopus spp are the most common etiological agents of mucormycosis, causing over 90% mortality in disseminated infection. Key to pathogenesis is the ability of fungal spores to swell, germinate, and penetrate surrounding tissues. Antibiotic treatment in at-risk patients increases the probability of the patient developing mucormycosis, suggesting that bacteria have the potential to control the growth of the fungus. However, research into polymicrobial relationships involving Rhizopus spp has not been extensively explored. Here we show that co-culturing Rhizopus microsporus and Pseudomonas aeruginosa results in the inhibition of spore germination. This inhibition was mediated via the secretion of bacterial siderophores, confirming the essential role of iron for fungal growth. Addition of P. aeruginosa siderophores to R. microsporus spores in the zebrafish larval model of infection resulted in inhibition of fungal germination and reduced host mortality. Therefore, during infection antibacterial treatment may relieve bacterial imposed nutrient restriction resulting in secondary fungal infections.

Interruption of Aspergillus niger spore germination by the bacterially produced secondary metabolite collimomycin

“…Bacterially produced inhibitors of fungal spore germination can shape the outcome of interactions between fungi and plants, animals or humans, and thus may have practical relevance for managing fungi that are pathogenic to such hosts (Fisher et al ., ). Mechanisms behind the observed bacterially induced arrest of fungal spore germination are not always known (Li et al ., ; Nogueira et al ., ) but include the bacterial synthesis of compounds with antagonistic activity, such as organic acids (Le Lay et al ., ) and cyclic lipopeptides (Chitarra et al ., ; Gong et al ., ), or metabolites that confer a competitive advantage, such as siderophores (Kousser et al ., ).…”