Visualizing Biomaterial Degradation by Candida albicans Using Embedded Luminescent Molecules To Report on Substrate
Bryan R Coad1,2, Thomas D Michl1, Christie A Bader3
1Future Industries Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
Abstract:
Microbial pathogens use hydrolases as a virulence strategy to spread disease through tissues and colonize medical device surfaces; however, visualizing this process is a technically challenging problem. To better understand the role of secreted fungal hydrolases and their role in Candida albicans virulence, we developed an in situ model system using luminescent Re(I) and Ir(III) containing probe molecules embedded in a biodegradable (poly(lactic-co-glycolic acid), PLGA) polymer and tracked their uptake using epifluorescent imaging. We found that secretion of esterases can explain how physically embedded probes are acquired by fungal cells through the degradation of PLGA since embedded probes could not be liberated from nonbiodegradable polystyrene (PS). It was important to verify that epifluorescent imaging captured the fate of probe molecules rather than naturally occurring fungal autofluorescence. For this, we exploited the intense luminescent signals and long spectral relaxation times of the Re and Ir containing probe molecules, resolved in time using a gated imaging system. Results provide a visual demonstration of a key virulence trait of C. albicans: the use of hydrolases as a means to degrade materials and acquire hydrolysis products during fungal growth and hyphal development. These results help to explain the role of nonspecific hydrolases using a degradable material that is relevant to the study of fungal pathogenesis on biotic (tissues) surfaces. Additionally, understanding how fungal pathogens condition surfaces by using nonspecific hydrolases is important to the study of fungal attachment on abiotic surfaces, the first step in biofilm formation on medical devices.
Insights
Fungal pathogens like Candida albicans use esterases to break down materials and acquire nutrients. This study visualized this virulence strategy using luminescent probes, revealing how fungi degrade polymers for growth and colonization.
Area of Science:
- Microbiology
- Biochemistry
- Pathogenesis
Background:
- Microbial pathogens utilize hydrolases for virulence, aiding tissue invasion and medical device colonization.
- Visualizing hydrolase activity during fungal pathogenesis is challenging.
- Candida albicans is a significant opportunistic fungal pathogen.
Purpose of the Study:
- To investigate the role of secreted fungal hydrolases in Candida albicans virulence.
- To develop and utilize an in situ model system for visualizing hydrolase activity.
- To understand how C. albicans acquires nutrients through material degradation.
Main Methods:
- Development of an in situ model using luminescent Re(I) and Ir(III) probes embedded in biodegradable poly(lactic-co-glycolic acid) (PLGA).
- Tracking probe uptake via epifluorescent imaging.
- Distinguishing probe luminescence from fungal autofluorescence using gated imaging and exploiting probe spectral properties.
Main Results:
- Secretion of esterases by C. albicans explains the acquisition of embedded probes through PLGA degradation.
- Probes embedded in non-biodegradable polystyrene were not acquired, confirming the role of degradation.
- Visual evidence demonstrated C. albicans using hydrolases to degrade materials and acquire hydrolysis products during growth and hyphal development.
Conclusions:
- Nonspecific hydrolases play a key role in C. albicans virulence, enabling material degradation and nutrient acquisition.
- This mechanism is relevant to fungal pathogenesis on biotic surfaces (tissues).
- Understanding hydrolase activity is crucial for studying fungal attachment to abiotic surfaces and biofilm formation on medical devices.
