MALDI-TOF for Yeast

The principle of MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization – Time of Flight) mass spectrometry is based on analyzing the mass-to-charge ratio (m/z) of ionized molecules to identify them, which is commonly used for the rapid identification of microorganisms.

Core Principle

1. Sample Preparation:

   • A microbial sample is mixed with a chemical matrix (usually a small organic acid) and applied to a metal plate.

   • The matrix absorbs UV laser energy and assists in the desorption and ionization of the sample.

2. Laser Ionization:

   • A laser pulse excites the matrix, which causes it to vaporize along with the sample and ionize the sample molecules (usually proteins, especially ribosomal proteins).

3. Acceleration:

   • The ionized molecules are accelerated in an electric field toward a detector. All ions receive the same kinetic energy.

4. Time-of-Flight (TOF) Analysis:

   • Lighter ions travel faster and reach the detector sooner than heavier ones.

   • The time taken to reach the detector is recorded and used to calculate the mass-to-charge ratio (m/z).

5. Spectrum Generation:

   • A mass spectrum is generated—a plot of intensity vs. m/z—representing the molecular fingerprint of the organism.

6. Identification:

• The obtained spectrum is compared with a reference database to identify the organism.

 Candida albicans Mutants

Mutants are organisms, cells, or genes that have undergone a mutation, which means a change or alteration in their DNA sequence compared to the original or normal forms.

Types of mutations leading to mutants:

• Point mutations: A single base change in DNA.

• Insertions or deletions: adding or removing DNA bases.

• Chromosomal mutations: Large-scale changes in chromosome structure or number.

Candida albicans mutants are strains or isolates of Candida albicans that have undergone genetic changes (mutations) resulting in differences from the wild-type (normal) Candida albicans. These mutations can affect various traits such as morphology, virulence, drug resistance, metabolism, or biofilm formation.

Examples of Candida albicans mutants:

• Mutants with defects in hyphal formation (affecting the fungus’s ability to switch from yeast to filamentous form).

• Mutants with altered drug resistance, such as resistance to antifungal agents like fluconazole.

• Mutants lacking specific virulence genes that reduce their ability to cause infection.

• Mutants with changes in biofilm formation capacity.

Other Candida species mutants refer to genetically altered strains of various Candida species (other than Candida albicans) that have mutations causing changes in their normal characteristics. Just like C. albicans mutants, these mutants can show differences in growth, morphology, virulence, antifungal resistance, biofilm formation, and metabolic activities.

Examples of other Candida species mutants:

• Candida glabrata mutants: Often studied for antifungal resistance, especially to azoles and echinocandins, or mutations affecting adhesion and biofilm formation.
• Candida tropicalis mutants: Mutations may affect virulence factors, filamentation, or biofilm development.
• Candida parapsilosis mutants: Mutants may show altered ability to form biofilms or changes in susceptibility to antifungal drugs.
• Candida krusei mutants: Known for intrinsic resistance to fluconazole, mutants may have further altered resistance or metabolic changes.
• Candida auris mutants: An emerging pathogen with high antifungal resistance; mutants can be studied for resistance mechanisms or virulence.

Other Candida species mutants are genetically modified or naturally mutated strains of Candida species (besides Candida albicans) that differ from the wild-type strains due to mutations affecting their biology, pathogenicity, or drug resistance. These mutants are essential for understanding species-specific features and developing targeted treatments.

References:

1. Fonzi, W. A., & Irwin, M. Y. (1993). Isogenic strain construction and gene mapping in Candida albicans. Genetics, 134(3), 717-728.
   https://www.genetics.org/content/134/3/717
   (Classic paper on genetic manipulation in C. albicans)
2. Noble, S. M., & Johnson, A. D. (2007). Genetics of Candida albicans, a diploid human fungal pathogen. Annual Review of Genetics, 41, 193-211.
   https://doi.org/10.1146/annurev.genet.41.110306.130304
   (Comprehensive review on genetic tools and mutants in C. albicans)
3. Brown, A. J. P., et al. (2014). Stress adaptation in a pathogenic fungus. Journal of Experimental Biology, 217(1), 144-155.
   https://doi.org/10.1242/jeb.089888
   (Discusses stress-related mutations and their roles in pathogenesis)
4. Sanglard, D., & Coste, A. T. (2016). Mechanisms of antifungal drug resistance in Candida. Cold Spring Harbor Perspectives in Medicine, 6(7), a019752.
   https://doi.org/10.1101/cshperspect.a019752
   (Details mutations involved in antifungal resistance in Candida species)
5. Selmecki, A. M., et al. (2010). Aneuploidy and isochromosome formation in drug-resistant Candida albicans. Science, 313(5785), 367-370.
   https://doi.org/10.1126/science.1128242
   (Study on genetic mutations leading to antifungal resistance)