Candida albicans morphologies revealed by scanning electron microscopy analysis

Abstract

Scanning electron microscope (SEM) observations were used to analyze particular morphologies of Candida albicans clinical isolate (strain 82) and mutants defective in hyphae-promoting genes EFG1 (strain HLC52) and/or CPH1 (strains HLC54 and Can16). Transcription factors Efg1 and Cph1 play role in regulating filamentation and adhesion of C. albicans’ morphologies. Comparative analysis of such mutants and clinical isolate showed that Efg1 is required for human serum-induced cell growth and morphological switching. In the study, distinct differences between ultrastructural patterns of clinical strain’s and null mutants’ morphologies were observed (spherical vs tube-like blastoconidia, or solid and fragile constricted septa vs only the latter observed in strains with EFG1 deleted). In addition, wild type strain displayed smooth colonies of cells in comparison to mutants which exhibited wrinkled phenotype. It was observed that blastoconidia of clinical strain exhibited either polarly or randomly located budding. Contrariwise, morphotypes of mutants showed either multiple polar budding or a centrally located single bud scar (mother-daughter cell junction) distinguishing tube-like yeast/pseudohyphal growth (the length-to-width ratios larger than 1.5). In their planktonic form of growth, blastoconidia of clinical bloodstream isolate formed constitutively true hyphae under undiluted human serum inducing conditions. It was found that true hyphae are essential elements for developing structural integrity of conglomerate, as mutants displaying defects in their flocculation and conglomerate-forming abilities in serum. While filamentation is an important virulence trait in C. albicans the true hyphae are the morphologies which may be expected to play a role in bloodstream infections.

The expression of the Candida albicans gene SAP4 during hyphal formation in human serum and in adhesion to monolayer cell culture of colorectal carcinoma Caco-2 (ATCC)

“…Thus in comparison to our previous findings [10] in this study the defect in filamentation of efg1/efg1 was partially restored under the conditions used in the Caco-2 infection experiment. In fact, we found that filamentous cells were produced by the efg1/efg1 mutant but the double cph1/cph1 efg1/efg1 mutant was extremely defective for filamentation.…”

“…Lo et al [5] and Znaidi et al [37] showed that strains lacking Efg1 or/ and Cph1 are defective in efficient hyphae formation and the cph1/cph1 efg1/efg1 double mutant is unable to fully undergo morphogenesis even under hyphae inducing conditions. Our previous data acquired in laboratory culture conditions [10] indicated that the cph1/cph1 strain forms true hyphae normally (even though very rarely) in comparison to efg1/efg1 as well as cph1/cph1 efg1/efg1 fully defective in true hyphae formation under human serum influence.…”

“…The morphological transition, adhesion, biofilm formation, phenotype switching, and production of hydrolytic enzymes are involved in virulence of these fungi [1][2][3][7][8][9][10][11][12]. Genes belonging to the SAP family (SAP1-10) encode secreted aspartyl proteases (hydrolytic enzymes) which may contribute to colonization and infection by degrading components of host cell membranes [2].…”

The roles of CDR1, CDR2, and MDR1 in kaempferol-induced suppression with fluconazole-resistant Candida albicans

“…After air drying, the samples were sputter coated with gold in a vacuum evaporator, and the morphological observation was performed by a scanning electron microscope (SEM, JSM-6700F, JEOL, Tokyo, Japan) as described previously (Staniszewska et al 2013). …”

Characteristics of metal-tolerant plant growth-promoting yeast (Cryptococcus sp. NSE1) and its influence on Cd hyperaccumulator Sedum plumbizincicola

“…After 3 days, the microbial morphology was observed by scanning electron microscope (SEM) according to Staniszewska et al (2013). All experiments were conducted with triplicate sample flasks for each time sample, with 25 mL of liquid growth media in 100-mL flasks.…”