Scanning Electron Microscopy of Colonies of Six Species of Candida

Abstract

Thirty strains of six species of Candida isolated from patients were cultured for 60 h on Sabouraud agar, freeze-dried, and examined with a scanning electron microscope. The colonies were circular (Candida albicans, C. guilliermondii) or oval (C. tropicalis, C. pseudotropicalis, C. krusei, C. parakrusei) in outline, and those of C. pseudotropicalis and C. krusei had an irregular outline due to a peripheral pseudomycelium. The morphology of individual microorganisms was examined at the margins and apex of those species which lacked a surface coat (C. pseudotropicalis, C. krusei, C. parakrusei, C. guilliermondii), and through cracks in the surface coating of those which showed a surface coat (C. albicans, C. tropicalis). All species showed buds, bud scars, and interconnecting intercellular processes, but were generally spherical (C. albicans, C. tropicalis) or ovoid (C. pseudotropicalis, C. krusei, C. parakrusei, C. guilliermondii) in fixed preparations. In unfixed material, individual organisms were almost invariably indented. Fixation with 3% glutaraldehyde and washing before freeze-drying caused partial removal of the surface coating of colonies of C. albicans and C. tropicalis, which persisted only as irregular sheets or as a filamentous meshwork. This filamentous meshwork was also present among the organisms of colonies of C. albicans, C. tropicalis, and C. pseudotropicalis. It is concluded that these filaments represent the precipitation or unmasking of some component of the intercellular matrix of these organisms.

Scanning Electron Microscopy of Candida albicans Chlamydospores

“…Further studies on C. albicans using the scanning electron microscopic method showed filamentous forms and yeast-like cells (3,5) as well as chlamydospores (1) but none of them showed suspensor cells. Shannon (4) observed long, narrow cylindrical elements of the pseudohypha of C. albicans suggesting a suspensor cell.…”

Adaptations of the Secretome of Candida albicans in Response to Host-Related Environmental Conditions

“…Three of the 11 corresponding genes ( CHT3 , which encodes the major chitinase; ENG1 , which encodes an endo-β-1,3-glucanase; and SCW11 , which encodes a β-1,3-glucan-modifying enzyme) are periodic genes with maximal expression in the M/G 1 period of the cell cycle and are target genes of the transcription factor Ace2 ( 17 – 20 ), consistent with a role in cell separation. Agar-grown colonies, mucosal biofilms, and biofilms formed on abiotic surfaces produce abundant amounts of extracellular matrix material ( 3 , 21 – 23 ). The transglucosylase Bgl2 and the exoglucanase Xog1 (together with the GPI-modified, putative β-1,3-glucan-elongating enzyme Phr1) seem to be directly involved in formation and modification of extracellular matrix material in biofilms ( 24 ).…”

Covalently linked cell wall proteins ofCandida albicans and their role in fitness and virulence

“…Such helical molecules can assume various conformations varying between a condensed and a fully extended state. Cells in colonies and biofilms are surrounded by an extracellular matrix (Joshi et al, 1973;Calderone et al, 1984;Blankenship & Mitchell, 2006). This matrix consists of proteins and polysaccharides, but its exact composition, its architecture, and its precise relationship with the cell wall are incompletely understood (Al-Fattani & Douglas, 2006).…”