Observation of baker’s yeast strains used in biotransformation by atomic force microscopy

Abstract

Different strains of baker's yeast (Saccharomyces cerevisiae) were imaged with an atomic force microscope (AFM). The images of uncoated and nonfixed samples were reproducible with high-constrast and nanometer-resolution. Molecules from the polysaccharide surface of the cell wall were pictured and the distance of atoms was measured. The preparation of samples was easy, suggesting that AFM is a useful tool in this type of analyses.

Adhesion forces measured between a calcium blocker drug and its receptor in living cells using atomic force microscope

“…With the advent of AFM, this fact changed and the cells are visualized uncoated and alive, at high resolution, producing excellent and reproducible images. Some years ago, the world's ¢rst micrographs of different industrial strains of S. cerevisiae were generated in an AFM and we could observe structures, on the cell wall, never described before and pores which vary from 50 to 250 nm [1,2]. 3.2.…”

“…Normally, in order to scan the samples of S. cerevisiae cells, each preparation is coated with a ¢lm of evaporated gold (approximately 20 nm in thickness [7,17,18]). The application of this conductive coating to the surface of the sample masks important structures which exist on the cell wall [1,2] and the cells are killed during the coating. With the advent of AFM, this fact changed and the cells are visualized uncoated and alive, at high resolution, producing excellent and reproducible images.…”

“…This property permits the use of ultra-pure water as a reaction medium, in order to avoid interferences of biochemicals (commonly used in reaction medium for equilibrating the osmotic pressure) which could produce artifacts. The experiments made, in this way, are clean, reproducible and reliable [1,6]. For this reason these are the most stable living cells to work with AFM and the images generated are very consistent with those generated by scanning electron microscopy (SEM) in terms of shape and size [9]; with the di¡erence that with AFM these cells are observed alive because the samples are not covered or ¢xed.…”

“…S. cerevisiae has cell walls which give a natural rigidity to the sample [7] and, consequently, it is not necessary to use additional methods [1,8] to give a certain rigidity to the membrane of these living cells (sample) [8]. This natural 'fortressP makes it possible to obtain images with these cells in a very natural way, with good resolution and with incredible reproducibility [1,6]. The cell wall protects S. cerevisiae against extreme hypotonic media (e.g.…”

“…For this reason these are the most stable living cells to work with AFM and the images generated are very consistent with those generated by scanning electron microscopy (SEM) in terms of shape and size [9]; with the di¡erence that with AFM these cells are observed alive because the samples are not covered or ¢xed. So, it is possible to visualize pores on the cell surface, which is impossible with SEM [1,2].…”