PubMed · 259649
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N Brooks. Filter validation. V. A synopsis of the PDA panel on filter validation.. https://pubmed.ncbi.nlm.nih.gov/259649/
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More and more researchers are interested in imaging living (Henderson, 1994) or fixed cells in their natural environment using the atomic force microscope (AFM). However, the AFM tip interacts strongly with the sample, and its z range freedom is limited to a few micrometers. This means that the cells to be imaged have to be strongly attached to the substrate, and imaging is restricted to cells having a flattened shape. Here we propose a simple and inexpensive solution to overcome these limitations. The method we propose is trapping living round shaped cells in a Millipore filter with a pore size comparable to the dimensions of the cell. The highest part of some of the blocked cells protrude through the holes of the filter and can this way be easily observed using the AFM without detachment.
Streptomycetes are Gram-positive bacteria growing as branching filaments. The filaments are able to deform. This ability allows the cells to squeeze through capillaries as small as 0.2 micron in diameter. After passage through the capillaries, numerous hyphae are morphologically altered to a helical structure.
The study of the morphology of the surface of several mycobacterial species differing in their pathogenicity by the methods of scanning and transmission electron microscopy has revealed that cells in such colonies and micrococlonies are associated and form one common layer of medium electron density. The cells in this layer are sharply outlined. The cover on the surface of mycobacterial colonies, revealed in this investigation, ensures the stability of mycobacteria in the environment and their resistance to the action of various chemical and physical factors.