Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

    120/152 (page 108)
    Structure and Development of Yeast. Some idea of the structure and normal method of re- production of Yeast cells will be given by a comparative examination of the different stages represented in Fig. 38. All the phenomena of life, digestion, division, reproduc- tion, excretion etc. are performed within the limits of a single cell, which is usually oval in shape, but it may elongate, and in some cases may even form a system of threads such as is shown in Fig. 38 b, that is to say typical fungal hyphae may be formed. In the above expeiiment probably only oval cells will be seen and the student by the com- parison of a large number of the cells will find all stages in the production of daughter cells from a parent cell by the process known as Budding. The small buds arise often from two or three points in a cell, and each very quickly attains a size equal to the cell which bore them. As they in turn also form new cells by the production of buds it is obvious that in a comparatively short time even in a test-tube culture there will be many mil- lions of cells. It is the presence of multitudes of these cells which causes the turbidity in beer-wort. Inside' the cell are the nucleus and the granules. In addition one or more spaces, apparently but not really empty, are seen in earh red. Close attention should be given to the granules and spaces and the different ways in which these are disposed should be noted. Also a few drawings should be made of the varying shapes that different yeast cells assume. Exercise 90 Wort-agar culture of Yeast. 1. Inoculate Wort-agar with a particle of pressed Yeast. 2. Incubate at 30 0 C. 0 Fig. 38.— Various stages in the “budding” of Yeast cells. In b the cells show a tendency to form a system of threads. This is formed by the slight elongation of the cells and the adherence of the daughter- to the parent-cells.