. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Figs. 7-8. Carbon replicas of spores of i?. 5///>r//M'. Magnifi- cation 27,000. more dense to electrons than the bacteria themselves and only a silhouette is seen. In a preliminary ex- amination, spores of Bacillus snhtilis and Bacillus hrevis were chosen and replicas prepared by the method outlined above. Figure 6 shows some typical spores of B. brevis. The surface seems to be relatively smooth save for a single rib which runs longitudinally down the cell. In the case of B. subtilis however, a larger num- ber
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Figs. 7-8. Carbon replicas of spores of i?. 5///>r//M'. Magnifi- cation 27,000. more dense to electrons than the bacteria themselves and only a silhouette is seen. In a preliminary ex- amination, spores of Bacillus snhtilis and Bacillus hrevis were chosen and replicas prepared by the method outlined above. Figure 6 shows some typical spores of B. brevis. The surface seems to be relatively smooth save for a single rib which runs longitudinally down the cell. In the case of B. subtilis however, a larger num- ber of ribs are present, and though these tend to run longitudinally down the cell (figure 7), they fre- quently intersect and form a network such as that shown in figure 8. It seems extremely unlikely that the ribbing is due to shrinkage, if only because of its form. Further- more, the water content of bacillus spores is very small and in addition, it is hardly possible that shrink- age would cause one rib running lengthwise down every cell as is the case with B. hrevis. It therefore seems certain that the structure is genuine. At this stage it is not possible to explain the ribs or their function, but it is hoped that a combined sectioning and replica study together with studies of spores after various treatments will provide much information on their structure. The author is grateful to Prof. B. C. J. G. Knight of the Department of Microbiology, University of Reading, for his valuable advice on the study of yeast, and also to Mr. D. J. Williams of The National Institute for Research in Dairying, who is collaborating with the author in the study of bacterial spores. Dr. Allibone, Director of the Research Laboratory, has kindly given permission to publish this paper. References 1. Agar, H. D. and Douglas, H. C, /. Bacteiiol. 70, 427 (1955). 2. Barton, A. A., /. Gen. Microbiol. 4, 84 (1950). 3. Bradley, D. E., Brit. J. Appl. Pins. 5, 65 (1954). 4. — /. Roy. Mi
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