270 



D. E. BRADLEY 



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. T.E. Allibone, 

 F.R.S. Director of the A.E.I. 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. Microscop. Sac. 75, 254 (1956). 



