INHERITANCE IN SINGLE BACTERIAL CELLS 



W. Howard Hughes 



Wright-Fleming Institute of Microbiology, St. Mary's Hospital, London 



When Demerec (1948) presented his views on stepwise 

 mutations he stimulated a number of independent workers to 

 challenge them (Hughes, 1952: Eagle, Fleischman and Levy, 

 1952; Mayr-Harting, 1955). While agreeing with the general 



005 



0-01 0-02 0-03 004 

 Penicillin concentration (u./ml.) 



Fig. 1. Titration of sensitivity of single-cell strains of staphylococci using 



small implants. Key to curves : , parent strain ; , single-cell strain 



I ; •-•-•, single-cell strain II. Parent strain and strain I give a value of 



0-0325 u./ml. for 0% survivors. Strain II gives a value of 0-035 u./ml. under 



identical conditions. (Hughes, W. H. (1952), J. gen. Microbiol, 6, 175.) 



picture of the emergence of resistance as he painted it, the 

 present author objected to his conclusions that there were 

 clearcut steps in the process, believing the steps might be 

 artifacts imposed by the limitations of titration methods 

 generally. It seemed that only by working throughout with 

 single cell isolates or by maintaining a continuous photo- 

 graphic observation would it be possible to settle this question 



