I certify that I have read this study and in my opinion 

 it conforms to acceptable standards of scholarly presenta- 

 tion and is fully adequate, in scope and quality, as a dis- 

 sertation for the degree of Doctor of Philosophy. 



Roy A.*J Jensdn, Chair 



Professor of Microbiology and Cell Science 



I certify that I have read this study and in my opinion 

 it conforms to acceptable standards of scholarly presenta- 

 tion and is fully adequate, in scope and quality, as a dis- 

 sertation for the degree of Doctor of Philosophy. 



^. 



r/)A^y^^J (y- ^ 



Lonnie 0. Ingram 



Professor of Microbiology and Cell Science 



I certify that I have read this study and in my opinion 

 it conforms to acceptable standards of scholarly presenta- 

 tion and is fully adequate, in scope and quality, as a dis- 

 sertation for the degree of Doctor of Philosophy. 



X J-S^Ah^^^ 



Schmidt 



Graduate Research Professor of 

 Microbiology and Cell Science 



