116 



S. S. COHEN 



possibility; an increase of these materials in patients with metastasizing 

 tumors warrants the exploration of both possibilities in connection with the 

 origin of metastases. 



3. Diaminopimelic Acid Deficiency 



As mentioned in the previous section, and as sunmiarized by Work (1955), 

 diaminopimelic acid (DAP) is confined to the cell wall in E. coli and indeed 

 in many microorganisms. In E. coli, this amino acid is the precursor to lysine, 

 although lysine is derived from another metabolite, a-aminoadipic acid, in 

 yeast (Davis, 1956). These relationships are given in formula (v). 



COOH 



+■ 



E.coli 



=cor 



CHNH, 



I 

 I 



T 



CHz 



I 



CHNH, 



I " 



COOH 



ci;,€-diaminopimelic acid 



GH,NH, 



I 



CH, 



I 



r ■ 



CHNH2 



COOH 

 Lysine 

 (V) 



Yeast 



COOH 



I 



CH, 



I 



CH, 



I 



CHNH, 



I 



COOH 

 ce-aminoadipic acid 



A number of workers have discovered independently that a DAP deficiency 

 can lead to cell lysis (Rhuland, 1957; Meadow et al., 1957; Bauman and 

 Davis, 1957) and, if the deficiency is maintained under conditions of growth 

 and in the presence of hypertonic sucrose, a protoplast will be formed. 

 Meadow et al. (1957) have demonstrated that lysine is essential for the 

 development of cell lysis in the absence of DAP. Under these conditions there 

 is thus a selective interference with cell wall formation, leading to continuous 

 cell growth without production of cell walls, as in the case of penicillin. 

 Bauman and Davis (1957) have exploited the use of thymine-deficiency in 

 strain 15^" and of DAP-deficiency in auxotrophic mutants for the selection 

 of other requirements in these bacteria, since the suicidal tendencies of these 

 organisms are minimized in the presence of multiple deficiencies, a fact also 

 used in the isolation of polyauxotrophs of the molds, Ophiostoma and 

 Aspergillus (Fries, 1948; Pontecorvo, 1953). 



4. Carotenoid Deficiencies in Photosynthetic Bacteria 

 The previous instances describe pathology causally related to the inability 

 to produce nuclear and cell wall constituents durmg continuing synthesis of 



