TO4 j. £2 HOLDEN 
chromatographic patterns (cf. VENKATA RaAm!®, CLosE%’). By far the most ambitious 
undertaking of this sort has been the examination of the lactobacilli and micrococci 
by the group at the University of Reading cited earlier’, 30-34, 62, 63, 119, 161. This 
work has included a study of 73 strains of the L. casei-plantarum group, 55 strains of 
micrococci and gi strains of heterofermentative lactobacilli. Recognizing the pitfalls 
arising from the variability of microbial pools and the necessity of using carefully 
controlled cultural and analytical conditions, apparently reliable separations of species 
have been achieved in some cases. An example of the separation of L. casei and L. 
plantarum is shown in Table XII. A common experience in this work was the finding 
that strains within a species could show considerable pool differences but would retain 
certain characters in a constant relation thereby permitting their distinction from 
the strains of another species. The separation of the heterofermentative lactobacilli 
into discrete groups was not attained even after an analysis of the data by an elec- 
tronic computer. On the whole, the authors retain a cautious optimism that the tech- 
nique as an adjunct to conventional biochemical tests may simplify the classification 
of the lactobacilli. 
CONCLUSION 
One of the most obvious conclusions of this survey is the lack of constancy of the 
microbial pool. This is most likely a consequence of the dependence of the pool com- 
position on the external environment and the ease with which the latter can be changed 
consciously or inadvertently. It is likely that this is not a property peculiar to this 
class of organisms and that pool variability will be generally encountered in cells 
cultured in vitvo. Thus, whereas Roperts ef al. (p. 284, this Symposium) has observed 
a remarkable constancy in the cellular pools in various mammalian tissues even in 
animals subjected to severe physiological stresses, EAGLE et al. (p. 694, this Sym- 
posium) find that mammalian cells grown in tissue culture can have a highly variable 
pool composition distinctly dependent on changes in composition of the extracellular 
fluid. 
Accordingly, the value of purely descriptive studies of pool composition in micro- 
organisms seems very much open to question. This would not extend, of course, to 
the examination of pools as an adjunct to studies of physiological and metabolic 
processes in a given microbial strain. However, even here, the high incidence of negative 
findings suggests that the examination of the pool should go beyond a description of 
the static state to include the turnover of its components. Indeed by combining 
isotopes and the chromatographic method to permit rapid monitoring of various 
components, examination of the multicomponent pool can provide a penetrating 
insight into the pathways of intracellular metabolism as they relate to physiological 
processes. 
ACKNOWLEDGEMENTS 
The preparation of this manuscript and the original observations of the author 
described here were made possible by Grant E-1487 from the U.S. Public Health 
Service, and by Contract No. Nonr-2702(00) between this institution and the Office 
of Naval Research. 
References p. 105/108 
