Uptake of P32 and Ca45 by
Pure and Mixed Cultures of Bacteria
MAN M. VARMA, Associate Professor
Department of Civil Engineering
Howard University
Washington, D. C.
DAVID H. STONEFIELD, Engineer
U. S. Army
Washington, D. C.
INTRODUCTION
A long time ago scientists conquered the frontier of the microbial world.
Since then, sanitary engineers have tried to detect various species of bacteria as
an indicator of pollution and to correlate the degree of pollution of water with the
bacterial concentration.
The usual method, employed by sanitary engineers for the detection of bacteria, consists of growing the colonies on selective media. These methods are
long and may take from 16 hrs to five days to complete (1). Differential tests,
based on biochemical behavior of the bacterium, are used to identify a particular
group of bacteria. Many of the tests must be carried out in several steps. These
tests are also long and time consuming.
Levin et al (2) used lactose broth tagged with carbon-14 to detect the presence of members of the coliform group. This method indicates that the usual presumptive test, as described in "Standard Methods" (1), can be duplicated, by
using radioactive material, in four hrs.
Varma andReid (3) measured the uptake of radioactive phosphorus by bacteria.
Their studies indicated a high degree of correlation between uptake of phosphorus-
32 and the growth of Seratia marcescens. Varma (4) contends that the total uptake
of a radioactive tracer by the bacteria will not only vary from species to species
but will also vary from one radioisotope to another.
The purpose of this research was to study the uptake of Ca4J> and p32 by pure
and mixed cultures of bacteria.
*
The pure cultures were Escherichia coli and Proteus vulgaris. The mixed
cultures were obtained from raw sewage, secured from a local treatment plant.
SELECTION OF ORGANISMS
a/z is a typical member of the coliform group which is found in sewage
ish water. P. vulgaris differs from E. coli m that it is not included in the
E. col
and in fresh water. P. vulga
coliform group and seldom is found in unpolluted water, however, it is often present in sewage. These bacteria are typical of the many species present in sewage.
Therefore, pure cultures of E. coli and P. vulgaris were selected as test organisms.
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