Sv. Avery, MICROBIAL INTERACTIONS WITH CESIUM - IMPLICATIONS FOR BIOTECHNOLOGY, Journal of chemical technology and biotechnology, 62(1), 1995, pp. 3-16
The continuing release of caesium isotopes into the environment has hi
ghlighted the necessity for efficient removal of Cs from industrial wa
ste effluents prior to discharge. Existing technologies, e.g. zeolite
ion-exchange for Cs removal, can be expensive and microbial metal adso
rption/accumulation may represent a cheap alternative. The distinct ch
emical properties of Cs+, which dictate a high degree of metabolism-de
pendent uptake via monovalent cation transport systems, indicate that
different approaches are required for biological Cs removal to those w
hich are generally adopted for other metals/radionuclides. The low tox
icity of Cs+ eliminates one potential problem in the use of live cells
for Cs removal. High levels of Cs+ accumulation have been reported in
a number of microorganisms, but uptake levels vary markedly in differ
ent organisms and are strongly influenced by a number of physico-chemi
cal and mechanical parameters, e.g. the use of batch or continuous-flo
w systems, biomass immobilization (which tends to increase Cs adsorpti
on at the expense of metabolism-dependent accumulation), pH and partic
ularly the prevalence of other monovalent cations such as K+ and Na+ I
nherent differences in Cs+ uptake capacities of different microorganis
ms appear to be largely attributable to differences in the affinity of
monovalent cation transport systems for Cs+. The application of rigor
ous screening procedures involving the use of autoradiography has grea
t potential for isolation of microorganisms with particularly high aff
inities for Cs+. Alternatively, manipulation of the physiological stat
us of microorganisms can dramatically alter the transport of Cs+ and o
ther monovalent cations. Hyper- and hypo-osmotic shock, respectively,
have so far proved to be the most successful treatments for stimulatin
g Cs removal and recovery. Other manipulations, at both the cellular a
nd molecular level, which are known to influence K+ fluxes but have ye
t to be characterized for Cs+, are outlined here.