Page 202 - The Biochemistry of Inorganic Polyphosphates

WU095/Kulaev
WU095-09
Applied aspects of polyphosphate biochemistry
186 March 9, 2004 15:44 Char Count= 0
approximately 75 % of the total phosphorus without pH adjustment. The formed precipitate
contained more phosphorus and less calcium than typical natural phosphorite deposits.
Hence, in combination with EBPR, the present method has a potential for development of
a simple process for recovering phosphorus in reusable form from wastewaters (Kuroda
et al., 2002).
There are many important problems remaining concerning the PolyP biochemistry of
EBPR. First, a clear definition of the microbial community structure of EBPR processes
and the mechanisms of ecological selection for such processes is needed. Since many
microorganisms from EBPR plants seem to be non-cultivated in pure cultures, molecular
methods are surely powerful tools for this purpose. A common EBPR metabolism seems to
include phylogenetic diverse microbial populations. This suggests a possibility of the key
genes of EBPR metabolism being common among different bacteria. It is important and
interesting to determine such key genes and to find out how they are regulated.

9.1.2 Removal of Heavy Metals from Waste

PolyPs have been implicated as strong chelators of divalent cations, including cations of
heavy metals. PolyP metabolism plays an important role in the bioremediation of phosphate
contamination in municipal wastewaters and may play a key role in heavy metal tolerance
and bioremediation (Boswell et al., 1999). Some genetic constructions for enhancing the
tolerance of bacteria to heavy metals have been developed (Keasling and Hupf, 1996;
Keasling et al., 2000). A plasmid was constructed for mercury bioaccumulation, using the
fusion of the well-known mer-operon from Pseudomonas with the ppk gene from Klebsiella
aerogenes. The E. coli strain with the plasmid accumulated 10-fold more Hg 2+ and two-fold
more phenylmercury from contaminated medium (Pan-Hou et al., 2002). A large amount of
PolyP was identified in the mercury-induced bacterium but not in the cells without mercury
induction. It was suggested that PolyP may play a direct role in mercury resistance, probably
via chelate formation rather than precipitation of mercury, by releasing P i from the PolyP
(Pan-Hou et al., 2002). A strain of Acinetobacter johnsonii was capable of removing La 3+
from solution via precipitation of cell-bound LaPO 4 (Boswell et al., 2001). The PolyP-
mediated accumulation from waste could serve as a useful strategy for the direct remediation
of organic and inorganic heavy-metal-containing pollutants.

9.2 Polyphosphates and
Polyphosphate-Metabolizing Enzymes
in Assay and Synthesis

The cheapness of PolyP, which may be easily obtained by chemical synthesis from P i ,is
the reason for attempts to employ methods where its high-energy phosphoanhydryde bonds
can be used in assay and synthesis processes. At the present time, many PolyP-depending
enzymes are available in large quantities and with high degrees of purification, and this has
facilitated the development of such methods.