Page 201 - The Biochemistry of Inorganic Polyphosphates

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WU095-09
WU095/Kulaev
Bioremediation of the environment 185
(Zilles et al., 2002). Certain species within the Rhodocuclus group should be mainly re-
sponsible for EBPR, at least under certain circumstances.
Modern approaches to the identification and quantification of microorganisms in acti-
vated sludge include use of the 16S rRNA-targeted oligonucleotide probe (Wagner et al.,
1994; Brdjanovic et al., 1999; Kawaharasaki et al., 1999; Onda and Takii, 2000; Liu et
al., 2001; Serafim et al., 2002) and quinone profiling (Hiraishi et al., 1998). The results of
16S rDNA clone library and fluorescence in situ hybridization (FISH) with rRNA-targeted,
group-specific oligonucleotide probes revealed many new bacterial species in activated
sludge. Staining of PolyP and PHA granules confirmed that these bacteria accumulate PHA
andPolyPjustaspredictedbythemetabolicmodelsforEBPR.Forexample,Corynebacteria
(Bark et al., 1993), Microthrix parvicella (Erhardt et al., 1997), Tetracoccus cechii (Blackall
et al., 1997), Gram-positive cocci belonging to a new genus, Tetrasphaera gen. nov., and two
new species of Tetrasphaera japonica, i.e. Tetrasphaera australiensis sp. nov. (Maszenan
et al., 2000) and Tetrasphaera elongata sp. nov. (Hanada et al., 2002), Gemmatimonas
aurantiaca gen. nov., sp. nov. (Zhang et al., 2003) and Accumulibacter phosphatis (Hessel-
mann et al., 1999; Liu et al., 2001) were identified in activated sludges. Unexpectedly, one
paper reported that the major PolyP-accumulating cells in the studied sludge were clustered
spores of yeast (Melasniemi and Hernesmaa, 2000).
DAPI and PHA staining procedures could be combined with FISH to identify directly
the PolyP- and PHA-accumulating traits of different phylogenetic groups. For example,
Accumulibacter phosphatis (Hesselmann et al., 1999; Liu et al., 2001) and the represen-
tatives of a novel gamma-proteobacterial group were observed to accumulate both PolyPs
and PHA. The representatives of another novel group, closely related to coccus-shaped
Tetrasphaera, and one filamentous group resembling Nostocoidia limicola, were found to
accumulate PolyPs but not PHA (Liu et al., 2001). An interesting example of PolyP accu-
mulation was observed in the denitrifying bacterium Paracoccus denitrificans (Barak and
Rijn, 2000). PolyP synthesis by this bacterium took place with either oxygen or nitrate as
the electron acceptor and in the presence of an external carbon source. It was concluded that
P. denitrificans is capable of combined P i and nitrate removal with no need of alternating
anaerobic–aerobic or anaerobic–anoxic switches. The observed diversified functional traits
suggested that different substrate metabolisms were used by predominant phylogenetic
groups in EBPR processes (Liu et al., 2001).
According to the modern data, EBPR is realized by complicate microbial communities
(Bond and Rees, 1999; Mino, 2000; Keasling et al., 2000; Blackall et al., 2002; Hollender
et al., 2002; Serafim et al., 2002; Seviour et al., 2003). Some bacteria of these communities
are very difficult to isolate and cultivate in pure cultures. The microbial community structure
of the EBPR process depends on waste composition, organic substrates and inorganic
compounds. High microbial diversity of the EBPR sludge has been demonstrated by new
techniques. It was suggested that EBPR sludges consist of several different chemotaxonomic
groups. In other words, the EBPR sludge phylogenetically consisted of several different
microbialgroups, and their metabolic co-operation allowsthem to grow in special conditions
such as wastewater treatment plants.
In EBPR processes, one of the problems is utilization of accumulated phosphate of the
sludge. It has been discovered that nearly all PolyPs could be released from activated sludge
simply by heating it to 70 ˚C for about 1 h (Kuroda et al., 2002). The chain lengths of the
released PolyPs ranged from 100 to 200 P i residues. The addition of CaCl 2 precipitated