Environmental Engineering Reference
In-Depth Information
5
6
7
8
4
3
O
2
O
2
2
9
10
1
OH
Pyrene
OH
OH
O
2
OH
O
2
OH
COOH
O
COOH
COOH
9-Hydroxy-perinaphthylidiene
pyruvate (product E)
hermal decomposition
in GC analysis
CO
2
OH
CH
2
OH
COOH
O
O
10-Hydroxy-1-Phenanthoric
Acid (product Ga)
(product G)
hermal decomposition
in GC analysis
Figure 7.5
Proposed pathway for the cometabolism of pyrene by
S. paucimobilis
strain
EPA 505.
grow on pyrene. In the
Sphingomonas
species, however, the specificity of the
enzymes involved in the cleavage of either a three-carbon fragment
(meta-cleavage) or a two-carbon fragment (ortho-cleavage) is apparently too
narrow to allow further metabolism of the pyrene products.
It is interesting to speculate that this may be true of
Sphingomonas
species
in general because, at the present time, there are no known
Sphingomonas
species that are able to grow on pyrene.
Mycobacterium
strains, on the other
hand, can be readily isolated for their ability to grow on pyrene. In prelim-
inary studies, we have observed transient pyrene degradation products from
selected
Mycobacterium
strains that have the same spectral characteristics as
the substituted perinaphthalene product produced by EPA 505. If this is the
case, then initial degradation of pyrene may be similar in both
Mycobacterium
and
Sphingomonas
species. Recent evidence demonstrates that
nah
-like genes
can be found in
Mycobacterium
and
Rhodococcus
species (Hamann et al., 1999).
However, the
Mycobacterium
strains clearly have the ability to further metab-
olize the intermediates produced from a naphthalene-like attack on pyrene.
This was verified by the work of Rehmann et al. (1998) and Heitkamp et al.
(1988a, 1988b), who observed further degradation products. Why
Sphingomo-
nas
strains have not acquired the necessary enzymes for this transformation
