Biofeniles

2.2.2.1
Chromosomally located PCB catabolic
genes of R. eutropha A5 (SHIELDS et al., 1985),
Achromobacter sp. LBS1C1 (PETTIGREW et al.,
1990), and Alcaligenes dentrificans sp. JB1
(PARSONS et al., 1988) were transferred into a
heavy metal resistant strain R. eutropha CH34
through natural conjugation. All donor strains
degraded biphenyl and monochlorobiphenyls
to corresponding benzoateand chlorobenzoates.
Benzoate was further metabolized via
the o-cleavage pathway in strains A5 and
LBS1C1, and via the m-cleavage pathway in
strain JB1. Strain A5 harbored a catabolic
transposon, Tn4317, which carried biphenyl
and 4-chlorobiphenyl degradation genes
(SPRINGEAL et al., 1993a). The dehalogenase
activity was mediated by plasmid pSS50 in
strain A5 (LAYTON et al., 1992).Transfer of PCB degradation genes from A5
to the heavy metal resistant strain CH34 was
carried out by conjugation (SPRINGAEL et al.,
1993b).The constructed strain,AE707, exhibited
phenotype of BphcCbpc, and degraded
4-chlorobiphenyl to 4-chlorobenzoate in the
presence of heavy metals. In resting cell assays
(grown on biphenyl), strain AE707 cometabolized
di- and trichlorinated congeners ofAroclor
1242T in the presence of heavy metals.The
PCB catabolic chromosomal genes of strain
JB1 were transferred into CH34 through
RP4::Mu3A mediated R-prime plasmid formation
(SPRINGAEL et al., 1994). A transconjugant,
strain AE1216, utilized 2-, 3- and 4-chlorobiphenyl
and exhibited properties of metal resistance.

2.2.2.2 Pseudomonas sp. –
Hybrid Strains
Pseudomonas putida BN10 grew onbiphenyl
and accumulated metabolites of 2-, 4-chlorobenzoate
and 3-chlorocatechol from corresponding
monochlorobiphenyls. 3-Chlorobiphenyl
degraders were obtained from conjugation
between Pseudomonas sp. B13 and
strain BN10.The resulting Pseudomonas strain
BN210 (gained chlorocatechol degradation
genes) and B131 (acquired biphenyl degradation
genes) were able to grow on 3-chlorobiphenyl.Both strains exhibited the capability to
degrade monochlorobiphenyls and 2 of the
dichlorobiphenyls found in Aroclor 1221T
(MOKROSS et al., 1990).
Another hybrid Pseudomonas sp. strain
UCR2 was isolated from multi-chemostat mating
between a chlorobenzoate degrader, P.
aeruginosa JB2, and a 2-chlorobiphenyl utilizer,
Arthrobacter sp. strain B1Barc (HICKEY et
al., 1992). Strain UCR2 exhibitedability to
mineralize 2-chloro- and 2,5-dichlorobiphenyl.
The UCR2 showed higher phenotypic similarity
and higher genomic DNA homology to
strain JB2. No hybridization was observed
when the parental strains were probed against
each other.
Recombinant Pseudomonas sp. strain CB15
was obtained by multi-chemostat mating by
chlorobiphenyl after 5 d in lake sediment microcosms
(DOWLING et al.,1993).The plasmid,
pDDPCB, was later transferred into a rhizosphere
pseudomonad, Pseudomonas fluorescens
F113, by conjugation to generate a genetically
modified strain F113pcb (BRAZIL et al.,
1995).The bph operon was chromosomally located
and was stable in non-sterile soil microcosms
for 25 d after inoculated onto sugar beet
seeds. Strain F113pcb gained the ability to
utilize biphenyl asa sole carbon source.

2.2.2.3 Pseudomonas cepacia
JHR22
HAVEL and REINEKE (1991) reported a hybrid
bacterium, Pseudomonas cepacia JHR2,
was constructed by filter mating with a biphenyl-
grown donor and a chlorobenzoate-grown
recipient (P. cepacia JH230). Strain 230 is a hybrid
strain that originated from the transfer of
chlorocatechol degradative genes from strain
B13 into Pseudomonassp. WR401 (HARTMANN
et al., 1989). Strain JHR2 was able to
grow on 3- and 4-chlorobiphenyl. A 2-chlorobiphenyl
degrader, JHR22, was obtained by
growing JHR2 with 4-chlorobenzoate (1 mM)
in the presence of 2-chlorobiphenyl (3 mM).
The new hybrid strain, P. cepacia JHR22,
showed capability to utilize 2-chloro-, 3-chloro-,
4-chloro-, 2,4-dichloro-, and 3,5-dichlorobiphenyl
as sole source...