Bioremediation of DDT in soil by genetically improved strains of soil fungus Fusarium solani

J. Mitra et al., Bioremediation of DDT in soil by genetically improved strains of soil fungus Fusarium solani, BIODEGRADAT, 12(4), 2001, pp. 235-245
Citations number
Categorie Soggetti
Biotecnology & Applied Microbiology
Journal title
ISSN journal
0923-9820 → ACNP
Year of publication
235 - 245
SICI code
Bioremediation of DDT in soil by genetically improved recombinants of the s oil fungus Fusarium solani was studied. The parent strains were isolated fr om soil enriched with DDD or DDE (immediate anaerobic and aerobic degradati on products of DDT), as further degradation of these products are slow proc esses compared to the parent compound. These naturally occurring strains is olated from soil, however, are poor degraders of DDT and differed in their capability to degrade its metabolites such as DDD, DDE, DDOH and DBP and ot her organochlorine pesticides viz. kelthane and lindane. Synergistic effect was shown by some of these strains, when grown together in the medium cont aining DDD and kelthane under mixed culture condition. No synergism in DDE degradation was observed with the strains isolated from enriched soil. DDD- induced proteins extracted from individual culture filtrate (exo-enzyme) wh en subjected to SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed co mplementary polypeptide bands in these strains i.e., each strain produced d istinct DDD degrading polypeptide bands and the recombinant or hybrid strai ns produced all of the bands of the two parents and degraded DDD better tha n the parental strains. Recombinant hybrid strains with improved dehalogena se activity were raised by parasexual hybridisation of two such complementa ry isolates viz. isolate 1(P-1) and 4(P-2) showing highest complementation and are compatible for hyphal fusion inducing heterokaryosis. These strains are genetically characterised as Kel(+)Ben(R)DBP(-)Lin(-) and Kel(-)Ben(r) DBP(+)Lin(+) respectively. Recombinants with mixed genotype, i.e., Kel(+)Be n(R)DBP(+)Lin(+) showing superior degradation quality for DDT were selected for bioremediation study. Recombination was confirmed by polypeptide band analysis of DDD induced exo-proteins from culture filtrate using SDS-Polyac rylamide Gel Electrophoresis (PAGE) and RAPD (Random Amplified Polymorphic DNA) of genomic DNA using PCR (Polymerase Chain Reaction) technique. SDS-PA GE showed combination of DDD induced polypeptide bands characteristic of bo th the parents in the recombinants or the hybrids. PCR study showed the par ent specific bands in the recombinant strains confirming gene transformatio n.