DEVELOPMENT OF HYBRID STRAINS FOR THE MINERALIZATION OF CHLOROAROMATICS BY PATCHWORK ASSEMBLY

• Published in: Annual review of microbiology Vol. 52; no. 1; pp. 287 - 331
• Main Author: Reineke, Walter
• Format: Journal Article
• Language: English
• Published: Palo Alto, CA 94303-0139 Annual Reviews 01-01-1998; 4139 El Camino Way, P.O. Box 10139 Annual Reviews, Inc; USA
• Subjects: Benzene - metabolism; Biodegradation; Biodegradation, Environmental; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Biphenyl Compounds - metabolism; Catechols - metabolism; Chlorine Compounds - metabolism; chlorocatechol; clustering of genes; conjugative gene transfer; Deoxyribonucleic acid; DNA; enzyme and effector specificity; Enzymes; Fundamental and applied biological sciences. Psychology; Genetic Engineering - methods; Genetics; Mineralization; Minerals; Mission oriented research; modified; Organic Chemicals - metabolism; Organochlorine compounds; ortho; pathway; Physiology and metabolism; Plasmids - genetics; Pseudomonas - genetics; Species Specificity; Structure-activity relationship; Toluene - metabolism; Xylenes - metabolism; Biodegradation; Recombinant microorganism; Gene organization; Metabolic pathway; Review; Metabolism; Genetic transfer; Plasmid; Gene; Chlorine Organic compounds; DNA; Bacteria; Aromatic compound
• ISSN: 0066-4227; 1545-3251
• DOI: 10.1146/annurev.micro.52.1.287

The persistence of chloroaromatic compounds can be caused by various
bottlenecks, such as incomplete degradative pathways or inappropriate
regulation of these pathways. Patchwork assembly of existing pathways in novel
combinations provides a general route for the development of strains degrading
chloroaromatics. The recruitment of known complementary enzyme sequences in a
suitable host organism by conjugative transfer of genes might generate a
functioning hybrid pathway for the mineralization of some chloroaromatics not
degraded by the parent organisms. The rational combination uses (
a
)
peripheral, funneling degradation sequences originating from
aromatics-degrading strains to fulfill the conversion of the respective
analogous chloroaromatic compound to chlorocatechols as the central
intermediates; (
b
) a central chlorocatechol degradation sequence, the
so-called modified
ortho
pathway, which brings about elimination of
chlorine substituents; and (
c
) steps of the 3-oxoadipate pathway to
reach the tricarboxylic acid cycle. The genetic organization of these pathway
segments has been well characterized. The specificity of enzymes of the xylene,
benzene, biphenyl, and chlorocatechol pathways and the specificity of the
induction systems for the chlorinated substrates are analyzed in various
organisms to illustrate eventual bottlenecks and to provide alternatives that
are effective in the conversion of the "new" substrate. Hybrid
pathways are investigated in "new" strains degrading chlorinated
benzoates, toluenes, benzenes, and biphenyls. Problems occurring after the
conjugative DNA transfer and the "natural" solution of these are
examined, such as the prevention of misrouting into the
meta
pathway, to
give a functioning hybrid pathway. Some examples clearly indicate that
patchwork assembly also happens in nature.