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Appl. Environ. Microbiol., May 1995, 1720-1726, Vol 61, No. 5
L Chernin, Z Ismailov, S Haran and I Chet
Three Enterobacter agglomerans strains which produce and excrete proteins
with chitinolytic activity were found while screening soil-borne bacteria
antagonistic to fungal plant pathogens. The chitinolytic activity was
induced when the strains were grown in the presence of colloidal chitin as
the sole carbon source. It was quantitated by using assays with chromogenic
p-nitrophenyl analogs of disaccharide, trisaccharide, and tetrasaccharide
derivatives of N-acetylglucosamine. A set of three fluorescent substrates
with a 4-methylumbelliferyl group linked by (beta)-1,4 linkage to
N-acetylglucosamine mono- or oligosaccharides were used to identify the
chitinolytic activities of proteins which had been renatured following
their separation by electrophoresis. This study provides the most complete
evidence for the presence of a complex of chitinolytic enzymes in
Enterobacter strains. Four enzymes were detected: two
N-acetyl-(beta)-d-glucosaminidases of 89 and 67 kDa, an endochitinase with
an apparent molecular mass of 59 kDa, and a chitobiosidase of 50 kDa. The
biocontrol ability of the chitinolytic strains was demonstrated under
greenhouse conditions. The bacteria decreased the incidence of disease
caused by Rhizoctonia solani in cotton by 64 to 86%. Two Tn5 mutants of one
of the isolates, which were deficient in chitinolytic activity, were unable
to protect plants against the disease.
Copyright © 1995, American Society for Microbiology
Chitinolytic Enterobacter agglomerans Antagonistic to Fungal Plant Pathogens
Otto Warburg Center for Biotechnology in Agriculture, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel, and Center "Bioengineering," Russian Academy of Sciences, 117334 Moscow, Russia
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