Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Abstract

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.

Red Soils Harbor Diverse Culturable Actinomycetes That Are Promising Sources of Novel Secondary Metabolites

“…Antagonistic activity against fungi can also be attributed to chitinolysis (68). Among the red soil actinomycetes, we detected a high rate of chitinolytic strains that correlated with a higher occurrence (39%) of activity against fungi than in nonchitinolytic strains (13%).…”

Connotation of Enterobacter cloacae-W6 and Serratia ficaria-W10 with or without carriers for improving growth, yield and nutrition of wheat

“…Biostimulators modulate plant growth by auxin, cytokinin, gibberellin and abscisic acid production (Upadhyaya et al, 1991;Frankenberger and Arshad, 1995;Roy and Basu, 2004;Chi et al, 2005). Bioprotectors induce stress (biotic and abiotic) tolerance or resistance in plants with the production of antibiotics, siderophores, HCN, exopolysaccharides and chitinases (Antoun et al, 1978;Kloepper et al, 1980;Liu et al, 1995;Antoun and Prevost, 2000;Neeraja et al, 2010;. The sole inoculation of PGPR strain may perform better if it could be connoted with other beneficial strain.…”

Synthesis of Long-Chain Chitooligosaccharides by a Hypertransglycosylating Processive Endochitinase of Serratia proteamaculans 568

“…Chitinases are found in a wide range of organisms, including bacteria, fungi, plants, and animals and are closely associated with the physiological roles of their substrates (4). Chitinases can be divided into two major categories: exochitinases acting from termini and randomly acting endochitinases (6,22). Based on amino acid sequence similarity, chitinases are classified into families 18 and 19 of the glycoside hydrolases (GH), described in the Carbohydrate Active enZYme (CAZy) database (http://www.cazy.org/) (14).…”