Abstract
Fungal chitinases play important roles in the decomposition of wastes, mycoparasitism, and biocontrol of nematodes and plant pathogens through chitin biodegradation. This study was conducted during 2013–2017 to investigate the presence of chitinase genes in <em>Trichoderma</em> and <em>Clonostachys</em> species from the Birjand plain, and to evaluate their ability to degrade chitin. Fungal spores and soil suspensions were cultured on minimal medium containing 1% colloidal chitin from crab bodies to isolate chitinolytic fungi. Chitinolytic ability of the isolates was evaluated on this medium by staining with 1% Lugol’s iodine solution and screening for the production of a bright halo around the colonies. Fifty-two isolates capable of degrading chitin were recovered. DNA extracted from the isolates was amplified using Chit2 or DECH degenerative primers that are related to the chitinase gene, and their sequences were aligned using the NCBI GenBank database. The Chit2 and DECH primers amplified 600-bp and 250-bp fragments, respectively, and according to sequence alignment, the isolates had sequences similar to that of the <em>chi18</em> chitinase genes. Morphological and molecular characterization allowed identifying the isolates as belonging to the species <em>Trichoderma harzianum</em> (<em>n</em> = 41), <em>T. longibrachiatum</em> (<em>n</em> = 1), <em>T. virens</em> (<em>n</em> = 3), <em>T. brevicompactum</em> (<em>n</em> = 1), <em>Clonostachys rosea</em> (<em>n</em> = 5), and <em>C. rogersoniana</em> (<em>n</em> = 1), some of which may potentially be used as biocontrol agents of pathogenic nematodes and fungi. This is the first report of isolation of fungi capable of chitin biodegradation from the South Khorasan Province in Eastern Iran.
Highlights
Chitin is a structural, long-chain polysaccharide of N-acetylglucosamine subunits with beta 1,4 glycosylated bonds and the second postcellulose polysaccharide in nature [1]
The presence of chitinase genes and the ability to express chitinolytic enzymes by the Trichoderma and Clonostachys isolates collected from the Birjand region of Eastern Iran were investigated using molecular screening for the chitinase genetic markers and in vitro analysis of enzymatic activity on solid culture medium containing chitin
The culture medium used in this study contained 1% colloidal chitin as a source of carbon and nitrogen
Summary
Long-chain polysaccharide of N-acetylglucosamine subunits with beta 1,4 glycosylated bonds and the second postcellulose polysaccharide in nature [1]. This compound is found in the exoskeleton of arthropods, flatworms, protozoans, and crustaceans [2]. Chitinolytic enzymes are capable of decomposing the insoluble chitin polymer [5]. Since chitin is resistant to degradation because of its crystalline structure, its decomposition usually requires the activity of more than one type of enzyme. Chitinases include exochitinases, endochitinases, N-acetylhexosaminidase, and transglucosylase enzymes. The products of chitinase activity can control microbes and tumors, wound healing, sewage treatment, and drug delivery [6,7,8]
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