Kambiz Morabbi Heravi1, Garshasb Rigi2, Maryam Rezaei Arjomand3, Amin Rostami3, Gholamreza Ahmadian3. 1. Institut für Industrielle Genetik, Universität Stuttgart, Allmandring 31, 70569 Stuttgart, Germany. 2. Department of Biology, Faculty of Science, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran. 3. Department of Industrial and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran.
Abstract
BACKGROUND: Chitin is an abundant natural polysaccharide found in fungi, algae, and exoskeleton of insects. Several bacterial species are capable of utilizing chitin as their carbon source. These bacteria produce chitinases for degradation of chitin into N-acetyl-D-glucosamine. So far, regulation of the chitinase encoding genes has been studied in different bacterial species. Among Bacillus species, B. pumilus strain SG2 encodes two chitinases, ChiS and ChiL. The promoter region of chiSL genes (P chiS ) is mainly regulated by the general carbon catabolite repression (CCR) system in B. subtilis due to the presence of a catabolite responsive element (cre). OBJECTIVES: Use of P chiS in constructing an inducible expression system in B. subtilis was investigated. MATERIALS AND METHODS: In the first step, complete and shortened versions of P chiS were inserted upstream of the lacZ on a pBS72/pUC18 shuttle plasmid. The β-galactosidase activity of B. subtilis carrying one of the relevant plasmids was measured in the presence of different carbon sources. RESULTS: An expression system based on the chitinase promoter of B. pumilus SG2 was established. Modification of P chiS and the culture medium resulted in production of β-galactosidase in B. subtilis up to 1,800 Miller unit (MU) activity. CONCLUSIONS: The chitinase promoter developed in this study, has potential to be used in an expression vector that could be induced by chitin. In addition, compared to the other inducers like IPTG and lactose, chitin is definitely cheaper and more available as an inducer.
BACKGROUND:Chitin is an abundant natural polysaccharide found in fungi, algae, and exoskeleton of insects. Several bacterial species are capable of utilizing chitin as their carbon source. These bacteria produce chitinases for degradation of chitin into N-acetyl-D-glucosamine. So far, regulation of the chitinase encoding genes has been studied in different bacterial species. Among Bacillus species, B. pumilus strain SG2 encodes two chitinases, ChiS and ChiL. The promoter region of chiSL genes (P chiS ) is mainly regulated by the general carbon catabolite repression (CCR) system in B. subtilis due to the presence of a catabolite responsive element (cre). OBJECTIVES: Use of P chiS in constructing an inducible expression system in B. subtilis was investigated. MATERIALS AND METHODS: In the first step, complete and shortened versions of P chiS were inserted upstream of the lacZ on a pBS72/pUC18 shuttle plasmid. The β-galactosidase activity of B. subtilis carrying one of the relevant plasmids was measured in the presence of different carbon sources. RESULTS: An expression system based on the chitinase promoter of B. pumilus SG2 was established. Modification of P chiS and the culture medium resulted in production of β-galactosidase in B. subtilis up to 1,800 Miller unit (MU) activity. CONCLUSIONS: The chitinase promoter developed in this study, has potential to be used in an expression vector that could be induced by chitin. In addition, compared to the other inducers like IPTG and lactose, chitin is definitely cheaper and more available as an inducer.