Purification and characterization of an antibacterial substance produced by pest-originated Serratia marcescens Mm3

Abstract

IntroductionSince the exploration of penicillin as a natural antibiotic and its subsequent production on a massive scale, antibiotics have revolutionized approaches to human health (Bennett and Chung, 2001). They have been used in human healthcare and in different fields such as the agricultural industry and veterinary medicine. As a result of the widespread use of antibacterials, antibiotic-resistant pathogens have been widely and continuously reported by the World Health Organization (WHO, 2000). In addition, synthetic chemicals that can negatively affect the environment and human and animal health have been used as antimicrobials (Hodgson and Levi, 1996;Zwir-Ferenc and Biziuk, 2004). Therefore, researchers always aim to find safe alternatives, such as natural and environmentally friendly antimicrobials (Tronsmo and Hjeljord, 1998).The need for novel antimicrobials to combat increasing antibiotic resistance in pathogenic bacteria has stimulated the exploration of nontraditional sources, such as terrestrial actinomycetes or fungi (Berdy, 2005). Marine organisms have been a rich source of novel antibacterial compounds (Zhang et al., 2005). Unfortunately, knowledge about antimicrobial substances of microorganisms isolated from pests is very limited.Serratia is a genus of gram-negative, facultative anaerobic, and rod-shaped bacteria of the family Enterobacteriaceae. The most common species in the genus, S. marcescens, is normally the only pathogen, and usually causes nosocomial infections (Hejazi and Falkiner, 1997). The ability of S. marcescens to inhabit a wide variety of ecological niches has been linked to its extracellular products, including proteases, chitinases, nucleases, lipases, wetting agents, bacteriocins, and the bright red pigment 2-methyl-3-penthyl-6-methoxyprodigiosin or prodigiosin (Matsuyama et al., 1995;Thomson et al., 1997). In addition, the genus Serratia is able to produce β-lactam antibiotic and 1-carbapen-2-em-3-carboxylic acid (carbapenem; Car) (Williams and Quadri, 1980;Parker et al., 1982). Furthermore, secondary metabolites such as antibiotics and bacteriocins produced by the genus Serratia are very important in various industrial fields because of their antibacterial activities. Additionally, several Serratia strains have the potential to control insect pests (Sezen and Demirbag, 2006;Jeong et al., 2010) and plant-pathogenic bacteria (Ordentlich et al., 1998).In the current study, in order to determine a novel antibacterial substance as an alternative to existing antimicrobials, we characterized an antibacterial substance