title: Characterization of putative virulence factors of Serratia marcescens strain SEN for pathogenesis in Spodoptera litura.
abstract: Two Serratia marcescens strains, SEN and ICC-4, isolated from diseased insect cadavers were observed to differ considerably in their virulence towards Spodoptera litura. The present study was aimed to characterize the possible virulence factors present in the virulent Serratia marcescens strain SEN. Both the S. marcescens strains were evaluated for the presence of various lytic enzymes such as chitinase, lipase, protease and phospholipase. The virulent S. marcescens strain SEN was observed to possess considerably higher activity of chitinase and protease enzymes; activity of phospholipase enzyme was also higher. Although, all the three toxin genes shlA, phlA and swr could be detected in both the S. marcescens strains, there was a higher expression of these genes in the virulent strain SEN. S. marcescens strain ICC-4 showed greater reduction in overall growth yield in the post-exponential phase in the presence of midgut juice and hemolymph of S. litura larvae, as compared to S. marcescens strain SEN. Proliferation of the S. marcescens strain SEN was also considerably higher in foregut, midgut and hemolymph of S. litura larvae, as compared to strain ICC-4. Peritrophic membrane treated with broth culture of the S. marcescens strain SEN showed higher damage as compared to strain ICC-4. The peritrophic membrane of larvae fed on diet treated with the virulent strain showed considerable damage while the peritrophic membrane of larvae fed on diet treated with the non-virulent strain showed no damage. This is the first report documenting the fate of ingested S. marcescens in S. litura gut and the relative expression of toxin genes from two S. marcescens strains differing in their virulence towards S. litura.
authors.affiliation: Division of Microbiology, Indian Agricultural Research Institute, New Delhi 110 012, India.
authors.forename: Chetana
authors.initials: C
authors.lastname: Aggarwal
authors.affiliation: Division of Microbiology, Indian Agricultural Research Institute, New Delhi 110 012, India. Electronic address: sangeeta_paul2003@yahoo.co.in.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Paul
authors.affiliation: School of Biotechnology, Gautam Buddha University, Greater Noida 201308, Uttar Pradesh, India.
authors.forename: Vishwas
authors.initials: V
authors.lastname: Tripathi
authors.affiliation: Division of Entomology, Indian Agricultural Research Institute, New Delhi 110 012, India.
authors.forename: Bishwajeet
authors.initials: B
authors.lastname: Paul
authors.affiliation: Department of Biology, Faculty of Science, Jazan University, Jazan, Saudi Arabia.
authors.forename: Md Aslam
authors.initials: MA
authors.lastname: Khan
mesh_terms: D000818:Animals; D020869:Gene Expression Profiling; D016133:Polymerase Chain Reaction; D016868:Serratia Infections / Q000662:veterinary*; D012706:Serratia marcescens / Q000472:pathogenicity*; D018411:Spodoptera / Q000382:microbiology*; D059467:Transcriptome; D014774:Virulence / Q000502:physiology*; D037521:Virulence Factors / Q000096:biosynthesis
chemical_list: D037521:Virulence Factors
keywords: Chitinase; Hemolysin; Peritrophic membrane; Protease; Serratia marcescens; Spodoptera litura