Molecular detection and analysis of a novel metalloprotease gene of entomopathogenic Serratia marcescens strains in infected Galleria mellonella

Abstract

Serratia marcescens strains isolated from entomopathogenic nematodes (Rhabditis sp.) were examined for their pathogenicity and establishment in wax moth (Galleria mellonella) larvae. All the Serratia strains were potently pathogenic to G. mellonella larvae, leading to death within 48 h. The strains were shown to possess a metalloprotease gene encoding for a novel serralysin-like protein. Rapid establishment of the bacteria in infected larvae was confirmed by specific polymerase chain reaction (PCR) detection of a DNA fragment encoding for this protein. Detection of the viable Serratia strains in infected larvae was validated using the SYBR Green reverse transcriptase real-time PCR assay targeting the metalloprotease gene. Nucleotide sequences of the metalloprotease gene obtained in our study showed 72 single nucleotide polymorphisms (SNP) and 3 insertions compared with the metalloprotease gene of S. marcescens E-15. The metalloprotease gene had 60 synonymous and 8 nonsynonymous substitutions relative to the closest GenBank entry, S. marcescens E-15. A comparison of the amino acid composition of the new serralysin-like protein with that of the serralysin protein of S. marcescens E-15 revealed differences at 11 positions and a new aspartic acid residue. Analysis of the effect of protein variation suggests that a new aspartic acid residue resulting from nonsynonymous nucleotide mutations in the protein structure could have the most significant effect on its biological function. The new metalloprotease gene and (or) its product could have applications in plant agricultural biotechnology.

Bacterial extracts for the control of Atta cephalotes (Hymenoptera: Formicidae) and its symbiotic fungus Leucoagaricus gongylophorus (Agaricales: Agaricaceae)

“…The extract of S. marcescens marcescens IBUN-090-00706 presented insecticide activity by ingestion. This result is in concordance with the study of Tambong et al (2014), in which the authors reported insecticidal activity against Galleria mellonella. However, the methodology was different as they injected active bacterial cells directly into the insect hemocele (most studies on entomopathogenic bacteria are done this way), contrary to this study, in which the insecticidal capacity of extracts without active bacterial cells was evaluated; in the case of this bioassay, extracts were demonstrated to act by ingestion against leaf-cutting ants.…”

Assessing the pathogenicity of gut bacteria associated with tobacco caterpillar Spodoptera litura (Fab.)

“…The S. litura larvae infected with S. marcescens and E. mundtii showed the symptoms of lethargy, dark colouration of body, flaccid with intact integument which are typical symptoms of bacterial infection 40 . Likewise P. interpunctella and E. kuehniella infected with S. marcescens showed similar symptoms of infection 32 , 34 , 36 , 41 .…”

Molecular Identification of Bacterial Pathogen Infecting Coconut Leaf Beetle

“…Serratia spp., is a gram-negative bacterium (Enterobacteriaceae) containing insect pathogenic strains (Tambong et al, 2014) against several insect species including locusts (Tao et al, 2006(Tao et al, , 2007. There are more than 70 spesies of insects are susceptible to Serratia infections including insects from order orthoptera, isopteran, coleoptera, lepidoptera, hymenoptera and diptera (Grimont et al, 1978).…”

“…However, further studies are needed to confirm the effects of this bacterium to human health and other important organisms. Metalloproteases produced by S. marcescens are potential to be developed for biological control of important insect pests (Tambong et al, 2014)…”