Common Virulence Factors and Tissue Targets of Entomopathogenic Bacteria for Biological Control of Lepidopteran Pests

Abstract

This review focuses on common insecticidal virulence factors from entomopathogenic bacteria with special emphasis on two insect pathogenic bacteria Photorhabdus (Proteobacteria: Enterobacteriaceae) and Bacillus (Firmicutes: Bacillaceae). Insect pathogenic bacteria of diverse taxonomic groups and phylogenetic origin have been shown to have striking similarities in the virulence factors they produce. It has been suggested that the detection of phage elements surrounding toxin genes, horizontal and lateral gene transfer events, and plasmid shuffling occurrences may be some of the reasons that virulence factor genes have so many analogs throughout the bacterial kingdom. Comparison of virulence factors of Photorhabdus, and Bacillus, two bacteria with dissimilar life styles opens the possibility of re-examining newly discovered toxins for novel tissue targets. For example, nematodes residing in the hemolymph may release bacteria with virulence factors targeting neurons or neuromuscular junctions. The first section of this review focuses on toxins and their context in agriculture. The second describes the mode of action of toxins from common entomopathogens and the third draws comparisons between Gram positive and Gram negative bacteria. The fourth section reviews the implications of the nervous system in biocontrol.

Diversity of fall armyworm, Spodoptera frugiperda and their gut bacterial community in Kenya

“…Notably, we identified Serratia , Lysinibacillus (formerly Bacillus ) and Pseudomonas , species of which have been reported to have entomopathogenic properties (Castagnola and Stock 2014). In addition, one sample had a high number of reads attributed to a relative of a non-bacterial entomopathogen, Metarhizium rileyi , which has been previously isolated and tested for efficiency against S. frugiperda (Maniania and Fargues 1985); Mallapur et al 2018).…”

Midgut microbiota and host immunocompetence underlieBacillus thuringiensiskilling mechanism

“…Comparatively less attention has been devoted to other important research aspects, such as the complex network of molecular interactions underpinning the host killing mechanism and the role of factors other than the pore-forming toxins that contribute to B. thuringiensis pathogenicity and virulence (20,21). A heated debate on the B. thuringiensis killing mechanism started almost a decade ago, and a consensus has not yet been reached.…”

Transgenic potato plants expressing cry3A gene confer resistance to Colorado potato beetle

“…In the study, we used the leaf and stem-specific ST-LS1 promoter to make no cry3A gene expression in stems and tubers, which seems to be more favorable to the transgenic biosafety for food. Up to now, the transgenic crops have widely appeared in many countries, and many insect-resistant strains, such as rice, cotton, creeping bentgrass, tall fescue, Arabidopsis and Brachypodium distachyon have been planted in the laboratory and in greenhouses [48][49][50][51][52][53][54]. In this study, the results from inoculation with first-instar larvae on plants showed that larvae in some transgenic lines led to higher mortality, lower insect biomass accumulation and foliage consumption.…”