Monday, 19 April
Rm 208, 2nd Floor
720 Cumberland Street, Dunedin.
Dr Mark Hurst
Forage Science, AgResearch, Lincoln Research Centre, New Zealand
Bio-Protection Research Centre, Lincoln, Christchurch, New Zealand
‘Insect pathogenicity determinants of Serratia and Yersinia bio-pesticidal agents’
Over the last several decades a range of unique NZ bacterial pathogens have been isolated from larvae of the NZ grass grub Costelytra giveni and the manuka beetle Pyronota spp. These pathogens range from the more host specific Serratia entomophila and Serratia proteamaculans, to the broad range entomopathogen Yersinia entomophaga. Bioassay assessments have found that each of the bacteria differ in their host range and virulence phenologies (slow to fast acting), with others causing more sporadic/subtle effects. The key virulence factors of these pathogens are members of two broad families of insect active proteins: i) the Toxin Complex, a composite of three proteins, A, B and C and ii) the Afp tailocin, a phage-like mobile type six secretion system able to deliver its protein toxin payload to a yet to be defined target cell. Chronic strains of S. entomophila remain confined within the gut, while similar to Y. entomophaga other S. proteamculans isolates can actively breech the gut. Only a single Y. entomophaga cell is required to overwhelm the insect immune system to cause lethality. In Serratia these virulence determinants are encoded on a large conjugative plasmid while those of Y. entomophaga are chromosomally encoded. The presentation will encompass facets of these bacteria from virulence determinants, mode of action, mechanisms of virulence regulation and their potential use as biopesticides.