Bacteria in oral secretions of an endophytic insect inhibit antagonistic fungi

  • Author(s): Cardoza, Yasmin J.; Klepzig, Kier D.; Raffa, Kenneth F.;
  • Date: 2006
  • Station ID: Miscellaneous Publication-SRS-


1. Colonisation of host trees by an endophytic herbivore, the spruce beetle, Dendroctonus rufipennis , is accompanied by invasion of its galleries by a number of fungal species. Four of these associated species were identified as Leptographium abietinum , Aspergillus fumigatus , Aspergillus nomius , and Trichoderma harzianum.

2. Trichoderma and Aspergillus significantly reduced spruce beetle survival and reproduction in controlled assays.

3. A previously undescribed behaviour was observed, in which spruce beetle adults exuded oral secretions, especially within fungus-pervaded galleries.

4. These oral secretions inhibited the growth of fungi except A. nomius , and disrupted the morphology of the latter. Administration of these secretions indicated a dosedependent inhibitory effect.

5. Oral secretions cultured on microbiological media yielded substantial bacterial growth.

6. Filter-sterilised secretions failed to inhibit fungal growth, evidence that the bacteria are responsible for the antifungal activity.

7. Nine bacterial isolates belonging to the Actinobacteria, Firmicutes, Gammaproteobacteria, and Betaproteobacteria taxa were obtained from the secretions.

8. Bacterial isolates showed species-specific inhibitory activity against the four fungi antagonistic to spruce beetle. The bacterium with the strongest fungal inhibition activity was the actinomycete Micrococcus luteus.

9. The production of bark beetle secretions containing bacteria that inhibit fungal growth is a novel finding. This suggests an additional level of complexity to ecological associations among bark beetles, conifers, and microorganisms, and an important adaptation for colonising subcortical tissue.

  • Citation: Cardoza, Yasmin J.; Klepzig, Kier D.; Raffa, Kenneth F. 2006. Bacteria in oral secretions of an endophytic insect inhibit antagonistic fungi. Ecological Entomology, Vol. 31: 636-645

Requesting Publications

You can order print copies of our publications through our publication ordering system. Make a note of the publication you wish to request, and visit our Publication Order Site.

Publication Notes

  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
  • Our on-line publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unuseable.
  • To view this article, download the latest version of Adobe Acrobat Reader.