Almost there: Transmission routes of bacterial symbionts between trophic levels

Elad Chiel, Einat Zchori-Fein, Moshe Inbar, Yuval Gottlieb, Tetsuya Adachi-Hagimori, Suzanne E. Kelly, Mark K. Asplen, Martha S. Hunter

Research output: Contribution to journalArticle

74 Scopus citations

Abstract

Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host's reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts - Rickettsia and Hamiltonella - from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH) and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected host, persists in adults and in females, reaches the ovaries. However, Rickettsia does not appear to penetrate the oocytes, but instead is localized in the follicular epithelial cells only. Consequently, Rickettsia is not vertically transmitted in Eretmocerus wasps, a result supported by diagnostic polymerase chain reaction (PCR). I n contrast, Rickettsia proved to be merely transient in the digestive tract of Encarsia and was excreted with the meconia before wasp pupation. Adults of all three parasitoid species frequently acquired Rickettsia via contact with infected whiteflies, most likely by feeding on the host hemolymph (host feeding), but the rate of infection declined sharply within a few days of wasps being removed from infected whiteflies. In contrast with Rickettsia, Hamiltonella did not establish in any of the parasitoids tested, and none of the parasitoids acquired Hamiltonella by host feeding. This study demonstrates potential routes and barriers to horizontal transmission of symbionts across trophic levels. The possible mechanisms that lead to the differences in transmission of species of symbionts among species of hosts are discussed.

Original languageEnglish (US)
Article numbere4767
JournalPloS one
Volume4
Issue number3
DOIs
StatePublished - Mar 10 2009

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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    Chiel, E., Zchori-Fein, E., Inbar, M., Gottlieb, Y., Adachi-Hagimori, T., Kelly, S. E., Asplen, M. K., & Hunter, M. S. (2009). Almost there: Transmission routes of bacterial symbionts between trophic levels. PloS one, 4(3), [e4767]. https://doi.org/10.1371/journal.pone.0004767