Bacterial community structures in honeybee intestines and their response to two insecticidal proteins.
In this study, the effects of the Bt-toxin Cry1Ab and a soybean trypsin inhibitor (SBTI) on intestinal bacterial communities of adult honeybees (Apis mellifera) were investigated. It was hypothesized that changes in intestinal bacterial communities of honeybees may represent a sensitive indicator for altered intestinal physiology. Honeybees were fed in a laboratory set-up with maize pollen from the Bt-transgenic cultivar MON810 or from the non-transgenic near isoline. Purified Cry1Ab (0.0014% w/v) and SBTI (0.1% or 1% w/v) represented supplementary treatments. For comparison, free-flying honeybees from two locations in Switzerland were analysed. PCR-amplification of bacterial 16S rRNA gene fragments and terminal restriction fragment length polymorphism analyses revealed a total of 17 distinct terminal restriction fragments (T-RFs), which were highly consistent between laboratory-reared and free-flying honeybees. The T-RFs were affiliated to Alpha-, Beta-, and Gammaproteobacteria, to Firmicutes, and to Bacteriodetes. Neither Bt-maize pollen nor high concentrations of Cry1Ab significantly affected bacterial communities in honeybee intestines. Only the high concentration of SBTI significantly reduced the number of T-RFs detected in honeybee midguts, a concentration that also increases bee mortality. Therefore, total bacterial community structures may not be a sensitive indicator for providing evidence for the impact of insecticidal proteins on honeybees at sublethal levels.
Babendreier
Dirk
D
Agroscope Reckenholz-Tänikon Research Station ART, Zürich, Switzerland. dirk.babendreir@art.admin.ch
Joller
David
D
Romeis
Jörg
J
Bigler
Franz
F
Widmer
Franco
F
D000818:Animals; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D001427:Bacterial Toxins / Q000009:adverse effects; D001516:Bees / Q000382:microbiology* / Q000502:physiology*; D007422:Intestines / Q000382:microbiology / Q000502:physiology; D030821:Plants, Genetically Modified / Q000009:adverse effects; D011058:Pollen; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D018570:Risk Assessment; D030262:Soybean Proteins / Q000009:adverse effects; D013557:Switzerland; D014361:Trypsin Inhibitors / Q000009:adverse effects; D003313:Zea mays
D001427:Bacterial Toxins; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D030262:Soybean Proteins; D014361:Trypsin Inhibitors