Bacterial community structures in honeybee intestines and their response to two insecticidal proteins

Abstract

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.

Characterization of selected Gram-negative non-fermenting bacteria isolated from honey bees (Apis mellifera carnica)

“…Microorganisms of that type, mostly Bacillus spp. are commonly found on honey bees, honey bee larvae, in honey bee gastrointestinal tract as well as in honey and the honey bees environment (Smolska-Szymczewska 1989;Snowdon and Cliver 1996;Gilliam 1997;Rada et al 1997;Kačániová et al 2004;Piccini et al 2004;Iurlina and Fritz 2005;Mohr and Tebbe 2006;Evans and Armstrong 2006;Mohr and Tebbe 2007;Babendreier et al 2007;López and Alippi 2007;Kačániová et al 2009). …”

“…Unfortunately, the abovementioned studies did not provide detailed characterization to demonstrate affiliation with an established species nor were sequence data provided. Very recently, Babendreier et al (2007) analyzed the bacterial community structures in honey bee intestines and their response to two insecticidal proteins. In this study, two derived sequences originating from uncultured bacteria clustered most closely with Pseudomonas indica IMT37 T and Pseudomonas aeruginosa strain 796.…”

“…Jeyaprakash et al (2003) reported about bacterial diversity in worker adults of A. mellifera capensis and A. mellifera scutellata in South Africa using 16S rRNA sequence analysis, but without cultivation of any bacteria. Babendreier et al (2007) investigated the effects of the Bt-toxin Cry1Ab and a soybean trypsin inhibitor on intestinal bacterial communities of adult honey bees applying culture-independent terminal restriction fragment length polymorphism followed by 16S rRNA gene sequencing. Recently, Tebbe (2006, 2007) compared bacterial diversity in the guts of A. mellifera ssp.…”

Honey bee gut microbial communities are robust to the fungicide Pristine® consumed in pollen

“…Fungicides may also impact cellular immunity in cases where mitochondria modulate cell death and innate immune signaling (Arnoult et al 2009). An alternative explanation for the sublethal effects of Pristine® on protein digestion and immunity might be that the fungicide altered the composition and diversity of gut microbial communities that may contribute to pollen digestion and pathogen defense (Babendreier et al 2007;Engel et al 2012;Koch and Schmid-Hempel 2011;Yang et al 2011). Though bacteria do not have mitochondria, electron transport occurs in the cell membrane and uses ubiquinone and cytochrome b as electron carriers.…”

Functional diversity within the simple gut microbiota of the honey bee

“…1B, SI Appendix, Fig. S1B) (10,17). Because of the very low representation of this lineage (indicated by small contigs and shallow read coverage) we did not include it in subsequent analyses.…”