Quantification of Cry1A.105 (A) and Cry3Bb1 (B) from mid- and hindgut samples of nurse bees exposed to Bt maize (treatment BT), other conventionally bred maize varieties (DKC, BEN) or other pollen sources (Phacelia, control); n indicates the numbers of replicate samples analyzed.

<p>Each individual sample is represented by a circle. Samples below the detection limit were set to zero.</p

Schematic figure on the incidence (A) and abundance (B) of bacterial phylotypes detected by T-RFLP based on 16S rRNA genes.

<p>The T-RF patterns for each treatment, i.e., exposure to Bt maize (BT), two conventional maize varieties (DKC, BEN) and mixed pollen sources including Phacelia (PHA), are based on 24 replicates from individual bees. Frequencies of incidences and abundances are indicated by squares and correlate with the grey scale. Abundance values in <b>B</b> indicate % of a particular T-RF in relation to total TRFs of the corresponding TRFP-profiles. Abundance values were averaged only from scored T-RFs. Significant differences in abundances of frequently occurring T-RFs are indicated with coloured boarder lines. Bacterial phylotypes indicated by the particular T-RFs were identified by DNA-sequencing (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059589#pone.0059589.s004" target="_blank">Table S2</a>).</p

Correlation between the contents of Cry proteins for Cry1A.105 and Cry3Bb1, and maize pollen detected in the hindgut of nurse bees from colonies caged in field plots with Bt maize MON 89034 × MON 88017 during anthesis.

<p>Correlation data in the graph excluded values below the detection limit (DTC).</p

Hypothetical numbers of sporulated cells of <i>B. thuringiensis</i> strains expressing natural Cry proteins required for the detection of a Cry1A.105 equivalent by ELISA.

a<p>refers to an extraction volume of 300 µL; DTC, detection threshold was 0.5 mg mL^−1.</p

Copy numbers of bacterial 16S rRNA genes in gut material from nurse bees as determined by qPCR.

<p>Different letters on top of columns indicate significant differences. Nurse bees originated from colonies exposed to Bt maize MON 89034 × MON 88017 (treatment BT), conventional maize varieties (DKC, BEN) or other pollen sources including Phacelia (PHA).</p

Nonmetric multidimensional scaling (NMDS) ordination plot of β-diversity patterns of bacterial community differences represented as Bray–Curtis distances of T-RFLP profiles.

<p>Stress values (0.21, 0.25) indicate that the distance between points in the ordination plot is a good representation of the degree of similarity between the bacterial communities in each sample. Each point represents the gut bacterial community obtained an individual nurse bee. Treatments: BT, exposure to pollen of Bt maize, DKC and BEN to conventional maize and PHA to other pollen sources including Phacelia.</p

Response of nurse bees after a 9 d exposure period either to Bt maize (treatment BT), or two conventional maize cultivars (DKC, BEN), or controls with <i>ad libitum</i> access to different pollen sources from colonies kept at a Phacelia field (PHA).

<p>The survival (A) was indicated by the retrieval rate of marked bees, their weight (B) was determined at the moment of their retrieval. Microscopic analysis of bee hindguts was performed to calculate a weighted average degree of maize pollen digestion (C). The error bars indicate 95% confidence intervals. *indicates significant difference of a specific treatment.</p