Do bacteria from pollinators reach the flower in blueberries?

Abstract

Insect pollinators exchange microbes with flowers during pollination, creating a tripartite interaction between pollinators, plants, and microorganisms in the flower. However, do any beneficial or commensal bacteria from pollinators reach the flower (and ultimately the fruit)? Known pathogenic bacteria use the floral interface during pollination to access its desired host. Through caged experiments, we tested this pathway of microbial transmission in the northern highbush blueberry with four different types of insect pollinators (bumble bee, honey bee, drone fly, and a solitary native bee). We captured epiphytic bacteria by washing the external surfaces of pollinators, blueberry nectaries, and blueberry fruits. All samples were processed via a standard metabarcoding pipeline, including total genomics DNA extraction, amplicon and indexing PCRs, library preparation, sequencing on the Illumina MiSeq platform (250x2 pairedend) and bioinformatics with dada2. We are analysing these data to (1) characterise the bacterial taxa present on pollinators and flowers and to (2) examine their exchange during pollination. We hypothesise that a small fraction of the pollinator-transmitted community will be discovered in blueberry flowers.