Propolis Envelope Promotes Beneficial Bacteria in the Honey Bee (Apis mellifera) Mouthpart Microbiome

Abstract

Honey bees collect and apply plant resins to the interior of their nest cavity, in order to form a layer around the nest cavity called a propolis envelope. Propolis displays antimicrobial activity against honey bee pathogens, but the effect of propolis on the honey bee microbiome is unknown. Honey bees do not intentionally consume propolis, but they do manipulate propolis with their mouthparts. Because honey bee mouthparts are used for collecting and storing nectar and pollen, grooming and trophallaxis between adults, feeding larvae, and cleaning the colony, they are an important interface between the bees’ external and internal environments and serve as a transmission route for core gut bacteria and pathogens alike. We hypothesized that the antimicrobial activity of an experimentally applied propolis envelope would influence the bacterial diversity and abundance of the worker mouthpart microbiome. The results revealed that the mouthparts of worker bees in colonies with a propolis envelope exhibited a significantly lower bacterial diversity and significantly higher bacterial abundance compared to the mouthparts of bees in colonies without a propolis envelope. Based on the taxonomic results, the propolis envelope appeared to reduce pathogenic or opportunistic microbes and promote the proliferation of putatively beneficial microbes on the honey bee mouthparts, thus reinforcing the core microbiome of the mouthpart niche.

Overwintering Honey Bee Colonies: Effect of Worker Age and Climate on the Hindgut Microbiota

“…Kešnerová et al reports Bartonella apis as a predominant member of the overwinter hindgut microbiome, a novel finding in the honey bee system. Nearly all 16S amplicon based studies report sparse prevalence and low abundance of Bartonella apis regardless of experimental or environmental conditions [ 20 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 32 , 33 , 34 ]. Based on two separate climate conditions overwinter, our results do not support the trend for Bartonella apis to increase in overwintering bees, a pattern that dominated both overwintering sample sets from Kešnerová et al [ 36 ].…”

“…Additionally, for one of their major experiments, Kešnerová et al (2019) [ 36 ] pooled 20 guts for each phenotype, whereas we examined individuals. Several recent studies indicate that when dysbiotic, the individual gut microbiome can increase substantially in size [ 34 , 35 ], such that a single dysbiotic individual could dominate the sampling results among 20 healthy individuals. Lastly, the microbiomes detailed by Kešnerová (2019) [ 36 ] may represent a recurrent enterotype because the non-winter seasons are dominated by Gilliamella with lesser amounts of Lactobacillus firm5 [ 27 ].…”

“…Lastly, the microbiomes detailed by Kešnerová (2019) [ 36 ] may represent a recurrent enterotype because the non-winter seasons are dominated by Gilliamella with lesser amounts of Lactobacillus firm5 [ 27 ]. Most nurse/forager honeybee hindgut microbiomes sampled from non-winter are dominated by Lactobacillus firm5 [ 20 , 21 , 22 , 23 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Although both hindgut enterotypes are potentially healthy, they may react differently to perturbation or seasonal changes.…”

“…Core hind gut bacteria Lactobacillus Firm5, Lactobacillus Firm4 and Bifidobacterium asteroides are associated with the rectum while Lactobacillus Firm5, Snodgrassella alvi , Gilliamella apicola and Frischella perrara are associated with the ileum/pylorus [ 28 , 29 ]. Found less frequently and in lower abundance in the worker hindgut are Bartonella apis , Bombella apis [ 30 , 31 ] and Lactobacillus kunkeei , the latter two being more commonly associated with the hive environment, mouthparts, larvae and queens [ 20 , 21 , 22 , 23 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Although the gut microbiota of workers, queens and larvae have been studied, the gut microbiota of the diutinus phenotype has been largely overlooked.…”

The Honeybee Gut Mycobiota Cluster by Season versus the Microbiota which Cluster by Gut Segment

“…Thus, the fight towards the obligate pathogens could lead to simultaneous eradication of bacteria that have essential functions, such as vitamin production [29]. A limitation of our study, however, is that we did not consider the microbiota in the mouth part, which could have a substantial influence on both the micro-and mycobiota in the honeybee gastrointestinal tract [30]. Nor did we do specific measurements of diet [31].…”