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March 09, 2015
from
IUB Website
Researchers used a painted dot
to track queen bees.
Photo by Steve Burl
BLOOMINGTON, Ind.
An Indiana University
researcher and collaborators have published the first comprehensive
analysis of the gut bacteria found in queen bees.
Despite the important role of gut microbial communities - also known
the "microbiome"
- in protecting against disease, as well as the central role of the
queen bees in the proper function and health of the hive, similar
analyses of honey bees have previously only been performed on worker
bees.
Apis mellifera - or the western honey bee - contributes
significantly to agriculture, including pollinating one out of every
three mouthfuls of food globally.
Understanding the role of
microbes in the productivity of queen bees and health of bee
colonies may provide critical insights into the decline of bees in
recent years, with colony losses as high as 40 percent over winter.
The research, "Characterization
of the Honey Bee Microbiome throughout the Queen-rearing Process,"
appears online and will appear in print in the journal Applied and
Environmental Microbiology.
Also contributing to the
study were researchers at Wellesley College and North Carolina State
University.
"This might be a case
in which 'mother does not know best'," said
Irene L.G. Newton, assistant
professor of biology in the College of Arts and Sciences'
Department of Biology at IU Bloomington, who is corresponding
author on the study.
"In many animals,
transmission of the microbiome is maternal. In the case of the
honey bee, we found that the microbiome in queen bees did not
reflect those of worker bees - not even the progeny of the queen
or her attendants.
In fact, queen bees
lack many of the bacterial groups that are considered to be core
to worker microbiomes."
The study's results are
the opposite of microbiome development in many mammals, including
humans, in which infants' microbiomes are influenced by their
mothers.
Babies delivered through
natural birth possess microbiomes similar to those found in their
mother's birth canal, for example, while babies born through
cesarean section harbor gut bacteria that resemble bacteria found on
the skin.
Honey bees, in contrast, acquire their gut bacteria from both the
surrounding environment and the social context - a phenomenon known
as horizontal transmission.
In a healthy colony, worker bees typically acquire their gut
bacteria through interaction with microbes inside the hive,
including fecal matter from adult bees.
But the most likely route
of microbiome transmission in queen bees is the "royal
jelly," protein-rich food source produced by worker bees
and responsible for the development of queen bees during the larval
stage.
Unlike other bees, queens
continue to feast on royal jelly through maturity, eschewing the
honey and "bee bread" consumed by workers.
The queen's royal isolation from the dirt and grime of everyday life
in the colony may account for the difference in her microbiome.
"In some ways, the
development of the queen microbiome mirrors that of workers,
with larval queens' associated bacteria resembling those found
in worker larvae," Newton said.
"But, by the time
they mature, queens have developed a microbial signature
distinct from the rest of the colony."
Irene L.G. Newton's
study tracked the development of the queen microbiome at every point
in the commercial rearing process - from the larval stage to their
emergence as adults capable of reproduction.
The scientists also
tracked worker populations interacting with the queens at each point
in their development, including the queens' introduction to new
colonies, a common practice in commercial beekeeping.
At the end of the
process, DNA collected from the honey bees' guts were sequenced and
analyzed.
Sequencing was performed at the
Indiana Center for Genomics and Bioinformatics
in Bloomington, Ind. The field research, including honey bee
collection, was conducted at the North Carolina State University
Lake Wheeler Honey Bee Research Facility in Raleigh, N.C.
The study's discovery that queen bees' microbiome remains unaffected
by workers' interaction with the queen, and by the movement of
queens to different colonies, suggests that modern beekeeping
practices - in which queen bees are regularly removed from their
home colonies and introduced into new hives - may not detrimentally
affect the health of the colony.
"Because the queen
microbiome does not reflect the workers within a specific
colony, the physical movement of queens from one colony
environment to another does not seem to have any major effects
on either the queen gut or worker gut communities," she said.
"The research
provides no evidence that beekeepers who regularly replace their
queens from outside genetic sources harm their colonies by
disrupting the gut microfauna of a particular colony.
In many ways, these
conclusions are very reassuring for the commercial-production
apiculture industry."
In addition to Irene L.G.
Newton, authors on the study are,
This work was supported
by a grant from the National Honey Board, as well as support from
the Knafel Endowed Chair in the Natural Sciences at Wellesley
College.
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