Gut Microbial Communities of Adult Honey Bee Workers (Apis Mellifera)

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BIOSCIENCES BIOTECHNOLOGY RESEARCH ASIA, June 2020. Vol. 17(2), p. 353-362
Published by Oriental Scientific Publishing Company © 2020
This is an Open Access article licensed under a Creative Commons license: Attribution 4.0 International (CC-BY).
*Corresponding author E-mail: mevalatawi@ut.edu.sa
Gut Microbial Communities of Adult Honey Bee Workers
(Apis Mellifera)
Marfat Alatawy1,2*, Sanaa G. Al-Attas1, Ahmad I. Assagaf1,
Abdullah Al-Shehri3, Khalid M. Alghamdi1 and Ahmed Bahieldin1,4
1Department of Biological Sciences, Faculty of Science, King Abdulaziz University,
Jeddah - 71491, Saudi Arabia.
2Department of Biology, College of Science, Tabuk University, Tabuk - 74191, Saudi Arabia.
3Department of Arid land Agriculture, Faculty of Metrology,
Environment and Arid land Culture, King Abdulaziz University, Jeddah - 80200, Saudi Arabia.
4Department of Genetics, Faculty of Agriculture, Ain Shams University, Cairo - 11241, Egypt.
http://dx.doi.org/10.13005/bbra/2838
(Received: 02 March 2020; accepted: 23 April 2020)
Apis mellifera honey bees are highly valued insects due to their roles in honey
production and pollinating some globally important crops. However, honey bee colonies have
been decreasing significantly around the world and this has drawn the attention to investigate
factors that can affects bees health such as gut microbiome. Gut microbiome is considered an
essential part of a honey bee system. Honey bees gut microbiome consists of a nine core species
which mostly obtained by social transmission. Current findings on gut microbiome specific strain
variations, results on their metabolic and nutritional roles, and links between gut microbial
disruption and disease states, have drawn the attention to how microbiota impacts bee health,
and also being a potential model to study ecology as well as gut symbionts development. Overall,
roles of gut microbiome in honey bees development are becoming much more evident.
Keywords: Apis Mallifera; Dysbiosis; Gut Microbiome; Symbionts.
Honey bees, such as Apis mellifera, are
pollinators for many important crops and they are
widely domesticated for their honey production.
Therefore, honey bees are essential for our food
supply. However, Beekeeping industry all over
the world is suffering from huge economic losses.
Since 20061, there was a signicant reduction in
the honey bee colonies. This decline is inuenced
by multiple factors such as environmental stresses,
pollution, exposure to pesticides or antibiotics, as
well as foreign pathogens. This decline has drawn
attention towards understanding the microbial
relations with these species, both symbiotic and
pathogenic relations. One way to overcome this
problem is to improve bee health by investigating
the microbial diversity in bees and its impact on
the host1. In this eld, the terms ‘microbiome’ and
‘microbiota’ are used interchangeably to represent
the microbial community living within a larger host
system or in any compact environment. However,
microbiome is usually used in science for the
collective genetic material of such microbiota.
This is the concept that will be used in this review
analysis, since microbiome characterisation
techniques are primary steps in microbiota
characterisation2.

354 ALATAWY et al., Biosci., Biotech. Res. Asia, Vol. 17(2), 353-362 (2020)
The gut microbiome highly impacts bees’
health as it are involved in metabolism, nutrient
absorption, immunity and development. Since
honey bee gut has a relatively simple microbial
composition and experimental amenability, they are
considered a promising organism to investigate the
essential aspects of gut microbiology3. The majority
of the bacterial 16S rRNA sequences (95%)
detected for the adult honey bee belongs to phyla
Firmicutes, Actinobacteria and Proteobacteria
(Alpha proteobacteria, Betaproteobacteria, Gamma
proteobacteria), and therefore, are considered the
core species of the gut microbial content in honey
bees. In addition, there is a high level of diversity in
gut bacterial species, with different compositions,
which could be associated with the nutritional and
health status of the honey bee4.
The microbial community within honey
bees has been studied and analyzed using culture-
based techniques5. However, with the advancement
in molecular tools, investigating the microbial
composition and structure of the honey bee’s gut
became much easier. Numerous publications were
published concerning this research, though, their
ndings needs rening and clarication of such
point for further reviewing and meta-analysis.
This review aims to summarize results regarding
the structure and transmission of microbiome in
adult honey bees guts. In addition, focuses on the
potential roles of the core bacterial species; the
essential structure of the normal gut microora.
Honey Bees (Apis Mellifera)
Honey bee, or Apis mellifera, belongs
to the order Hymenoptera and the superfamily
Apoidea, and it is that is highly regarded due to its
importance to human health and ecosystems (Table
1). For instance, in addition to honey production,
the honey bee plays a major role in the pollination
process of different economically important crops6.
Without these pollinators, the yields of some seed,
fruit and nut crops have decreased by more than
90%7,8.
Honey bees live in a eusocial system of
perennial colonies with overlapping generations,
a reproductive section of labour and a brood care
division. In addition, each colony is composed of
three castes7 as the following: the female worker
bees, which uctuate in number between 15,000
in the winter and 50,000 in the summer, the male
drones, which usually exist only in the spring and
have numbers in the few hundreds, and the female
reproductive queen bee.
Worker bees are further classied based
on age, as they have different roles in the hive
depending on their ages. Firstly, Younger bees,
which feed on the lipid and protein contents
of processed pollens (bee bread), are normally
constrained to the hive and are involved in the
rearing of the brood. For this reason, they are called
‘nursing bees’. Secondly, Older bees ‘‘foragers’’,
are tasked with looking for nectar and pollen
outside of the hive. Food is then brought into the
hive and passed from bee to bee by an exchange
process called trophallaxis, which turns the honey
bee bread into food products9.
In recent decades, the number of honeybee
colonies has decreased dramatically throughout
the world10. The International Cost Action
FA0803 COLOSS (Colony LOSS) network
which developed by the European Union, is an
association of 161 members from more than 40
different countries that was established to address
and prevent global honeybee colony collapse
worldwide. A monitoring study carried out by the
COLOSS team during the winters of 2007-2008
reported honeybee losses of in the USA about 30%,
25% in Japan, 1.8%-53% in Europe, and 10%-85%
in the Middle East11. These losses were inuenced
by multiple factors, such as environmental stress
conditions, lack of nutrition (nectar and pollen),
extensive use of insecticides, and biotic stresses
such as infection by pathogenic parasites (e.g.
Acarapis woodi, Varroa destructor, Tropilaelaps
spp., microsporidia Nosema spp.), pathogenic
fungi (e.g. Ascosphaera apis) or bacteria (e.g.
Paenibacillus larvae, Melissococcus plutonius),
in addition to more than 18 different viruses,
including deformed wing virus (DWV)12.
The Honey Bee as a Model System for Gut
Microbiota Research
As previously mentioned, the honeybee
system model is promising for investigating gut
microbiota and understanding essential aspects
of gut microbiology because of its relatively
simple microbial composition and experimental
amenability. In addition, honey bees can serve as
microbiota-free hosts, which enable the researchers
to investigate how microbiotas relate to the host’s

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ALATAWY et al., Biosci., Biotech. Res. Asia, Vol. 17(2), 353-362 (2020)
phenotype (e.g. conditions and diseases) more
accurately. In mammals, it is only possible to obtain
microbiota-free individuals through Caesarean
sections, and then the mammals must be kept in
special housings. However, a germ-free insect
can be produced by chemical sterilisation of the
egg surface, nevertheless, the use of antibiotics
to obtain large numbers of microbiota-free hosts
interferes with, and threatens the normal honeybee
life cycle.
The honeybee microbiome shares many
features with the human microbiome, which other
insects do not, such as the following: At rst, some
bacterial species have adapted to, and dominated
the host’s gut microbiome and usually are not
seen elsewhere. In addition, microbiome is highly
important element in overall health of both systems.
Moreover, the strains of the local bacterial species
are highly diverse. Furthermore, when exposed
to antibiotics or chemicals, the continuous use of
antibiotics has impacted the microbial diversity
within the human gut, resulting in high rates of
resistance factors. Similarly, antibiotic use has
interfered with honeybee gut communities3.
The Gastrointestinal Tract of Worker Honey
Bees
The digestive tract of the honey bee is
divided into three different compartments: foregut,
midgut and hindgut. The foregut contains the crop,
the midgut is the middle part of the tract and the
hindgut includes the ileum and rectum (Figure 1).
Different areas of the digestive system provide
different environments for the bacterial symbionts,
which have different roles in essential biological
activities (e.g. metabolism and absorption). Food
collected by the foraging workers is transported
through the oesophagus into the crop. The crop is
a muscle-lined organ that has the ability to expand
for large quantities of nectar. Accordingly, it is
sometimes called the ‘honey stomach’. Although
the crop can carry large amounts of nectar and
nutrients that the microbes utilise for energy, it
accommodates only small amounts of bacteria.
In the process of honey production, the crop is
continuously lled with and emptied of nectar. This
can compromise the integrity of the gut microbiome
and inhibit bacterial colonisation. In addition, the
crop produces different enzymes to process nectar.
It has been hypothesized that these enzymes are
Table 1. Classication of
Apismelifera
Taxa Names
kingdom Animalia
Phylum Arthropoda
Class Insecta
Order Hymenoptera
Family Apiidae
Genus Apis
Species Apismelifera
Fig. 1. Illustration of the honey bee’s digestive tract with the three different gut compartments identied. Food passes
through the oesophagus into the crop, undergoes digestion in the midgut and then moves to the ileum and rectum
(https://americanbeejournal.com/whos-got-guts-the-microbes-living-in-bees)

356 ALATAWY et al., Biosci., Biotech. Res. Asia, Vol. 17(2), 353-362 (2020)
responsible for the antimicrobial activity of the
honey, as they prevent bacterial growth within the
crop13. Then, food and nutrients are moved into
the midgut through the proventriculus, a muscular
tissue located under the crop, which contains
valves and can protect the midgut against foreign
particles. The midgut is the biggest compartment of
the gastrointestinal (GI) tract in which most of the
food digestion and absorption occur. This is why
it is also called the ventriculus, or ‘true stomach’.
The epithelial layer of the midgut contains different
enzymes that can metabolize protein, fat and sugar.
Anything that remains after digestion is then moved
to the ileum through the pylorus, an interceptive
valve between the midgut and the ileum. Lastly, in
the hindgut, the ileum is a smaller part of the GI
tract between the midgut and rectum that has deep
infoldings to provide a large surface area to collect
nutrients that were not absorbed in the midgut.
The rectum is the distal part of the GI tract, and
similar with the crop, it has the ability to distend
to t waste products after food digestion. This
allows the workers to retain waste materials so
they can dispose them through defecation outside
of the hive. The rectum is a relatively stationary
environment, and its waste products (mostly
empty pollen exines) can provide a good source of
nutrition for bacteria, as the carbohydrates found in
the exine layer are recalcitrant to the honey bee’s
digestive enzymes14.
Honeybee Gut Microbiome
Because honey bees are social insects that
have close relations within their community and
have large colonies, they can provide unique ways
for bacterial microbiome nutrition9. As previously
mentioned, the honeybee gut microbiome is
essential to the host’s entire system and plays
a major role in metabolism, food absorption,
immunity and development15. The majority bacterial
sequences detected for the adult honey bee consists
of eight characteristics bacterial phylotypes (Table
2). They are two alpha proteobacteria, Alpha1
and Alpha2, of Acetobacteraceae; two gamma
proteobacteria, Gamma 1, recently identied as
Gilliamella apicola16, and Gamma 2, recently
identied as Frischella perrar17; two lactobacillus,
Firm-4 and Firm-5; one betaproteobacteria, which
identified as Snodgrassella alvi16; with one
Bidobacterium, identied as Bido. While many
bacterial phylotypes of the honeybee gut are closely
Table 2. The core gut microbiota and its distribution41, 42
Taxonomic classication of core gut microbiota for adult Apis melliferaworkers
Phylotype Bacteria phylum Order Family Genus Species Primary locations
Gamma1 Gamma proteobacteria Orbales Orbaceae Gilliamella apicola Adult midgut, hindgut (ileum)
Gamma2 Gamma proteobacteria Orbales Orbaceae Frischella perrara Adult hindgut (ileum)
Beta Betaproteobacteria Neisseriales Neisseriaceae Snodgrassella alvi Adult hindgut (ileum)
Firm4 Firmicutes lactobacillales Lactobacillaceae Lactobacillus mellifer Adult hindgut (rectum)
Firm5 Firmicutes lactobacillales Lactobacillaceae Lactobacillus apis Adult hindgut (ileum, rectum)
Bido Actinobacteria Bidobacteriales Bidobacteriaceae Bidobacterium asteroides Adult hindgut (rectum)
Alpha1 Alpha proteobacteria Rhizobiales Bartonellaceae Bartonella apis Adult gut
Alpha2 Alpha proteobacteria Rhodospirillales Acetobacteraceae Acetobacter aceti Larval gut, adult crop, nectar,
honey, hive, adult hindgut

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Fig. 2. Life history of the honey bee and related changes in gut microbiota. The worker caste (top panel) microbiota
is well understood; the composition of other reproductive castes revealed different microbiota than that of workers.
Newly emerged workers mostly have no or few bacteria and obtain their normal gut microbiota mainly from faecal
material, along with the other potential routes42
related to those found in other insects, three specic
phylotypes (G. apicola, F. perrara and S. alvi) have
only been found in honey bees and bumble bees,
up to date1.
Although the identied core microbiotas
are comprised of few phylotypes, their underlying
species have shown relatively high strain variations.
Two species in particular have demonstrated high
strain variations. They are G. apicola (belonging
to gamma proteobacteria: Orbales) and S. alvi
(belonging to Betaproteobacteria: Nesseriales)18.
This has also been observed with Lactobacilli
and Bidobacterium spp., which are associated
with honey bees19. Despite the fact that there are
different honey bees, colonies and distributions
around the world, it has been suggested that this
coherent structure of the same phylotypes plays a
major role in the health of all bees. Moreover, the
strain variation within the different phylotypes may
offer different functionalities and could also play a
major role in bees’ health18.
Studies conducted on colonization trends
and the bacterial composition of the honeybee GI
tract reveals that there is a lack of bacteria until
the honey bees reach the age of 4-6 days. Young
workers can be inoculated in different ways,
including environmental factors (via bee bread
and comb) and also through interactions with older
bees within the colony. Once they are inoculated,
different gut compartments will have different
bacterial communities; for example, the crop and
midgut are occupied by very few bacteria (104 and
106, respectively). In contrast, the hindgut, which
made up of the ileum and rectum, harbours large
communities with distinct compositional proles.
The ileum and rectum have total bacterial amounts
of around 107 and 108, respectively14.
Honeybee Microbiota Transmission
Honey bees share their gut bacteria
with other members of the colony through oral-
faecal routes. This occurs through trophallactic
interactions, consumption of the stored pollen and
bee bread, contact with older bees in the hive, and
exposure to hive materials during the early-adult
stage20, 21. A number of studies showed a slight
difference in microbial gut composition due to
factors such as host age, diet, caste, seasonal
or geographical alterations. These factors were
shown to be inuential to the bee microbiome. In
fact, a lack of nutrition leads to gut microbiome
disruption, resulting in high disease and mortality
rates22.

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Furthermore, honey bees are highly
social insects within the hive, and this is the key
element in the transmission of microbiota between
hosts (Figure 2). After pupating in capped cells
within the colony, adult honey bees with germ-
free guts emerge21,23. The honey bees’ gut was
manually extracted just after they were removed
from honeycomb cells and were kept in sterile
conditions, but they did not show any signicant
microbial composition. This was validated using
qPCR with broadly used primers. In this study,
Kwong et al.20, 21 found that newly emerging bees,
after freely leaving honeycomb cells, can be
inoculated on the frame surface with residual gut
symbionts.
In another study, the developmental
stages of gut microbiota were characterized by
testing marked cohorts of colonial workers, using
16S rDNA amplicons to assess microbial size
and composition of different areas of the gut24.
Initially, the microbial composition was relatively
small and random and environmental species
were predominant with no signicant difference
between microbial compositions in different areas
of the gut. Around three days later, microbial
compositions were found to be about >107 bacteria.
These are predominantly characteristic species of a
conventional bee’s gut. The ileum and rectum also
started to show ‘ordinary’ bacterial compositions.
By the eighth day, this microbial concentration
plateaued around 109. It has also been found
that when established, gut microbial populations
are usually stable throughout a worker bee’s
transitional states25. This shifting from an initial
chaotic microbial community to one dominated
by ‘adult’ bacteria, greatly mimics human infant’s
gut microbiota growth26.
Since a sustained microbial community
is established before worker bees emerge from
the hive, it can be determined that bacterial
transmissions occur in between nestmates or
through hive components, such as wax surfaces.
In the laboratory, in order to obtain typical gut
microbiome development, this was highly achieved
through interacting younger bees with older ones,
or fed their macerated hindguts23. In studies on
potential routes of transmission, researchers
found that oral trophallaxis, a common way for
bees to communicate and exchange food, was not
essential for bacterial transmission. These results
are consistent with other results which stated
that foregut regions are occupied by a limited
number of bacteria15. Although many members
of the gut microbiome can be obtained through
interacting with different hive components that
had been previously contacted by other hive
bees, a faecal route remains important, especially
for Snodgrassella alvi, Gilliamella apicola and
Frischella perrara27. On the other hand, species of
the Acetobacteraceae family could be transmitted
through pollens that are stored for nutrition10.
Metabolic Characterisation
Meta-transcriptomic datasets and
metagenomic and total genomic sequencing for
many members of honey bees gut microbiota
have provided insight into the lifestyles and
prospective roles of gut microbiota19, 20, 21, 27, 28, 29.
As in the human gut, microbiota are involved in
the metabolism of carbohydrates in the bee gut.
In honey bees, this is carried out by bee-specic
species, Lactobacillus and Bidobacterium, which
are genera that have members in mammalian guts.
Experimental tests on the B. asteroids
species cluster in bees have identified highly
abundant and diverse genes involved in carbohydrate
use, but they were not found in both of its relatives
or in other microbial community members30. In
terms of phylogenetics, Bifidobacterium spp.
associated with bees are branches of the same major
groups of Bidobacterium spp. found in mammals
and, therefore, this exhibits a great parallel model
system to study microbiota adaptation in human as
well31. Indeed, bee-derived B. asteroids have shown
clear differences from those in mammals, such
as their capacity for aerobic respiration4, which
may indicate specic conditions within the bee’s
gut (e.g. different oxic conditions). On the other
hand, strains of Lactobacillus in honey bees were
found to be different from those in mammals, and
in general, the strains found in bees and mammals
fall under two separate phylogenetic clades, Firm-4
and Firm-5, but also rare under a third clade, Firm-
327. Current genome sequencing of Lactobacillus
Firm-4 and Firm-5 identied multiple phospho-
transferase enzyme systems essential for sugar
uptake in both, but mainly in Lactobacillus Firm-5.
In addition, both Lactobacillus and
Bifidobacterium strains in bees carries large
proteins on their cell-surface with putative
structure. Their functions are unknown, but it is

359 ALATAWY et al., Biosci., Biotech. Res. Asia, Vol. 17(2), 353-362 (2020)
suggested that the proteins have roles in adhesion or
degradation of plant materials10. Bees also harbour
gene clusters of B. asteroids and Lactobacillus
Firm-5 that are responsible for the production and
utilization of trehalose, which is a disaccharide
molecule used as an energy reservoir in insects. On
the other hand, mammals use glycogen for energy
storage. Moreover, in mammals, Lactobacillus spp.
and Bidobacterium spp. normally carries genes
responsible for biosynthesis and degradation of
glycogen. However, these genes are not present in
bees19.
Gilliamella apicola is another dominant
fermentative bacteria in honey bees’ guts. It
belongs to the bacterial order Orbales, which is
mostly linked to insects16. Genomic analysis has
identied a wide range of genes in G. apicola
strains involved in the uptake and fermentation
of sugars, but it has also identied an incomplete
tricarboxylic acid cycle and a degenerate aerobic
respiratory chain20,21. Another two microbial
members found in bees and associated with
Orbales are Schmidhempelia bombi and Frischella
perrara, which have similar activities but are also
carbohydrate fermenters17, 32,33.
Since bees thrive on nectar, honey and
pollen, which are high in carbohydrates, it is
expected that their microbiota includes members
that can process these types of foods. They do
indeed have F. perrara,G. apicola, Lactobacillus
Firm-4, Lactobacillus Firm-5 and bee-associated
B. asteroids, which have the ability to metabolise
glucose and fructose, the main sugars types of bee’s
diet. Some other strains carry genes capable for
utilization of other rare sugars such as arabinose,
mannose, rafnose, lactose and galactose, which
are indigestible by bees and potentially toxic15.
Different microbial species lead to different end
products of the fermentation process, but usually,
their end products are lactic acid and acetate. DNA
and RNA Metagenomic sequencing analysis have
revealed high levels of expression of those genes
involved in fermentation27. This was also veried
using culture-based assays10.
The last core member of the honey bees’
microbiota is S. alvi, an obligate microaerophilic
bacterium that belongs to the Neisseriaceae family.
The distribution of S. alvi in the peripheral areas of
the gut lumen is consistent with their dependence
on aerobic respiration, where the epithelial
surface of insects’ guts has the maximum oxygen
concentrations35. Remarkably, S. alvi no longer
relies on carbohydrate glycolysis for the production
of energy, but rather, it depends on aerobic
oxidation of carboxylates, such as acetate, malate,
citrate and lactic acid. Since different resources can
be used for energy, S. alvi can coexist with other
fermentative bacteria in the same gut environment.
Besides, this metabolic difference is indicative for
the syntrophic interaction, as many carbohydrates
fermentation products (acetate, formate and lactic
acid) are substrates used by S. alvi 16, 20, 21.
Parasaccharibacter apium is another
bacterium that has a specic niche. Although rare
in adult worker bees’ guts, P. apium appears to be
abundant within the hive food stores, larvae’s and
queens’ guts. Remarkably, P. apium is able to thrive
on royal jelly, which is a toxic environment to most
other bacteria, and is found in royal jelly-producing
glands of worker bees. Although P. apium is an
Acetobacteraceae member, genomic data from
P. apium26 and other closely related phenotypes
indicated that P. apium do not produce acetic acid
through sugar and alcohol oxidation. On the other
hand, it looks to be well suited to the aerobic, acidic
and high-sugar conditions found in royal jelly,
nectar and honey37.
Role of the Bee Gut Microbiome in Health,
Nutrition and Protection against Pathogens
The commensal microora bacteria are
potential symbionts. These bacterial symbionts
evolve with their host15, and many bacteria
have been identified to have a protective role
against foreign pathogens27. In addition, different
symbionts have unique roles within the gut, and
their specific positioning is important for the
functional integrity of the gut10. Hamdi et al.12
showed that gut symbionts are signicant for bee
health, and dysbiosis within the gut microbiota can
lead to diseases. In fact, a lack of nutrition leads to
disruption of the gut microbiome, resulting in high
disease and mortality rates. This disruption of the
microbiome (dysbiosis) affects the development of
adult worker bees through inhibition of important
gene expression, such as vitellogenin. Vitellogenin
is a phospholipoglyco-protein that affects multiple
aspects of the honeybee life cycle. It is a female-
specic egg yolk protein with an essential function
related to oogenesis4, 38, 39. Moreover, dysbiosis
may cause bees to be unable to adapt to stressful

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conditions, such as heat or poor nutrition, and in
turn, these conditions can impact the microbiome.
The consistency in the microbiota system
of honey bees has led to hypotheses about its
potential role in honey bee lives, whether symbiotic
or not. Different bacterial groups have been shown
to produce short-chain fatty acids, such as acetic
acid or lactic acid (e.g. Lactobacilli, Bidobacteria,
Acetobacteraceae and Simonsiella), which honey
bees consume as a food supplement. Moreover, gut
bacteria makes it possible for honey bees to degrade
pollen, which is coated with exine layers that are
resistant to most digestive enzymes, in order to
use the intine for nutrition. Gut bacteria species of
honey bees show a high level of diversity and have
different compositions, which could be associated
with the nutritional and health status of the host15.
Genomic and metabolic analyses of
core species in the bee gut (Lactobacillus,
Bidobacterium, and G. apicola) indicate that
these bacteria are able to utilize different groups
of plant-origin carbohydrates. In a comparative
study of microbiota-free bees and bees with a
conventional gut microbiome, the gut microbiome
was shown to have many physiological effects. The
study showed a major positive effect on gut size,
weight gain, insulin and vitellogenin signalling and
sucrose sensitivity27. These physiological changes
may impact bees’ immunity, stress tolerance and
overall health. In addition, the gut microbiome has
been proven to be a cofactor in ghting infections in
both honey bees and bumble bees. In two different
studies, the faecal matter of wild-type worker bees
was inoculated with a microbiota-free B. terrestis,
which showed immunity against the trypanosomatid
gut parasite Crithidia bombi in contrast to other
workers that were not inoculated. Moreover, the
transplanted bacteria’s ability to protect against
infections was dependent upon their source rather
than the bees’ original colonies, indicating that the
level of protection was dependant on the different
microbiota compositions10. Two symbionts of the
honey bee, S. alvi and G. apicola, were found to be
enriched in gene encoding for biolm formation.
When these were viewed using fluorescence
microscopy, it appeared that the epithelium layer of
the host ileum was enveloped by the two species,
suggesting protective characteristics related to
biolm functions, such as providing a protective
layer against parasites4, 38, 39.
CONCLUSION
Honey bees are highly valued insects
throughout the world, owing to their role in honey
production and pollinating many globally important
crops. However, their populations have recently
declined and this drew attention to the potential
factors affecting their health, such as microbiota
4, 38, 39. Bee guts occupies a unique and stable
microbiome, therefore, it is an essential part of bee
biology. In addition, current experimental studies
have revealed a crucial roles of the gut microbiome
in bees health such as nutrition and immunity.
Understanding this microbial community provides
visions into how to improve bee health, and into
overall unresolved aspects of host-microorganism
symbiosis. This consequently helps to overcome
the reductions in bee populations around the world
and maintains food security.
ACKNOWLEDGMENTS
The authors would like to acknowledge
Prof. Dr. Rashad R. Al-Hindi, Professor of food
Microbiology and Head of Microbiology program,
Department of Biological Sciences, Faculty of
Science, King Abdulaziz University, Jeddah, Saudi
Arabia, for revising of the nal version of the
manuscript.
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