3 very different but related papers from a bee health management
perspective. (Links below)

One discusses the differences in bee gut microbiota between summer and
winter bees (ref1), the other is about nurse bees preference for fresh
pollen and that pollen is stored/preserved as bee bread vs improved via
fermentation (ref2) and the third discusses the high pathogen loads found
in common hive products in Brazil (ref3). If I am going to look at winter
bee guts, I might as well as learn more about the winter gut biology. Also,
like mentioned in the previous post, I tend to notice Nosema late fall
(September/October), and then again after January and February in one or
two colonies. It makes for a slow spring and typically non-productive
season for those colonies. I knew feces was one of the potential vectors
but after seeing a bee gut full of late season pollen full of Nosema with
indications of pollens from as early as May in the same gut, it made me
think. Ignorance is bliss sometimes, but my foray into microscopy has
opened up a whole other world.



My google searches – longterm storage of pollen in bee hive; bee bread as
Nosema reservoir; honey bee gut pollen content over winter



Summary:

·      Gut microbiota differs between bees based on season (Winter/Summer)
and type – forager (nectar + honey) = clear feces; nurse bees
(honey+“fresher” pollen) = Yellow/brown feces; winter bees (honey + older
stored pollen) = Yellow/brown feces. (ref1)

 ·      Function of bee bread is likely for preservation vs altering
nutritional profile (ref2)

·      Nurse bees prefer fresh pollen (<3 days old) (ref2). Limitation of
study – it didn’t look at true pollen (bee bread) storage frames typically
in frames adjacent to brood nest. It looked at pollen storage in locations
around the brood (my perception when reading it). The time frames is also
very short ~96H.

·      Honey, pollen and bee bread is a clear pathogen vector (AFB, Nosema,
Chalkbrood, etc…) (ref3)



https://www.nature.com/articles/s41396-019-0568-8

(ref 1)   Gut microbiota structure differs between honeybees in winter and
summer (2019)



“What drives the observed changes in bacterial loads and community
composition in winter bees, nurses, and foragers? A possible explanation
could be dietary differences between the analyzed bee types. Foragers
mainly feed on nectar and honey, while nurses and winter bees also consume
pollen [48]. These dietary differences were also evident in our study, as
we found consistent changes in appearance and weight of the dissected guts
of foragers, nurses, and winter bees”

“In the case of honeybees, the larger amount of food in the gut is likely
to increase the carrying capacity for the gut microbiota. In addition,
pollen is a more nutrient-rich diet than nectar, honey, or sucrose,
offering a larger diversity of different metabolic niches for gut bacteria.
Both factors are likely to contribute to the increased bacterial loads in
bees fed on pollen as compared with those fed on sugar water only.”

“Winter bees feed on pollen that has been stored in the hive for several
weeks to months. It has previously been shown that the consumption of an
aged pollen diet affects the gut microbiota composition of nurses [12]. It
will be important to characterize metabolic differences between the pollen
diet of winter and summer bees, and to associate such differences with the
metabolic capabilities of the different bee microbiota members. For
example, Commensalibacter and Bartonella, the two community members
that increased
the most in winter bees, carry out aerobic respiration, while most of the
other microbiota members are saccharolytic fermenters [15, 65].”

“Notably, winter bees retain their feces in the gut for extended periods of
time, which is likely to affect the physicochemical conditions and the
availability of nutrients in the gut. Moreover, in the absence of defecation,
bacteria may accumulate over time in the gut of winter bees, while in
nurses or foragers more frequent defecation may result in a faster turnover
of the microbiota. Together with differences in the body temperature of
bees—in winter it is at ~21 °C and in summer at ~35 °C [66]—this may
influence bacterial growth rates. Indeed, in a recent metagenomic study, it
was shown that gut bacteria have lower average population replication in
old winter bees as compared with young nurse bees, which is indicative
of decreased
replication rates [18].”



https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4285803/

(ref2)   Hive-stored pollen of honey bees: many lines of evidence are
consistent with pollen preservation, not nutrient conversion (2014)



“In previous work, we determined that pollen taken from the hind leg
corbicular baskets of returning foragers (newly collected) and hive-stored
pollen contains incidental amounts of core hind-gut bacteria, “

“(1) The preferential consumption of freshly collected pollen indicates
that bees have not evolved to rely on microbes or other time-related
factors for pollen predigestion (Fig. (Fig.1).1). (2) Relative to other
plant material involving microbial digestion or extensive fermentation,
hive-stored pollen contains very few microbes. (3) The absolute number of
bacteria in hive-stored pollen decreases with storage time, indicating that
it is not a suitable medium for microbial growth (Fig. (Fig.2).2). (4) The
microbe to pollen grain ratio is many orders of magnitude removed from that
required to alter hive-stored pollen (Fig. (Fig.4).4). (5) Regardless of
sampled season or the taxonomic character of microbial communities,
microscopic examination revealed no intermediate stage of pollen digestion
in hive-stored pollen (Table S5, Supporting information). (6) The bacterial
communities found in hive-stored pollen did not differ from those of newly
collected pollen, but both sample types varied significantly by season (Fig.
(Fig.5).5).”



https://www.scielo.br/j/rbent/a/HcG9sZDxFqRpFqYHmBtTfCq/?lang=en#

(ref3)   Spores of Paenibacillus larvae, Ascosphaera apis, Nosema ceranae
and Nosema apis in bee products supervised by the Brazilian Federal
Inspection Service (2018)

“Of the 41 samples of bee products analyzed, only one showed no
contamination by any of these pathogens. *N. ceranae* and *P. larvae* had
the highest prevalence considering all the samples analyzed (present in
87.80% and 85.37% of the total, respectively), with *N. apis* present in
26.83% and *A. apis* present in 73.17% of the samples.”

 ------

*I guess my next search will look into winter bee diet, I had always
assumed they predominantly fed on stored honey. I would like to understand
more about the non-carbohydrate nutritional needs of the winter bees. Do
they fill up on pollens in late fall and let it sit in their guts? Also, I
guess if anyone has a bee gut dissecting guide handy, I would like to learn
how to do that this winter.*

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