Bacteria Increases Pollen Protein Digestibility

Updated: Jul 23

  • Honey bees must have protein in their diet

  • Pollen is a source of protein

  • Proteins are broken down into amino acids

  • Bacteria assists in preserving pollen, extracting and breaking down protein from pollen

  • A healthy gut contains hundreds of non-core bacterial species

Honey bees foraging for pollen store pollen on a specialized area on their hind legs.

Honey Bees Need Protein in their Diet

While we usually think of honey bees collecting nectar, an average-size colony may bring in 100 pounds of pollen in a season. Pollen is an essential part of the honey bee diet, providing a wide range of nutrients: protein, carbohydrates, lipids, vitamins, and minerals.

Honeybee food is digested in the ventriculus and ileum. Honey bees need to break down dietary proteins into smaller units, amino acids, with the help of other specialized proteins, called proteolytic enzymes. Honey bees secrete proteolytic enzymes such as trypsin, but gut microbes are a great source of proteolytic enzymes that support digestion.

What is Protein?

Proteins are large biological molecules that perform many different functions in living cells. Proteins are building materials in body tissues, muscles, and glands. Proteins are made up of smaller units called amino acids. There are twenty different types of amino acids. If a correct amino acid can’t be found, whole proteins can’t be synthesized. The most abundant protein in honey bees is vitellogenin, a protein that influences stress resilience and is important to honey bee social organization. Honey bees can’t make some amino acids, and these amino acids, called essential amino acids, must come from food (pollen and bee bread). The essential amino acids for honey bees are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine (De Groot, 1953). The nutritional composition of the honey bee diet affects survival.

Role of Bateria in the Digestive Process in Honey Bee Gut

Honey bee gut bacteria contribute to digestion of pollen and other honeybee food within the ileum. Bacteria ferment pollen and nectar to produce nutritional molecules called Short-Chain Fatty Acids (SCFAs). SCFAs are small fuel molecules that can be metabolized (absorbed into hemolymph and used for energy) by honey bees directly.

In 2017 study1, Zheng and colleagues treated honeybees with an antibiotic to remove bacteria (GF) and compared these honey bees to conventional (CV) bees with normal microbiomes. They showed that microbes increase the production of SCFAs (acetate, propionate, lactate, succinate, and butyrate) in the ileum, rectum, and for their absorption into the hemolymph. These SCFAs are decreased when bacteria are removed from honey bees (GF). In conventional (CV) honey bees, SCFAs levels are higher in the hemolymph, where these fuel molecules support honey bee development, hormonal signaling, and weight gain.