Honey Bee

The European honey bee, also known as the common or western honey bee (Apis mellifera) is so named because it produces large amounts of honey. It is believed that the honey bee originated in Africa and spread to northern Europe, India, and China. The honey bee is not native to North America, but was brought here with the first colonists. The honey bee is now distributed world wide. European honey bees are variable in color, but are some shade of black or brown intermixed with yellow. The bee ranges from 3/8 to 3/4 of an inch long, with workers being the smallest and the queen being the largest. A queen bee is elongate and has a straight stinger with no barbs. A worker bee has hind legs specialized for collecting pollen - each leg is flattened and covered with long fringed hairs that form a pollen basket. A worker bee's stinger has barbs. A drone bee is stout-bodied and has large eyes. Wild European honey bee nests are found in hollow trees or man-made structures. Managed colonies are often kept in wooden hives. Flowers in meadows, open woods, agricultural areas, and yards and gardens are visited by worker bees.

European honey bees are social insects with a hive typically consisting of a single queen, between 6,000 and 60,000 workers, and a few hundred to a few thousand drones. Upon hatching in the spring, the queen bee destroys all unhatched queens, kills any hatched queens, and takes a mating flight where she mates with several males. The queen stores the sperm and uses it throughout her life to fertilize eggs. After returning from her mating flight, the queen begins to lay eggs and continues to do so throughout the summer. Three days after being laid, an egg hatches into a worm-like larva. The larva then molts each day for four days into a pupa. The pupa goes into a resting stage for a few days and emerges as an adult honey bee. New European honey bee hives are created by swarming - the original queen and several thousand workers will leave the nest, typically in May or June but sometimes in September or October, and seek a new location in which to build a wax comb hive. The swarm will cluster on a branch near the original nest while scouts locate a suitable nesting site. This process can take a few hours or days. A honey bee colony can survive for up to several years.

The genome sequence of the honeybee was first reported in 2006 (Weinstock et al. 2006, Wilson 2005). Notable characteristics of this genome include high A+T and CpG contents, the lack of major transposon families, relatively slow evolution, and similarity to vertebrates for circadian rhythm, RNA interference and DNA methylation genes. The honeybee was found to have relatively few genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, but a fairly high number of genes for odorant receptors. Novel genes were found for nectar and pollen utilization (Weinstock et al. 2006).

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Chemical Structure

Melittin is the main component of apitoxin (Apis mellifera venom), accounting for approximately 50% of its dry weight (Terra et al., 2006). The water-soluble, 26 amino acid-long polypeptide chain, weighing 2,840 Da, is largely composed of hydrophobic residues, with the exception of the cationic and hydrophilic carboxy-terminal sequence (Vogel et al., 1986). It is this amphiphilic nature that gives melittin its characteristic detergent-like properties (Maulet et al., 1980).

Using a range of techniques, including X-ray crystallography, NMR spectroscopy, and molecular dynamics simulations, melittin was found to adopt a variety of conformations, depending on factors including the pH and the type of aqueous medium. For instance, when dissolved in water, the hydrophilic residues 22-26 were shown to form a non-helical segment, whereas the remaining hydrophobic residues of melittin were reported to form a bent helix, composed of two smaller α-helical segments of residues 1-11 and 12-21. The concave side of the bent helix was found to be hydrophobic, while the convex side was shown to be hydrophilic (Vogel, et al., 1986). Additionally, melittin was found to be tetrameric at high pH, a random coil at pH 7.0, and monomeric in plasma (Terra, et al., 2006).

Mode of Action

In the bloodstream, melittin is able to rapidly bind to erythrocytes (red blood cells), inducing the release of haemoglobin and other cellular contents into the extracellular medium. Once melittin has penetrated the erythrocyte, it causes micellisation of phosphatidylcholine bilayers, ultimately leading to haemolysis and cell death (Dempsey, et al., 1990).

Apart from its ability to disrupt lipid bilayers, melittin can also inhibit transmembrane proteins, including Na⁺/K⁺-ATPase, leading to a rise in sodium concentration within cells (Yang, et al., 2001). The increase in sodium induces an increase in the concentration of intracellular calcium, which results in the increased contraction of cardiac and smooth muscle.

Potential Therapeutic Use

Melittin is currently one of the most extensively used peptides in the research on lipid-peptide and peptide-peptide interactions (Wessman, et al., 2010). The presence of a single tryptophan residue at position 19 allows for a facilitated interpretation of fluorescence data via the tryptophan fluorescence technique, whereby intrinsic fluorescence emissions can be measured via the excitation of tryptophan residues (Raghuraman, et al., 2004).

More recently, the peptide has been shown to possess a variety of therapeutic uses. For instance, melittin is currently being analysed as a potential treatment and preventative for HIV. In a study currently being conducted at Washington University School of Medicine in St. Louis, a melittin-nanoparticle complex was shown to effectively destroy the AIDS-causing virus by forming pores in its protective viral envelope, required for viral reproduction (Evangelou Strait, 2013).

Another use of melittin is in the treatment of cancer. A promising study, once again conducted by researchers at Washington University School of Medicine in St. Louis, involves the attaching of melittin to a different nanoparticle. The novel melittin-nanoparticle complex, named the “nanobee”, selectively targets tumour cells, thus avoiding healthy cells. Once attached to a tumour cell, melittin is able to break down the tumour by forming pores in the cell membrane (Loftus, 2009).

The European honey bee is particularly well adapted for pollination. Each colony has many individuals available to collect pollen and, therefore provide pollination services. Honey bees have a complex communication system, allowing individuals to "point out" food sources to other members of the colony. The European honey bee also has a well developed sense of smell and is easily able to locate flowers. When a worker bee visits a flower, pollen is dusted all over its body and is then transferred between flowers. In a single day, one bee can make more than 12 trips from the hive and can visit several thousand flowers. In the United States, honey bees pollinate over 90 commercial crops and add billions of dollars per year to agricultural output. In fact, over 3.5 million acres of crop land in the United States is reliant upon honey bees for pollination. Some specific crops pollinated by the honey bee include apple, strawberry, almond, cotton, broccoli, carrot, pepper, and squash.

The Dancing Honeybee: An adobe flash program introducing the basics of honeybee waggle dance communication to a wide audience.