What’s all the buzz around microbes?

What’s all the buzz around microbes?

Researchers in Rowan’s Social Insect Lab are studying the gut of the honey bee
In Rowan's Social Insect Lab, researchers are examining whether gut bacteria play a role in fending off pathogens that threaten the honey bee population.

After more than a decade of crushing declines in the honey bee population worldwide, whole colonies of one of our most important pollinators are disappearing at unsustainable rates.

Svjetlana Vojvodic, assistant professor in the Department of Biological Sciences at Rowan University, believes that one part of the solution might be found in an unexpected place: inside the gut of the honey bee.

Could gut bacteria known as a gut microbiome hold the key to fending off colony-killing pathogens? That’s just one of the vital questions Vojvodic and her students are tackling in her Social Insect Lab in the College of Science & Mathematics csm.rowan.edu.

What bees’ gut microbiome is telling us

The honey bee’s gastrointestinal systems are colonized by billions of microbes composed of bacteria and fungi.

“All animals, including humans, have a distinct gut microbiome,” explained Vojvodic. “There are many different species of bacteria living in the gut, and they can influence everything from digestion to weight to behavioral disorders.” Most of those species are considered beneficial symbiotes – in other words, “good bacteria” that help, rather than harm, the host in which they are found.

In humans, hundreds of different species of bacteria – by some accounts, up to a thousand – make up the microbiome. In honey bees, the microbiome consists of just nine dominant bacterial groups.

“We know what these bacteria are in the honey bee, and we can manipulate them in my lab,” Vojvodic said. In doing so, she may just find a remedy against the common fungal pathogen of honey bees. This project will contribute to solving the global bee losses, including the most baffling beekeeping mystery in modern times: Colony Collapse Disorder (CCD).

A decade of unexplained colony collapses

In early spring of 2007, keepers around the world reopened their honey bee colonies after the winter’s hibernation to find something shocking: their bees were gone.

More specifically, the worker bees – the ones who perform the work needed to maintain and grow the colony, both within and outside the hive – had disappeared. The queen remained in the hive, along with the young, called the brood.

Typically, beekeepers find very few dead bees near these devastated hives. The remaining supplies of honey and pollen suggest that the worker bees didn’t simply starve over the winter. Yet their vanishing act is permanent. They never come back, and without the workers, the colony can’t survive for long.

As ongoing collapses have led to a drastic decline in managed honey bee populations across the globe, researchers have struggled to understand this disastrous phenomenon.

“A single cause of CCD hasn’t been identified,” Vojvodic said. Bee scientists now view CCD as the result of a combination of factors: a loss of diversity in the flowers that comprise a colony’s food supply, the harm caused to bees by agricultural pesticides and fungicides and a slew of worrying diseases.

Pathogens plaguing the honey bee population

“Bees have specific pathogens they have to fend off before winter,” explained Vojvodic. These pathogens can result from several different types of dangers, including exposure to viruses and “bad” bacteria – as opposed to the good bacteria found in gut microbes.

Perhaps the biggest threats come from parasites like the blood sucking Varroa destructor mite that can also transmit viruses. Very common also are fungal infections such as Ascosphaera apis, which is responsible for chalkbrood disease that affects bee larvae. As the young prepare to become adult bees within a wax-capped cell of the hive’s honeycomb, the fungus kills the infected bee, leaving behind what’s essentially a mummified corpse.

Many of the pathogens that infect honey bees currently have no cure. That’s one of the things Vojvodic’s research aims to change.

“Some bacteria present in honey bees’ guts can directly suppress fungi that can lead to deadly infections,” she said. “We’re trying to isolate specific compounds produced by gut microbes to understand which microbes influence these pathogens.”

The goal is to identify one microbe or compound that could be used as a medicine to help bees fend off the disease. “We have preliminary data saying that bees who have established normal gut microbiome survive longer when exposed to this fungal pathogen than those who don’t,” Vojvodic said.

One way to describe this occurrence is “extended immunity.” The bees gain protection from other organisms – the microscopic ones inhabiting their own guts.

Hands-on research for undergraduates

Since Vojvodic first established her lab in 2015, she has mentored 20 undergraduate students. Students gain a lot from their work in the Social Insect Lab, from cultivating hands-on research experience to having opportunities to deliver presentations at local and national conferences in the scientific community.

“I learned about the role of being a scientist, particularly the importance of sharing research with people who can make changes. Research in Dr. Vojvodic’s lab has given me the scientific skillset, professionalism, and confidence I have needed and will need in the future,” said Mathew Pekora, a 21-year-old senior biological science major from Delmont.

This month, Pekora and Olivia Smithson, also a senior biological science major, gave an award-winning poster presentation, “Behavioral consistencies of honey bee nurses,” at the Third Annual Evolution in Philadelphia Conference (EPiC) at Temple University.

“I don’t only speak for myself but for everyone who has done research under Dr. Vojvodic that it has been one of the most rewarding experiences we’ve had at Rowan,” Pekora said.

Vojvodic’s research into how gut microbes could affect fungal diseases in bees recently received a $40,000 funding grant from Project Apis m., a non-profit foundation whose name is taken from the scientific name for honey bees.

In so many ways, these studies are important – and not just for bees. The bee population decline has major implications for humans that go well beyond a shortage of honey.

“Bees pollinate a lot of the food we eat,” Vojvodic said. “If you don’t have pollinators, you’re not going to have apples, almonds and many other foods.”

Vojvodic’s research also could shed light on the interaction between diseases and good microbes that potentially occur in other organisms – even humans. Although gut microbes have been studied in several species, research into the interactions between these microbes and specialized pathogens is novel.

The worldwide decline in the bee population may be the most urgent area of Vojvodic’s bee research, but possible medicines aren’t the only focus of her work. These gut microbes also play a part in learning.

Honey bees are surprisingly smart, able to navigate of flight paths miles beyond their hives and communicate the locations of flowers to hive mates by performing a “waggle dance.” These intelligent insects can be trained through associative learning. Much like dogs learning to salivate at the sound of a bell, a bee can learn to stick out its proboscis, or “tongue,” upon smelling an odor it associates with the offering of a sugar-water reward.

Researchers have found that a bee’s gut microbiome affects how it learns. Laboratory bees that lack the beneficial microbes they would acquire naturally in a hive setting don’t learn as well as the bees who have a full microbiome. By isolating and testing different microbes, Vojvodic and her students discovered that one specific microbe increased bees’ abilities to learn.

“We don’t know why learning is affected,” Vojvodic said, which is why ongoing research into honey bee learning involves exploring brain gene expression. What’s clear is that the field of gut microbe research--in bees and other species--remains abuzz with opportunity.