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Tom writes:

I just finished listening to the Original Antigenic Sin episode where you were talking about Wolbachia's protective effect against virus infection in Drosophila. I was delighted that you were speculating about the effect in bees because Wolbachia has been one of my favorite subjects for years. Some key things to know is that:

1. Beekeepers have used (overused) tetracycline routinely since I think the 1950s against a bacterial disease of the brood called American Foulbrood. This usage has almost certainly cleared any Wolbachia infections in domestic bees, if they once had it. Interestingly, we now have developed bees that are resistant to that disease, which make antibiotics unnecessary, though unfortunately they are still widely applied.

2. Wolbachia has been found to be very common in African bees (but only in Africa) in at least two subspecies. One of these races, Apis mellifera capensis, has the unusual trait of worker bees producing diploid (female) offspring parthenogeneticaly, possibly due to an effect of Wolbachia. Our European workers can only produce haploid offspring, which are always male.

3. Another well studied Wolbachia effect is something called cytoplasmic incompatibility. This can result in sperm produced by infected males killing eggs of uninfected females. Infected females on the other hand produce viable offspring using either infected or uninfected sperm. This gives infected females a huge reproductive advantage. Wolbachia is very selfish, and since it is passed on only maternally, in the cytoplasm the egg, it uses the genetically dead end male to kill off the competition.

My own pet hypothesis is that this could explain how descendants from 26 African honeybee queens released in Brazil in 1956 were able to make a nearly complete genetic sweep all the way to the southern US. Supporting evidence for this hypothesis is still lacking, since Wolbachia has yet to be found in this hemisphere, we are actively looking though. If found, it could be very useful not only for the possible protection from virus, but also for driving good genes into the population.

A person who we are working with to find Wolbachia in bees is David Schneider at Stanford. Here's a quote from his article in Science last year,

"One might guess that an insect would be safe from having its microbiota altered. Honeybees are an exception, however, because we’ve been dosing commercial colonies of bees with antibiotics for decades. Before the rise of colony collapse disorder, one of the most important honeybee diseases was American foulbrood, caused by the bacterium Bacillus larvae. To deal with this threat, many beekeepers prophylactically treat their hives with tetracycline derivatives—the same antibiotics used to cure flies of Wolbachia. If these treatments cured queen bees, then all hives descending from these queens would also be Wolbachia free, because the microbe is transmitted maternally. A Wolbachia-virus sensitivity experiment may have already been performed on honeybees nationwide and may change the way bees interact with previously characterized pathogens."

I find you and Dick brilliant in the way you come up with great ideas on the fly. It's a pleasure to listen to such intelligent people bounce ideas around. Thanks for such interesting program.

Sincerely, Tom

 

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