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New paper

February 6, 2014

I’m pleased to announce that I have a new paper out in the Proceedings of the Royal Society B – Biological Sciences. My coauthors and I (Ulrich Mueller of UT Austin and Rosalind James of the USDA) studied the bacteria and fungi associated with the alfalfa leafcutting bee (ALCB for short) Megachile rotundata.  The ALCB is the second most important field crop pollinator (after the honey bee), but it also has a nasty fungal pathogen that causes the disease chalkbrood (the fungus is Ascosphaera aggregata).

We wanted to look for interactions between microbes, so we applied several treatments to the pollen provisions of the bees: 1) antibacterials 2) antifungals 3) Ascosphaera aggregata spores and 4) a no treatment control. We then sequenced bacteria and fungi from the guts of the larvae that we applied these treatments to.

We found that when we applied antifungals, fungal diversity went up. This seems odd at first, but when we looked at the data we saw that we were knocking down chalkbrood, which seemed to be allowing other fungi to grow. This could have been just been an artifact of sampling, i.e. the other fungi could be showing up simply because there were so many chalkbrood sequences in the other treatments that they were swamped out and not detected. So we did some more analyses that suggest that the finding is not an artifact but due to some sort of inhibition (competitive, inhibitive, or otherwise, we don’t know yet) of other fungi by A. aggregata. 

One other really interesting thing we found was that my current favorite bacteria, Lactobacillus kunkeei, was resistant to the antibiotic cocktail that we threw at it. Nancy Moran’s group found that a honey bee-associated  bacteria is resistant to antibiotics. L. kunkeei is also associated with honey bees (though not as part of the core honey bee gut microbiota), and we think that L. kunkeei may be exposed to antibiotics while associated with honey bees. This suggests that antibiotic treatments to honey bee colonies may have far-reaching effects on wild bees, which is a really novel result. This is a really interesting hypothesis that we need to test further.

If you want to see the whole paper, check out my publications page. Here is one of the more important figures in the paper, which shows the relative abundances of fungi and bacteria from our different treatments. Note that L. kunkeei is present in the antibacterial treatments, and fungi are more diverse in the antifungal treatment, but A. aggregata shows low relative abundance.


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