Origin and effect of Acetobacteraceae Alpha 2.2 in honey bee larvae and description of Parasaccharibacter apium, gen. nov., sp. nov

Authors: Corby-Harris, Vanessa; Snyder, Lucy; SCHWANN, MELISSA - Former ARS Employee; MAES, PATRICK - University Of Arizona; MCFREDERICK, QUINN - University Of California - Cooperative Extension Service; Anderson, Kirk

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2014
Publication Date: 9/19/2014
Publication URL: http://handle.nal.usda.gov/10113/60031
Citation: Corby-Harris, V.L., Snyder, L.A., Schwann, M.R., Maes, P., Mcfrederick, Q.S., Anderson, K.E. 2014. Origin and effect of Acetobacteraceae Alpha 2.2 in honey bee larvae and description of Parasaccharibacter apium, gen. nov., sp. nov. Applied and Environmental Microbiology. doi: 10.1128/AEM.02043-14.

Interpretive Summary: Honey bees harbor a diverse array of microorganisms in their gut and in their hive. One of these bacteria, Alpha 2.2, is found in the hive food stores, the social stomach or crop of foragers, and larvae, but not in the portion of the gut exclusive of the crop. The distribution of Alpha 2.2 – in the social stomach and in larvae who are fed by nurse worker bees in the hive – therefore suggests that it may be passed through social contact as nurses care for the colony’s developing brood. If this hypothesis were true, we would expect that Alpha 2.2 would be found in high abundance in the hypopharyngeal glands (HGs) that secrete the brood food, the nurse crop that regurgitates sugar for the developing brood, and the brood food itself (royal jelly, RJ). Using high-throughput DNA sequencing of all of the bacteria in these substrates we did indeed find a high degree of Alpha 2.2. By comparing the DNA sequence of the Alpha 2.2 found in RJ, the HGs, and the crops with other Alpha 2.2-like seqeunces found in floral sources and the guts of other pollinators, we show that the Alpha 2.2 found in honey bees is unique to larvae, the RJ, the HGs, and the crop and has exploited these niches in order to be passed from nurse worker to larvae as the workers feed the developing brood. Lastly, we show that one strain of Alpha 2.2 increases the survival of larvae raised under laboratory conditions. This is the first direct evidence that a bacteria living with the honey bee in nature can benefit the health of their honey bee host.

Technical Abstract: The honey bee hive environment contains a rich microbial community that differs according to niche. Acetobacteraceae Alpha 2.2 (Alpha 2.2) are present in the food stores, the forager crop, and larvae but at negligible levels in the remainder (non-crop portion) of the nurse and forager gut. We first sought to determine the source of Alpha 2.2 in young larvae by assaying the diversity of microbes in nurse crops, hypopharyngeal glands (HGs), and royal jelly (RJ). Amplicon-based pyrosequencing showed that Alpha 2.2 occupy each of these environments along with a variety of other bacteria, including Lactobacillus kunkeei. RJ and the crop contained fewer bacteria than the HGs, suggesting these tissues are rather harsh, selective environments. Acetobacteraceae are known to form symbiotic relationships with insects, and so we next tested whether Alpha 2.2 benefits larval fitness. We cultured 44 strains of Alpha 2.2 from young larvae and these isolates grouped into nine distinct clades. Three isolates from these nine clades flourished in royal jelly and one isolate also increased larval survival in vitro. These results suggest that Alpha 2.2 have exploited the royal jelly niche as a way to be passed to larvae through nurse worker feeding behavior and provides the first direct and biologically plausible evidence that symbiotic bacteria from honey bees can benefit their host.