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Figure 2: Effect of PPQ-ADH mutant bacteria on fly growth and metabolism
Eleven of the fourteen mutations the authors examined in Figure 1 were associated with the same protein: periplasmic pyrroloquinoline quinon-dependent alcohol dehydroenase (PPQ-ADH). Furthermore, five of the mutations were located in the gene for PPQ-ADH-I. To better understand the role of bacterial PPQ-ADH-I on host development and metabolism, they chose one mutation, P3G5, to study in particular depth. P3G5 mutant A. pomorum colonize larvae guts just as effectively as WT bacteria, and both P3G5 mutants and WT bacteria displayed similar growth rates in vitro, making it a suitable comparison.
Image from Shin et al., 2011
Panel A: The growth rates of germ-free larvae exposed to WT A. pomorum and P3G5 A. pomorum are compared with diets supplemented with casamino acid or 0.1% yeast. Days to puparium formation (y-axis) are significantly greater for larvae containing P3G5 mutant A. pomorum compared to those containing the WT bacteria (x-axis) for both casamino acid and 0.1% yeast enriched diets. Numerically, larvae with mutant bacteria required roughly 14 days to form puparia while those with WT bacteria required less than 10. Images show larvae after 120 hours for each condition.
Panel B: The body sizes (mass; y-axis) of both male and female adult flies (five days old) exposed to either WT or P3G5 A. pomorum (x-axis) are compared. The body sizes of flies containing mutant bacteria are significantly smaller (almost half the size) of their counterparts containing WT bacteria. Images show adult flies (five days old) in both conditions.
Panel C: Wing size, cell size, and cell number (y-axis) are compared in flies exposed to either WT or P3G5 A. pomorum (x-axis). Wing size, cell size, and cell number are all significantly reduced in flies containing mutant bacteria compared to those containing WT bacteria. Images show wings of five-day old adult flies.
Panel D: Two measures of metabolism, blood sugar levels and circulating lipid levels (y-axis), are compared between flies exposed to WT or P3G5 mutant A. pomorum. Both blood sugar and circulating lipid leves are siginificantly increased in flies containing the mutant bacteria.
Reference:
Shin, C. S., Kim, S., You, H., Kim, B., Kim, A. C., Lee, K., Yoon, J., Ryu, J., Lee, W. 2011. Drosophila Microbiome Modulates Host Development and Metabolic Homeostasis via Insulin Signaling. Science. 334: 670-674.
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