Fig. 3: The insecticide-degradation product, 3M4N, is highly bactericidal but efficiently eliminated by the host from the gut symbiotic organ.

a Bactericidal abilities of MEP and 3M4N on cultured SFA1 cells (in vitro) and midgut symbiont cells (in vivo). b Effects of 3M4N on crypt-colonizing symbiont population in the bean bug gut. Insects infected with SFA1 (wt) and its ΔpnpA1/ΔpnpA2 mutant were fed on soybean seeds and either distilled water (DW) or DW containing 5 mM 3M4N. Symbiont titer between the groups was compared by qPCR of the dnaA gene of the symbiont. Mean ± SEM of eight replicates are indicated. ns indicates statistical insignificance (two-sided Fisher’s exact test). Fluorescent microscopy images of the midgut crypts colonized by GFP-labeled SFA1 (wt) and ΔpnpA1/ΔpnpA2 are shown on top of the bar graph. Fluorescent microscopy was independently repeated 10 times. c MEP degradation and 3M4N production in the gut harboring the MEP-degrading symbiont SFA1. The degradation rate is compared with that of SFA1 grown in culture. The data represent the results of three independent experiments. d A schematic illustration of the MEP detoxification governed by host–symbiont mutualistic interactions.