Lysophosphatidylcholine acts in the constitutive immune defence against American foulbrood in adult honeybees

Abstract

Honeybee (Apis mellifera) imagines are resistant to the Gram-positive bacterium Paenibacillus larvae (P. larvae), causative agent of American foulbrood (AFB), whereas honeybee larvae show susceptibility against this pathogen only during the first 48 h of their life. It is known that midgut homogenate of adult honeybees as well as a homogenate of aged larvae exhibit strong anti-P. larvae activity. A bioactivity-guided LC-HRMS analysis of midgut homogenate resulted in the identification of 1-oleoyl-sn-glycero-3-phosphocholine (LPC) pointing to a yet unknown immune defence in adult honeybees against P. larvae. Antimicrobial activity of LPC was also demonstrated against Melissococcus plutonius, causative agent of European Foulbrood. To demonstrate an AFB-preventive effect of LPC in larvae, artificially reared larvae were supplemented with LPC to evaluate its toxicity and to assess whether, after infection with P. larvae spores, LPC supplementation prevents AFB infection. 10 μg LPC per larva applied for 3 d significantly lowered mortality due to AFB in comparison to controls. A potential delivery route of LPC to the larvae in a colony via nurse bees was assessed through a tracking experiment using fluorescent-labelled LPC. This yet undescribed and non-proteinous defense of honeybees against P. larvae may offer new perspectives for a treatment of AFB without the utilization of classic antibiotics.

Natural Products Diversity in Plant-Insect Interaction between Tithonia diversifolia (Asteraceae) and Chlosyne lacinia (Nymphalidae)

“…We found out that, in general, the putatively annotated lysophospholipids were detected in higher abundance in C. lacinia pupae and butterflies. Taken together, our findings suggested that lysophospholipids, along with their structural function, may play important roles by protecting the insects against microorganisms, as corroborated by previous reports [53], during pupation and by acting as an energy source for diapause and metamorphosis. Moreover, 1-(9-octadecenoyl)-glycero-3-phosphoserine ( 23 ) and 1-stearoyl-2-hydroxy-glycero-3-phosphoethanolamine ( 26 ) were predominately found in C. lacinia butterflies, which indicated that these metabolites may be important substrates for flight in the adult life stage, as previously reported [51,52].…”

“…Besides, several insect pheromones and growth hormones exhibit lipophilic character [51,52]. Recently, lysophosphatidylcholine has been associated with antimicrobial activity in adult honeybees [53]. We found out that, in general, the putatively annotated lysophospholipids were detected in higher abundance in C. lacinia pupae and butterflies.…”

Virulence of Melissococcus plutonius and secondary invaders associated with European foulbrood disease of the honey bee

“…The most interesting case concerning virulence was strain 119 which can cause variable mortality depending on the host background (Figure ). In a previous study, M. plutonius strain 119 showed high virulence leading to mortality rates of 70% in 2 weeks (Riessberger‐Gallé, Hernández‐López, Rechberger, Crailsheim, & Schuehly, ). This corresponds to the higher virulence in colony B of the current study (Figure ).…”

Atypical <i>Melissococcus plutonius</i> strains: their characteristics, virulence, epidemiology, and mysteries

“…48–72 hr old 1.92 × 10 5 CFU/larva 21 days 100% − 1.94 × 10 5 CFU/larva 87.5% [ 44 ] No infection control N/A N/A N/A N/A N/A 0 CFU/larva 21 days ≤14.6% DAT561 (atypical) 12 12 − Japan approx. 48–72 hr old 2.2–4.6 × 10 4 CFU/larva 21 days 77.1–80.6% [ 55 ] No infection control N/A N/A N/A N/A N/A 0 CFU/larva 14 days approx. 15% e 119 (typical) 20 13 − Switzerland 5–10 hr old ~6.0 × 10 4 CFU/larva 14 days approx.…”