Drosophila attraction, colonization, contagion, and mortality by Pseudomonas spp. and toxicity of their biosurfactants.

Abstract

Oil bioremediation may be achievable via Pseudomonas spp. leading to low-cost biosurfactant (BSF) production, but the environmental impact is unclear. Here, we studied P. aeruginosa PA14 and PAO1; P. putida mt-2 and F1; and P. citronellolis 620C, P3B5, and SJTE-3, for their ability to degrade oily wastewater (OW), produce BSFs, and impact the model insect, Drosophila melanogaster. Biodegradation was > 86% by day 1 and > 93% by day 7, while BSF production was > 200 mg/L by day 1 and > 400 mg/L by day 7 for all strains. P. aeruginosa PAO1 and PA14 produce rhamnolipids and glycolipopeptides, respectively. P. putida mt-2 and F1 formed glycolipopeptides and glycolipids, respectively. P. citronellolis P3B5 and SJTE-3 yielded glycolipids, whereas 620C produced lipopeptides. Strikingly, Drosophila was mostly attracted to food contaminated with any of the P. aeruginosa strains or P. putida mt-2, which were the most virulent. To the contrary, Drosophila was repelled from food containing the low in virulence P. putida F1 or any of the P. citronellolis strains. All strains exhibited high ability to colonize Drosophila and disperse from fly to fly, but the colonization and contagion extend by P. aeruginosa strains were slightly higher. Moreover, the virulence of Pseudomonas spp. aligned with the toxicity of their BSFs. BSFs produced by P. aeruginosa were the most toxic, followed by P. putida and P. citronellolis, indicating a correlation between BSF toxicity and microbial origin. We concluded that P. citronellolis strains and their BSFs are relatively innocuous to the fly populations, yet highly potent in biodegrading OW. KEY POINTS: • >93% biodegradation of oily wastewater by all Pseudomonas spp. strains by day 7 • The virulence of Pseudomonas spp. aligns with the toxicity of their BSFs • P. citronellolis strains and their BSFs are more innocuous to Drosophila than those of P. putida and P. aeruginosa.