Bacteria-Mediated Effects of Antibiotics on Daphnia Nutrition

Abstract

In polluted environments, contaminant effects may be manifested via both direct toxicity to the host and changes in its microbiota, affecting bacteria-host interactions. In this context, particularly relevant is exposure to antibiotics released into environment. We examined effects of the antibiotic trimethoprim on microbiota of Daphnia magna and concomitant changes in the host feeding. In daphnids exposed to 0.25 mg L(-1) trimethoprim for 24 h, the microbiota was strongly affected, with (1) up to 21-fold decrease in 16S rRNA gene abundance and (2) a shift from balanced communities dominated by Curvibacter, Aquabacterium, and Limnohabitans in controls to significantly lower diversity under dominance of Pelomonas in the exposed animals. Moreover, decreased feeding and digestion was observed in the animals exposed to 0.25-2 mg L(-1) trimethoprim for 48 h and then fed 14C-labeled algae. Whereas the proportion of intact algal cells in the guts increased with increased trimethoprim concentration, ingestion and incorporation rates as well as digestion and incorporation efficiencies decreased significantly. Thus, antibiotics may impact nontarget species via changes in their microbiota leading to compromised nutrition and, ultimately, growth. These bacteria-mediated effects in nontarget organisms may not be unique for antibiotics, but also relevant for environmental pollutants of various nature.

Food availability affects the strength of mutualistic host–microbiota interactions in Daphnia magna

“…to be the dominant taxon, this is in accordance with earlier studies who also found this taxon to be a major constituent of the Daphnia microbiota (Freese & Schink, 2011;Eckert & Pernthaler, 2014;Gorokhova et al, 2015). However, by specifically characterizing the gut microbiota, we found that in our cultures Aeromonas sp.…”

“…Its presence furthermore enabled the uptake of protein macromolecules and influenced gut motility (Bates et al, 2006). Interestingly, Gorokhova et al (2015) found a strong decrease in feeding activity, digestion efficiency and carbon uptake in Daphnia of which the gut microbiota was affected by antibiotic exposure. Possibly, Aeromonas sp.…”

Ecotoxicological assessment of antibiotics: A call for improved consideration of microorganisms

“…stimulation of fungal activity following inhibition of bacterial growth (Rousk et al, 2008). Alternatively, antibiotics may indirectly affect animal nutrition and, ultimately growth, via direct effects on their gut microbiota (Gorokhova et al, 2015). We encourage more basic research on how antibiotics may disturb food webs and affect the structure and function of the immediate ecosystem.…”

Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum

“…Antibiotics can alter the microflora in the gut of invertebrates and consequently their efficiency to assimilate nutrients and energy from the ingested food. For instance, Gorokhova et al (2015) observed a lower diversity in the gut microflora that was associated with a lower assimilation efficiency in Daphnia magna exposed to one of the antibiotics assessed in the present study (trimethoprim) and at a similar concentration (250 µg/L). Such impacts on the gut microflora could explain the lack of growth observed for G. fossarum exposed to 200 µg/L of the antibiotic mixture, if the ability of G. fossarum to profit from a potentially higher food quality was lost at this high antibiotic concentration.…”