Bacteria-Mediated Effects of Antibiotics on <i>Daphnia</i> Nutrition
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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<sup>–1</sup> 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 <i>Curvibacter</i>, <i>Aquabacterium,</i> and <i>Limnohabitans</i> in controls to significantly
lower diversity under dominance of <i>Pelomonas</i> in the
exposed animals. Moreover, decreased feeding and digestion was observed
in the animals exposed to 0.25–2 mg L<sup>–1</sup> trimethoprim
for 48 h and then fed <sup>14</sup>C-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