Antibiotic disturbance affects aquatic microbial community composition and food web interactions but not community resilience

Abstract

Notwithstanding the fundamental role that environmental microbes play for ecosystem functioning, data on how microbes react to disturbances are still scarce, and most factors that confer stability to microbial communities are unknown. In this context, antibiotic discharge into the environment is considered a worldwide threat for ecosystems with potential risks to human health. We therefore tested resilience of microbial communities challenged by the presence of an antibiotic. In a continuous culture experiment, we compared the abundance, composition and diversity of microbial communities undisturbed or disturbed by the constant addiction of tetracycline in low (10 µg/L) or intermediate (100 µg/L) concentration (press disturbance). Further, the bacterial communities in the three treatments had to face the sudden pulse disturbance of adding an allochthonous bacterium (Escherichia coli). Tetracycline, even at low concentrations, affected microbial communities by changing their phylogenetic composition and causing cell aggregation. This, however, did not coincide with a reduced microbial diversity, but was mainly caused by a shift in dominance of specific bacterial families. Moreover, the less disturbed community (10 µg/L tetracycline) was sometimes more similar to the control and sometimes more similar to heavily disturbed community (100 µg/L tetracycline). All in all, we could not see a pattern where the communities disturbed with antibiotics were less resilient to a second disturbance introducing E. coli, but they seemed to be able to buffer the input of the allochthonous strain in a similar manner as the control.

Antibiotic Pollution in the Environment: From Microbial Ecology to Public Policy

“…For example, antibiotic pollution in aquatic environments was found to reduce overall microbial diversity, including taxa responsible for carbon cycling and primary productivity [146,166,167,168]. Similarly, the presence of antibiotics in soil was found to alter microbial community structure, leading to a loss of biomass and a reduction in microbial activity including nitrification, denitrification, and respiration [169,170,171].…”

Characterizing antibiotics in LCA—a review of current practices and proposed novel approaches for including resistance

“…(15) Ecotoxicological modelling according to USEtox, damage to the ecosystem from increased AB concentrations in the environment is characterized as freshwater ecotoxicity impacts. (16) Weak evidence for damage to ecosystem from ABR (Eckert et al 2019). ( 17 Szumilas (2010, p227) as the representation of "the chance that an outcome will occur given a particular exposure compared to the odds of the outcome occurring in the absence of that exposure".…”

“…(15) Ecotoxicological modelling according to USEtox, damage to the ecosystem from increased AB concentrations in the environment is characterized as freshwater ecotoxicity impacts. (16) Weak evidence for damage to ecosystem from ABR(Eckert et al 2019). (17) End-point measurement of ecotoxicological effects, no clear ecosystem effect from ABR…”

Zooplankton as a transitional host forEscherichia coliin freshwater

“…While on one hand these bacteria are known to not be competitive in such environments and to be grazed easily when entering freshwaters through faecal pollution (i.e. (González, et al 1992;Eckert, et al 2019)), the evolution of freshwater E. coli (Touchon, et al 2020) and renaturation of these bacteria have been observed (Ishii, Ksoll, et al 2006;Ishii and Sadowsky 2008), showing that at least part of the incoming E. coli must survive over longer time periods in water. In a previous study we found that lake zooplankton could show remarkable quantities of E. coli related 16S rRNA gene sequences and we confirmed this here by quantifying the abundance of uidA gene, an unambiguous indicator for E. coli presence (Figure 2) .…”

“…Particularly, pelagic cold waters are a very hostile environment for such gut symbionts. If they are not grazed by flagellated predators upon arrival, they are surely not favoured by resource competition (González, et al 1992;Wanjugi and Harwood 2013;Eckert, et al 2019). Since evolution, as seen in the genome reduction of E. coli (Touchnon, et al 2020), takes time, a certain long-term persistence of vertebrate commensal strains in the aquatic habitat is crucial, and the question remains: In which niche does persistence take place?…”