Changes in Antibiotic-Resistance Genes Induced by the Grazing Effect in Three Cladoceran Species

Abstract

The acquisition of Antibiotic-Resistance Genes (ARGs) by natural bacteria caused by antibiotic abuse is causing serious problems for human and animal welfare. Here, we evaluated the influence of three cladoceran species on Antibiotic-Resistant Bacteria (ARB) and tetracycline-resistance gene (tet(A)) copies, and discussed the effect of these biological interactions on the distribution and diffusion of ARGs in freshwater ecosystems. Bacterial community and tet(A) abundances in water samples collected from wetlands were strongly influenced by cladoceran presence. The presence of Daphnia obtusa dramatically decreased ARB and tet(A) abundance compared to that with other cladoceran species (Chydorus sphaericus and Simocephalus vetulus). Interestingly, we found a high abundance of Flavobacteriales in the microbiomes of cladoceran species. Considering that Flavobacteriales species are potential carriers of the tet(A) gene, their adsorption and assimilation with cladocerans could significantly impact the reduction of tet(A) in water. Field surveys also showed that tet(A) abundance could be low if the dominance of D. obtusa in each wetland was high. This study highlighted the need for ecological interactions and a broad range of niches in the food web when discussing the fate of ARGs in freshwater ecosystems.

Impact of the antibiotic doxycycline on the D. magna reproduction, associated microbiome and antibiotic resistance genes in treated wastewater conditions

“…3 and 4). This could indicate that D. magna is able to filtrate bacteria and ARGs from water, as reported in previous studies (Choi & Kim, 2021;Olanrewaju et al, 2019).…”

“…Interestingly, the genera Ideonella, Flavobacterium and Acidovorax were present in both Daphnia exposed to treated wastewater (W and WA) and to antibiotics in lab conditions (A) but not in control Daphnia (C). Previous studies showed that Flavobacteriales could be carriers of the ARG tet(A) (Choi & Kim, 2021). In addition, the PLS-DA showed that bacteria from the genus Enterococcus was relevant explaining the differences in Daphnia-associated microbiomes by both antibiotic (in lab water conditions) and wastewater treatment (compared to controls in lab water).…”

“…These included a previous step of three freeze and thaw cycles and homogenization with DNA lysis buffer using a TissueLyser® (Qiagen, Germantown, MA, USA). We extracted DNA from the whole animal instead of that from the guts to study the Daphnia-associated microbiome, as the few existing studies on ARGs in Daphnia (Eckert et al, 2016;Choi & Kim, 2021). Total DNA was re-suspended in 50 μl of RNAse free water.…”

“…Regarding ARG studies in Daphnia, researchers found that Enterococcus faecalis were transferring antibiotic resistant genes with each other in the Daphnia gut from both D. magna and D. pulex (Olanrewaju et al, 2019). Previous studies in other species, Daphnia obtuse, showed that the individuals may also act as biofilters for the tet(A) antibiotic resistance gene, since the abundance of tet(A) was reduced in surface water when Daphnia individuals were present (Choi and Kim, 2021;Eckert et al, 2016). However, to our knowledge, the interplay between antibiotics modulating D. magna microbiome and ARGs and how this affect the animals' health has not been deeply studied.…”

Effect of Protists on Horizontal Transfer of Antimicrobial Resistance Genes in Water Environment

“…It is reported that the presence of Daphnia obtusa dramatically decreased ARB and tet(A) abundance compared to that with other cladoceran species (Chydorus sphaericus and Simocephalus vetulus) [31]. Field surveys showed that tet(A) abundance could be low if the D. obtusa in wetland was dominant [32]. It is suggested that the consuming of bacteria by various grazers decreases ARGs.…”