Under unrealistic conditions (e.g., low community diversity 15, 16, 20 and high bacterial densitiesįurthermore, culture-based studies are limited Microcosm studies such as the ones mentioned above often are operated 14 On the other hand, when introduced to soils, fecal bacteriaĬoncentrations tend to decline, 18, 19 limiting the time spanįor potential ARG transfer to soil bacteria. Soil provides nutrients and a high density of potential ARG-carryingīacteria, thus creating favorable HGT conditions. (10 –4 T/D) with an IncP1 plasmid in nonsterile soil,īut only when nutrients were added. (1990) reported 10 2 transconjugant CFU/g soil Including studies using Escherichia coli as donor, in which the transconjugant abundance reached 10 2 and 10 3 CFU/g soil (10 –2 and 10 –4 transconjugants-to-donor ratios T/D). Microcosm setups have indeed shown HGT potential, Often used for quantification of HGT, microcosm systems representĪ better approximation of the natural environment as they preserve Representative mating conditions is critical to characterize the risk The quantification of AMR-relevant plasmid transferĮvents together with the identification of the new plasmid hosts in Soils is challenging, and the identity of the new plasmid hosts is Observed, 12− 14 but the quantification of these transfer events in In soils has been extensively studied, 11 and plasmid transfer from fecal bacteria to soil bacteria has been In the introduction of fecal bacteria, their plasmids, and antimicrobial 3− 5 Plasmid-mediated gene transfer by conjugation is considered a majorĪgricultural application of manure as organic Particular concern because it drives bacterial evolution 2 and is connected with the rise of AMR. 1 Horizontal gene transfer (HGT) of resistance genes is of Most significant global public health challenges. The risks of AMR spread via manure application. This study provides important information to determine Shortly after manure application, and the plasmid did not colonize When transferred to soils, but these events were rare, mainly happened This work showed that gene transfer from fecal to soil bacteria occurredĭespite the less-than-optimal conditions faced by manure bacteria Sequence variants (ASVs) of genera whose origin was traced to soils In the pool of recovered transconjugants, we found amplicon (1.00–2.49 log CFU/g of manured soil, ranging between 10 –5 and 10 –4 transconjugants-to-donor Were only observed within the first 4 days after manure applicationĪnd at values close to the detection limits of this experimental system To soils and identify the transconjugants resulting from these events.Ĭonjugation was quantified at multiple time points by plating andįlow cytometry, and the transconjugants were recovered by fluorescence-activatedĬell sorting and identified by 16S rRNA sequencing. This studyĪimed to quantify conjugation events resulting from manure application The risk of horizontal gene transfer in the environment. The quantification and identification of new plasmid-acquiringīacteria in representative mating conditions is critical to characterize
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