Rapid Changes in Microbial Community Structures along a Meandering River

Abstract

Streams and rivers convey freshwater from lands to the oceans, transporting various organic particles, minerals, and living organisms. Microbial communities are key components of freshwater food webs and take up, utilize, and transform this material. However, there are still important gaps in our understanding of the dynamic of these organisms along the river channels. Using high-throughput 16S and 18S rRNA gene sequencing and quantitative PCR on a 11-km long transect of the Saint-Charles River (Quebec, CA), starting from its main source, the Saint-Charles Lake, we show that bacterial and protist community structures in the river drifted quickly but progressively downstream of its source. The dominant Operational Taxonomic Units (OTUs) of the lake, notably related to Cyanobacteria, decreased in proportions, whereas relative proportions of other OTUs, such as a Pseudarcicella OTU, increased along the river course, becoming quickly predominant in the river system. Both prokaryotic and protist communities changed along the river transect, suggesting a strong impact of the shift from a stratified lake ecosystem to a continuously mixed river environment. This might reflect the cumulative effects of the increasing water turbulence, fluctuations of physicochemical conditions, differential predation pressure in the river, especially in the lake outlet by benthic filter feeders, or the relocation of microorganisms, through flocculation, sedimentation, resuspension, or inoculation from the watershed. Our study reveals that the transit of water in a river system can greatly impact both bacterial and micro-eukaryotic community composition, even over a short distance, and, potentially, the transformation of materials in the water column.

Effect of Snowmelt on Groundwater Bacterial Community Composition and Potential Role of Surface Environments as Microbial Seed Bank in Two Distinct Aquifers from the Region of Quebec, Canada

“…Furthermore, our results from microbial source tracking also suggest a minor contribution of subsurface environments to river communities through groundwater discharge. These results are consistent with previous study by Villeneuve et al [30].Our results also confirmed that most of the bacterial diversity for river was attributed to unknow sources which can be explained by rapid changes in community composition as a result of water transit [41].…”

Community Composition of Bacteria Isolated from Swiss Banknotes Varies Depending on Collection Environment

“…The same taxa that we identified as being relatively abundant above resurfaced when we calculated the core microbiome for each shop type (taxa found in >50% of samples per shop type at abundance >0.1%). We identified seven dominant core ZOTUs (Dawson et al , 2017; Cruaud et al , 2020) shared between all shop types, attributed to the genera: Corynebacterium , Propionibacterium , Pseudomonas , Streptococcus (n = 2) and Staphylococcus (n = 2) (Fig. S2; detection threshold = 0.001, prevalence threshold = 0.5; Table S8).…”

Community composition of bacteria isolated from Swiss banknotes varies depending on collection environment

“…The linked map contains the symbols for all shops in a town from which banknotes were collected. (Dawson et al, 2017;Cruaud et al, 2020) Due to the size of the file this table is available separately (suppTable_08.csv).…”