Biology subjects

Taranu, Z. E.

Publications and source records attributed to Taranu, Z. E..

4 recordsLinked to original sources

bioRxiv2025

Deciphering the dynamics of Cyanobacteria-Phage in a natural lake: Insights from a decade-long investigation

Phages - viruses that infect bacteria - are often seen as key players in bacterial community dynamics and the ecosystem services those communities support. However, much of our understanding of phage-bacteria interactions comes from in vitro studies, which provide limited insights into how these interactions occur in natural environments. In this study, we used cyanobacterial blooms as a model microbial community to evaluate the potential role of phages in driving cyanobacterial populations. These blooms are characterized by massive and usually rapid accumulation of cyanobacterial biomass and occur worldwide, threatening aquatic systems. The frequency and intensity of cyanobacterial blooms are increasing over time, likely due to human activities, and, until now, the role of predators like phages has remained unclear. We used a deep amplicon sequencing approach targeting the g20 capsid gene to profile the cyanophage community in eutrophic Lake Champlain over time, comparing their dynamics and diversity with bacterial communities and examining their associations. We evaluated whether phages simply followed bacterial dynamics, with limited impact on bacterial composition, or instead whether they played an active role in drving bacterial community structure. We found that phages exhibited similar dynamics to their potential bacterial hosts and shared environmental niches. However, we also observed strong differences specific to the phage community, such as inter-annual variation and an increase in Shannon diversity over time. Phage-bacteria and phage-cyanobacteria co-variance uncovered potential interactions that resulted in strongly modular networks. However, while the network structure remained modular, the composition of the modules differed significantly between environmental and temporal conditions. Lastly, viral phylogeny partially explained phage-bacteria co-variance, but only for a small proportion of bacterial ASVs. Our results indicate that phage-bacterial interactions are partly genetically structured and vary within modules across environmental conditions.

ecology↗

bioRxiv2022

Agricultural and urban land use explain substantial variation in lake water quality across national-scale physiographic and climatic gradients

Despite decades of research and mitigation efforts, declines in freshwater quality resulting from anthropogenic nutrient input remain a persistent issue worldwide. Canada has the greatest number of freshwater lakes in the world, yet we have a limited understanding of the magnitude and scale at which most lakes have been affected by human activities, namely Land Use/Land Cover (LULC) alterations. In response, the NSERC Canadian Lake Pulse Network has compiled the first nationwide systematic database of lake quality metrics by surveying 664 lakes across 12 ecozones over three years. To assess the influence of catchment development on water quality and its spatial variation, we built models quantifying the association between watershed LULC and water quality. We found that agricultural and urban land use explained the greatest proportion of variation in water quality among LULC categories (R2 = 0.20-0.29). Overall, our study highlights that drivers of water quality are similar across regions; however, baseline conditions vary, so freshwater ecosystem management strategies must consider their geographic context to better predict where water quality thresholds will be surpassed.

ecology↗

bioRxiv2019

The evolution of biotic and abiotic realized niches within freshwater Synechococcus

Understanding how ecological traits have changed over evolutionary time is a fundamental question in biology. Specifically, the extent to which more closely-related organisms share similar ecological preferences due to phylogenetic conservation - or if they are forced apart by competition - is still debated. Here we explored the co-occurrence patterns of freshwater cyanobacteria at the sub-genus level to investigate whether more closely-related taxa share more similar niches, and to what extent these niches were defined by abiotic or biotic variables. We used deep 16S rRNA gene amplicon sequencing and measured several abiotic environmental parameters (nutrients, temperature, etc.) in water samples collected over time and space in Furnas Reservoir, Brazil. We found that relatively more closely-related Synechococcus (in the continuous range of 93-100% nucleotide identity in 16S) had an increased tendency to co-occur with one another (i.e. had similar realized niches). This tendency could not be easily explained by shared preferences for measured abiotic niche dimensions. Thus, commonly measured abiotic parameters might not be sufficient to characterize, nor to predict community assembly or dynamics. Rather, co-occurrence between Synechococcus and the surrounding community (whether or not they represent true biological interactions) may be a more sensitive measure of realized niches. Overall, our results suggest that realized niches are phylogenetically conserved, at least at the sub-genus level and at the resolution of the 16S marker. Determining how these results generalize to other genera and at finer genetic resolution merits further investigation. Originality-Significance StatementWe address a fundamental question in ecology and evolution: how do niche preferences change over evolutionary time? Using time-series analysis of 16S rRNA gene amplicon sequencing data, we develop an approach to highlight the importance of biotic factors in defining realized niches, and show how niche preferences change proportionally with the 16S gene molecular clock within the genus Synechococcus. Ours is also one of few studies on the ecology of freshwater Synechococcus, adding significantly to our knowledge about this abundant and widespread lineage of Cyanobacteria.

ecology↗

bioRxiv2017

Niche separation increases with genetic distance among bloom-forming cyanobacteria

Bacterial communities are composed of distinct groups of potentially interacting lineages, each thought to occupy a distinct ecological niche. It remains unclear, however, how quickly niche preference evolves and whether more closely related lineages are more likely to share ecological niches. We addressed these questions by following the dynamics of two bloom-forming cyanobacterial genera over an 8-year time-course in Lake Champlain, Canada, using 16S amplicon sequencing and measurements of several environmental parameters. The two genera, Microcystis (M) and Dolichospermum (D), are frequently observed simultaneously during bloom events and thus have partially overlapping niches. However, the extent of their niche overlap is debated, and it is also unclear to what extent niche partitioning occurs among strains within each genus. To identify strains within each genus, we applied minimum entropy decomposition (MED) to 16S rRNA gene sequences. We confirmed that at a genus level, M and D have different preferences for nitrogen and phosphorus concentrations. Within each genus, we also identified strains differentially associated with temperature, precipitation, and concentrations of nutrients and toxins. In general, niche similarity between strains (as measured by co-occurrence over time) declined with genetic distance. This pattern is consistent with habitat filtering - in which closely-related taxa are ecologically similar, and therefore tend to co-occur under similar environmental conditions. In contrast with this general pattern, similarity in certain niche dimensions (notably particulate nitrogen and phosphorus) did not decline linearly with genetic distance, and instead showed a complex polynomial relationship. This observation suggests the importance of processes other than habitat filtering - such as competition between closely-related taxa, or convergent trait evolution in distantly-related taxa - in shaping particular traits in microbial communities.

ecology↗