Abundance and Distribution of Microbial Cells and Viruses in an Alluvial Aquifer

Abstract

Viruses are the most abundant biological entity on Earth and their interactions with microbial communities are recognized to influence microbial ecology and impact biogeochemical cycling in various ecosystems. While the factors that control the distribution of viruses in surface aquatic environments are well-characterized, the abundance and distribution of continental subsurface viruses with respect to microbial abundance and biogeochemical parameters have not yet been established. In order to begin to understand the factors governing virus distribution in subsurface environments, we assessed microbial cell and virus abundance in groundwater concurrent with groundwater chemistry in a uranium impacted alluvial aquifer adjoining the Colorado River near Rifle, CO. Virus abundance ranged from 8.0 × 104 to 1.0 × 106 mL−1 and exceeded cell abundance in all samples (cell abundance ranged from 5.8 × 104 to 6.1 × 105 mL−1). The virus to microbial cell ratio ranged from 1.1 to 8.1 and averaged 3.0 ± 1.6 with virus abundance most strongly correlated to cell abundance (Spearman's ρ = 0.73, p < 0.001). Both viruses and cells were positively correlated to dissolved organic carbon (DOC) with cells having a slightly stronger correlation (Spearman's ρ = 0.46, p < 0.05 and ρ = 0.54, p < 0.05; respectively). Groundwater uranium was also strongly correlated with DOC and virus and cell abundance (Spearman's ρ = 0.62, p < 0.05; ρ = 0.46, p < 0.05; and ρ = 0.50, p < 0.05; respectively). Together the data indicate that microbial cell and virus abundance are correlated to the geochemical conditions in the aquifer. As such local geochemical conditions likely control microbial host cell abundance which in turn controls viral abundance. Given the potential impacts of viral-mediated cell lysis such as liberation of labile organic matter from lysed cells and changes in microbial community structure, viral interactions with the microbiota should be considered in an effort to understand subsurface biogeochemical cycling and contaminant mobility.

Impact of hydrologic boundaries on microbial planktonic and biofilm communities in shallow terrestrial subsurface environments

“…More recently, the distribution of viruses within subsurface groundwaters and the impact on microbial abundance has been studied (Pan et al . 2017 ). Thorough reviews on cell count abundances within different areas of the subsurface have been synthesized (Goldscheider, Hunkeler and Rossi 2006 ; Akob and Küsel 2011 ) and cell count surveys have consistently shown differences in the abundances between attached and free-living phases (Griebler and Lueders 2009 ) dependent upon variations in physicochemical parameters (Sinclair and Ghiorse 1989 ).…”

Prokaryotic and Viral Community Composition of Freshwater Springs in Florida, USA

“…However, the abundance of both groups was approximately an order of magnitude higher in the samples from Volusia Springs. Prior studies in groundwater systems have revealed cellular abundances ranging from 10 3 to 10 5 ml Ϫ1 and viral abundances of 10 4 to 10 7 ml Ϫ1 (21,(30)(31)(32)(33)(34). Both the bacterial and viral counts from the springs fall in the lower range of reported abundance values from other groundwater systems.…”

Viral and bacterial community responses to stimulated Fe(III)‐bioreduction during simulated subsurface bioremediation

“…The abundance of viruses and bacterial cells were strongly correlated (Fig. B), consistent with previous studies of virus–host abundance in aquatic and sedimentary environments (Säwström and Pollard, ; Chow et al ., ; Finke et al ., ; Pan et al ., ). Viruses were more abundant in the influent sections presumably where bacterial production was stimulated by constant acetate supply.…”