## 3 Results
### Distribution of Strains by Origin and Capacity to Reduce Nitrate/Nitrite
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Taxonomic Group** & **Genus \({}^{*}\) (Total \# of Strains)** & **Brine/Oil** & **Oil** & **Prairie** \\ \hline \multirow{6}{*}{Bacilli} & _Brevibacillus_ (8) & 3 NR & 0 & 4 NR, 1\({}^{\prime\prime}\)None\({}^{\prime\prime}\) \\ \cline{2-5}  & _Bacillus_ (3) & 2 NR & 0 & 1\({}^{\prime\prime}\)None\({}^{\prime\prime}\) \\ \cline{2-5}  & _Paenibacillus_ (1) & 1 NR & 0 & 0 \\ \cline{2-5}  & _Lysinibacillus_ (2) & 0 & 0 & 1 NR, 1\({}^{\prime\prime}\)None\({}^{\prime\prime}\) \\ \cline{2-5}  & _Total \# Bacilli_ (14) & 6 & 0 & 8 \\ \hline \multirow{6}{*}{Flavobacteria} & _Chrysebacherium_ (1) & 0 & 1 NR & 0 \\ \cline{2-5}  & Total \# Flavobacteria (1) & 0 & 1 & 0 \\ \cline{2-5}  & Total \# strains isolated & 20 & 12 & 43 \\ \cline{2-5}  & Total \# NR + DN & 17 & 9 & 28 \\ \cline{2-5}  & \#NR, \#DN & 14, 3 & 9, 0 & 25, 3 \\ \hline \hline \end{tabular}  
*: Genus assignments as determined by submitting the 165 rRNA gene sequence of the individual strains to The Ribosomal Database Project (RDP) Classifier. All classifications were at the 98\({}^{\prime\prime}\) threshold level or higher. Origin: type of site from which the strain was isolated. See Supplementary Table S2. Brine/oil: isolated from sites contaminated primarily by oil field brine but also by crude oil, G5, and G7. Oil: isolated from sites contaminated by crude oil, J6-F, J6-NF, and LF. Prairie: isolated from uncontaminated sites, GSP, G7P, J6P, and LFP. **: number and type of strain. Strain type: NR, DN, None: confirmed as NR or DN by reduction of nitrate to nitrite, or no nitrate or nitrite detected (”DN”) after growth in nitrate broth and testing with Griess reagents. Strains that did not reduce nitrate were designated as ”None”. See materials and methods for more information.  
\end{table} 
Table 1: _Cont._  
Figure 1: Taxonomic Affiliation of Strains. The number of strains affiliated with different higher taxonomic level bacterial groups found in oil-, brine-, and prairie- soils. The 165 rRNA gene sequences of seventy-five strains were classified by the RDP Classifier tool. Brine: isolated from sites contaminated primarily by oil field brine but also by crude oil (10:1 vol/vol), G5 and G7. Oil: isolated from sites contaminated by crude oil, J6-F, J6-NF, and LF. Prairie: isolated from uncontaminated sites, G5P, G7P, J6P, and LFP. “All” indicates the distribution of the 75 strains isolated after enrichment in nitrate broth, and “NR/DN” indicates the distribution of 54 strains confirmed as nitrate/nitrite reducers after incubation in nitrate broth as described in Materials and Methods. The microtiter plate test conditions using Griess reagents did correctly identify nitrate-reducing control strains as nitrate reducers, while neither nitrate nor nitrite was detected after the growth of control strain denitrifiers. The Griess protocol does not screen for gaseous nitrogen compounds that are products of later steps in the denitrification pathway. Therefore, for the purpose of this study, strains that reduced both nitrate and nitrite are designated as denitrifiers (DN), with the understanding that strains labeled as \"DN\" may either be bacteria capable of reducing nitrate to nitrite and nitrite to gaseous nitrogen compounds that are not dinitrogen (e.g., incomplete denitrification) or \"true\" denitrifying bacteria, the latter capable of reducing nitrate completely to dinitrogen (\"complete denitrification\").