Background: The sinorhizobia are amongst the most well studied members of nitrogen-fixing root nodule bacteria and contribute substantial amounts of fixed nitrogen to the biosphere. While the alfalfa symbiont Sinorhizobium meliloti RM 1021 was one of the first rhizobial strains to be completely sequenced, little information is available about the genomes of this large and diverse species group. Results: Here we report the draft assembly and annotation of 48 strains of Sinorhizobium comprising five genospecies. While S. meliloti and S. medicae are taxonomically related, they displayed different nodulation patterns on diverse Medicago host plants, and have differences in gene content, including those involved in conjugation and organic sulfur utilization. Genes involved in Nod factor and polysaccharide biosynthesis, denitrification and type III, IV, and VI secretion systems also vary within and between species. Symbiotic phenotyping and mutational analyses indicated that some type IV secretion genes are symbiosis-related and involved in nitrogen fixation efficiency. Moreover, there is a correlation between the presence of type IV secretion systems, heme biosynthesis and microaerobic denitrification genes, and symbiotic efficiency. Conclusions: Our results suggest that each Sinorhizobium strain uses a slightly different strategy to obtain maximum compatibility with a host plant. This large genome data set provides useful information to better understand the functional features of five Sinorhizobium species, especially compatibility in legume-Sinorhizobium interactions. The diversity of genes present in the accessory genomes of members of this genus indicates that each bacterium has adopted slightly different strategies to interact with diverse plant genera and soil environments.

Bioretention cells (BRCs) are stormwater control measures that integrate water quantity and quality management. Previous research primarily focused on the performance of cells less than two years old, before potential clogging and sorption site saturation. To assess long-term effectiveness, this project evaluated the performance of a BRC after seven years to determine reductions in flow rate, flow volume, suspended solids, nitrogen, phosphorus, and fecal indicator bacteria (FIB). These observations were compared with analyses conducted immediately postconstruction. Inflow and outflow water samples were collected for sediment, nutrients, and FIB. Soil media samples were collected from multiple depths and analyzed for denitrifying bacteria. Results indicate the BRC remains effective at reducing storm flows, nutrients, and FIB. These reductions were correlated to outflow volume, rather than storm characteristics. The majority of denitrifying bacteria were present in the top media layers, despite the presence of an internal water storage layer for denitrification. This finding suggests denitrification primarily occurs at anoxic microsites in the upper layers and that a lack of carbon at deeper depths may limit significant microbial growth.