Comparison of transcriptional change of B. melitensis M5-90 after macrophage infection highlights the role of ribosome gene L31 in virulence.

Brucella, a facultative intracellular bacterium, can survive and replicate in various cell types such as epithelial cell, fibroblasts and macrophage. Macrophage is the most important sites for the survival of Brucella in vivo. The mechanisms of pathogenesis are difficult to address, since the unknown virulence genes are still exist. RNA-seq is available to study transcriptional changes that occur during disease as a way to identify important virulence-related genes. Here we described and analyzed the transcriptional change of avirulent strain Brucella melitensis M5-90 (B. melitensis M5-90) during macrophage infection using RNA-seq technology. We detected 601 significant changed genes of which 428 were upregulated after infection. The upregulated gene L31 which involved in ribosome KEGG pathway was selected to illustrate its effect on virulence in a vaccine strain B. melitensis M5-90 and a virulent strain B. melitensis M28. Deletion of L31 significant attenuates the spleen colonization in model of M5-90 or M28 infection mouse at 7, 21 and 35 days post-infection (P < 0.05). We further examine the role of L31 in a macrophage cell infection model, and the result showed a significant reduction of intracellular M28ΔL31 cells at 48 h post-infection (P < 0.001). In total, our study provided a view of transcriptional landscape of B. melitensis M5-90 intracellular, and found L31 gene is required for the full virulence of B. melitensis.

Linking fish tolerance to water quality criteria for the assessment of environmental flows: A practical method for streamflow regulation and pollution control.

The survival of aquatic biota in stream ecosystems depends on both water quantity and quality, and is particularly susceptible to degraded water quality in regulated rivers. Maintenance of environmental flows (e-flows) for aquatic biota with optimum water quantity and quality is essential for sustainable ecosystem services, especially in developing regions with insufficient stream monitoring of hydrology, water quality and aquatic biota. Few e-flow methods are available that closely link aquatic biota tolerances to pollutant concentrations in a simple and practical manner. In this paper a new method was proposed to assess e-flows that aimed to satisfy the requirements of aquatic biota for both the quantity and quality of the streamflow by linking fish tolerances to water quality criteria, or the allowable concentration of pollutants. For better operation of water projects and control of pollutants discharged into streams, this paper presented two coefficients for streamflow adjustment and pollutant control. Assessment of e-flows in the Wei River, the largest tributary of the Yellow River, shows that streamflow in dry seasons failed to meet e-flow requirements. Pollutant influx exerted a large pressure on the aquatic ecosystem, with pollutant concentrations much higher than that of the fish tolerance thresholds. We found that both flow velocity and water temperature exerted great influences on the pollutant degradation rate. Flow velocity had a much greater influence on pollutant degradation than did the standard deviation of flow velocity. This study provides new methods to closely link the tolerance of aquatic biota to water quality criteria for e-flow assessment. The recommended coefficients for streamflow adjustment and pollutant control, to dynamically regulate streamflow and control pollutant discharge, are helpful for river management and ecosystems rehabilitation. The relatively low data requirement also makes the method easy to use efficiently in developing regions, and thus this study has significant implications for managing flows in polluted and regulated rivers worldwide.