Spatio-Temporal Variations of High and Low Nucleic Acid Content Bacteria in an Exorheic River.

Bacteria with high nucleic acid (HNA) and low nucleic acid (LNA) content are commonly observed in aquatic environments. To date, limited knowledge is available on their temporal and spatial variations in freshwater environments. Here an investigation of HNA and LNA bacterial abundance and their flow cytometric characteristics was conducted in an exorheic river (Haihe River, Northern China) over a one year period covering September (autumn) 2011, December (winter) 2011, April (spring) 2012, and July (summer) 2012. The results showed that LNA and HNA bacteria contributed similarly to the total bacterial abundance on both the spatial and temporal scale. The variability of HNA on abundance, fluorescence intensity (FL1) and side scatter (SSC) were more sensitive to environmental factors than that of LNA bacteria. Meanwhile, the relative distance of SSC between HNA and LNA was more variable than that of FL1. Multivariate analysis further demonstrated that the influence of geographical distance (reflected by the salinity gradient along river to ocean) and temporal changes (as temperature variation due to seasonal succession) on the patterns of LNA and HNA were stronger than the effects of nutrient conditions. Furthermore, the results demonstrated that the distribution of LNA and HNA bacteria, including the abundance, FL1 and SSC, was controlled by different variables. The results suggested that LNA and HNA bacteria might play different ecological roles in the exorheic river

Flow cytogram example of LNA and HNA bacteria in the Haihe River.

<p>Dashed lines indicate LNA bacteria, and solid lines indicate HNA bacteria.</p

Functional Characterization of the γ-Aminobutyric Acid Transporter from Mycobacterium smegmatis MC2 155 Reveals Sodium-Driven GABA Transport

Characterizing the mycobacterial transporters involved in the uptake and/or catabolism of host-derived nutrients required by mycobacteria may identify novel drug targets against tuberculosis. Here, we identify and characterize a member of the amino acid-polyamine-organocation superfamily, a potential gamma-aminobutyric acid (GABA) transport protein, GabP, from Mycobacterium smegmatis. The protein was expressed to a level allowing its purification to homogeneity, and size exclusion chromatography coupled with multiangle laser light scattering (SEC-MALLS) analysis of the purified protein showed that it was dimeric. We showed that GabP transported gamma-aminobutyric acid both in vitro and when overexpressed in E. coli. Additionally, transport was greatly reduced in the presence of beta-alanine, suggesting it could be either a substrate or inhibitor of GabP. Using GabP reconstituted into proteoliposomes, we demonstrated that gamma-aminobutyric acid uptake is driven by the sodium gradient and is stimulated by membrane potential. Molecular docking showed that gamma-aminobutyric acid binds MsGabP, another Mycobacterium smegmatis putative GabP, and the Mycobacterium tuberculosis homologue in the same manner. This study represents the first expression, purification, and characterization of an active gamma-aminobutyric acid transport protein from mycobacteria. IMPORTANCE The spread of multidrug-resistant tuberculosis increases its global health impact in humans. As there is transmission both to and from animals, the spread of the disease also increases its effects in a broad range of animal species. Identifying new mycobacterial transporters will enhance our understanding of mycobacterial physiology and, furthermore, provides new drug targets. Our target protein is the gene product of msmeg_6196, annotated as GABA permease, from Mycobacterium smegmatis strain MC2 155. Our current study demonstrates it is a sodium-dependent GABA transporter that may also transport beta-alanine. As GABA may well be an essential nutrient for mycobacterial metabolism inside the host, this could be an attractive target for the development of new drugs against tuberculosis.Peer reviewe

Sampling sites in the Haihe River.

<p>Black solid circles (●) indicate the sampling stations, and the black dash-dot curve (—·—) and blue solid curve (<b>━</b>) indicate the coastline and river, respectively.</p

Citrate-Regulated Surface Morphology of SiO₂@Au Particles To Control the Surface Plasmonic Properties

In this work, SiO₂@Au core–shell particles under ambient conditions were prepared by using 120 nm SiO₂ spheres with ca. 4 nm Au nanoparticles decorated on the surfaces as seeds, the aqueous solutions of sodium citrate/HAuCl₄ mixtures as growth solutions, and hydroxylamine as reducing agent. The morphology of the Au shells obtained on the SiO₂ spheres was readily regulated only by the citrate-to-HAuCl₄ molar ratio; no deliberate adjustment of the temperature and pH of the reaction media was needed. When the citrate-to-HAuCl₄ molar ratio in the growth solution was below 4:1, the surfaces of the SiO₂ spheres were covered with sparsely packed Au nanoparticles with sizes in the range of 20–40 nm, depending on the citrate-to-HAuCl₄ molar ratio. When the citrate-to-HAuCl₄ molar ratio in the growth solution was above 8:1, the surfaces of the SiO₂ spheres were coated by complete, uniform Au nanoshells. Concomitant with this citrate-regulated morphology, the localized surface plasmon resonance peaks of the resulting SiO₂@Au particles shifted from 611 nm for the sparse Au nanoparticle coating to 784 nm for the complete Au nanoshell coating. Furthermore, the sparsely packed Au nanoparticle coating showed stronger surface enhancement Raman spectroscopic signals than the uniform Au nanoshell coating, while the latter exhibit higher photothermal efficiency than the former

Spatio-Temporal Variations of High and Low Nucleic Acid Content Bacteria in an Exorheic River - Fig 6

<p><b>Response of the abundance (A), FL1 (B) and SSC (C) of LNA and HNA bacteria to environmental ordination axis in RDA.</b> GLM and GAM were selected to fit the response analysis in a stepwise manner, as well environmental explanatory ordination axis 1 and 2 in RDA analysis, where only explanatory axis be of significance was drawn in the analysis processes.</p

Redundancy analysis of LNA and HNA bacterial characteristic parameters with environmental factors in the Haihe River.

<p>(A) Biplots between characteristics of LNA\HNA and environmental variables, (B) Samples ordination. Abbreviations: TSS, total suspended solids; TN, total nitrogen; NO₃, nitrate; TP, total phosphorus; TDP, total dissolved phosphorus; TOC, total organic carbon; Chl-a, chlorophyll-α; FL1L and FL1H, FL1 of LNA and HNA bacteria, SSCL and SSCH, SSC of LNA and HNA bacteria; VFL1, FL1_HNA/FL1_LNA; VSSC, SSC_HNA/SSC_LNA; LNA and HNA, the LNA and HNA bacterial concentration, HNA%, the percentage of HNA in total bacterial concentration. Samples were connected with lines according to location along with the Haihe River in subgraph B.</p

Spatio-Temporal Variations of High and Low Nucleic Acid Content Bacteria in an Exorheic River - Fig 4

<p><b>Temporal changes of fluorescence intensity (FL1) (A), side scatter (SSC) (B) and variance between LNA and HNA of FL1 and SSC (C) in the Haihe River.</b> The box represents the range from 25% to 75% percentiles, whisker lines represent the outlier percentiles and the middle line in the box shows the median value of all data points. X-marks and square dots represent the outlier and mean values, respectively. Letters with and without underline represent seasonal differences of HNA and LNA bacteria respectively. Different lowercase letters indicate significant difference of 0.05. The symbols "**" and "*" indicate significant differences of 0.01 and 0.05, respectively.</p