Simultaneous Microcystis Algicidal and Microcystin Degrading Capability by a Single Acinetobacter Bacterial Strain.

Measures for removal of toxic harmful algal blooms often cause lysis of algal cells and release of microcystins (MCs). In this study, Acinetobacter sp. CMDB-2 that exhibits distinct algal lysing activity and MCs degradation capability was isolated. The physiological response and morphological characteristics of toxin-producing Microcystis aeruginosa, the dynamics of intra- and extracellular MC-LR concentration were studied in an algal/bacterial cocultured system. The results demonstrated that Acinetobacter sp. CMDB-2 caused thorough decomposition of algal cells and impairment of photosynthesis within 24 h. Enhanced algal lysis and MC-LR release appeared with increasing bacterial density from 1 × 103 to 1 × 107 cells/mL; however, the MC-LR was reduced by nearly 94% within 14 h irrespective of bacterial density. Measurement of extracellular and intracellular MC-LR revealed that the toxin was decreased by 92% in bacterial cell incubated systems relative to control and bacterial cell-free filtrate systems. The results confirmed that the bacterial metabolite caused 92% lysis of Microcystis aeruginosa cells, whereas the bacterial cells were responsible for approximately 91% reduction of MC-LR. The joint efforts of the bacterium and its metabolite accomplished the sustainable removal of algae and MC-LR. This is the first report of a single bacterial strain that achieves these dual actions.

Doped Multiple Nanoparticles with Hydroxyapatite Coating Show Diverse Health Effects in vivo.

Introduction: The lack of osteoinductive, angiogenic and antimicrobial properties of hydroxyapatite coatings (HA) on titanium surfaces severely limits their use in orthopedic and dental implants. Therefore, we doped SiO2, Gd2O3 and CeO2 nanoparticles into HA to fabricate a HASiGdCe coating with a combination of decent antibacterial, angiogenic and osteogenic properties by the plasma spraying technique. Methods: The HASiGdCe coating was analyzed by SEM (EDS), surface roughness tests, contact angle tests, XRD, FTIR spectroscopy, tensile tests and electrochemical dynamic polarization tests. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO-1) were used as representative bacteria to verify the antibacterial properties of the HASiGdCe coating. We evaluated the cytocompatibility and in vitro osteoinductivity of the HASiGdCe coating by investigating its effect on the cell viability and osteogenic differentiation of MC3T3-E1 cells. We assessed the in vitro angiogenic activity of the HASiGdCe coating by migration assay, tube formation assay, and RT‒PCR analysis of angiogenic genes in HUVECs. Finally, we used infected animal femur models to investigate the biosafety, antimicrobial and osteointegration properties of the HASiGdCe coating in vivo. Results: Through various characterization experiments, we demonstrated that the HASiGdCe coating has suitable microscopic morphology, physical phase characteristics, bonding strength and bioactivity to meet the coating criteria for orthopedic implants. The HASiGdCe coating can release Gd3+ and Ce4+, showing strong antibacterial properties against MRSA and PAO-1. The HASiGdCe coating has been shown to have superior osteogenic and angiogenic properties compared to the HA coating in in vitro cellular experiments. Animal implantation experiments have shown that the HASiGdCe coating also has excellent biosafety, antimicrobial and osteogenic properties in vivo. Conclusion: The HASiGdCe coating confers excellent antibacterial, angiogenic and osteogenic properties on titanium implants, which can effectively enhance implant osseointegration and prevent bacterial infections, and it accordingly has promising applications in the treatment of bone defects related to orthopedic and dental sciences.

Spatiotemporal distribution and potential risk assessment of microcystins in the Yulin River, a tributary of the Three Gorges Reservoir, China.

Microcystins (MCs) pose potential threat for both aquatic organisms and humans, whereas their occurrence in response to hydrodynamic alterations are not clearly understood. Here, spatiotemporal variations of dissolved MC-RR and MC-LR were evaluated monthly in 2016 in the Yulin River, a tributary of the Three Gorges Reservoir (TGR). The environmental factors that linked to MCs concentration were discussed. The results revealed that MC-RR maximumly reached 3.55 µg/L, and the maximum MC-LR concentration exceeded the threshold value of 1.0 µg/L recommended by the WHO. MCs concentrations were higher during the flood season and decreased from the estuary to the upstream reach of the Yulin River. Ecological risk assessment confirmed that MC-LR had significant adverse effects on the benthonic invertebrates Potamopyrgus antipodarum. MCs content in the sediment was 1.70- to 20-fold higher than that in suspended particulate matter (SPM). The impacts of environmental factors on the MCs profile differed between flood and dry seasons and the longitudinal differences of MCs were determined by the longitudinal profile of water velocity and SPM content, which were affected by TGR operations. This study suggested that the occurrence of MCs in the Yulin River were influenced by hydrologic regime in TGR.

New insights into the impacts of suspended particulate matter on phytoplankton density in a tributary of the Three Gorges Reservoir, China.

Phytoplankton density can be influenced by a wide range of factors whereas the role of suspended particulate matter (SPM) are not clear in river that annually subjected to hydrodynamics shift. Here, spatial-temporal variation of environmental parameters and phytoplankton density were studied from January 2013 to December 2014 in Yulin River, a tributary of the Three Gorges Reservoir, China. Laboratory experiments were conducted to elucidate the key parameter and interpret how it impacted phytoplankton density. SPM is negatively correlated with phytoplankton density. Despite SPM in Yulin River revealed weaker NH3-N, NO3-N and PO4-P adsorption capabilities in comparison to that in other aquatic ecosystems, increase of water velocity from 0.1 to 0.8 m/s led to approximately 6.8-times increase of light attenuation rate. In experiments evaluating the aggregation of Chlorella pyrenoidosa upon SPM, floc size showed 7.4 to 22% fold increase compared to the SPM or algae itself, which was due to the interaction between SPM and phytoplankton extracellular polymeric substances. Our results suggest that SPM could contribute to the variation of phytoplankton density through the integrated process including light attenuation, nutrient adsorption and algae aggregation. This is the first evaluation of the multiple processes underlying the impact of SPM on phytoplankton.

Effect of flow rate on growth and oxygen consumption of biofilm in gravity sewer.

The function of sewer as reactors must rely on the biofilm in it. In this paper, the formation, structure, oxygen transfer, and activity of the biofilm under different hydraulic conditions were studied by the microelectrode technology, oxygen uptake rate (OUR) technology, and 454 high-throughput pyrosequencing technology. Results showed that when the wall-shear stresses were 1.12, 1.29, and 1.45 Pa, the porosity of the steady-state biofilm were 69.1, 64.4, and 55.1 %, respectively. The maximum values of OUR were 0.033, 0.027, and 0.022 mg/(L*s), respectively, and the COD removal efficiency in the sewers reached 40, 35, and 32 %, respectively. The research findings had an important significance on how to improve the treatment efficiency of the sewers. Fig. a Graphical Abstract.