[Occurrence Characteristics of Microplastics in Mangrove Sediments in the Jiulong River Estuary and the Association with Heavy Metals].

The abundance and morphological characteristics of microplastics in the surface sediments of mangrove wetlands in the Jiulong River estuary were analyzed. The main sources of microplastics were also explored in detail. The results showed that the abundance of microplastics ranged from 640 to 1140 n·kg-1 (dry sediment), with an average of 935 n·kg-1, exhibiting a medium level compared with other domestic and abroad mangrove areas. The microscopic observation found that the microplastics were granular (39%), fragmented (31%), and fibrous (30%); the color was mainly transparent (55%); and the particle size was less than 1 mm (92%). As observed via Raman spectroscopy, the main polymer types of the microplastics were identified to be polyethylene, polyethylene terephthalate, and polypropylene, accounting for 57%, 34%, and 9%, respectively. The main sources of microplastics were the plastic waste from aquaculture nearby, urban and rural domestic or industrial wastewater in the basin, and the plastic waste transported here by the tide. Additionally, SEM-EDS results showed that the surface of the microplastics had the characteristics of depression, porosity, and tearing, and some heavy metal elements such as Pb, Cd, Hg, Cr, Fe, Mn, Zn, and Cu were attached to the microplastics. Microplastics may be transferred to the sediments as carriers of heavy metals, posing a potential threat to wetland ecological security.

[Effects of Low-level Nutrition and Trace Antibiotics on the Fitness Cost of Plasmids Bearing Antibiotic Resistance].

The effects of nutrition and antibiotic level on fitness costs of plasmid containing antibiotic resistance in drinking water system were investigated in this study. Three plasmids harboring different antibiotic resistances, i.e. pACYC184, RP4, and PBR322, were selected. It was found that the antibiotic resistance imposed cost on the fitness of all plasmids at different nutrition levels, which was universal. Moreover, the fitness costs were larger at lower nutrition levels. Besides, the fitness costs of plasmid bearing antibiotic resistance were also affected by trace antibiotics. In this study, when exposed to antibiotics (lower than 50% MIC), the fitness costs of plasmid imposed to the bacteria were more apparent than the injury or inhibition effect by antibiotics. The plasmids were unstable. Therefore, it was inferred that the plasmid containing antibiotic resistance imposed large fitness costs on bacteria in drinking water system (with low-level nutrition and ng·L-1 level antibiotic), and it was not stable. Thus, the risk of plasmid bearing antibiotic resistance transmission and spread in drinking water system was low.

[Effect of Three Typical Disinfection Byproducts on Bacterial Antibiotic Resistance].

The effect of typical disinfection byproducts (DBPs) on bacterial antibiotic resistance was investigated in this study. chlorodibromomethane (CDBM), iodoacetic acid (IAA) and chloral hydrate (CH) were selected, which belong to trihalomethanes (THMs), haloacetic acids (HAAs) and aldehydes, respectively. After exposure to the selected DBPs, the resistance change of the tested strains to antibiotics was determined. As a result, all of the three DBPs induced Pseudomonas aeruginosa PAO1 to gain increased resistance to the five antibiotics tested, and the DBPs ranked as IAA > CH > CDBM according to their enhancement effects. Multidrug resistance could also be enhanced by treatment with IAA. The same result was observed in Escherichia coli K12, suggesting that the effect of DBPs on antibiotic resistance was a common phenomenon. The mechanism was probably that DBPs stimulated oxidative stress, which induced mutagenesis. And the antibiotic resistance mutation frequency could be increased along with mutagenesis. This study revealed that the acquisition of bacterial antibiotic resistance might be related to DBPs in drinking water systems. Besides the genotoxicological risks, the epidemiological risks of DBPs should not be overlooked.

[Real-time PCR detection and quantification of emerging waterborne pathogens (EWPs) and antibiotic resistance genes (ARGs) in the downstream area of Jiulong River].

The emerging waterborne pathogens (EWPs) and antibiotic resistance genes (ARGs) are important for drinking water safety. The detection and quantification of 7 EWPs and 4 ARGs were carried out in Jiulong River, which is the main water source of southwestern Fujian Province. The water samples were collected from four sites of the Jiulong River downstream area and a drinking water treatment plant nearby. DNA was extracted and quantified by real-time (SYBR Green) PCR methods after the samples were filtered through 0.22 pim membranes. The results showed that the amount of Salmonella enterica (Salmonella spp.), Legionella pneumophila (L. pneumophila) and Pseudomonas aeruginosa (P. aeruginosa) could reach up to 10(3), 10(4) and 10(5) copies x mL(-1), respectively. The concentration of organic matter in water may affect the copy numbers significantly. The water plant could effectively remove most EWPs and ARGs except Salmonella spp.. Therefore, more efforts should be made on water pollution source control, water treatment technology and point-of-use system to make sure the safety of drinking water.

Differences in soil properties and bacterial communities between the rhizosphere and bulk soil and among different production areas of the medicinal plant Fritillaria thunbergii.

To explore rhizosphere effects, geographical differences and their effects on the bacterial community associated with the geoherb Fritillaria thunbergii, some physicochemical properties of soil samples (3 sampling sites × 2 habitats (rhizosphere and bulk soil)) were measured and the soil bacterial community detected by PCR-denaturing gradient gel electrophoresis (DGGE). Among the three regions, soil pH varied between 4.48 and 7.73 indicating that F. thunbergii could grow both in acid and slightly alkaline soil. As the authentic Dao-di producing area, Ningbo showed the highest soil quality with the highest content of organic matter (OM) (2.46%), phosphatase (268 mg kg(-1) 24 h(-1)) and urease activity (1481 mg kg(-1) 24 h(-1)). In comparison with the bulk soil, pH, organic carbon content, and phosphatase and urease activities were all lower in the rhizosphere, suggesting that the roots may secrete some unique metabolites in root exudates. Statistical analyses showed that soil properties of Ningbo and Panan in Zhejiang province were more similar to each other than those in Nantong in Jiangsu province. In addition, PCR-DGGE analysis showed that main bacterial population identified in F. thunbergii was proteobacteria (18 bands, 55%), acidobacteria (4, 12%), actinobacteria (4, 12%) and bacterioidetes (6, 18%). Overall, soil properties and microbial communities varied not only between the rhizosphere and bulk soil but also among the three regions. We suggest that the plant, together with the soil properties, cooperatively shape the structure of the rhizosphere bacteria, and that the soil properties have a close relationship with the geoherbalism of F. thunbergii.

Enhancement of copper availability and microbial community changes in rice rhizospheres affected by sulfur.

The role of sulfur on the availability of Cu and the bacterial community in rice rhizospheres was investigated by pot experiments. With sulfur addition, pH in rhizosphere soil decreased and Mg(NO3)2 extractable Cu increased significantly. The bacterial community composition also changed with sulfur addition. Some specific clones having high similarity to Thiobacillus, which indicated that sulfur oxidation in the rice rhizosphere could increase the availability of Cu. These results suggested that sulfur source which could provide substrate to sulfur oxidizing bacteria and enhance the availability of Cu was not a suitable sulfur fertilizer for Cu polluted soil.

[Effects of sulfur on microbial activity and community structure in a lead-polluted paddy soil].

A pot experiment was conducted to study the microbial activity and community structure in a lead-polluted paddy soil under effects of amendment with different concentration sodium thiosulfate. The amendment of the sulfur-containing substrate increased the soil oxidation-reduction potential and respiration rate, promoted the growth of soil sulfur-oxidizing bacteria, and induced some changes in soil microbial community structure. The clone sequencing indicated that the specific bands of soil microbes in sodium thiosulfate treatments had very high similarity to Bateroidetes, Thiobacillus, beta-proteobacteria, and Acidobacteria. Significant changes were observed in the contents of soil carbonate- and Fe/Mn oxide- bound Pb after the amendment of sodium thiosulfate.

Applications of ultra-performance liquid chromatography to traditional Chinese medicines.

Ultra-performance liquid chromatography (UPLC), as a development of the chromatographic technique, was used in the quality control of Panax ginseng C.A. Mey. In the study, the UPLC methods were transferred from conventional high-performance liquid chromatography (HPLC) methods according to chromatographic equations. The results demonstrated that UPLC analysis methods could be transferred from HPLC without loss of efficiency. Compared with conventional HPLC, UPLC made a surprising 10-fold increase in speed and 20-fold decrease in solvent consumption. The study indicated UPLC as a suitable alternative to HPLC and can be reliably applied to quality control of traditional Chinese medicines.