Methylparaben toxicity and its removal by microalgae Chlorella vulgaris and Phaeodactylum tricornutum.

The widespread occurrence of methylparaben (MPB) has aroused great concern due to its weak estrogenic endocrine-disrupting property and potential toxic effects. However, the degradation potential and pathway of MPB by microalgae have rarely been reported. Here, microalgae Chlorella vulgaris and Phaeodactylum tricornutum were used to investigate their responses, degradation potential and mechanisms towards MPB. MPB showed low-dose stimulation (by 86.02 ± 0.07% at 1 mg/L) and high-dose inhibition (by 60.17 ± 0.05% at 80 mg/L) towards the growth of C. vulgaris, while showed inhibition for P. tricornutum (by 6.99 ± 0.05%-20.14 ± 0.19%). The degradation efficiencies and rates of MPB were higher in C. vulgaris (100%, 1.66 ± 0.54-5.60 ± 0.86 day-1) than in P. tricornutum (4.3-34.2%, 0.04 ± 0.01-0.08 ± 0.00 day-1), which could be explained by the significantly higher extracellular enzyme activity and more fluctuation of the protein ratio for C. vulgaris, indicating a higher ability of C. vulgaris to adapt to pollutant stress. Biodegradation was the main removal mechanism of MPB for both the two microalgae. Furthermore, two different degradation pathways of MPB by the two microalgae were proposed. MPB could be mineralized and completely detoxified by C. vulgaris. Overall, this study provides novel insights into MPB degradation by microalgae and strategies for simultaneous biodegradation and detoxification of MPB in the environment.

Exposure to microplastics reduces the bioaccumulation of sulfamethoxazole but enhances its effects on gut microbiota and the antibiotic resistome of mice.

Microplastics (MPs) have aroused a global health concern and their coexistence with antibiotics is inevitable. However, how MPs would affect the bioaccumulation and risks of antibiotics in humans remains poorly understood. Here a mouse model was used, and through dietary exposure, we observed that while the relative distributions of sulfamethoxazole (SMX) in tissues were relatively stable, MPs significantly reduced the bioaccumulation of SMX in mice tissues (liver, lung, spleen, heart and kidney). Notably, while SMX and MPs showed a differential effect, MPs could exacerbate the effects of SMX on gut microbiota and antibiotic resistance gene (ARG) profile, with the relative abundances of sulfonamide resistance genes and multidrug genes being significantly increased. We further identified that shifts in gut microbiota contributed to the changes in ARG profiles in mice. Combined, our results demonstrate that MPs reduced the bioaccumulation of SMX, but they enhanced its effects on gut microbiota and the antibiotic resistome of mice, indicating they might have high risks to humans.

Isolation and characterization of a marine bacterium Vibrio diabolicus strain L2-2 capable of biotransforming sulfonamides.

Sulfonamides (SAs) have attracted much attention because of their high detection rates in natural water. In this study, a marine bacterium Vibrio diabolicus strain L2-2 was isolated which could metabolize 9 SAs to a different extent. Compared with SAs and their analogs, SAs with N-oxides of heterocyclic structure were easier to be transformed to their N4-acetylated metabolites or their isoxazole ring rearrangement isomers by strain L2-2. And, gene vdnatA and vdnatG were likely to be the key genes in SAs acetylation process, which might code Arylamine N-acetyltransferase. The biotransformation rates of sulfathiazole(STZ), sulfamonomethoxine(SMT), sulfadiazine(SDZ), sulfamethoxazole(SMX) and sulfisoxazole(SIX) could reach 29.39 ± 5.63, 24.97 ± 4.45, 79.41 ± 4.05, 64.64 ± 1.71, 32.82 ± 4.46% in 6 days, respectively. Besides, the overall optimal conditions for SAs biotransformation were less than 100 mg/L for total SAs in neutral or weakly alkaline medium with the salinity of 10-20‰ and additional nutrients like glucose, sucrose or glycerine. Furthermore, toxicity was demonstrated to be significantly reduced after biotransformation. Together, this study introduced a strategy to use V. diabolicus strain L2-2 to realize simultaneous removal and detoxification of multiple SAs in freshwater and seawater, and revealed SAs removal pathways and relevant molecular mechanism.

Salinactinospora qingdaonensis gen. nov., sp. nov., a halophilic actinomycete isolated from a salt pond.

A novel halophilic, filamentous, actinomycete strain, designated CXB832T, was isolated from a salt pond in Qingdao, China. Optimal growth occurred at 37 °C, pH 7.0-8.0 and 9-12 % (w/v) NaCl. Strain CXB832T formed pale yellow to deep yellow branched substrate mycelium without fragmentation. Abundant white aerial mycelium differentiated into long chains of spores and the spores were rod-shaped with smooth surfaces. Strain CXB832T contained meso-diaminopimelic acid as the diagnostic diamino acid of the cell-wall peptidoglycan, and glucose and xylose as the major whole-cell sugars. The phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phospholipids, glycolipid and unidentified lipids. MK-10(H8), MK-9(H8), MK-10(H2) and MK-10(H6) were the predominant menaquinones. The major fatty acids were i-C16:0 (30.71 %), ai-C17:0 (13.31 %) and C16:0 (11.28 %). The G+C content of the DNA was 60.1 mol%. Comparative analysis of 16S rRNA gene sequences showed that the novel strain was most closely related to genera within the family Nocardiopsaceae, but formed a separate lineage. The highest sequence similarities were to Nocardiopsis arabia DSM 45083T (95.4 %) and Haloactinospora alba DSM 45015T (94.9 %). On the basis of phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain CXB832T represents a new genus and novel species in the family Nocardiopsaceae, for which the name Salinactinospora qingdaonensis gen. nov., sp. nov. is proposed. The type strain of the type species is CXB832T (=DSM 45442T=LMG 25567T).

Spinactinospora alkalitolerans gen. nov., sp. nov., an actinomycete isolated from marine sediment.

A novel marine actinomycete, designated CXB654(T), was isolated from marine sediment collected at a depth of 17.5 m near the Yellow Sea Cold Water Mass, China. Optimal growth occurred at 37.0 °C, at pH 7.0-8.0 and in 3-8% (w/v) NaCl. Strain CXB654(T) formed branched substrate mycelium without fragmentation. Abundant aerial mycelium differentiated into long or short chains of spores and spores were elliptical and cylindrical with spiny surfaces. Strain CXB654(T) contained meso-diaminopimelic acid as the diagnostic diamino acid, and ribose and glucose as the major whole-cell components. Phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol and phosphatidylinositol. MK-10(H(8)), MK-10(H(6)) and MK-9(H(8)) were the predominant menaquinones. The major fatty acids were i-C(16:0) (24.46%), ai-C(17:0) (20.66%) and C(18:0) (20.14%). The DNA G+C content was 71.1 mol%. Comparative analysis of 16S rRNA gene sequences showed that the novel strain was most closely related to genera within the family Nocardiopsaceae, but formed a separate lineage. Highest sequence similarities were to Murinocardiopsis flavida DSM 45312(T) (96.6%), Thermobifida halotolerans YIM 90462(T) (96.5%) and Marinactinospora thermotolerans DSM 45154(T) (96.1%). On the basis of phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain CXB654(T) was considered to represent a novel species in a new genus in the family Nocardiopsaceae, and the name Spinactinospora alkalitolerans gen. nov., sp. nov. is proposed; the type strain is CXB654(T) (=DSM 45414(T)=LMG 25485(T)).

[Application of uniform design in optimizing the condition of arsenic determination by atomic fluorescence spectrometry].

In the present paper, uniform design U10* (10(8)) was used to optimize the condition of arsenic determination in vegetable samples by hydride generation-atomic fluorescence spectrometry. Mathematical model was established and regression analysis was done, and the optimized solutions to those equations were obtained by making use of the UD3.0 software. Combining the life-span of hollow cathode filament, noise of negative voltage and other factors, the optimal condition was obtained as follows: negative voltage was 280-360 V; lamp current was 50-70 mA; carrier gas flow rate was 500-700 mL x min(-1); KBH4 concentration was 15.0-20.0 g x L(-1); HCL concentration was 0.6-1.2 mol x L(-1); sample size was 0.5-1.0 mL. Two samples of vegetable were analyzed under the optimized condition. The results showed that the relative standard deviation was less than 3.6%, and the recovery was within 94.1%-101.3%, with their detection limits of 0.42 microg x L(-1). In this paper, as an effective method of experiment design, uniform design was introduced to hydride generation-atomic fluorescence spectrometry analysis with multifactors, which offered a good idea for the optimization of experiment conditions.