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In a field survey in the Taiwan Strait during April 2016, the species composition and the domoic acid production of the diatom genus Pseudo-nitzschia were investigated. A total of 80 strains of Pseudo-nitzschia were established, and species identification was determined based on a combination of morphological and molecular data. Fourteen taxa were recognized, i.e., P. americana, P. brasiliana, P. calliantha, P. cuspidata, P. galaxiae, P. lundholmiae, P. multiseries, P. multistriata, P. pseudodelicatissima, P. pungens var. aveirensis, P. pungenus var. pungens and P. sabit, as well as two novel species P. chiniana C.X. Huang & Yang Li and P. qiana C.X. Huang & Yang Li. Morphologically, P. chiniana is characterized by striae comprising one or two rows of poroids, and valve ends that are normally dominated by two rows of poroids within each stria. Whereas P. qiana is unique by having a narrow valve width (1.3–1.5 μm) and sharply pointed valve ends. Both taxa constitute their own monophyletic lineage in the phylogenetic analyses inferred from LSU and ITS2 rDNA, and are well differentiated from other Pseudo-nitzschia species. Pseudo-nitzschia chiniana forms a group with P. abrensis and P. batesiana in LSU and ITS trees, whereas P. qiana is sister to P. lineola. When comparing ITS2 secondary structure, five CBCs and seven HCBCs are recognized between P. chiniana and P. abrensis, and four CBCs and ten HCBCs between P. chiniana and P. batesiana. Two CBCs and eight HCBCs are found between P. qiana with P. lineola. The ability of the strains to produce domoic acid was assessed, including a potential toxin induction by the presence of brine shrimps. Results revealed production of domoic acid in six strains belonging to three species. Without presence of brine shrimps, cellular DA (pDA) was detected in four P. multiseries strains (1.6 ± 0.3, 26.6 ± 2.7, 68.3 ± 4.2 and 56.9 ± 4.7 fg cell−1, separately), one strain of P. pseudodelicatissima (0.8 ± 0.2 fg cell−1) and one strain of P. lundholmiae (2.5 ± 0.4 fg cell−1). In the presence of brine shrimps, pDA contents increased significantly (p

To explore the species diversity and toxin profile of Pseudo-nitzschia, monoclonal strains were established from Chinese southeast coastal waters. The morphology was examined under light and transmission electron microscopy. The internal transcribed spacer region of ribosomal DNA was sequenced for phylogenetic analyses, and the secondary structure of ITS2 was predicted and compared among allied taxa. A combination of morphological and molecular data showed the presence of two new species, Pseudo-nitzschia hainanensis sp. nov. and Pseudo-nitzschia taiwanensis sp. nov. Pseudo-nitzschia hainanensis was characterized by a dumpy-lanceolate valve with slightly blunt apices and a central nodule, as well as striae comprising two rows of poroids. Pseudo-nitzschia taiwanensis was characterized by a slender-lanceolate valve, and striae comprising one row of split poroids. The poroid structure mainly comprised two sectors. Both taxa constituted their own monophyletic lineage in the phylogenetic analyses inferred from ITS2 rDNA and were well differentiated from other Pseudo-nitzschia species. Morphologically, P. hainanensis and P. taiwanensis could be assigned to the Pseudo-nitzschia delicatissima and the Pseudo-nitzschia pseudodelicatissima complex, respectively. Particulate domoic acid was measured using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), but no detectable pDA was found. With the description of the two new species, the species diversity of genus Pseudo-nitzschia reaches 58 worldwide, among which 31 have been recorded from Chinese coastal waters.

The genus Pseudo-nitzschia has attracted attention because of production of the toxin, domoic acid (DA), causing Amnesic Shellfish Poisoning (ASP). Pseudo-nitzschia blooms occur frequently in Chinese coastal waters, and DA has been detected in several marine organisms, but so far no Pseudo-nitzschia strains from Chinese waters have been shown to produce DA. In this study, monoclonal Pseudo-nitzschia strains were established from Chinese coastal waters and examined using light microscopy, electron microscopy and molecular markers. Five strains, sharing distinct morphological and molecular features differentiating them from other Pseudo-nitzschia species, represent a new species, Pseudo-nitzschia simulans sp. nov. Morphologically, the taxon belongs to the P. pseudodelicatissima group, cells possessing a central nodule and each stria comprising one row of poroids. The new species is characterized by the poroid structure, which typically comprises two sectors, each sector located near opposite margins of the poroid. The production of DA was examined by liquid chromatography tandem mass spectrometry (LC-MS/MS) analyses of cells in stationary growth phase. Domoic acid was detected in one of the five strains, with concentrations around 1.05-1.54 fg cell-1. This is the first toxigenic diatom species reported from Chinese waters.

Based on the self-ordered ring (SOR) fluorescent microscopic imaging technique on a hydrophobic glass slide with Mn2+ and cetyltrimethyl ammonium bromide (CTMAB) as sensitizer, poly(vinyl alcohol)-124 (PVA-124) and NH3-NH4Cl buffer (pH 9.30) as the medium, a method has been developed for determining levofloxacin (LVFX) residues in chicken tissue, chicken manure and the concentrations in chicken serum. Sample preparation used the PBS and acetic acid-methanol as extracting agents for chicken breast muscle, liver and manure, respectively, the protein from chicken serum samples was removed with methanol. When the droplet volume is 0.2 μL, LVFX in the range of 5.7 × 10−14−1.0 × 10−13 mol/ring can be detected, and the limit of detection (LOD) can reach 5.7 × 10−15 mol/ring (2.8 × 10−8 M). Compared to reference [16], the sensitivity of SOR method enhances 1.7 times. It is a viable method for the determination of LVFX in chiken samples with the recoveries of 90.0–104.1% and relative standard deviations (RSDs) less than 3.6%. The results indicate that the method applied to chicken tissue, manure and serum is reliable and applicable.

With the development of antimicrobial drugs, drug residue in animal products has a serious potential hazards for the environment and public health, it is urgent to set up drug residue detection method with low detection limit and good selectivity. In our paper, with poly (vinyl alcohol)-124 (PVA-124) and NH3-NH4Cl (pH 10.50) as the medium, Mn2+ and cetyltrimethyl ammonium bromide (CTMAB) as sensitizer, tosufloxacin tosylate (TSFX) formed a self-ordered ring (SOR) on a hydrophobic glass slide support. When the droplet volume is 0.20 microL, the TSFX can be detected in the range of 4.05 x 10(-14) approximately 4.28 x 10(-13) mol x ring(-1) (2.02 x 10(-7) approximately 2.14 x 10(-6) mol x L(-1)), and the limit of detection (LOD) can reach 4.1 x 10(-15) mol x ring(-1) (2.0 x 10(-8) mol x L(-1)). The established method had been applied satisfactorily to determine the content of TSFX in tablet, which close to the marked value of 0.15 g x piece(-1)) found value: 0.144 g x piece(-1)) and the results of TSFX concentrations in rabbit serum at different time after dosing with the recoveries of 90.0% - 105.0% and RSDs 1.9% - 3.3% were satisfactory. Xilinguole of Inner Mongolia is the national important livestock products ground, whose lamb is the main suppling source for Beijing-Tianjin-Tangshan region. It is very urgent to detect residue of antibacterial drug in its sheep tissue samples (meat, liver, kidney). In this paper, when acetonitrile was used as extraction agent in pretreatment of sheep tissue samples in six rangelands including Sonid Right Banner, Xiwuzhumuqin Banner, Xilinhot City, Duolun County, The white Flag Town and The Blue Flag Town, the extract can be directly determined with SOR technology without filtering process, the sample standard addition recovery of sheep tissues were 92.0%-101.0% and RSDs were less than 2.7%. The results indicated that the SOR technique can be successfully applied to pharmaceuticals and biological samples, which broaden the applied range of SOR technique. The assay would provide reliable experimental data and theoretical basis for the relevant departments.