Yongding Liu - Academia.edu (original) (raw)

Papers by Yongding Liu

Fresenius Environmental Bulletin

ABSTRACT

Acta Hydrobiologica Sinica, 2009

In the present study, we investigated the effects of sa-linity stress, one of the main stress in ... more In the present study, we investigated the effects of sa-linity stress, one of the main stress in polluted water bodies, on the photosynthetic activity of Wolffia arrhiza. High salinity stress (1-4%) significantly decreased photo-synthetic CO 2 assimilation activity, while the chlorophyll a, chlorophyll b and carotenoid contents were not affected after treatment with salinity stress for 24 h. The fluores-cence yields at phases J, I and P were clearly decreased by salinity stress above 1%, and the addition of DCMU to the control resulted in the transformation of an O-J-I-P ris e into an O-J rise. Salinity stress decreased the quantum yield of primary photochemistry (φPo), the quantum yield of electron transport (φEo) and the efficiency per trapped excitation (Ψo) in Wolffia arrhiza simultaneously; the number of active PSII reaction centers per excited cross section (RC/CS), the total number of active reaction cen-ters per absorption (RC/ABS) and the performance index of PSII (PI ABS a...

We had investigated the colonization of soils in Mars-like environments in Chinese deserts by pho... more We had investigated the colonization of soils in Mars-like environments in Chinese deserts by phototrophs. Some extreme cyanobacteria and algae strains were collected and mass-cultured in desert regions to investigated their ability to artificially form desert crusts. These crusts had the capacity to resist sand storm erosion after just 15 days of growth. Similar to the surface of some Chinese deserts, the surface of Mars is characterized by a layer of fine dust, which will challenge future human exploration and settlement, particularly in confined spaces such as greenhouses. In this paper we describe experiments on the formation of artificial desert crusts and we discuss the implications of these approaches for the local amelioration of desert conditions on Mars, which is essential to establish CELSS in habitat. These approaches might also be applicable to the interior of lunar habitats. Finally, more ambitiously, our findings may be a first step in addressing the issues of terrafo...

Soil Biology and Biochemistry, 2014

ABSTRACT The development of Biological Soil Crusts (BSCs) is widely recognized as beneficial to s... more ABSTRACT The development of Biological Soil Crusts (BSCs) is widely recognized as beneficial to soil fertility due to their contribution to the stabilization of soils and to the increase in their carbon and moisture content. An important role in these processes is played by the extracellular polysaccharidic (EPS) matrix embedding microbial cells and soil particles in BSCs. The present study was aimed at investigating the molecular and chemical features of the EPSs and the degradation processes of the polysaccharidic matrix (i.e. dehydrogenase and sucrase activities) in Induced Biological Soil Crusts (IBSCs) of different ages displayed within an investigation area in Hobq Desert (Dalatequi County, Inner Mongolia, China). Two operationally-defined EPS fractions, the colloidal (C-EPS) and the EDTA extractable (tightly bound, TB-EPS) fractions, were analyzed. In BSCs, C-EPSs are loosely bound to cells and sediments while TB-EPSs are tightly bound to the crustal biotic and abiotic constituents of the crusts. In this study, the C-EPS and TB-EPS fractions extracted from the IBSCs of different age (4-, 6- and 8-years old IBSCs) were found present in comparable amounts but showed marked differences in terms of their molecular size distribution and monosaccharidic composition. C-EPS showed to be mostly constituted by sugar fractions with molecular weight (MW) distributed in the range 2000 - 76 kDa and in the range 64 - 0.34 kDa. Conversely, the TB-EPSs showed to be prominently constituted by one fraction having a MW in the range 2000 - 76 kDa. While the chemical and macromolecular characteristics of TB-EPSs did not show significant changes with the age of the crusts, the older IBSCs showed a lower content of low MW C-EPSs, as well a higher number of different types of monosaccharides constituting the C-EPS. Moving from these results, it can be hypothesized that C-EPSs, which are dispersed in the soil and thus more accessible, have been rather easily degraded by the heterotrophic microorganisms dwelling in mature IBSCs and reduced to low MW carbohydrates that are easily metabolized by chemoheterotrophs. This hypothesis is supported by the higher activity observed in older IBSCs of the two enzymes associated with sugar degradation in the soil, dehydrogenases and sucrases, that is consistent with an increased release of low MW carbohydrates in the crusts. The results obtained suggest that the colloidal fraction of the EPSs, which is more dispersed in the soil, is more easily degradable by the microflora, while the EPS fraction tightly bound to the soil particles, which is characterized by a high MW, plays a key role in giving a structural stability to the crusts and in affecting the hydrological behavior of the soil covered by IBSCs.

Chinese Journal of Oceanology and Limnology, 2009

In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macroph... more In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorum, but no significant effect is found in this study.

Toxicon, 2006

Our previous studies showed that microcystin-RR could induce oxidative damage in plant cells as t... more Our previous studies showed that microcystin-RR could induce oxidative damage in plant cells as they do with animal cells. However, whether microcystin can induce plant cell apoptosis is still unknown. In this study, the morphological changes of tobacco BY-2 suspension cells exposed to microcystin-RR were observed under light microscopy and transmission electron microscopy, and apoptosis was clearly distinguished by intense perinuclear chromatin margination, condensation of nuclear chromatin after 6 d exposure of 50 mg/L (about 50 mM) microcystin-RR. We also found that microcystin-RR can induce tobacco cell apoptosis in a dose-and time-dependent manner with flow cytometry analysis. Our study provides the first evidence that microcystins can induce plant cell apoptosis. r

Toxicon, 2005

Microcystins are cyclic heptapeptide hepatoxins produced by cyanobacteria. It has been shown that... more Microcystins are cyclic heptapeptide hepatoxins produced by cyanobacteria. It has been shown that microcystins have adverse effects on animals and on plants as well. Previous researches also indicated that microcystins were capable of inducing oxidative damage in animals both in vivo and in vitro. In this study, tobacco BY-2 suspension cell line was applied to examine the effects of microcystin-RR on plant cells. Cell viability and five biochemical parameters including reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxide (GPX) and peroxide dismutase (POD) were investigated when cells were exposed to 50 mg/L microcystin-RR. Results showed that microcystin-RR evoked decline of the cell viability to approximately 80% after treating for 144 h. ROS levels, POD and GPX activities of the treated cells were gradually increased with a time dependent manner. Changes of SOD and CAT activities were also detected in BY-2 cells. After 168 h recovery, ROS contents, POD, GPX and CAT activities returned to normal levels. These results suggest that the microcystin-RR can cause the increase of ROS contents in plant cells and these changes led to oxidant stress, at the same time, the plant cells would improve their antioxidant abilities to combat mirocystin-RR induced oxidative injury. q

Toxicon, 2005

Microcystins are cyclic heptapeptide hepatoxins produced by many species of cyanobacteria. The to... more Microcystins are cyclic heptapeptide hepatoxins produced by many species of cyanobacteria. The toxic effects and mechanism of microcystins on animals have been well studied both in vivo and in vitro. It was also reported that microcystins had adverse effects on plants. However, to our knowledge, there is no information about the toxic effects and mechanism of microcystins on plant suspension cells. In this study, Arabidopsis thaliana suspension cells were exposed to a range dose of microcystin-RR. Lipid peroxidation, a main manifestation of oxidative damage, was studied and a time-and dose-dependent increase in malondiadehyde was observed. In contrast, glutathione (GSH) levels in the cells decreased after 48 h treatment with 1 and 5 mg/L of microcystin-RR. The activities of superoxide dismutase (SOD) and catalase (CAT) increased significantly after 48 h exposure to 1 and 5 mg/L of microcystin-RR, but glutathione S-transferase (GST) activity showed no difference compared with the control. These results clearly indicate that microcystin-RR is able to cause oxidative damage in A. thaliana suspension cells. Decrease of GSH content and increases of SOD and CAT activities reveal that the antioxidant system may play an important role in eliminating or alleviating the toxicity of microcystin-RR. The possible toxicity mechanism of microcystin-RR on the A. thaliana suspension cells is also discussed in this paper. q

Toxicon, 2003

The freshwater, bloom-forming cyanobacterium (blue-green alga) Microcystis aeruginosa produces a ... more The freshwater, bloom-forming cyanobacterium (blue-green alga) Microcystis aeruginosa produces a peptide hepatotoxin, which causes the damage of animal liver. Recently, toxic Microcystis blooms frequently occur in the eutrophic Dianchi Lake (300 km 2 and located in the South-Western of China). Microcystin-LR from Microcystis in Dianchi was isolated and purified by high performance liquid chromatography (HPLC) and its toxicity to mouse and fish liver was studied . In this study, six biochemical parameters (reactive oxygen species, glutathione, superoxide dismutase, catalase, glutathione peroxide and glutathione S-transferase) were determined in common carp hepatocytes when the cells were exposed to 10 mg microcystin-LR per litre. The results showed that reactive oxygen species (ROS) contents increased by more than one-time compared with the control after 6 h exposure to the toxin. In contrast, glutathione (GSH) levels in the hepatocytes exposed to microcystin-LR decreased by 47% compared with the control. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxide (GSH-Px) increased significantly after 6 h exposure to microcystin-LR, but glutathione S-transferase (GST) activity showed no difference from the control. These results suggested that the toxicity of microcystin-LR caused the increase of ROS contents and the depletion of GSH in hepatocytes exposed to the toxin and these changes led to oxidant shock in hepatocytes. Increases of SOD, CAT and GSH-Px activities revealed that these three kinds of antioxidant enzymes might play important roles in eliminating the excessive ROS. This paper also examined the possible toxicity mechanism of microcystin-LR on the fish hepatocytes and the results were similar to those with mouse hepatocytes. q

Toxicon, 2002

Microcystin-LR, a speci®c and potent hepatotoxin, was tested for its effects on loach embryo-larv... more Microcystin-LR, a speci®c and potent hepatotoxin, was tested for its effects on loach embryo-larval and juvenile development. The results of this study showed that loach embryos were more sensitive when exposed to microcystin-LR at a later than at an earlier stage of development. Juveniles were far less sensitive to MC-LR than were embryos and larvae. Mortality and developmental abnormality were proven to be dose-dependent and to be stage-speci®c sensitive. Among the abnormal changes noted were: pericardial edema and tubular heart, bradycardia, homeostasis, poor yolk resumption, small head, curved body and tail, and abnormal hatching. Liver and heart were the main targets of microcystin-LR toxicity. Ultrastructural analysis documented a complex set of sublethal effects of microcystin-LR on loach hepatocytes, chie¯y including morphological alteration in nuclear and RER of loach liver cells. In addition, microcystin-LR was lethal to loach juvenile in the subacute (7 days) exposure (LC 50 593.3 mg/l). q

Soil Biology and Biochemistry, 2007

In the desert areas of China investigated by the authors, various biological crusts were predomin... more In the desert areas of China investigated by the authors, various biological crusts were predominately associated with three blue-green algal (cyanobacterial) species, Microcoleus vaginatus Gom., Phormidium tenue (Menegh.) Gom. and Scytonema javanicum (Ku¨tz.) Born et Flah. Their biomass and their compressive strength were measured simultaneously in the field in this study. It was also found that the compressive strength of algal crusts was enhanced with the increasing of algal biomass from an undetectable level to a value as high as 9.6 mg g À1 dry soil. However, when the algal biomass decreased, the compressive strength did not descend immediately, but remained relatively steady. The higher the algal biomass became, the thicker were the algal crusts formed. Given the same biomass, the highest compressive strength of man-made algal crusts in fields was found at an algal ratio of 62.5% M. vaginatus, 31.25% P. tenue and 6.25% S. javanicum, and it reached 0.89 kg cm À2 . When the biomass of the crusts increased above the value of 8.16 mg chla g À1 dry soil, the compressive strength would not ascend easily. It indicated that the compressive strength of man-made algal crusts appeared temporarily saturated in the field. r

Phycological Research, 1998

Toxic cyanobacterium Microcystis viridis was isolated from the eutrophic Dianchi Lake of south-we... more Toxic cyanobacterium Microcystis viridis was isolated from the eutrophic Dianchi Lake of south-western China. Three microcystins were detected from this strain by high-pressure liquid chromatography. Among them, [Dha 7 ] microcystin-RR is the major component and represents about 70-80% of the total toxins of this strain. We examined its microcystin production pattern in relation to culture conditions such as light intensity, nutrition, temperature, pH and growth phase. Of all the factors examined, light intensity and pH influenced the toxin production much more than other factors. At 25ЊC, a high production of [Dha 7 ] microcystin-RR was obtained at light intensity 15 E s Ϫ1 m Ϫ2 , and both low and high pH (pH 7.0 and pH 9.2) enhanced the yield of microcystin-RR. No strong relationships were found between total toxin and temperature ranging from 15ЊC. The highest production of total toxins was measured in the mid-exponential growth phase and lowest production towards the declining growth phase. Remarkable changes in toxin production and morphology emerged coincidentally following the transfer of nitrogen-deficient cells into fresh MA medium during the time course. These findings may shed light on the correlation between toxin production and morphogenesis of this strain.

Phycological Research, 1998

ABSTRACT

Phycological Research, 1998

ABSTRACT Four strains of the unicellular, colonial cyanobacteria, Microcystis were isolated from ... more ABSTRACT Four strains of the unicellular, colonial cyanobacteria, Microcystis were isolated from P.R. China and Thailand, and showed greyish-brown to dark brown color of cell mass. Their cells were almost spherical, 3.8–5.5 μm in diameter and had gas vesicles. Their colony forms have some differences among the strains but still have common characteristics including being irregular, reticulate, elongated and lobated. These characteristics are remarkably similar to Microcystis aeruginosa (Kutz.) Kutz. In addition, three of the strains also have the characteristics of Microcystis ichthyoblabe Kutz at times, and another sometimes shows characteristics similar to Microcystis novacekii (Kom.) Comp. The absorption spectra of both intact cells and extracted phy-cobiliproteins showed an absorption peak at 560–570 nm in wavelength, which is the absorption range of phycoerythrin. Since no species of Microcystis has ever been reported to have phycoerythrin, the existence of phycoerythrin separates these four strains from the known species of Microcystis, and might enable them to be classified as a new species. Phycoerythrin might give these organisms the advantage to live underwater where the light is predominantly green in color.

Journal of Phycology, 2001

A strain of Raphidiopsis (Cyanobacteria) isolated from a fish pond in Wuhan, P. R. China was exam... more A strain of Raphidiopsis (Cyanobacteria) isolated from a fish pond in Wuhan, P. R. China was examined for its taxonomy and production of the alkaloidal hepatotoxins cylindrospermopsin (CYN) and deoxy-cylindrospermopsin (deoxy-CYN). Strain HB1 was identified as R. curvata Fritsch et Rich based on morphological examination of the laboratory culture. HB1 produced mainly deoxy-CYN at a concentration of 1.3 mg ؒ g Ϫ 1 (dry wt cells) by HPLC and HPLC-MS/MS. CYN was also detected in trace amounts (0.56 g ؒ g Ϫ 1 ). A mouse bioassay did not show lethal toxicity when tested at doses up to 1500 mg dry weight cells ؒ kg Ϫ 1 body weight within 96 h, demonstrating that production of primarily deoxy-CYN does not lead to significant mouse toxicity by strain HB1. The presence of deoxy-CYN and CYN in R. curvata suggests that Raphidiopsis belongs to the Nostocaceae, but this requires confirmation by molecular systematic studies. Production of these cyanotoxins by Raphidiopsis adds another genus, in addition to Cylindrospermopsis , Aphanizomenon , and Umezakia , now known to produce this group of hepatotoxic cyanotoxins. This is also the first report from China of a CYN and deoxy-CYN producing cyanobacterium.

Journal of Integrative Plant Biology, 2006

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus, a cyanobacterium ... more The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus, a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K + concentrations of stressed cells decreased significantly and H + -ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra-and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na + and K + by H + -ATPase. (2006). Effects of salt stress on carbohydrate metabolism in desert soil alga Microcoleus vaginatus. J Integr Plant Biol 48(8), 1-1.

Journal of Freshwater Ecology, 2004

Compared with other approaches for modeling and predicting, artificial neural networks are more e... more Compared with other approaches for modeling and predicting, artificial neural networks are more effective in describing complex and non-linear systems. The occurrence of cyanobacterial blooms has been a continuous and serious problem over the past decades in hypereutrophic Lake Dianchi. Yet, the main factor(s) initiating these blooms remain(s) unclear. During 2001–2002 at 40 sampling sites in Lake Dianchi, physicochemical parameters possibly relating to the blooms were measured. Parameters directly or indirectly relating to the cyanobacterial blooms were used as driving factors in a back-propagation network to model the concentration of chlorophyll a. According to sensitivity analysis, chemical oxygen demand was identified as a very significant environmental factor for algal growth in Lake Dianchi.

Journal of Environmental Sciences, 2011

After the appalling "Wuxi Drinking Water Crisis", increasing investigations concerning the contam... more After the appalling "Wuxi Drinking Water Crisis", increasing investigations concerning the contaminations of cyanobacterial blooms and their toxins in Lake Taihu have been performed and reported in the last two years. However, information regarding these issues before the crisis in 2007 remained insufficient. To provide some background data for further comparisons, the present study reported our investigations conducted in 2004, associated with the cyanotoxin contaminations as well as the eutrophication status in Lake Taihu. Results from the one-year-study near a drinking water resource for Wuxi City indicated that, unlike the status in recent two years, cyanobacteria and chlorophyta are the co-dominance species throughout the year. The highest toxin concentration (34.2 ng/mL) in water columns occurred in August. In bloom biomass, the peak value of intracellular toxin (0.59 µg/mg DW) was determined in October, which was lag behind that in water column. In addition, MC-RR was the major toxin variant throughout the year. During the study period, nutrients levels of total nitrogen and phosphorus were also recorded monthly. Results from the present study will lead to a better understanding of the eutrophication status and the potential risks before "Wuxi Drinking Water Crisis".

Fresenius Environmental Bulletin

ABSTRACT

Acta Hydrobiologica Sinica, 2009

Soil Biology and Biochemistry, 2014

Chinese Journal of Oceanology and Limnology, 2009

Toxicon, 2006

Toxicon, 2005

Toxicon, 2003

Toxicon, 2002

Soil Biology and Biochemistry, 2007

Phycological Research, 1998

ABSTRACT

Phycological Research, 1998

Journal of Phycology, 2001

Journal of Integrative Plant Biology, 2006

Journal of Freshwater Ecology, 2004

Journal of Environmental Sciences, 2011