Reactive oxygen species and antioxidant enzymes activity of Anabaena sp. PCC 7120 (Cyanobacterium) under simulated microgravity.

It was found that reactive oxygen species in Anabaena cells increased under simulated microgravity provided by clinostat. Activities of intracellular antioxidant enzymes, such as superoxide dismutase, catalase were higher than those in the controlled samples during the 7 days' experiment. However, the contents of glutathione [correction of gluathione], an intracellular antioxidant, decreased in comparison with the controlled samples. The results suggested that microgravity provided by clinostat might break the oxidative/antioxidative balance. It indicated a protective mechanism in algal cells, that the total antioxidant system activity increased, which might play an important role for algal cells to adapt the environmental stress of microgravity.

[Lipid peroxidation in microalgae cells under simulated microgravity].

Objective. To provide direct evidences for effects of microgravity on structure and function of plasma membrane. Method. Malondialdehyde (MDA) content was examined on the basis of quantitative reaction of both MDA and thiobarbituric acid (TBA), and electrolyte leaking was determined with conductometer model DDS-11A. Result. Experiments showed that under simulated microgravity, lipid peroxidation and the content of MDA increased. Meanwhile, the membrane permeability increased in cells of two microalgae: Anabaena sp PCC7120 and Synechococcus 7942. Conclusion. Our results suggest that there is some commonness between microgravity stress and certain other environmental stresses. And cellular membrane might be the site of perception of gravity in unicells without special gravity sensitive structure, such as alga cells.

Silver nanoparticles induced accumulation of reactive oxygen species and alteration of antioxidant systems in the aquatic plant Spirodela polyrhiza.

Silver nanoparticles (AgNPs) are widely used commercially because of their antibacterial properties. Oxidative stress is known to be involved in the toxicity of AgNPs to bacteria, animals, and algae. The authors used Spirodela polyrhiza to investigate whether AgNPs can induce oxidative stress in higher plants. Results showed that there was a dose-dependent increase in levels of reactive oxygen species, superoxide dismutase and peroxidase activity, and the antioxidant glutathione content in 6-nm AgNP treatments. Catalase activity and malondialdehyde content in 6-nm AgNP treatments was significantly higher than the control at silver concentrations of 5 mg L(-1) . Superoxide dismutase and catalase activity and antioxidant glutathione and malondialdehyde content were not significantly different at 10 mg L(-1) of AgNPs (6 nm and 20 nm). Treatment with 20 µg L(-1) Ag(+) (the amount almost equal to 10 mg L(-1) AgNPs released) did not change the reactive oxygen species level or antioxidant enzymes activity. Micron-sized Ag particles had no effect on S. polyrhiza. Transmission electron microscopy showed that, compared with the control, chloroplasts in S. polyrhiza treated with 6-nm and 20-nm AgNPs accumulated starch grains and had reduced intergranal thylakoids. These results clearly indicate that AgNPs are able to cause oxidative stress and affect the chloroplast structure and function of S. polyrhiza, and this effect was not caused by Ag(+) released from particles.

[Dianchi Lake macroinvertebrate community succession trends and retrogressive analysis].

Historical records and data from yield surveys conducted in 2009 and 2010 were used to investigate macroinvertebrate community succession trends in Dianchi Lake. Species richness has declined from 57 in the 1980s to 32 in 2010, representing a species loss of 44%. Among the major benthic groups, the highest rate of loss was recorded for mollusks (75%) and aquatic insects (39%). Surveys in 2009 and 2010 across the lake revealed that the total density was 1776 ind/m2, comprising oligochaetes (1706 ind/m2) and chironomids (68 ind/m2). Over a nearly twenty-year span (1992-2010), the density and biomass of oligochaetes first increased sharply (1992-2002) and then declined gradually (2002-2010). Further, chironomids have decreased gradually while the proportion of abundant species has increased. Limnodrilus hoffmeisteri became the sole dominant species with an average relative abundance of 74.1%. Cosmopolitan species, such as Einfeldia sp., disappeared across the lake; instead, tolerant species such as Chironomus plumosus, Ch. attenuatus and Tanypus chinensis became the common. Mollusk community structure has become simpler and many native species have gone extinct. Species of concern include Margarya melanioides, M. mondi, M. mansugi and Cipangopaludina dianchiensis, all rated as critically endangered by the IUCN. We found that the Shannon-Wiener index declined in Dianchi Lake, particularly in Caohai Lake, from 2.70 in the 1950s to 0.30 in 2009 and 2010. Species richness and biodiversity was significantly negative correlated with total phosphorus and total nitrogen. Factors responsible for the benthic community retrogression described here include habitat destruction, lowering of water quality, outbreaks of blue-green algae, extinction of submerged plants and lack of germplasm resources.