Isolation, Identification and Characterization of Blue-green Algae-lysing Strain DC-L14 from Lake Dianchi, China

An algae-lysing strain DC-L14 was isolated from an area with dense blue-green algae in Lake Dianchi, southwestern China and it was identified as Lysinibacillus fusiformis based on 16S rDNA sequence analysis. The toxicity test on mouse primarily showed that the strain was non-toxic. Under the laboratory condition, the strain could cause Microcystis aeruginosa cells to agglomerate, sinking to bottom and becoming yellow. The reduction rate of chlorophyll a after 4 days was 67.2% on an average, with the highest of 70.1% and lowest of 65.5% in the cultures of Microcystis viridis, M wesenbergii, Aphanizomenon flos-aquae and Anubaena flos-aquae. The strongest algae-lytic ability was found at the stable phase of DC-L14 culture, which could reduce chlorophyll a content of M aeruginosa by 82.1% in four days. After centrifugation and sedimentation, the cells of bacteria showed no algae-lytic ability, but the cell-free supernatant displayed the same algae-lytic ability as that of the whole bacteria culture, and the heated bacterial culture showed the highest algae-lytic ability, indicating that some extracellular and thermo-stable substances produced by this strain had the algae-lytic ability, and high temperature possibly reinforced the algae-lytic ability

Effects of alkalinity variations on photosynthetic activity and exopotysaccharides of Chlorella pyrenoidosa

Effects of bicarbonate (HCO3-) alkalinity on the photosynthetic performance of Chlorella pyrenoidosa was investigated in present study. Photosynthetic activity, pigments, MDA and ultrastructure of Chlorella pyrenoidosa were measured for when they were cultured at two different alkalinities including 2.3mmol/L (ALK2.3) and 12.4mmol/L (ALK12.4), respectivily. At ALK2.3, photosynthetic activity was stimulated at the prophase of culture and then inhibited at the anaphase. At ALK 12.4, it represented the same phenomenon, but inhibition effects were weaker than those at ALK2.3. Ratios of Chl.b/Chl.a was increased, but Caro/TChl ratios was decreased at elevated alkalinities. The contents of MDA increased at ALK2.3 and decreased at ALK12.4. In addition, secretion of glycocalix-like layer was remarkably stimulated at elevated alkalinities. These results showed that elevated alkalinities promoted algae carbon assimilation and stimulated secretion of glycocalix-like layer. Carbohydrate could alleviate stresses at elevated alkalinities. Secretion of glycocalix-like layer could decrease the synthesis of excess products of photosynthesis and relieve feedback inhibition, which will increase the stress tolerance of C. pyenoidosa at elevated alkalinities

Effects of Wall Vessel Rotation on the Growth of Larval Zebrafish Inner Ear Otoliths

Stimulus dependence is a general feature of developing sensory systems. It has been shown earlier that the growth of otoliths of late-stage Cichlid fish (Oreochromis mossambicus) and Zebrafish (Danio rerio) was slowed down by hypergravity, whereas microgravity during spaceflight yielded an opposite effect, i.e., larger than 1 g otoliths, in Swordtail (Xiphophorus helleri) late-stage embryos. Using ground-based techniques to apply simulated weightlessness, long-term clinorotation (exposure on a fast-rotating clinostat with one axis of rotation for 7 days) led to larger than 1 g otoliths in late-stage Cichlid fish, which is fully in line with the results obtained on Swordtails from spaceflight. Hitherto, early-staged fish have not yet been subjected to (simulated or real) long-term (i.e., more than 3 or 4 days) weightlessness to investigate otolith growth. The present study was carried out in order to fill this gap. Therefore, we subjected Zebrafish at a somite-stage to Wall Vessel Rotation (WVR; a method regarded to provide simulated weightlessness), when the anlage of the inner ear already is present (10 h post fertilisation, hpf). Siblings were maintained under WVR for 3, 6, 9 and 12 days. Further short-term experiments (3 days) were carried out on 10 hpf animals as well as on very early larvae (1 K cell stage, 3 hpf) at two different rotation speeds. WVR (both rotation speeds) had no effect on otolith biogenesis in both stages as all otoliths were present after the experiments. In comparison with 1 g controls, WVR had significantly increased otolith growth (normalised by fish length) after 3 and 6 days of exposure, but significant differences of otolith growth between experimental animals and controls were not found after 9 and 12 days. In conclusion, WVR (at least within a time-span of exposure of up to 6 days) brings, comparable to the situation in real microgravity, a kind of feedback mechanism into action, resulting in larger otoliths. Later, possible effects of WVR might be overruled by normal allometric growth since the action of the feedback mechanism may be discontinued in the course of an adaptation

The correlation between the variation of microcystin content and environment factors in Dianchi Lake

This paper analyzed the distribution and variation of microeystin ( M C) and physicochemical factors in Macun and Haidong bay of Dianchi Lake from April to December in 2003. The correlation of some physiochemical factors, including the concentration of total nitrogen, total phosphorous, dissolve oxygen, chlorophyll-a and Seechi depth, light intensity, pH, water temperature and dominance of Microcystis population, with microcystin was evaluated. Correlation analysis showed that the distribution of MC was significantly positive correlated with TN and N: P (P < 0. 01); and affected by Seechi depth, light intensity, dominance of Microcystis ( P < 0. 05). Multiple continuously factors analysis indicated that the distribution of MC in water of the two bays was mainly affected by total nitrogen, Seechi depth, chlorophyll-a, dissolve oxygen and total phosphorous (R-2= 0. 560, P < 0. 017)

Nostoc sphaeroides Kutzing, an excellent candidate producer for CELSS

Some phytoplankton can be regarded as possible candidates in the establishment of Controlled Ecological Life Support System (CELSS) for some intrinsic characteristics, the first characteristic is that they should grow rapidly, secondly, they should be able to endure some stress factors and develop some corresponding adaptive strategies; also it is very important that they could provide food rich in nutritious protein and vitamins for the crew; the last but not the least is they can also fulfill the other main functions of CELSS, including supplying oxygen, removing carbon dioxide and recycling the metabolic waste. According to these characteristics, Nostoc sphaeroides, a potential healthy food in China, was selected as the potential producer in CELSS. It was found that the oxygen average evolution rate of this algae is about 150 mu mol O(2) mg(-1) h(-1), and the size of them are ranged from 2 to 20 mm. Also it can be cultured with high population density, which indicated that the potential productivity of Nostoc sphaeroides is higher than other algae in limited volume. We measured the nutrient contents of the cyanobacterium and concluded it was a good food for the crew. Based on above advantages, Nostoc sphaeroides was assumed to a suitable phytoplankton for the establishment of Controlled Ecological Life Support System. We plan to develop suitable bioreactor with the cyanobacterium for supplying oxygen and food in future space missions. Crown copyright (C) 2011 Published by Elsevier Ltd. on behalf of COSPAR. All rights reserved

DIVERSITY AND SUCCESSIONAL DYNAMICS OF PICOCYANOBACTERIAL COMMUNITY IN LAKE ERHAI (CHINA) AS INFERRED FROM 16S rRNA GENE SEQUENCES

The biomass of autotrophic picoplankton (APP) and the biodiversity of planktonic cyanobacteria in Lake Erhai (China) were investigated. Results showed that chlorophyll a concentration in phytoplankton size &lt;2.7 mu m ranged from 0.1 mu g l(-1) (February 2008) to 1.2 mu g l(-1) (September 2007) in the surface water during July 2007 August 2008. The contribution of APP to the total chlorophyll a concentration in phytoplankton varied from 1.6 to 5.1%. The pattern of seasonal changes in the concentration of APP was similar to that of total nitrogen and total phosphorus. Phylogenetic analyses as inferred from the partial 16S rRNA gene sequences showed great diversity of the picocyanobacterial community in Lake Erhai, which comprised both previously identified (less abundant) and unique clusters (more abundant). Group B and Lake Erhai cluster 4 (LE-4) were ubiquitous in Lake Erhai picocyanobacterial community. Different numbers and types of clusters constituted the picocyanobacterial community with seasonal variations. A novel cluster LE-10 composed exclusively of sequences obtained in this study was found in July 2008

SUCCESSION OF THE PHYTOPLANKTON COMMUNITY IN RESPONSE TO ENVIRONMENTAL FACTORS IN NORTH LAKE ERHAI DURING 2009-2010

Phytoplankton samples were taken weekly from September 2009 to November 2010 in Lake Erhai. The purpose was to obtain detailed information about the composition variations in the phytoplankton community during the serious drought in 2009 - 2010 and to determine the driving force for the succession of the dominant genera. A total of 147 phytoplankton species were identified during our investigation. Among the 7 main divisions, the maximum contribution (69%) belongs to the Chlorophyta division. The alternation of the dominant group was Cyanophyta, Chlorophyta, and Bacillariophyta. The weekly variations in cell abundance and biomass of the dominant phytoplankton genera were examined. A succession characterized by Psephonema and Asterionella (spring) -&gt; Melosira (summer) -&gt; Microcystis (autumn) -&gt; Microcystis and Psephonema (winter) emerged from the monthly average biomass. Weekly variations in the Shannon Weaver index ranged between 0.269 and 2.183. Redundancy analysis results showed varied effects of environmental factors on the different phytoplankton dominant genera, with water temperature as the driving force for the seasonal succession of the dominant genera. The shift in succession pattern is induced by light intensity variation. In addition, the dominance of Psephonema in winter is the first report in Lake Erhai in recent years