The growth and toxin content of the dinoflagellate Alexandrium tamarense ATHK was markedly affected by culture methods. In early growth phase at lower cell density static or mild agitation methods were beneficial to growth, but continuous agitation or aeration, to some extent, had an adverse effect on cell growth. Static culture in 2 L Erlenmeyer flasks had the highest growth rate (0.38 d−1) but smaller cell size compared with other culture conditions. Cells grown under aerated conditions possessed low nitrogen and phosphorus cell yields, namely high N and P cell-quota. At day 18, cells grown in continuous agitated and 1 h aerated culture entered the late stationary phase and their cellular toxin contents were higher (0.67 and 0.54 pg cell−1) compared with cells grown by other culture methods (0.27–0.49 pg cell−1). The highest cell density and cellular toxin content were 17190 cells mL−1 and 1.26 pg cell−1 respectively in an airlift photobioreactor with two-step culture. The results indicate that A. tamarense could be grown successfully in airlift photobioreactor by a two-step culture method, which involved cultivating the cells statically for 4 days and then aerating the medium. This provides an efficient way to enhance cell and toxin yield of A. tamarense. 相似文献
Bioprocess and Biosystems Engineering - A substantial amount of organic matter is wasted in current wastewater treatment processes. To reclaim the value of organic matter, a two-stage... 相似文献
Bioprocess and Biosystems Engineering - To overcome the contamination in open pond, microalgal strain selection should focus on species with tolerability to extreme environments. In this study, a... 相似文献
It is important for water utilities to provide esthetically acceptable drinking water to the public, because our consumers always initially judge the quality of the tap water by its color, taste, and odor (T&O). Microorganisms in drinking water contribute largely to T&O production and drinking water distribution systems (DWDS) are known to harbor biofilms and microorganisms in bulk water, even in the presence of a disinfectant. These microbes include T&O-causing bacteria, fungi, and algae, which may lead to unwanted effects on the organoleptic quality of distributed water. Importantly, the understanding of types of these microbes and their T&O compound-producing mechanisms is needed to prevent T&O formation during drinking water distribution. Additionally, new disinfection strategies and operation methods of DWDS are also needed for better control of T&O problems in drinking water. This review covers: (1) the microbial species which can produce T&O compounds in DWDS; (2) typical T&O compounds in DWDS and their formation mechanisms by microorganisms; (3) several common factors in DWDS which can influence the growth and T&O generation of microbes; and (4) several strategies to control biofilm and T&O compound formation in DWDS. At the end of this review, recommendations were given based on the conclusion of this review.
Most information on the dose-response of radiation-induced cancer is derived from data on the A-bomb survivors. Since, for radiation protection purposes, the dose span of main interest is between zero and one Gy, the analysis of the A-bomb survivors is usually focused on this range. However, estimates of cancer risk for doses larger than one Gy are becoming more important for radiotherapy patients. Therefore in this work, emphasis is placed on doses relevant for radiotherapy with respect to radiation induced solid cancer.
Materials and methods
For various organs and tissues the analysis of cancer induction was extended by an attempted combination of the linear-no-threshold model from the A-bomb survivors in the low dose range and the cancer risk data of patients receiving radiotherapy for Hodgkin's disease in the high dose range. The data were fitted using organ equivalent dose (OED) calculated for a group of different dose-response models including a linear model, a model including fractionation, a bell-shaped model and a plateau-dose-response relationship.
Results
The quality of the applied fits shows that the linear model fits best colon, cervix and skin. All other organs are best fitted by the model including fractionation indicating that the repopulation/repair ability of tissue is neither 0 nor 100% but somewhere in between. Bone and soft tissue sarcoma were fitted well by all the models. In the low dose range beyond 1 Gy sarcoma risk is negligible. For increasing dose, sarcoma risk increases rapidly and reaches a plateau at around 30 Gy.
Conclusions
In this work OED for various organs was calculated for a linear, a bell-shaped, a plateau and a mixture between a bell-shaped and plateau dose-response relationship for typical treatment plans of Hodgkin's disease patients. The model parameters (α and R) were obtained by a fit of the dose-response relationships to these OED data and to the A-bomb survivors. For any three-dimensional inhomogenous dose distribution, cancer risk can be compared by computing OED using the coefficients obtained in this work. 相似文献
Puccinia striiformis f. sp. tritici (Pst) secretes an array of specific effector proteins to manipulate host immunity and promote pathogen colonization. In a previous study, we functionally characterized a glycine-serine-rich effector PstGSRE1 with a glycine-serine-rich motif (m9). However, the mechanisms of glycine-serine-rich effectors (GSREs) remain obscure. Here we report a new glycine-serine-rich effector, PstGSRE4, which has no m9-like motif but inhibits the enzyme activity of wheat copper zinc superoxide dismutase TaCZSOD2, which acts as a positive regulator of wheat resistance to Pst. By inhibiting the enzyme activity of TaCZSOD2, PstGSRE4 reduces H2O2 accumulation and HR areas to facilitate Pst infection. These findings provide new insights into the molecular mechanisms of GSREs of rust fungi in regulating plant immunity. 相似文献