Effects of Phenylethyl Alcohol on Chlorella pyrenoidosa

Asynchronous as well as synchronous cultures were used to study the effect of phenylethyl alcohol on Chlorella pyrenoidosa. The following observations were made:

• 1 Autotrophic growth and the synthesis of DNA and chlorophyll were inhibited more than 80% by 8.4 mM phenylethyl alcohol when added to synchronous suspensions containing autospores.
• 2 Autospore formation did not occur when fully grown cells capable of division were transferred to 4.2 mM phenylethyl alcohol.
• 3 Photosynthetic oxygen evolution of asynchronous cultures was inhibited more than 70 % by 21 mM phenylethyl alcohol.
• 4 Endogenous respiration in the dark was stimulated by 8.4 mM, while higher concentrations were inhibitory.
• 5 Glucose respiration in the dark was inhibited by all concentrations in the range from 8.4 mM to 21 mM. Assimilation of glucose in darkness was retarded by phenylethyl alcohol at concentrations which gave maximal stimulation of endogenous respiration.

It is concluded that phenylethyl alcohol is not a specific inhibitor of DNA synthesis. The prime effect appears to be on respiration and photosynthesis.     

A short note on the effects of 6-methyl purine on the revolution of the cell cycle of Chlorella pyrenoidosa in synchronous culture

Short exposure of Chlorella pyrenoidosa cells to a high concentrationof 6-methyl purine atan early stage of the cell cycle causedan apparent "return-to-start" effectin which the cellsseemedto return to the starting point of a new cell cycle, with concurrentabortion of the cell cycle in process. (Received November 25, 1975; )     

Mixotrophic culture of Chlorella pyrenoidosa with olive-mill wastewater as the nutrient medium

With olive-mill wastewater (`alpechín') as the nutrient medium, theinfluence of specific rate of aeration and initial alpechín concentrationhave been analysed in cultures of Chlorella pyrenoidosa, exposed bothto continuous and intermittent illumination (12/12 h light/dark cycles). The stirring rate in the bioreactor, as well as pH and temperature werefixed previously at 180 rpm, 6.5 and 30 ^°C, respectively. Themaximum specific growth rate (_m) and biomass productivity(b) were determined as kinetic parameters. The chlorophyll, protein andcarbohydrate contents were evaluated, as well as the fatty-acid compositionof the lipid fraction. The experimental conditions most conducive to abalanced biomass composition with regard to proteins and lipids were: initial alpechín concentration of 10% (v/v), continuous illumination,and aeration rate of 1 L (litre cell suspension)^-1 min^-1. Under these conditions, the highest values of _m and b wereclose to 0.04 h^-1 and 1.4 10^-3 g L^-1 h^-1, respectively.     

硫和pH对蛋白核小球藻光照产氢的影响

在有无硫及pH5.0-8.0下对蛋白核小球藻(Chlorella pyrenoidosa)光照产氢的影响进行了研究。结果表明,在持续光照(165μmolm-2s-1)条件下,从有硫培养液(TAP培养液)内叶绿素a含量、Fv/Fm值及ΦPSII值的变化表明蛋白核小球藻在pH6.0-7.0时生长最佳,生长旺盛易形成暂时的无氧环境而利于藻产氢。最高的产氢速率和总产氢量出现在pH7.0,分别是0.10mlmg-1chlh-1和1.39ml。从无硫培养液(TAP-S培养液)内叶绿素a含量、Fv/Fm值及ΦPSII值的变化表明蛋白核小球藻生长明显受抑制,形成的无氧环境持久,故产氢持久,总产氢量比有硫培养液内高。蛋白核小球藻在pH5.5培养液内的Fv/Fm值后期高于其他4种pH值的,表明潜在的PSII光化学效率高,在光照条件下产氢电子主要来源于PSII,故pH5.5的无硫培养液内藻的产氢速率和总产氢量最大,分别是0.58mlmg-1chlh-1和10.98ml。说明pH为5.5的无硫培养液是蛋白核小球藻产氢的最佳条件。     

The Growth of Chlorella pyrenoidosa on Glycollate

The utilization of glycollate as a substrate for photoheterotrophicgrowth by a strain of Chlorella pyrenoidosa has been demonstrated.Glycollate stimulated growth of this alga in basal medium overthe pH range 4.0 to 8.0 in the light, but did not support growthin the dark. Stimulation of growth in the light occurred overa wide range of glycollate concentrations and was optimal at30 mM. Enzyme and inhibitor experiments suggested that the synthesisof cell constituents during growth on glycollate is achievedby the same pathway which operates during the metabolism ofexogenous glycollate by autotrophically-grown cells. For algaeto metabolize and grow on exogenous glycollate the cells mustbe readily permeable to this compound. When the cells readilytake up exogenous glycollate, the level of activity of enzymesin the cell, in particular glycollate:DCPIP oxidoreductase,may regulate the over-all rate of glycollate metabolism.     

Algicidal effect of bromine and chlorine on Chlorella pyrenoidosa

Chlorella pyrenoidosa was found to grow rapidly in tap water. Peak growth was reached after 2 to 3 days. Chlorine and bromine, added to such water, were shown to be effective inhibitors of algal growth. Bromine and bromamine were primarily algicidal, whereas chlorine and chloramines were mainly algistatic. It is assumed that the mechanisms of action of these halogens on Chlorella are not the same.     

超声波对铜绿微囊藻与蛋白核小球藻生理特征及竞争生长的影响

铜绿微囊藻是常见的水华蓝藻,常常在湖泊中与蛋白核小球藻共存或竞争生长。超声波可用于藻华即时治理,能够降低藻类生理活性,影响藻类生长,还可能改变藻类种间竞争关系。为了探究超声胁迫(35 kHz,0.035 W·cm^-3)对铜绿微囊藻与蛋白核小球藻的生理特征及种间竞争的影响,本研究设置纯藻组和1:1混合组(细胞浓度比)进行试验。结果表明: 铜绿微囊藻对超声胁迫更加敏感。超声处理600 s后,铜绿微囊藻的光合活性(F_v/F_m)和酯酶活性存在显著变化,纯藻组和混合组的F_v/F_m分别降低了51.8%和64.7%。而各组中蛋白核小球藻的光合活性变化较小。同时,铜绿微囊藻释放的荧光溶解性有机物(类色氨酸、类酪氨酸、类富里酸物质)含量多于蛋白核小球藻。两种藻的细胞浓度对超声波的响应也不同,蛋白核小球藻变化较小,而铜绿微囊藻的细胞浓度出现不同程度的下降。尤其是600 s超声处理大幅降低了混合组中铜绿微囊藻的细胞浓度(-42.6%),在超声胁迫解除后的8 d内蛋白核小球藻占优势,种间关系由铜绿微囊藻单边抑制蛋白核小球藻转变为两者互相抑制。在超声处理后,铜绿微囊藻的活性能够逐渐恢复,为了提高控藻效果的持久性,建议在一周后再次进行超声处理。     

Effects of Flashes of Red or Blue Light on the Composition of Starved Chlorella pyrenoidosa

Autotrophically grown cells of Chlorella pyrenoidosa (211-8b) were starved 3 to 4 days in darkness, flashes of blue light, or flashes of red light. The blue flashes were sufficient to maintain the maximal rate of light-stimulated oxygen uptake during short term experiments. However, after 24 hours, the respiration rate in red flashes was equal to, or greater than, the rate in blue flashes. Starvation in darkness reduced the chlorophyll content by 11%, altered the blue absorbance of the nonsaponifiable material only 1 to 2%, and reduced the dry weight by 13%. Starvation in the presence of blue or red flashes reduced the dry weight by an additional 11 or 12% respectively. Protein per unit cell volume was not changed significantly during 3 to 4 days starvation in darkness or in blue flashes, even though dry weight per unit cell volume decreased 13% in darkness and 23% in blue flashes. In contrast, cells starved under red flashes showed a 20% decrease in protein per unit cell volume and a 24% decrease in dry weight per unit cell volume.     

High CO2 partial pressure depresses productivity and bioenergetic growth yield of Chlorella pyrenoidosa culture

When low-CO₂ grown Chlorella pyrenoidosa (YSK strain) cells were exposed to high CO₂ partial pressures (pCO₂), the specific growth rate (μ) declined exponentially reaching a steady state value in about 20 h. A short interruption (up to 1 h) by temporarily lowering the pCO₂ did not prevent the continuous decline in μ when high pCO₂ was restored. In chemostate studies, light-limited cultures were supplied with 2 to 90 kPa of CO₂. The steady state biomass production rate and bioenergetic growth yield were related inversely to pCO₂ and the average energy uptake rate. The maintenance energy coefficient was, however, independent of dissolved pCO₂ in the pCO₂ range studied.     

Effects of Interspecific Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa on Their Growth and Physiology

Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa were analyzed by flow cytometry and by phytoplankton pulse‐amplitude‐modulated fluorimetry (Phyto‐PAM) in joint cultures as well as in cultures separated by dialysis membranes. Results showed that the growth of C. pyrenoidosa was greater than that of M. aeruginosa, and that the growth of M. aeruginosa but not the growth of C. pyrenoidosa was significantly inhibited by the interactions between M. aeruginosa and C. pyrenoidosa. Culture filtrates of these two algae showed no apparent effects on the growth of the competing species. For M. aeruginosa, decreases in esterase activity, chlorophyll a fluorescence, and maximum quantum yield were observed in joint cultures, indicating that the metabolic activity and photosynthetic capacity of M. aeruginosa were suppressed. Light limitation from the shading effect of C. pyrenoidosa may be the main reason for such inhibition. For C. pyrenoidosa, esterase activity was suppressed in membrane‐separated and joint cultures, suggesting that C. pyrenoidosa was probably affected by allelopathic substances secreted by M. aeruginosa. However, no significant difference was observed in the chlorophyll a fluorescence and maximum quantum yield of C. pyrenoidosa in the two cultures. In addition, interspecific interactions induced a reduction in size in both M. aeruginosa and C. pyrenoidosa, which may contribute to the development of C. pyrenoidosa dominance in the present study. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)