Induction of a Metallothionein-like Protein in Tetrahymena pyriformis by Metal Ions

Trametes hirsuta produced cellulose-degrading enzymes when it was grown in a cellulosic medium such as Avicel or wheat bran. An endo-β-1,4-glucanase (ThEG) was purified from the culture filtrate, and the gene and the cDNA were isolated. The gene consisted of an open reading frame encoding 384 amino acids, interrupted by 11 introns. The whole sequence showed high homology with that of family 5 glycoside hydrolase. The properties of the recombinant enzyme (rEG) in Aspergillus oryzae were compared with those of the En-1 from Irpex lacteus, which showed the highest homology among all the endoglucanases reported. The rEG activity against Avicel was about 8 times higher than that of En-1 when based on CMC degradation. A remarkable structural difference between the two enzymes was the length of the linker connecting the cellulose-binding domain to the catalytic domain.     

Effects of Calcium Ion on Growth and Behavior of Tetrahymena pyriformis

The chelator GEDTA was used to show that Ca²⁺ is required for the growth of Tetrahymena pyriformis strain W and for normal galvanotactic responses and swimming.     

Some Effects of Chloramphenicol and Ethidium Bromide on Tetrahymena pyriformis

SYNOPSIS. Very similar results are obtained by the addition of 300 μg/ml chloramphenicol or of 15 μg/ml ethidium bromide to cultures of Tetrahymena pyriformis strain ST. In such cultures the exponential growth rates and the yields are reduced. Unlike the untreated ciliates, which retain the pyriform shape throughout the exponential and stationary phases, those exposed to either of the drugs become more spherical. In the control organisms progressively less surface area/unit of cell volume is exposed to the environment during the growth cycle; in the drug-treated ciliates this pattern is reversed. Increased endogenous respiration, reduced specific activities of states 3 and 4, and reduction in the levels of cytochromes a, a₃, b , and c + c ₁ are found in mitochondria from ciliates exposed to chloramphenicol and ethidium bromide.     

Nonadaptive Growth Responses of Tetrahymena pyriformis Grown on Single Bacterial Species*

SYNOPSIS. Turbidity changes caused by ingestion of bacterial cell suspensions by Tetrahymena pyriformis W were used to measure feeding capabilities. Tetrahymena was grown on washed killed cells of Aerobacter aerogenes, Azotobacter agile, Arthrobacter sp., Bacillus megaterium, Mycobacterium lacticola, Pseudomonas fragi, Sarcinia lutea, Serratia marcescens, and Thiobacillus thioparus for 6 months with serial transfers. After this time the rate of feeding on each bacterium gave no indication of an adaptation to the food bacterium.     

Monotertiarybutylhydroquinone effects on Tetrahymena pyriformis.

The molecular toxicity of monotertiarybutylhydroquionone (TBHQ) was studied using $\text{Tetrahymena}$$\text{pyriformis}$ as a model cell system. TBHQ at 26 ppm in the media inhibited cell growth by 50%. TBHQ inhibited the oxidation of ¹⁴C-acetate to ¹⁴CO₂. In addition, increasing concentrations of TBHQ decreased the incorporation of ¹⁴C-acetate into lipids and protein, ¹⁴C-amino acids into protein, ³H-uridine into RNA and ³H-thymidine into DNA. The incorporation of ¹⁴C-acetate into glycogen increased with concentrations up to 20 ppm TBHQ in the media while glycogen synthesis decreased with 40 ppm TBHQ.     

金属离子对氧化硫硫杆菌生长及产酸的影响

目的:在前期研究中选育出的氧化硫硫杆菌TT03,为了解其对各种金属离子的适应能力而进行了试验.方法:在史塔克培养基中添加规定量的各种金属离子,接种TT03后进行摇动培养,测定培养液中的产酸以代表其实际生长状况.结果:在Co<'3+>、Zn2+为100mg/L而其他微量元素为1000mg/L时没有产生抑制作用,其中有些微量元素还表现出促进作用;除pb2+、Cd2+以外,重金属在1000mg/L下普遍表现出轻微的抑制作用,对产酸没有明显影响;当pb2+、Cd2+的含量分别在10mg/L、1mg/L时,对TT03产酸没有影响.在试验的金属离子中Cd2+对TT03产酸的抑制作用最强,在浓度30mg/L时,生长产酸被完全抑制.结论:在正常土壤环境中的金属离子含量,不会对氧化硫硫杆菌TT03的生长和产酸造成致命影响.     

Isocitrate dehydrogenase of Tetrahymena pyriformis

Summary We have studied the isocitrate dehydrogenase ofTetrahymena pyriformis. This enzyme is able to utilize both NAD and NADP, but kinetic studies suggest that the enzymatic activity with NAD is not of physiological significance.Some of the factors that might regulate the NADP-dependent isocitrate dehydrogenase were also studied. This enzyme has an absolute requirement for divalent cations; Mg²⁺ and Mn²⁺ will serve as cofactors but the latter is more effective than the former.It is known that this enzyme is subject to a concerted inhibition by oxaloacetate and glyoxylate. Either glyoxylate or oxaloacetate alone also are capable of inhibiting the enzyme although higher concentrations are required. We have found concerted inhibition also for the NAD-dependent isocitrate dehydrogenase from rat liver and yeast. The activity of theTetrahymena pyriformis enzyme is inhibited by NADPH. This inhibition is competitive with NADP. The Ki and Km values are, respectively, 23µm and 18µm.     

Temperature Effects on Maturity Periods in Tetrahymena pyriformis Syngen 1*

Cells of Tetrahymena pyriformis syngen 1 grown at 30 C after conjugation achieve sexual maturity more quickly than do cells grown at 19 C, whether time is measured in numbers of cell divisions or in terms of absolute time. This result is achieved regardless of the temperature at which conjugation and nuclear reorganization occur. These observations differ from those of other workers investigating Paramecium, and suggest that the long term “chronometer” is more tightly coupled to cell division in Paramecium multimicronucleatum and Paramecium caudatum than in Tetrahymena pyriformis.     

Effects of AGEPC on the intracellular levels of ions in Tetrahymena pyriformis

1-0-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine(Platelet Activating Factor) is a very potent stimulator of Ca2+ influx into the cells of Tetrahymena pyriformis; increases the levels of bound and free intracellular Ca2+ and this effect is time- and dose-dependent. Also AGEPC enhances the Na+ influx into the cells, while has no effect on the intracellular levels of K+ and on the packed cell volume. The effects of AGEPC on intracellular Ca2+ and Na+ are completely inhibited by verapamil which also inhibits the Ca2+ influx observed in the control, but has not any effect on the Na+ uptake observed in the control. These results provide evidence that the effect of AGEPC on Na+ influx, depends on its effect on free intracellular Ca2+. The non acetylated derivative of AGEPC, lyso-GEPC has no effect on all the studied parameters.     

Sublethal Cytotoxic Effects of Mercuric Chloride on the Ciliate Tetrahymena pyriformis*

SYNOPSIS. The behavior and ultrastructure of Tetrahymena pyriformis was assessed after exposure to dosages of 8 and 16% of the lethal concentration of HgCl² (TLm 96 hr). The lower dosage caused no abnormal changes in cell motility, activity of the water explusion vesicles, or cell shape; the higher dosage caused deleterious changes in these parameters. The higher sublethal HgCl² concentration (0.50 mg/liter) elicited damage of several cell structures. This damage persisted and accumulated with time up to 24 hr. At the lower HgCl² dosage (0.25 mg liter) there were extensive changes after 1-hr exposure involving primarily mitochondria; however, all major changes were repaired after 24 hr of constant exposure to the HgCl², indicating adaptation to the toxicant. Based solely on cytotoxic evidence an attempt is made to apply the findings defining what constitutes a “safe'’concentration of HgCl₂ in the cell's environment.     

Effects of oxidative and nitrosative stress on Tetrahymena pyriformis glyceraldehyde-3-phosphate dehydrogenase

Previous reports showed that hydrogen peroxide and the NO-generating reagent sodium nitroprusside (SNP)-modulated enzymatic activity of animal glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12). These modifications are suggested to have a physiological regulatory role. To gain further insight into this regulatory process the model ciliated protozoan Tetrahymena pyriformis was chosen. Both reagents inhibited growth of T. pyriformis cultures and produced a specific increase of GAPDH protein but only NO seemed to reduce GAPDH activity in cell-free extracts. Both specific activity and pI were found to be altered in the in vivo NO-treated purified enzyme, but no effect was detected by the in vivo H(2)O(2) treatment. Analytical chromatofocusing showed a single basic isoform (pI 8.8) in enzyme preparations from control and H(2)O(2)-treated cells. In contrast to this, three more acidic isoforms (pIs, 8.6, 8.0 and 7.3) were resolved in purified fractions from SNP-treated cells, suggesting post-translational modification of the enzyme by NO. Nevertheless, a decrease of GAPDH activity by H(2)O(2) and NO, mainly due to a decrease in its V(max) without apparent change in substrate affinity, was observed in vitro in the whole enzyme population. The increase of GAPDH protein level found in vivo suggests a cell response in order to compensate for the inhibitory effect on activity observed in the purified enzyme. This is the first report of NO- and H(2)O(2)-dependent effects on GAPDH of T. pyriformis, and identifies this key protein of central carbon metabolism as a physiological target of oxidative and nitrosative stress in this ciliated protozoan.