Population growth kinetics and bulk membrane lipid alterations in Tetrahymena pyriformis: exposure to pentachlorophenol

This study describes effects of exposure of the freshwater ciliate Tetrahymena pyriformis to the "classic" weak acid respiratory uncoupler pentachlorophenol (PCP) on the population growth kinetics and membrane lipid profiles. The assessment of growth kinetics of naive populations exposed to PCP, at concentrations eliciting <50% growth inhibition, showed generation times of exposed cultures similar to generation times of controls but preceded by a short lag phase (<2 h). Assessment of exposed cultures exhibiting >50% growth inhibition revealed generation times that increased with increasing concentrations of toxicant. In addition, the relative percentages of selected fatty acid methyl esters (FAMEs) in both pellicle and mitochondrial membranes were examined. Upon exposure to PCP the relative percentages of FAMEs 12:0, 14:0, 16:0, 16:1, and 18:0 did not change. However, with exposure to PCP a decrease was observed for FAMEs 15:0 and 17:0. Conversely, with PCP exposure there was an increase in FAME 18:1. A comparison of these results with those elicited upon exposure to the model narcotic 1-octanol reveals marked differences in both growth kinetics and fatty acid shifts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phytate as the sole phosphate source for growth of Tetrahymena

Phytate, the storage form of phosphate in seeds and grains, is a major form of environmental phosphate loading from fertilizer inputs and agricultural runoff. We have investigated the ability of Tetrahymena populations to grow on phytate as their sole phosphate source. Populations grew equally well in chemically defined medium with phosphate and medium in which the phosphate was replaced with phytate in comparable concentrations between 0.5 mM and 6 mM. Intracellular phytate concentrations of cells grown in phytate showed a 4-6-fold increase over those grown in phosphate when measured during the late stage of exponential growth. These results demonstrate that phytate can provide a source of adequate phosphate for sustained growth in phytate-rich environments.     

Industrial media and fermentation processes for improved growth and protease production by Tetrahymena thermophila BIII

Tetrahymena thermophila was cultivated on industrial by-product media. The composition of the best medium (with milk proteins) was optimised by a central composite design for growth and protease secretion. The optimal combination [1.07% (w/v) of yeast extract and 0.99% (w/v) of skimmed milk] improved biomass production by 46%. In a fermentation strategy, the pH must be regulated to produce no cell damage, lengthening the stationary phase and resulting in a more abundant protease production. To increase cell concentration and protease secretion, a continuous culture with cell recycling by microfiltration was successfully tested on ciliated protozoa. Journal of Industrial Microbiology & Biotechnology (2000) 24, 285–290. Received 28 July 1999/ Accepted in revised form 20 January 2000     

Endocytosis and the adaptive acid hydrolases in Tetrahymena pyriformis GL

Endocytosis of yeast cells by Tetrahymena pyriformis GL for a period of 2.5 h produced changes in cellular acid hydrolases. Acid phosphatase, acid deoxyribonuclease and acid proteinase activities were markedly increased, whereas there was a decrease in acid ribonuclease activity and little change in -glucosidase activity. These alterations do not appear to be due to any alteration in the rates of secretion of these enzymes into the milieu. Evidence is presented that the cellular enzyme increases found upon endocytosis of yeast reflect changes in lysosomal enzymes, because it was shown that the acid phosphatase activity increase resulted in an increased amount of latent enzyme within the cell. The results also support the idea that there are at least 3 distinct populations of lysosomes, in addition to phagolysosomes, present in Tetrahymena pyriformis GL, with different modes of formation. There appears to be a large excess of lysosomes, uncombined with phagosomes, present in these fed cells since latency averaged 66% in broken-cell preparations which contained very few intact phagolysosomes. The phagolysosomal acid phophatase activity cannot account for more than 34% of that present in the cell. The endocytosis of yeast in the presence of growth medium resulted in a marked drop in the rate of cell division as compared to cells growing in the growth medium alone. The results are discussed.     

Automated image analysis to improve bead ingestion toxicity test counts in the protozoan Tetrahymena pyriformis

AIMS: To improve bead ingestion counts in Tetrahymena pyriformis by automated image analysis as an alternative to direct-counts. METHODS AND RESULTS: Fluorescent latex beads were added to T. pyriformis cultures for ingestion tests. The number of beads ingested by 25 cells was counted directly by epifluorescence microscopy and compared with similar data from image analysis. anova indicated that counts were not significantly different (P < 0.05). The image analysis particularly provided advantages in terms of speed. CONCLUSIONS: The image analysis is superior to direct beads counting in T. pyriformis particularly in terms of speed of analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: The image analysis method is very rapid and will allow many more toxicological analyses to be undertaken with less operator error.     

Survival for specific life intervals of smallmouth bass, Micropterus dolomieu, during parental care

We tested whether daily mortality rates (DMR) of smallmouth bass offspring were influenced by life interval, offspring density and growth, parental male attributes, and selected mortality factors during parental care in a regulated Virginia stream. Mortality averaged 9.5% per day (range 5.2–13.9%) and 94.1% total (range 80.9–99.5%) from egg deposition to the juvenile period (29–36 d) for individual broods. Offspring losses were primarily attributed to fungus (Saprolegnia parasitica) infection of eggs and to American eel, Anguilla rostrata, predation. DMR were significantly higher for the interval from swim-up of larvae to metamorphosis relative to earlier and later intervals. There was no significant autocorrelation of DMR among life intervals for individual broods, indicating that relative mortality rates were inconsistent among broods through time. DMR were also uncorrelated with the number of offspring per brood, offspring growth rates, and parental male attributes, except during egg and embryo intervals. Daily egg mortality was negatively related to male size and positively related to the number of eggs per nest, suggesting that density-dependent egg mortality may have been partially offset in nests of larger males. Larger males received more eggs, tended to maintain larger broods throughout parental care, and contributed a high proportion of the total number of juveniles reared. This revised version was published online in August 2006 with corrections to the Cover Date.     

细胞松弛素对嗜热四膜虫皮层细胞骨架蛋白的影响

测定了细胞松弛素B对嗜热四膜虫RF1株和BF5在生殖接合期的皮层骨架蛋白,尤其是在接合子接合膜形成和原核交换阶段影响甚大。作者发现VB处理后,与对照组相比较,皮层骨架蛋白146KD消失,27KD,43KD,47KD和174KD含量下降,32KD,41KD,51KD和54KD保持不变,结果显示,松弛素B对微纤毛蛋白27KD、43KD、47KD、146KD和174KD有影响。     

KIN‐BASED RECOGNITION AND SOCIAL AGGREGATION IN A CILIATE

Aggregative groups entail costs that must be overcome for the evolution of complex social interactions. Understanding the mechanisms that allow aggregations to form and restrict costs of cheating can provide a resolution to the instability of social evolution. Aggregation in Tetrahymena thermophila is associated with costs of reduced growth and benefits of improved survival through “growth factor” exchange. We investigated what mechanisms contribute to stable cooperative aggregation in the face of potential exploitation by less‐cooperative lines using experimental microcosms. We found that kin recognition modulates aggregative behavior to exclude cheaters from social interactions. Long‐distance kin recognition across patches modulates social structure by allowing recruitment of kin in aggregative lines and repulsion in asocial lines. Although previous studies have shown a clear benefit to social aggregation at low population densities, we found that social aggregation has very different effects at higher densities. Lower growth rates are a cost of aggregation, but also present potential benefits when restricted to kin aggregations: slow growth and crowd tolerance allow aggregations to form and permit longer persistence on ephemeral resources. Thus in highly dynamic metapopulations, kin recognition plays an important role in the formation and stability of social groups that increase persistence through cooperative consumptive restraint.     

Molecular identification of Tetrahymena species

Mitochondrial cox1 689 bp barcodes are routinely used for identification of Tetrahymena species. Here, we examine whether two shorter nuclear sequences, the 5.8S rRNA gene region and the intergenic region between H3 and H4 histone genes, might also be useful either singly or in combination with each other or cox1. We obtained sequences from ~300 wild isolates deposited at the Tetrahymena Stock Center and analyzed additional sequences obtained from GenBank. The 5.8S rRNA gene and portions of its transcribed flanks identify isolates as to their major clade and uniquely identify some, but not all, species. The ~330 bp H3/H4 intergenic region possesses low intraspecific variability and is unique for most species. However, it fails to distinguish between two pairs of common species and their rarer counterparts, and its use is complicated by the presence of duplicate genes in some species. The results show that while the cox1 sequence is the best single marker for Tetrahymena species identification, 5.8S rRNA, and the H3/H4 intergenic regions sequences are useful, singly or in combination, to confirm cox1 species assignments or as part of a preliminary survey of newly collected Tetrahymena. From our newly collected isolates, the results extend the biogeographical range of T. shanghaiensis and T. malaccensis and identify a new species, Tetrahymena arleneae n. sp. herein described.     

An Ultrastructural Investigation of 180°-Rotated Ciliary Meridians in Tetrahymena pyriformis*

SYNOPSIS. An ultrastructural investigation has been carried out on 180°-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (mol^b/mol^b), syngen 1, strain B. The longitudinal, transverse and postciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180° angle to their normal positions or orientations. Other abnormalities are as folows: the first 2 basal bodies of the inverted meridian fail to organize into “couplets” and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines.