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On the investigated territory three species of the complex were identified, namely Paramecium biaurelia, P. triaurelia, and P. novaurelia. P. novaurelia dominated over the other species with regard to the number of clones established from nature as well as to habitats.
The present studies with application of classical strain crosses and RAPD-PCR analyses showed the existence of different genetic species (syngens) within Paramecium jenningsi. So far the existence of only one syngen has been accepted. It was found that strains from Saudi Arabia, India, and China compose one genetic species (syngen 1) and six strains from Japan compose second genetic species (syngen 2).
The presence of Paramecium sexaurelia (two strains) was recorded in the National Park "Krka" in Croatia. This is the first record of the species, rare in Europe, in Croatia.
New light and electron microscope data on the initial steps of endocytobiosis establishment between the ciliate Paramecium and specific intranuclear bacteria Holospora are provided. At the cytoplasmic step of infection bacteria of all Holospora species are found in a vesicle originating from the membrane of the host cell phagosome. The association between host cell microfilaments and the bacterium bearing vesicle may suggest a possible involvement of the ciliate cytoskeleton in the transportation of bacteria to the host cell nucleus. The authors subdivide the process of infection into 6 steps. Some strains of P. caudatum never take up infectious Holospora bacteria in the course of phagocytosis.
The presence of Paramecium dodecaurelia (three strains) was recorded in Hawaii.
Dynamics of structural changes of nucleoli, complex nucleolar aggregates and chromatin bodies in macronuclei (Ma) of ciliates Paramecium candatum and Bursaria truncatella under hypotonic conditions was studied. It was shown that after a 3 min hypotonic treatment nuclei swelled and became highly vacuolated. 3D-reconstruction showed that such nucleoli were formed by nucleolonema-like threads about 100-200 nm in thickness. Intranucleolar chromatin bodies decompacted, but remained bound with fibrillar component of the nucleolus by thin fibres about 10 nm thick. After 6 min hypotonic treatment the nucleolar material loosened and had a "gauze", or network-like appearence. After 10 min hypotonic treatment nucleoli dissociated completely. It was shown that a transition of chromatin bodies from completely compact to partially and fully decompacted state occurred cooperatively in different regions of Ma. In particular, chromatin bodies in the central part of complex nucleolar aggregates decompacted much faster than those in the Ma karyoplasm. It evidences for a specific, well-ordered chromatin organization in Ma. Prolonged hypotonic treatment led to a complete dissociation of Ma components; fibres 6-10 nm thick were solely observed in such preparations. Such fibres may represent remnant structures of the nuclear matrix. Dynamics of Ma chromatin bodies decompaction correlates well with that of chromomeres in the nuclei of higher eukaryotes. Our data confirm that chromatin 100-200 nm bodies in the ciliate Ma are analogues of chromomeres--looped discrete chromatin domains, observed in the nuclei of higher eukaryotes.
A method for the evaluation of Paramecium caudatum motility was proposed as a tool for the investigation of magnetobiological as well as other physical and chemical effects. The microscopically observed movement of paramecia is recorded and processed using a special software program. The protozoan motility is determined as a function of their mean velocity in a definite time. The main advantages of the method are that it is easily modified for determining various characteristics of the motor activity of paramecia and that the video data obtained can be reused.
Species of the Paramecium aurelia complex occurred in the studied regions of the Carpathians and the Sudetes Mts with varying frequency. P. novaurelia appeared most often, P. biaurelia occurred less frequently but was also very characteristic, both species prevailed over P. primaurelia. P. tetraurelia and P. triaurelia were very rare.
Host-parasite coevolution is often described as a process of reciprocal adaptation and counter adaptation, driven by frequency-dependent selection. This requires that different parasite genotypes perform differently on different host genotypes. Such genotype-by-genotype interactions arise if adaptation to one host (or parasite) genotype reduces performance on others. These direct costs of adaptation can maintain genetic polymorphism and generate geographic patterns of local host or parasite adaptation. Fixation of all-resistant (or all-infective) genotypes is further prevented if adaptation trades off with other host (or parasite) life-history traits. For the host, such indirect costs of resistance refer to reduced fitness of resistant genotypes in the absence of parasites. We studied (co)evolution in experimental microcosms of several clones of the freshwater protozoan Paramecium caudatum, infected with the bacterial parasite Holospora undulata. After two and a half years of culture, inoculation of evolved and naive (never exposed to the parasite) hosts with evolved and founder parasites revealed an increase in host resistance, but not in parasite infectivity. A cross-infection experiment showed significant host clone-by-parasite isolate interactions, and evolved hosts tended to be more resistant to their own (local) parasites than to parasites from other hosts. Compared to naive clones, evolved host clones had lower division rates in the absence of the parasite. Thus, our study indicates de novo evolution of host resistance, associated with both direct and indirect costs. This illustrates how interactions with parasites can lead to the genetic divergence of initially identical populations.
Uptake rates of a variety of 14C-labeled fatty acids and complex lipids by Paramecium tetraurelia during 48 h of log-phase growth varied. Fatty acid uptake was maximal during lag phase of growth when phagosome (food vacuole) formation was minimal. Food vacuole formation was shown to be suppressed by the presence of exogenous lipids and by starvation. The rates of uptake of lipids were significantly greater than those of small organic compounds such as amino acids, cyclitols, fatty acid precursors and metabolic intermediates. Significant amounts of radioactivity from 14C-labeled fatty acids were metabolized to 14CO2. The uptake rates of different saturated, straight-chain fatty acids of even carbon numbers were different and were not correlated with chain length, results suggesting that the primary mechanism for uptake of these compounds was neither by bulk transport nor simple diffusion and that carrier-mediated processes could possibly be involved.
Two soluble cAMP-dependent protein kinases were purified from the cytoplasm of Paramecium tetraurelia. Both kinases consisted of a 40-kDa catalytic subunit and a 44-kDa regulatory subunit. The two forms of the enzyme were separated by anion-exchange chromatography. Affinity chromatography on cAMP-Sepharose separated the regulatory subunit (retained by the column) from the cAMP-independent catalytic subunit (not retained). Four classes of monoclonal antibodies were generated. One class was specific for the catalytic subunit of both cAMP-dependent protein kinases, and three classes recognized the regulatory subunit of both forms of the enzyme. Subunits of 40 and 44 kDa were detected on immunoblots of purified cilia and of crude cell extracts. In addition, one class of antibodies specific for the regulatory subunit detected a ciliary protein with a molecular mass of 48 kDa. The monoclonal antibodies did not recognize type I or type II cAMP-dependent protein kinase from rabbit muscle nor did they cross-react with proteins from several unicellular eucaryotes, with one exception: antibodies specific for the catalytic subunit recognized a 40-kDa protein of Tetrahymena pyriformis.
We found that different polyamino compounds trigger the instantaneous and simultaneous release of trichocysts from Paramecium tetraurelia cells (monoxenically bacterized cultures), provided amino groups are spaced in intervals of approximately 1.0 nm; in this case even diamines or oligopeptides exert some trigger effect. The most potent trigger agent found was aminoethyldextran (AED, MW = 40 kDa) which was used mainly as a derivative with 40 -NH2/molecule. A maximal response (strain K401) was achieved at 1.38 X 10(-6) M, a half maximal response at 1.08 X 10(-6) M. AED acts by a dual effect, i.e., not only by statistically properly spaced amino groups but also by some additional effect of the dextran molecule, since this greatly enhances the effect of oligoamines, although it exerts no trigger effect per se. From a total of approximately 1120 or approximately 1230 trichocysts per cell (strain K401 or 7S) approximately 95% are releasable by AED. In these strains the number of non-releasable trichocysts corresponds closely to the number of undocked trichocysts floating in the cytoplasm, so that practically all trichocysts which are docked to the cell membrane, can be released. (We also analysed different mutant strains for their response to AED.) Massive trichocyst release does not impair cell viability or culture growth, and multiple release-redocking cycles can be performed; up to 5 trigger-docking cycles were tested with individual cells in 12 h intervals. AED-triggered exocytosis requires a free extracellular [Ca2+] of greater than or equal to 10(-5) M; it is inhibited by EGTA (ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate), by a short pH 5.5 shock or by neomycin at 10(-5) M concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
Several methods for the metabolic radiolabeling of proteins in axenically grown Paramecium tetraurelia were examined. Less than 5% of the initial radioactivity from exogenously supplied radiolabeled compounds was incorporated into cellular proteins under all conditions tested. The relatively low uptake rates of 14C-labeled amino acids and other small organic compounds by the cells and the subsequent metabolism of these molecules producing radioactive CO2 under conditions of rapid culture growth suggested that the transport of most or all of these compounds may be limited to bulk transport in solution and possibly accounted for by the volume transported by food vacuoles. Active transport of these molecules against a concentration gradient via carrier-mediated mechanisms was not apparent. The low rate of amino acid uptake explains the inefficient in vivo radiolabeling of cellular proteins by radioactive amino acids.
This review is the first on the composition and metabolism of Paramecium lipids. This ciliated protozoa is a useful system for studying the structure and function of biomembranes since it can be grown under chemically defined culture conditions in large numbers; much is known about its genetics, membrane electrophysiology, and ultrastructure; and mutants with defective membrane functions are available which are reported to have lipid alterations. Pure preparation of the cell surface ciliary membrane are readily isolated. The organism and its ciliary membrane contain a variety of polar lipids, sterols, and steryl esters. The polar lipids include substantial amounts of ether lipids, sphingolipids, and phosphonolipids. the biosyntheses of fatty acids and specific moieties of complex lipids in this organism are beginning to be examined with promises of elucidating biosynthetic mechanisms that are more difficult to study in other organisms. More information on lipid metabolism is required to identify the bases for the defects in putative lipid/membrane mutants.
In vivo labeling of Paramecium cells with 32Pi most heavily labels a minor 63-kDa protein that undergoes a rapid, Ca2+-dependent dephosphorylation when the cell is stimulated to release. This stimulus-sensitive phosphoprotein was isolated and purified to apparent homogeneity. A polyclonal affinity purified antibody made against the purified protein recognizes both the phosphorylated and dephosphorylated forms of the protein. The phosphorylated 63-kDa protein is found in the cytosolic fraction; it is slightly acidic with two isoelectric forms at pI 5.8 and 6.2 and probably exists as a monomeric 60-65-kDa polypeptide in the native state. The labeled phosphoamino acid of the protein is phosphoserine. The affinity purified antibody recognizes a third isoelectric form at pI 6.3 that appears unlabeled. The specificity of the antibody was confirmed by showing that it immunoprecipitates the correct protein, i.e. the stimulus-sensitive 63-kDa phosphoprotein. The availability of purified 63-kDa protein as well as an antibody against it will now allow molecular, biochemical, and immunocytochemical studies into the role of this protein in the mechanism of exocytosis.
We used aminoethyldextran (AED) as a secretagogue for the simultaneous exocytosis of a great proportion of secretory organelles (trichocysts) from Paramecium tetraurelia cells and we applied freeze-fracturing and ultrathin sectioning for a quantitative analysis of the re-arrangement of ultrastructural details within the cell membrane during re-insertion of new trichocysts. Characteristic arrangements of membrane-intercalated particles (MIPs) occur over trichocyst docking sites: 300 nm large double rings of MIPs and a MIP rosette in the middle. Empty sites, displaying a compressed ring ("parenthesis") without a rosette, are expanded to full size rings when a trichocyst is docked. We obtained a first hint on the possible existence of a short lived (approximately 5 min) adaptation stage, represented by rings without a rosette. This could mean that docking of a trichocyst would induce the assembly of rosette MIPs over a newly docked trichocyst. The reformation of rosettes is paralleled by an increasing number of extrudable trichocysts which underscores the causal role of rosette MIPs in exocytosis performance. New trichocysts are inserted at the old predetermined sites after removal of ghosts and formation of a "plug" as a receptor-type structure. The number of non-docked, free trichocysts in the cytoplasm is only slightly changed, indicating a continuous synthesis and docking rate (approximately 2-3 organelles per min). Since in strain 7S ghosts are removed within approximately 10 min and docking goes on over 9 h, there occur many empty docking sites in the time period in between, with a maximum of approximately 1 h after AED triggering, thus providing a unique situation for further experiments.
Cells of Paramecium caudatum were shock-frozen without pretreatment for cryoultramicrotomy and freeze-dried for subsequent X-ray microanalysis. Na, Mg, P, S, Cl, K, and Ca were detected in different amounts in several subcellular compartments. In particular, calcium was localized below the cell surface (pellicle). Trichocysts were found to contain significant amounts of Na in their base but not in the tip. Na, Mg, P, S, Cl, K, Ca were found in electron dense deposits within the lumen of the contractile vacuole. A small K concentration was found in the cytoplasm and in the mitochondria. X-ray microanalysis of the element distribution in different subcellular compartments provides information for the understanding of cellular functions such as exocytosis, locomotion, and ion regulation.
Internalization of cycloheptaamylose-dansyl chloride complex during surface labelling of living long-term starved Paramecium aurelia cells has been observed. This process may be inhibited by pretreatment of the ciliates with dichloroisoproterenol. Uptake of cycloheptaamylose-dansyl chloride may be visualized only after UV preirradiation: the appearance of orange-fluorescing vacuoles of diameter 2.3-4.5 micron may then be observed. Microspectrographic analysis performed on the cells and dansyl derivatives indicates that this fluorescence is produced by a photochemical reaction of dansyl chloride - released from CDC complex inside the digestive vacuoles-under the influence of UV irradiation.