Hyper-production and Characterization of the ι-Carrageenase Useful for ι-Carrageenan Oligosaccharide Production from a Deep-sea Bacterium, <Emphasis Type="Italic">Microbulbifer thermotolerans</Emphasis> JAMB-A94<Superscript>T</Superscript>, and Insight into the Unusual Catalytic Mechanism

A gene of unknown function from the genome of the agar-degrading deep-sea bacterium Microbulbifer thermotolerans JAMB-A94^T was functionally identified as a ι-carrageenase gene. This gene, designated as cgiA, is located together with two β-agarase genes, agaA and agaO in a cluster. The cgiA gene product is 569 amino acids and shares 29% identity over 185 amino acids with the ι-carrageenase from Zobellia galactanivorans Dsij DSM 12802. Recombinant, cgiA-encoded ι-carrageenase (55 kDa) was hyper-produced in Bacillus subtilis. The recombinant enzyme shows maximal activity at 50°C, the highest reported optimal temperature for a carrageenase. It cleaved β-1,4 linkages in ι-carrageenan to produce a high ratio of ι-carrageenan tetramer, more than 75% of the total product, and did not cleave the β-1,4 linkages in κ- or λ-carrageenan. Therefore, this enzyme may be useful for industrial production of ι-carrageenan oligosaccharides, which have demonstrated antiviral potential against diverse viruses. Furthermore, we performed site-directed mutagenesis on the gene to identify the catalytic amino acid residues. We demonstrated that a conserved Glu351 was essential for catalysis; however, this enzyme lacked a catalytic Asp residue, which is generally critical for the catalytic activity of most glycoside hydrolases.     

Purification and characterization of κ-carrageenase from a novel γ-proteobacterium,<Emphasis Type="Italic">Pseudomonas elongata</Emphasis> (MTCC 5261) syn.<Emphasis Type="Italic">Microbulbifer elongatus</Emphasis> comb. Nov.

The phenotypic and carrageenolytic features of a novel halo tolerant marine bacterium, isolated from decayed red algal samples collected along the west coast of India were studied. This gram-negative strain was identified asPseudomonas elongala (MTCC 5261) syn.Microbulbifer elongalus comb. nov according to its morphological, physiological and molecular characterization. The extracellular κ-carrageenase was purified 106.54-fold by a combination of ammonium sulfate precipitation (40∼60%) and successive gel filtration chromatography. The purified protein fraction yielded significantly high activity of 426.19 units/mg protein and migrated as a single band on a sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular weight of ∼128 kDa. For κ-carrageenase activity, optimum temperature was 40°C whereas two pH optimai.e. 5.6 and 7.7 were observed. For κ-carrageenan, the enzyme gave aK _m value of 6.66 mg/mL and aV _max value of 4 μmol/min/mg when the reaction was carried out at 40°C and pH 5.6. Isolated κ-carrageenase could successfully generate protoplasts ofKappaphycus alvarezii. This is the first report on the production of κ-carrageenase by this bacterium isolated from west coast of India. Molecular mass and various characteristics showed that the carrageenase fromP. elongata was much different from those previously reported.     

Use of enzymatic cell wall degradation for improvement of protein extraction from Chondrus crispus,Gracilaria verrucosa and Palmaria palmata

The effect of polysaccharidases (κ-carrageenase, β-agarase, xylanase, cellulase) on the protein extraction from three rhodophytes has been studied. The kinetic parameters (apparent V _m, apparent K _m) and the optimum activity conditions (pH, temperature) of each enzyme were determined by using pure substrates. All the tested enzymes possess Michaelis Menten mechanism with estimated substrate saturating concentrations of 8 000 mg l⁻¹(carrageenan) for κ-carrageenase, 8 000 mg l⁻¹ (agar) for β-agarase, 5000 mg l⁻¹ (xylane) for β-xylanase and 6 000 mg l⁻¹ (carboxymethylcellulose) for cellulase. The optimum activity conditions are pH 6.5–6.8 at 45°C for carrageenase, pH 6–6.5 at 55°C for agarase, pH 5 at 55°C for xylanase and pH 3.8 at 50°C for cellulose. Different alga/enzymes couples (κ-carrageenase/Chondrus crispus, β-agarase/Gracilaria verrucosa, β-xylanase/Palmaria palmata) were tested under the optimum activity conditions. Alga/cellulase + specific enzyme (e.g. Chondrus crispus/carrageenase + cellulase) systems were also studied at the optimum activity conditions of a specific enzyme (e.g. carageenase). The use of the only cellulose was also tested on each alga. Except for Palmaria palmata, the highest protein yields were observed with the procedures using cellulase coupled with carrageenase or agarase for an incubation period limited to 2 h. The Chondrus crispus/carrageenase + cellulose and Gracilaria verrucosa/agarase + cellulase systems gave ten-fold and three-fold improvements, respectively, in protein extraction yield as compared to the enzyme-free blank procedure. The combined action of xylanase and cellulose on protein extraction from Palmaria palmata does not significantly improve protein yield. The best overall protein yield for P. palmata is for P. palmata/xylanase with a 14-h incubation time. This study shows the interest in the use of a polysaccharidase mixture for improving protein extractibility from certain rhodophytes. This biotechnology approach, adapted from procedures for protoplast production or enzymatic liquefaction of higher plants, could be tested as an alternative method to obtain proteins from seaweeds of nutritional interest.     

A κ-carrageenase from a newly isolated pseudoalteromonas-like bacterium, WZUC10

A bacterial strain able to produce κ-carrageenase, designated WZUC10, was isolated from a live specimen of the red alga Plocamium telfainae collected in the East China Sea. The phylogenetic evidence and phenotypic features indicate that this strain belongs to the genus Pseudoalteromonas. WZUC10 requires NaCl for growth and κ-carrageenan to induce κ-carrageenase synthesis; galactose and lactose do not induce it. The optimal growth temperature is 23∼27°C. The secreted enzyme, which has a molecular mass of 45 kDa, breaks down κ-carrageenan into κ-neocarratetraose sulfate and larger oligosaccharides with a repeating β-D-Galp4S-(1→4)-α-D-AnGalp structure, but cannot degrade κ-neocarratetraose sulfate or κ-neocarrahexaose sulfate into κ-neocarrabiose sulfate. The enzyme retains 90% of its activity after 2 h at 40°C and is completely inactivated after 7.5 min at 70°C. The enzyme’s optimal temperature is 30°C and its optimal pH is 7.5. The enzyme-catalyzed reaction follows Michaelis-Menten kinetics, with the Michaelis constant (K _m) and the turnover number (k) being 0.015 mM and 125 s⁻¹, respectively. WZUC10 produces 50 U/mL κ-carrageenase after cultivation at 25°C for 35 h on a medium containing 80 g/L glucose, 5 g/L corn steep liquor, 3 g/L κ-carrageenan, and 15 g/L NaCl. κ-Neocarratetraose sulfate was prepared simply with precipitation by ethanol:water (5:1, v/v).     

Carrageenans from Cystocarpic and Sterile Plants of Chondrus Pinnulatus (Gigartinaceae, Rhodophyta) Collected from the Russian Pacific Coast

The chemical structure, gel properties and biological activity of the carrageenans isolated from cystocarpic and sterile plants of Chondrus pinnulatus were investigated. The total carrageenan content of the sterile plant was observed to be twice that of the cystocarpic plants. According to data obtained by ¹³C-NMR and FT IR, the gelling polysaccharides from cystocarpic and sterile plants of C. pinulatus have similar structures and were identified as κ/ι-carrageenans. The difference between these polysaccharides was in the ratio of the κ- and ι-segments, with a predominant content of κ-segments in cystocarpic plants (80%). Moreover, KCl-insoluble fractions possibly contain hetero-disperse μ/ν precursor: amounts of this in the polysaccharide from sterile plants were more than that extracted from the cystocarpic plants. The KCl-soluble fractions (non gelling) were λ-carrageenans with another carrageenan type that had a low amount of 3,6-anhydrogalactose. Carrageenans from cystocarpic stages showed good gelling properties, whereas those from sterile plants formed a very weak gel. Structural differences and molecular weight of carrageenans obviously determine the biological activity of the polysaccharides. Non gelling-carrageenans from both types of ιt C. pinnulatus plants showed high macrophage-phosphatase activity and κ/ι-carrageenan from cystocarpic plant possessed a potent anti-coagulant activity, which was extremely strong in a low concentration of 100 μg ml⁻¹.     

Purification and characterization of a thermostable λ-carrageenase from a hot spring bacterium,Bacillus sp.

Purpose of work The purpose of this study is to report a thermostable λ-carrageenase that can degrade λ-carrageenan yielding neo-λ-carrabiose at 75 °C. A thermophilic strain Lc50-1 producing λ-carrageenase was isolated from a hot spring in Indonesia and identified as a Bacillus sp. The λ-carrageenase, Cga-L50, with an apparent molecular weight of 37 kDa and a specific activity of 105 U/mg was purified from the culture supernatant. The optimum pH and temperature of Cga-L50 were 8.0 and 75 °C, respectively. The enzyme was stable from pH 6–9 and retained ~50 % activity after holding at 85 °C for 10 min. Significant activation of Cga-L50 was observed with K⁺, Ca²⁺, Co²⁺, and Na⁺; whereas, the enzyme activity was inhibited by Sr²⁺, Mn²⁺, Fe²⁺, Cu²⁺,Cd²⁺, Mg²⁺, and EDTA. Cga-L50 is an endo-type λ-carrageenase that hydrolyzes β-1,4-linkages of λ-carrageenan, yielding neo-λ-carrabiose as the main product. This study is the first to present evidence of thermostable λ-carrageenase from hot spring bacteria.     

Controlling Carrageenan Structure Using a Novel Formylglycine-Dependent Sulfatase, an Endo-4S-iota-Carrageenan Sulfatase

Carrageenans are sulfated polysaccharides that are found in the cell walls of red algae. These polysaccharides have gelling and texturizing properties that are widely appreciated in industrial applications. However, these functional properties depend strongly on the sulfation of the moieties of the carrabiose repetition unit. Here we aimed to monitor the sulfate composition of gelling carrageenan. To do so, we screened and purified from Pseudoalteromonas atlantica a 4S-iota carrageenan sulfatase that converts ι-carrabiose into α-carrabiose units. The sequence of this protein matched the annotated Q15XH3 (Uniprot databank) formylglycine-dependent sulfatase found in the P. atlantica genome. With pure enzyme, ι-carrageenan could be transformed into a hybrid ι-/α-carrageenan or pure α-carrageenan. Analysis of the distribution of the carrabiose moieties in hybrid carrageenan chain using enzymatic degradation with Alteromonas fortis ι-carrageenase, coupled with chromatography and NMR spectroscopy experiments, showed that the sulfatase has an endo mode of action. The endo-character and the specificity of the sulfatase made it possible to prepare hybrid κ-/ι-/α-carrageenan and κ-/α-carrageenan starting from κ-/ι-carrageenan.     

Enzymatic degradation of hybrid ι-/ν-carrageenan by Alteromonas fortis ι-carrageenase

Hybrid ι-/ν-carrageenan was water-extracted from Eucheuma denticulatum and incubated with Alteromonas fortis ι-carrageenase. The degradation products were then separated by anion-exchange chromatography. The three most abundant fractions of hybrid ι-/ν-carrageenan oligosaccharides were purified and their structures were analyzed by NMR. The smallest hybrid was an octasaccharide with a ι-ι-ν-ι structure. The second fraction was composed of two decasaccharides with ι-ι-ι-ν-ι and ι-[ι/ν]-ι-ι structures. The third fraction was a mixture of dodecasaccharides which contained at least a ι-ι-ι-ι-ν-ι oligosaccharide. The carbon and proton NMR spectra of the octasaccharides were completely assigned, thereby completely attributing the ν-carrabiose moiety for the first time.     

Intradiurnal periodicity of fungal spore concentrations (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) in Cracow, Poland

Aerobiological monitoring enables the definition of seasonal fungal spore concentrations and also intradiurnal time when the highest concentrations of spores could cause or increase allergy symptoms. These data are useful to estimate symptoms of disease, duration of infection and how advanced the illness is in people suffering from fungal allergens. The aim of the study was to compare the concentrations of fungal spores (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) during dry and rainy periods and to analyse their intradiurnal changes. Average daily spore concentrations in dry and rainy periods were compared, using z test, separately for each taxon, season and for a combined 3-year period. Intradiurnal periodicity of fungal spore concentrations was analysed on the basis of three complementary diagrams. These spore concentrations were presented using three curves for all, dry and rainy days in 1997–1999 (April–November). The spore percentage in particular hours was normalized in relation to the daily spore sum accepted as 100%. Two further diagrams enabled the more precise analysis of the highest concentrations in dry days. Daily Botrytis and Cladosporium spore concentrations did not show significant differences between dry and rainy periods. In the case of Didymella and Ganoderma spore concentrations, there were no significant differences between both weather types in the single years, although there was a significant difference when a 3-year period was considered. The differences between daily concentrations of Alternaria spores in dry and rainy periods occurred in 1997 and in a 3-year period. Intradiurnal periodicity of spore concentrations was different for ‘dry’ and ‘wet’ fungal spores. Dry spores are released from the spore-producing parts of the fungus under conditions of decreasing humidity and increasing airflow. Examples of dry spores are those from Alternaria, Cladosporium and Botrytis. Wet spores, such as those from many Ascomycetes (Didymella) and Basidiomycetes (Ganoderma), are released into the atmosphere by processes related to humidity conditions or rain. The highest concentrations of ‘dry’ spores were observed early in the afternoon, while highest values of ‘wet’ spore concentrations occurred in the predawn hours. Statistically non-significant differences between daily spore concentrations in dry and rainy periods of single seasons were found except for Alternaria. Statistically significant differences could occur when the studied period was longer than one season (Alternaria, Didymella, Ganoderma). The highest concentrations of Alternaria, Botrytis and Cladosporium spores were recorded at noon and early in the afternoon. Concentrations of Didymella and Ganoderma spores were highest in the predawn hours.     

Time course solutions of the Sax-Markov binary eurejoining/misrejoining model of DNA double-strand breaks

The Sax-Markov binary eurejoining/misrejoining (SMBE) model is a stochastic representation of Sax’s breakage-and-reunion mechanism of misrejoining DNA double-strand breaks (DSBs). In this model, to approximate DSB misrejoining probabilities that decrease with increasing distance, the nucleus is treated as a collection ofη isolated nuclear subvolumes called sites; DSB free ends within the same site interact with a probability that is independent of distance, and DSB free ends within different sites never interact. In our previous work, SMBE steady-state solutions were used to estimateη from a combination of high-dose PFGE (pulsed-field gel electrophoresis) data and moderate-dose chromosomal aberration data. Here, analytic SMBE transient solutions (i.e., time courses of DSBs and misrejoinings) are derived and used to estimateη from various sets of misrejoining DSB kinetic data. The time courses are multiexponentials with rate constantsκ, 6κ, 15κ, ... j(2j–1)κ corresponding to different nuclear site states and not different types of DSBs. For example, theκ component corresponds to nuclear sites with two DSB free ends and thus only one possible rejoining interaction, and the 6κ component corresponds to sites with four DSB free ends and thus six (four choose two) potential rejoining interactions – four of these six potential interactions lead to a final state of two misrejoinings and the other two of six lead to a final state of correct repair (unrejoinable DSBs are not represented in the SMBE model). The SMBE time course solutions provide site number estimates that fall in the range ofη≈10–100 for premature chromosome condensation (PCC) data andη≈1000 for PFGE data. Received: 23 December 1999 / Accepted: 1 July 2000     

Cloning and expression of the Apa LI, Nsp I, Nsp HI, Sac I, Sca I, and Sap I restriction-modification systems in Escherichia coli

The genes encoding the ApaLI (5′-G^TGCAC-3′), NspI (5′-RCATG^Y-3′), NspHI (5′-RCATG^Y-3′), SacI (5′-GAGCT^C-3′), SapI (5′-GCTCTTCN1^-3′, 5′-^N4GAAGAGC-3′) and ScaI (5′-AGT^ACT-3′) restriction-modification systems have been cloned in E.␣coli. Amino acid sequence comparison of M.ApaLI, M.NspI, M.NspHI, and M.SacI with known methylases indicated that they contain the ten conserved motifs characteristic of C5 cytosine methylases. NspI and NspHI restriction-modification systems are highly homologous in amino acid sequence. The C-termini of the NspI and NlaIII (5′-CATG-3′) restriction endonucleases share significant similarity. 5mC modification of the internal C in a SacI site renders it resistant to SacI digestion. External 5mC modification of a SacI site has no effect on SacI digestion. N4mC modification of the second base in the sequence 5′-GCTCTTC-3′ blocks SapI digestion. N4mC modification of the other cytosines in the SapI site does not affect SapI digestion. N4mC modification of ScaI site blocks ScaI digetion. A DNA invertase homolog was found adjacent to the ApaLI restriction-modification system. A DNA transposase subunit homolog was found upstream of the SapI restriction endonuclease gene. Received: 15 April 1998 / Accepted: 3 August 1998     

Immunolocalization of Lacrimal Gland PKC Isoforms. Effect of Phorbol Esters and Cholinergic Agonists on Their Cellular Distribution

In previous studies, we showed that lacrimal gland acini express three isoforms of protein kinase C (PKC): PKCα,-δ, and -ε. In the present study, we report the identification of two other PKC isoforms, namely PKCμ and -ι/λ. Using immunofluorescence techniques, we showed that these isoforms are differentially located. PKCα and -μ showed the most prominent membrane localization, whereas PKCδ, -ε and -ι/λ were mainly cytosolic. Using cell fractionation and western blotting techniques, we showed that the phorbol ester, phorbol 12, 13-dibutyrate (PdBu, 10⁻⁶ m), translocated all PKC isoforms, except PKCι/λ, from the soluble fraction into the particulate fraction. The effect was maximum at 5 min and persisted at 10 min. PKCε was the most responsive to PdBu reaching almost maximal translocation at a PdBu concentration as low as 10⁻⁹ m. The cholinergic agonist, carbachol (10⁻⁵ and 10⁻³ m), induced translocation which was transient for PKCδ, and -μ, but persisted for 10 min for PKCε. Carbachol did not translocate PKCα and, like PdBu, did not translocate PKCι/λ. We concluded that lacrimal gland PKC isoforms are differentially localized and that they translocate differentially in response to phorbol esters and cholinergic agonists. Received: 25 June 1996/Revised: 24 December 1996     

Karyotype analysis and physical mapping of 45S rDNA in eight species of Sophora, Robinia , and Amorpha

The karyotype analysis and physical locations of 45S rDNA were carried out by means of fluorescence in situ hybridization in three species, and two forms of Sophora, two species of Robina, and one species of Amorpha. S. japonica L., S. japonica L. f. oligophylla Franch., S. japonica L. f. pendula Loud., and S. xanthantha C. Y. Ma. are all tetraploids with 2n = 28. There were four 45S rDNA sites in pericentromeric regions of two pairs of chromosomes in each of them. S. rubriflora Tsoong. is a triploid with 2n = 21, and three sites were located in each satellite of group 5 chromosomes. In R. pseudoacacia L. (2n = 2x = 22), we examined four intensive signals in telomeric regions of two pairs of satellite chromosomes. In R. hispida L. (2n = 2x = 30), there were four other signals in centromeric regions besides those like in R. pseudoacacia. Amorpha fruticosa L. has most chromosomes (2n = 40) among the eight materials, however, there were only six 45S rDNA loci and they laid in centromeric regions, and satellites of three pairs of chromosomes. 45S rDNA is a valuable chromosomal landmark in karyotype analysis. The distribution and genomic organization of rDNA in the three genera were also discussed. __________ Translated from Acta Botanica Yunnanica, 2005, 27(3): 261–268 [译自: 云南植物研究, 2005, 27(3): 261–268]     

ι-Crystallin and vitamin A2 isomers in lenses of diurnal geckos

The ocular lenses of several genera of strictly diurnal dwarf geckos contain the monomeric ι-crystallin, which is closely related to the cellular retinol-binding protein type I (CRBP I). The contents of ι-crystallin vary between 2 and 12% of the total amount of crystallins depending on species. The endogenous ligand of ι-crystallin of all species investigated so far turns out to be 3,4-didehydroretinol (vitamin A₂). No other lenticular retinoids were detected. In lenses of Old World species (Lygodactylus, Pristurus, Quedenfeldtia), this ligand occurs exclusively in the all-trans form. In lenses of species of the neotropical genus Gonatodes, however, it occurs in two isomeric forms: all-trans and 11-cis. ι-Crystallin of Gonatodes is the first CRBP-like protein which naturally binds an 11-cis isomer of vitamin A. All-trans 3,4-didehydroretinol and its ester are present in eye cups of Lygodactylus. In contrast, eye cups of nocturnal geckos without ι-crystallin lack these retinoids. The retinal pigment epithelium is suggested to be the site of conversion of retinol to 3,4-didehydroretinol, which finally serves as ligand of ι-crystallin. Accepted: 13 March 1999     

Molecular cytogenetic study of three common Mediterranean limpets, Patella caerulea, P. rustica and P. ulyssiponensis (Archaeogastropoda, Mollusca)

The present paper shows the results of chromosome banding and rDNA-FISH study performed on several specimens of different populations of Patella caerulea, Patella rustica and Patella ulyssiponensis. The taxonomic attribution of specimens was ascertained by the molecular phylogenetic analysis of the mitochondrial 16S rRNA gene. P. caerulea and P. rustica had 2n = 18 chromosomes with first seven of biarmed pairs and the remaining two uniarmed pairs. P. ulyssiponensis had 2n = 16 with all biarmed chromosomes. Ag-NOR loci were on the short arms of the first metacentric pair in the three studied limpets, whereas they showed a different pattern of heterochromatin distribution and composition. A chromosome mosaicism was observed in several P. caerulea specimens, which exhibited an unpaired metacentric element and loss of a telocentric pair. The obtained results suggest that in the genus Patella specific diversification was accompanied by variations in heterochromatin distribution and composition and reduction of chromosome number by Robertsonian centric fusion.     

Translesion DNA polymerases Pol ζ, Pol η, Pol ι, Pol κ and Rev1 are not essential for repeat-induced point mutation inNeurospora crassa

Pol ζ, Pol η, Pol ι, Pol κ and Rev1 are specialized DNA polymerases that are able to synthesize DNA across a damaged template. DNA synthesis by such translesion polymerases can be mutagenic due to the miscoding nature of most damaged nucleotides. In fact, many mutational and hypermutational processes in systems ranging from yeast to mammals have been traced to the activity of such polymerases. We show however, that the translesion polymerases are dispensable for repeat-induced point mutation (RIP) inNeurospora crassa. Additionally, we demonstrate that theupr-1 gene, which encodes the catalytic subunit of Pol ζ, is a highly polymorphic locus in Neurospora. Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession Nos DQ 231523, DQ 231524, DQ 235021, DQ 235525-DQ 235541, DQ 240287, DQ 240288, DQ 354228, DQ 354235-DQ 354237, DQ 386416-DQ 386422, DQ 387872, DQ494492-DQ494503 and DQ417211-DQ417220.     

Effects of photon flux density and agricultural fertilizers on the development of <Emphasis Type="Italic">Sarcothalia crispata</Emphasis> tetraspores (Rhodophyta,Gigartinales) from the Strait of Magellan,Chile

Tetraspores of Sarcothalia crispata from San Juan Bay, Strait of Magellan, Chile, were cultivated under different combinations of photon flux densities and agricultural fertilizers in the laboratory. In the experiment, the S. crispata specimens were cultured in combinations of different photon flux densities (50, 100, 150 μmol photons m^-2 s^-1) and enriched seawater solutions (sodium nitrate + monocalcium phosphate, urea + monocalcium phosphate, ammonium nitrate + monocalcium phosphate), always adjusting the N and P concentrations to 10 and 3 mg L^-1, and in sea water as control. After 45 days, the tetrasporeling plants were found to be larger at photon flux densities of 50 and 100 μmol photons m^-2 s^-1 in the nutrient enrichment experiments; growth was greatest in the sea water enriched with ammonium nitrate and urea. An analysis of the combined effect of the photon flux density and nutrients revealed that the best combination for sporeling growth was the ammonium nitrate and urea solution at 50–100 μmol photons m^-2 s^-1.     

Multiple tubulin forms in ciliated protozoan Tetrahymena and Paramecium species

Summary. Tetrahymena and Paramecium species are widely used representatives of the phylum Ciliata. Ciliates are particularly suitable model organisms for studying the functional heterogeneity of tubulins, since they provide a wide range of different microtubular structures in a single cell. Sequencing projects of the genomes of members of these two genera are in progress. Nearly all members of the tubulin superfamily (α-, β-, γ-, δ-, ɛ-, η-, θ-, ι-, and κ-tubulins) have been identified in Paramecium tetraurelia. In Tetrahymena spp., the functional consequences of different posttranslational tubulin modifications (acetylation, tyrosination and detyrosination, phosphorylation, glutamylation, and glycylation) have been studied by different approaches. These model organisms provide the opportunity to determine the function of tubulins found in ciliates, as well as in humans, but absent in some other model organisms. They also give us an opportunity to explore the mechanisms underlying microtubule diversity. Here we review current knowledge concerning the diversity of microtubular structures, tubulin genes, and posttranslational modifications in Tetrahymena and Paramecium species. Correspondence and reprints: Institute of Molecular Genetics, Czech Academy of Sciences, Vídeňská 1083, 14220 Prague, Czech Republic.