Manganese and iron encrustations and other features ofPlanctomyces crassus Hortobágyi 1965, morphotype Ib of theBlastocaulis-Planctomyces group of budding and appendaged bacteria,examined by electron microscopy and X-ray micro-analysis

Water samples collected in August, 1980, from a pond in Budapest, Hungary, have permitted transmission and scanning electron microscopic observations to be made ofPlanctomyces crassus Hortobágyi 1965, which—to remain taxonomically noncommittal—we designated as morphotype Ib of theBlastocaulis-Planctomyces group of appendaged and budding bacteria. The detailed cell morphology of morphotype Ib (cellular shape, size and distribution pattern of crateriform structures, pili, spires) was similar to that of morphotype Ia,Planctomyces bekefii Gimesi 1924. The major appendage—a seemingly tubular, multifibrillar stalk—differed somewhat from the stalk of morphotype Ia, in that the morphotype Ib stalk was generally shorter than the morphotype Ia stalk, was tapered (the morphotype Ia stalk was uniformly cylindrical), and apparently lacked the organizing matrix of the morphotype Ia stalk. Energy-dispersive X-ray spectroscopy of the metallic-oxide encrustations of morphotype Ib rosettes revealed manganese and iron to be the predominant elements present. Moreover, localized differences were found in the relative amounts of the two elements deposited in different rosettes and at different loci on the same rosette.     

Morphotype V of theBlastocaulis-Planctomyces group of budding and appendaged bacteria:Planctomyces guttaeformis Hortobágyi (sensu Hajdu)

The ultrastructure of a budding and appendaged bacterium resemblingPlanctomyces guttaeformis Hortobágyi (sensu Hajdu) was examined by transmission electron microscopy in negative-contrast and thin-section preparations from samples of pond and lake water in which natural blooms of this organism had occurred. Its prokaryotic nature was established, and observations were reported regarding its characteristic bulbiform or bulbose cell shape (cylindrical with one globose or swollen end), budding process, crateriform surface structures, rosettes (cell clusters) radiating from the narrow (nonglobose) ends of the adhering cells, cell envelope profile, and distinctive appendages (a single, relatively broad and long, gradually tapered, rigid, multifibrillar, polar or slightly subpolar, noncellular spike—without the adherence function of a stalk—located at the swollen pole of the bulbiform cell; numerous pili/fimbriae all over the globose portion). These traits establish the organism as a putative member of theBlastocaulis-Planctomyces group of budding and appendaged bacteria, but sufficiently distinctive (bulbiform cell shape; spike; adherent material at narrow end of cell rather than at the end of a noncellular appendage) to warrant its delineation as morphotype V of this group.     

Some ultrastructural features ofPlanctomyces bekefii,morphotype I of theBlastocaulis-Planctomyces group of budding and appendaged bacteria

The ultrastructure ofPlanctomyces bekefii, a budding and appendaged bacterium, has been examined using samples obtained directly from pond water, its natural habitat. The prokaryotic nature of this morphologically unusual microbe was verified by observations of thin sections. Its major appendage, the nonprosthecate stalk, is shown to have a tubular structure, with a substructure of hollow fibers. Some details of the budding process and other ultrastructural features are presented.     

Inhibition of chlamydial class Ic ribonucleotide reductase by C‐terminal peptides from protein R2

Chlamydia trachomatis ribonucleotide reductase (RNR) is a class Ic RNR. It has two homodimeric subunits: proteins R1 and R2. Class Ic protein R2 in its most active form has a manganese–iron metal cofactor, which functions in catalysis like the tyrosyl radical in classical class Ia and Ib RNRs. Oligopeptides with the same sequence as the C‐terminus of C. trachomatis protein R2 inhibit the catalytic activity of C. trachomatis RNR, showing that the class Ic enzyme shares a similar highly specific inhibition mechanism with the previously studied radical‐containing class Ia and Ib RNRs. The results indicate that the catalytic mechanism of this class of RNRs with a manganese–iron cofactor is similar to that of the tyrosyl‐radical‐containing RNRs, involving reversible long‐range radical transfer between proteins R1 and R2. The competitive binding of the inhibitory R2‐derived oligopeptide blocks the transfer pathway. We have constructed three‐dimensional structure models of C. trachomatis protein R1, based on homologous R1 crystal structures, and used them to discuss possible binding modes of the peptide to protein R1. Typical half maximal inhibitory concentration values for C. trachomatis RNR are about 200 µ m for a 20‐mer peptide, indicating a less efficient inhibition compared with those for an equally long peptide in the Escherichia coli class Ia RNR. A possible explanation is that the C. trachomatis R1/R2 complex has other important interactions, in addition to the binding mediated by the R1 interaction with the C‐terminus of protein R2. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Spectroscopic studies of the iron and manganese reconstituted tyrosyl radical in Bacillus cereus ribonucleotide reductase R2 protein

Ribonucleotide reductase (RNR) catalyzes the rate limiting step in DNA synthesis where ribonucleotides are reduced to the corresponding deoxyribonucleotides. Class Ib RNRs consist of two homodimeric subunits: R1E, which houses the active site; and R2F, which contains a metallo cofactor and a tyrosyl radical that initiates the ribonucleotide reduction reaction. We studied the R2F subunit of B. cereus reconstituted with iron or alternatively with manganese ions, then subsequently reacted with molecular oxygen to generate two tyrosyl-radicals. The two similar X-band EPR spectra did not change significantly over 4 to 50 K. From the 285 GHz EPR spectrum of the iron form, a g ₁-value of 2.0090 for the tyrosyl radical was extracted. This g ₁-value is similar to that observed in class Ia E. coli R2 and class Ib R2Fs with iron-oxygen cluster, suggesting the absence of hydrogen bond to the phenoxyl group. This was confirmed by resonance Raman spectroscopy, where the stretching vibration associated to the radical (C-O, ν_7a = 1500 cm⁻¹) was found to be insensitive to deuterium-oxide exchange. Additionally, the ¹⁸O-sensitive Fe-O-Fe symmetric stretching (483 cm⁻¹) of the metallo-cofactor was also insensitive to deuterium-oxide exchange indicating no hydrogen bonding to the di-iron-oxygen cluster, and thus, different from mouse R2 with a hydrogen bonded cluster. The HF-EPR spectrum of the manganese reconstituted RNR R2F gave a g ₁-value of ∼2.0094. The tyrosyl radical microwave power saturation behavior of the iron-oxygen cluster form was as observed in class Ia R2, with diamagnetic di-ferric cluster ground state, while the properties of the manganese reconstituted form indicated a magnetic ground state of the manganese-cluster. The recent activity measurements (Crona et al., (2011) J Biol Chem 286: 33053–33060) indicates that both the manganese and iron reconstituted RNR R2F could be functional. The manganese form might be very important, as it has 8 times higher activity.     

Effect of artificial destratification on iron,manganese, and zinc in the water,sediments, and two species of benthic macroinvertebrates in an Oklahoma lake

Ham's Lake was destratified in the summers of 1977 and 1978 by pumping surface water to the bottom. However, an arm was prevented from mixing by a submerged dam of a former farm pond and remained stratified. The concentration of manganese in the water increased to over 5 000 µg 1^–1 in the hypolimnion of the anoxic arm in summer. Soluble manganese averaged 28% of total concentration. Total iron concentrations were relatively high in the water and sorbed iron values were extremely low in the sediments. Soluble iron averaged 12% of total concentration. Zinc values were low in the water and sediments. Chaoborus punctipennis and Chironomus riparius concentrated iron and zinc and discriminated against manganese. Concentration factors were unaffected by mixing.     

Characterization of Alder Phytophthora Isolates from Wallonia and Development of SCAR Primers for their Specific Detection

Isolates of alder Phytophthora were collected in the southern part of Belgium on riverbanks planted with Alnus glutinosa and A. incana. They were compared with strains isolated in other European countries in terms of maximum temperature for growth, oogonia shape, pathogenicity on Alnus seedlings and genetic traits. Using both molecular techniques [random amplified polymorphic DNA (RAPD) and random amplified microsatellite (RAMS)], two groups of isolates were identified, the first group being further divided into two subgroups, Ia and Ib, using RAPD. Most of the Walloon alder Phytophthora isolates as well as the standard type from UK (formally designated P. alni subsp. alni) fell into group Ia. One isolate was classified in group Ib with the German and Dutch variants (P. alni subsp. multiformis), while three isolates were placed with the Swedish variant (P. alni subsp. uniformis) in group II. In terms of morphological properties, isolates from groups Ia and Ib developed colonies with a felt‐like appearance and usually produced numerous oogonia, varying from wavy to warty after 1 week (group Ia) or 2–3 weeks (Ib) in darkness. In contrast, colonies from group II isolates were generally irregular, and smooth oogonia were produced in low quantities after approximately 1 month in culture. A polymerase chain reaction (PCR) using sequence‐characterized amplification region (SCAR) primers derived from a polymorphic amplification product generated with a RAPD primer was developed for the specific detection of alder Phytophthora. The specificity and sensitivity of this test are discussed here.     

Major outer membrane proteins of E. coli K12 serve as receptors for the phages T2 (protein Ia) and 434 (protein Ib).

Summary Mutants of E. coli resistant to bacteriophage T2 have lowered amounts of protein Ia in their outer membrane. Bacteriophage T2 was inactivated by a mixture of protein Ia-lipopolysaccharide. Protein Ia or lipopolysaccharide alone had no neutralizing activity. However, only protein Ia was required to inactivate a T2 host range mutant. In the presence of polymyxin B T2 receptor activity of protein Ia — lipopolysaccharide mixtures could not be restored. E. coli strains missing protein Ib were resistant against the lambdoid phage 434. Purified protein Ib inactivated 434 and virh ⁴³⁴. Addition of lipopolysaccharide did not enhance the neutralizing activity of protein Ib, indicating that lipopolysaccharide may not be necessary for the inactivation of the phage.     

Spatial structure-mediated indirect effects of an aquatic plant, Trapa japonica, on interaction between a leaf beetle, Galerucella nipponensis, and a water strider, Gerris nepalensis

The spatial structure-mediated indirect effects of an aquatic host plant, Trapa japonica (Trapaceae), on survival of a leaf beetle, Galerucella nipponensis (Coleoptera: Chrysomelidae), with regard to predation by a water strider, Gerris nepalensis (Hemiptera: Gerridae), were investigated in an irrigation pond and under indoor conditions. Beetle density, particularly in the first-instar stage of the larvae, became extremely low in the second generation in the pond, even though food resources were abundant. The biological check method, which excludes natural enemies by caging, suggested that a causal factor of the low density was predation by Gerris nepalensis in midsummer and thereafter. Normally growing rosettes extend their leaves horizontally on the water surface. However, some rosettes of T. japonica grew leaves vertically in the later seasons, and such overgrown rosettes were distributed patchily in the ponds. Beetle density was higher on the latter rosettes than on the former ones. The indoor experiment showed that the water strider can feed on the eggs of beetles on normally grown rosettes but not on the overgrown rosettes. Furthermore, female adults of Galerucella nipponensis preferred the overgrown rosettes over the normally grown rosettes for oviposition when water striders were present. These facts suggest that the spatial structure-mediated indirect effects of the host plant modify the interaction between herbivore and predator. Received: November 22, 2001 / Accepted: February 26, 2002     

A bloom of Mallomonas acaroides,a silica-scaled chrysophyte,in the crater pond of a pingo,Northwest Greenland

For the first time, phytoplankton has been collected from the extreme environment of a crater pond of a pingo (Arctic mud volcano), situated in Svarlenhuk, Northwest Greenland. It contained a bloom of a special morphotype of the silica-scaled chrysophyte Mallomonas acaroides. This morphotype proved to be widely distributed in Northwest Greenland, between 69 and 73°N.     

Horizontal zonation of macrovegetation,water properties and macrofauna in a littoral stand of Glyceria aquatica (L.) Wahlb. in a pond in South Bohemia

Summary The littoral stand of Glyceria aquatica (L.) Wahlb. under study was not a homogeneous living environment. In most of the factors studied there was a gradient, which led from the open pond water to the shore. As to the growth properties of Glyceria, this phenomenon may be explained by the various age of the stand and the trophic state of the environment. The gradient of the water properties may be explained by the combined effect of different isolation of water from the open pond, shading by vegetation, and decomposition of plant remains. On the basis of these factors it is possible to differentiate the part of the stand under the influence of the open pond (station D) from the isolated part (A and B). Between both parts there were transitions in several factors (station C). The part of the stand, which was influenced by the open pond water, had more favourable living conditions as compared with the isolate part, which was inhabited by different species of animals (macrofauna).

---

Zusammenfassung Der studierte Uferpflanzenbestand von Glyceria aquatica (L.) Wahlb. (Fig. 1, 2) war kein homogenes Lebensmilieu. Beim Großteil der untersuchten Faktoren wurde ein Gradient in der Richtung freies Wasser — Ufer festgestellt (Fig. 1, 2, 3). Bei den Eigenschaften des Wachstums von Glyceria kann these Erscheinung durch verschiedene Alter des Geleges und durch trophische Einflüsse des Milieus erklart werden. Der Gradient der Eigenschaften des Wassers kann durch gemeinsame Einflüsse der verschiedenen Stufen der Isolation des Wassers in dem Gelege von dem Pelagial des Teiches, durch Beschattung mit Vegetation und Zersetzung der Pflanzenreste erklärt werden. Auf Grunt dieser Tatsachen kann man einen Teil des Pflanzenbestandes, der durch den Teich beeinflußt ist (Standort D), von dem isolierten Teil (Standort A und B) unterscheiden. Zwischen beiden wurde dann bei einigen Faktoren ein Übergang gefunden (Standort C). Der Teil des Pflanzenbestandes, der durch den Teich beeinflußt war, hatte bessere Lebensbedingungen als der isolierte Teil und war mit unterschiedlichen Tierarten besiedelt (Fig. 4, Tab. III).

     

Residues involved in the pore‐forming activity of the Clostridium perfringens iota toxin

Clostridium perfringens iota toxin is a binary toxin that is organized into enzyme (Ia) and binding (Ib) components. Ib forms channels in lipid bilayers and mediates the transport of Ia into the target cells. Here we show that Ib residues 334–359 contain a conserved pattern of alternating hydrophobic and hydrophilic residues forming two amphipathic β‐strands involved in membrane insertion and channel formation. This stretch of amino acids shows remarkable structural and functional analogies with the β‐pore‐forming domain of C. perfringens epsilon toxin. Several mutations within the two amphipathic β‐strands affected pore formation, single‐channel conductance and ion selectivity (S339E‐S341E, Q345H N346E) confirming their involvement in channel formation. F454 of Ib corresponds to the Φ‐clamp F427 of anthrax protective antigen and F428 of C2II binary toxins. The mutation F454A resulted in a loss of cytotoxicity and strong increase in single‐channel conductance (500 pS as compared with 85 pS in 1 M KCl) with a slight decrease in cation selectivity, indicating that the Φ‐clamp is highly conserved and crucial for binary toxin activity. In contrast, the mutants Q367D, N430D, L443E had no or only minor effects on Ib properties, while T360I, T360A and T360W caused a dramatic effect on ion selectivity and single‐channel conductance, indicating gross disturbance of the oligomer structure. This suggests that, at least in the iota toxin family, T360 has a structural role in the pore organization. Moreover, introduction of charged residues within the channel (S339E‐S341E) or in the vestibule (Q367D, N430D and L443E) had virtually no effect on chloroquine or Ia binding, whereas F454A, T360I, T360A and T360W strongly decreased the chloroquine and Ia affinity to Ib. These results support that distinct residues within the vestibule interact with chloroquine and Ia or are responsible for channel structure, while the channel lining amino acids play a less important role.     

Seasonal and diurnal changes in the water temperature of a temperate pond (England) and a tropical pond (Kenya)

Seasonal changes in water temperatures, embracing periods of low, rising, high and declining temperatures, were recorded in both a temperate and a tropical pond. In the course of a year, the range between the lowest and highest average weekly temperatures was greater in the temperate pond. The spans between the average minimum and the average maximum weekly water temperatures in the warmest months of the year in the tropical pond were greater than those found at any time of the year in the temperate pond. The average weekly air and water temperatures showed the same pattern of seasonal fluctuations; in the tropical pond the average weekly air temperatures were always less than the average minimum weekly water temperatures, whereas they were below, within or above the spans between the average minimum and average maximum weekly aquatic temperatures, according to the time of year, in the temperate pond.In both ponds, diurnal fluctuations were absent during the cooler months; the amplitudes of the fluctuations in the warmer months varied according to the time of year, and were greater, during the warmest months, in the tropical pond. In both ponds lowest temperatures were recorded sometime between 0200 and 1000 hours and highest between 1200 and 2000 hours.The influence of temperature on the life-cycles of invertebrates in both ponds is discussed briefly.

---

Zusammenfassung Jahreszeitlich bedingte Schwankungen in der Wassertemperatur, welche Perioden mit niedriger, ansteigender, hoher und abfallender Temperatur einschlossen, wurden in einem gemäßigten und in einem tropischen Teich festgestellt. Im Laufe eines Jahres war der Unterschied zwischen den tiefsten und höchsten wöchentlichen Durchschnittstemperaturen im gemäßigten Teich größer. Hingegen war der Abstand zwischen Mindest- and Höchsttemperatur des Wassers im Wochendurchschnitt während der warmsten Monate des Jahres im tropischen Teich größer als zu irgendeiner Jahreszeit im gemäßigten Teich. Der Wochendurchschnitt der Luft- und Wassertemperaturen wies das gleiche jahreszeitlich bedingte Schwankungsmuster auf. In dem tropischen Teich war die wöchentliche Durchschnittstemperatur der Luft stets niedriger als die Mindestdurchschnittstemperatur des Wassers in einer Woche. Jedoch lag sie — je nach Jahreszeit — unterhalb, auf gleicher Höhe oder oberhalb der Spannweite der niedrigsten and der höchsten wöchentlichen Dutchschnittstemperaturen des Wassers im gemäßigten Teich.In beiden Teichen traten die taglichen Schwankungen während der kÜhleren Monate nicht auf. Der Umfang der Schwankungen in den wärmeren Monaten variierte je nach Jahreszeit and war in den wärmsten Monaten in dem tropischen Teich größer. In beiden Teichen wurden die tiefsten Temperaturen zwischen 2.00 and 10.00 Uhr and die höchsten zwischen 12.00 and 20.00 Uhr gemessen.

     

Genotypic control of chromosome pairing in Avena longiglumis × A. sativa hybrids

In normal fourth larval instar Chironomus larvae, the secretory protein component I (or 1, according to Grossbach, 1969) consists of two subfractions, Ia and Ib, with an average molecular weight of 850.000 D (Rydlander and Edström, 1980). Data in the preceding paper suggest that component I is coded for by 75S RNA derived from the two large Balbiani rings, BR1 and BR2 (Rydlander et al., 1980). If Chironomus pallidivittatus larvae are exposed to galactose, the size relations between BR1 and BR2, which are usually in favour of BR2, are inverted and upon prolonged exposure a new BR, BR6, appears (Beermann, 1973). Here we describe how one or two new subfractions within component I, Ic₁ and Ic₂, appear during treatment with galactose, in parallel with the development of BR6. During the treatment there is also a change in the ratio between Ia and Ib proteins so that Ia becomes dominant, whereas in controls Ib is more pronounced. Fractions Ia, Ib and Ic are at least partially immunologically different but Ic₁ and Ic₂ cannot be distinguished from each other. Since the relative amounts of Ic₁ and Ic₂ do not vary in extracts from single animals, we have assumed that they represent alle lic products. —Fraction Ic can become the dominating protein within component I during galactose treatment. Since component I accounts for about 50% of the total protein synthesis, the sugar treatment is accompanied by major quantitative changes in genetic expression. —The correlation between the occurrence of particular Balbiani rings and protein fractions, evident from measurements of either protein mass or amino acid incorporation remains in agreement with the general relation earlier shown to exist between the large Balbiani rings and the total component I. Our data support the hypothesis that BR1 codes for fraction Ia, BR2 for Ib and BR6 for Ic. Conclusive evidence will, however, have to be provided by molecular techniques.     

Manganese and iron interactions on their uptake and distribution in soybean (Glycine max (L.) Merr.)

Summary The uptake and distribution of iron and manganese were studied in a manganese-sensitive soybean cultivar (‘Bragg’) grown over a range of supply levels of these nutrients in solution culture. At high (90 and 275 μM) manganese levels, increasing the iron concentration in solution from 2 to 100 μM partially overcame the effects of manganese toxicity. Interactions between manganese and iron occurred for dry matter yields, rate of Mn absorption by the roots, and the proportions of manganese and iron transported to the tops. No interaction was observed for the rate of root absorption of iron. The percentage distribution of manganese in the plant top increased with increasing iron, despite a reduced rate of Mn uptake. On the other hand, iron uptake was independent of solution Mn concentration and increased with increasing solution Fe. Also more iron was retained in the roots at high Mn and/or Fe levels in solution. Concentrations of manganese and iron in roots, stems and individual leaves were affected independently by the manganese and iron supplyi.e. without any interaction occurring between the two elements. In general, the concentration in a plant part was related directly to the solution concentration. Symptoms resembling iron deficiency correlated poorly with leaf Fe concentrations whereas high levels of manganese were found in leaves displaying Mn toxicity symptoms.     

Population structure of some pond Microcrustacea

Summary The aestival species composition of microcrustacea of eight ponds in southwestern Kansas is described. Two benthic Ostracoda and three planktonic Copepoda and eight planktonic Cladocera were collected.On the whole, the Copepoda were more abundant than the Cladocera. Patterns of relative abundance varied from week to week and were more varied than the patterns described for the limnetic zone of lakes. There were two or three copepods in each pond. Except for one pond which had no Cladocera, there were two to five species of Cladocera per pond.There were fourteen significant affinities among the plankters. Two species showed no affinity. The relationships among four recurrent groups were established. Group I contained one cyclopoid, one calanoid and two cladocerans, a pattern not unlike the typical limnetic community.The population structure of each species that occurred in more that one pond was analyzed by analysis of variance. Significant differences between the ponds occurred from various species in per cent copepodids in the population, per cent females with eggs, and the number of eggs per egg sac. There was no significant difference among the ponds regarding the mean number of eggs per ovigerous female for any cladoceran.Interactions among the species and faunal characteristics of the ponds are discussed in relation to the environmental characteristics of the ponds.

---

Zusammenfassung Die Zusammensetzung der estivalen Arten von Mikrocrustacean von acht Teichen im Südwesten von Kansas wird beschrieben. Zwei benthische Ostracoden, drei planktonische Copepoden und acht planktonische Cladoceren wurden gefunden.Die Copepoden waren im allgemeinen häufiger als die Cladoceren. Die Schemen der relativen Anzahl wechselten von Woche zu Woche und waren unterschiedlicher als die Schemen für die limnische Seezone. Zwei oder drei Copepoden, sowie zwei bis fünf Arten von Cladoceren kamen in jedem Teich vor, ausser in einem Teich, in dem keine Cladoceren gefunden wurden.Vierzehn wichtige Übereinstimmungen wurden unter den Planktonern gefunden. Zwei Arten zeigten keine Affinität. Der Zusammenhang zwischen vier wiederkehrenden Gruppen wurden nachgewiesen. Gruppe I enthielt einen Cyclopoiden, einen Calanoiden und zwei Cladoceren, ein für typisch limnische Gemeinschaften übliches Schema.Die Bevölkerungsstruktur jeder Art, die in mehr als einem Teich vorkam, wurde durch Streuungsanalyse untersucht. Es wurden signifikante Unterschiede im Prozentsatz der Copepoden: Bevölkerung, der Weibchen mit Eiern, der Anzahl Eier im Brutraum für die verschiedenen Arten zwischen den Teichen gefunden. Keine signifikanten Unterschiede wurden in der Anzahl Eier pro eitragendem Weibchen der Cladoceren zwischen den Teichen gefunden.Auch der Einfluss der Umweltfaktoren der Teiche auf die Arten und auf die Fauna des Teiches wurde untersucht.

     

Purification and characterization of a novel extracellular β-1,3-glucanase complex (Glu<Emphasis Type="Italic">Ggt</Emphasis>) secreted by <Emphasis Type="Italic">Gaeumannomyces graminis</Emphasis> var. <Emphasis Type="Italic">tritici</Emphasis>

β-1,3-Glucanases produced by the take-all disease pathogen Gaeumannomyces graminis var. tritici (Ggt) have been suggested to be implicated in infection and colonization process of the pathogen in wheat. For further studying the role of these enzymes in pathogenesis by cytochemical technique, an extracellular β-1,3-glucanase complex (GluGgt), was purified from culture filtrate of Ggt by (NH₄)₂SO₄ precipitation, hydrophobic-interaction, anion-exchange and size-exclusion chromatography. The complex consisted of two interconvertible isoforms (Ia and Ib), both active proteins Ia and Ib appeared to be glycosylated in native polyacrylamide gel electrophoresis (PAGE). The pI of the active proteins Ia and Ib determined by IEF-PAGE were 6.3 and 6.4, respectively. GluGgt yielded two subunits with molecular masses of 66.2 and 56.0 kDa, respectively, in 15% SDS–PAGE. The complex had a pH optimum of 5.0 and the optimal temperature was 50°C. The enzyme complex proved to be stable at a temperature up to 60°C and retained an optimal high activity in the pH range from 4.0 to 7.0. Enzyme activity of GluGgt was obviously stimulated by Mn²⁺ ions and moderately inhibited in the presence of Hg²⁺ and Co²⁺ ions and KMnO₄. The K _m of GluGgt was estimated to be 1.08 mg ml⁻¹ for laminarin as substrate and the V _max 0.20 μmol min⁻¹.