Effect of PPX1 inactivation on the exopolyphosphatase spectra in cytosol and mitochondria of the yeast Saccharomyces cerevisiae

Inactivation of PPX1 encoding exopolyphosphatase PPX1 in Saccharomyces cerevisiae results in a change in the exopolyphosphatase spectrum in the yeast cells. In the PPX1-deficient strain, elimination of an 45 kD exopolyphosphatase is observed in the cytosol, and activity of an exopolyphosphatase with molecular mass of 830 kD increases fivefold. The latter activity differs greatly in properties from the low-molecular-mass enzyme of the parent strain. In the soluble fraction of the mutant mitochondria, exopolyphosphatase of 45 kD characteristic of the soluble mitochondrial fraction in the parent strain is eliminated, and exopolyphosphatase with a molecular mass of 440 to 830 kD is found. On PPX1 inactivation, a membrane-bound form of mitochondrial exopolyphosphatase is unaffected in its activity level and properties. Therefore, the membrane-bound exopolyphosphatase of mitochondria and the high-molecular-mass enzyme of the cytosol of S. cerevisiae are not encoded by the PPX1 gene, unlike the soluble low-molecular-mass exopolyphosphatase of mitochondria, which is probably a product of this gene with a posttranslational modification. In the PPX1 mutant, exopolyphosphatase properties in the cell as a whole undergo modifications including the ability to hydrolyze polyphosphates (polyP) with different polymer degree.     

Freeze-fracture studies on the cockroach hemocyte membrane complex: Symmetric and asymmetric membrane particle distributions

Summary Freeze-fracture studies were conducted on the membranes of normal cockroach hemocytes. The plasmalemma is asymmetric with the A fracture face containing 80–100 Å membrane intercalated particles at a concentration of 2500/². The B fracture face contains 120–150 Å particles with a relatively low density (800/²). The nuclear envelope displays an asymmetry with the A fracture face containing 1500 particles/² and the B face containing 300/ ². No significant particle size differences were observed in nuclear envelope fracture faces. Two types of symmetric membranes were also found in these cells. Both A and B fracture faces of the membrane surrounding the numerous cytoplasmic inclusion bodies contain particle sizes and concentrations similar to the B face of the plasmalemma. A second type of symmetry was observed in cells apparently engaged in exocytosis. Vesicles (0.1 D) from this process were completely particle free on both fracture faces. Such particle free vesicles could be found in the cytoplasm, attached to the plasmalemma, or completely separated from the cell.Supported by a Pharmaceutical Manufacturers Association Foundation Fellowship.The author wishes to thank Ms. Annalena K. Charla for assistance in plate preparation, Dr. Julius Schultz and the Papanicolaou Cancer Research Institute for use of the freeze-etch device, and Dr. David Smith for the electron microscope facilities.     

Identification of a ∼30S size non-ribosomal Saccharomyces cerevisiae RNA that is rapidly labeled on its 3′ end by ATP or UTP

Cell-free extracts prepared from S. cerevisiae cells were incubated in the presence of [-³²P]-labeled ATP, CTP, GTP or UTP. An RNA larger than ribosomal 25S RNA with an apparent size of approximately 30S was prominently labeled on its 3 end in the presence of ATP or UTP but not with CTP or GTP. This labeled RNA was not hybrid-selected by cloned yeast ribosomal DNA; in addition, this 30S RNA was not cleaved by RNase H in the presence of complementary deoxyribooligonucleotides to rRNA. These two lines of evidence show that this 30S RNA is not structurally related to ribosomal RNA gene repeat. The cell-free extracts prepared from yeast cells containing temperature-sensitive poly(A) polymerase adenylated this novel yeast RNA at restrictive temperature with efficiency similar to extracts prepared from wild-type yeast cells. These data show that the enzyme responsible for adenylation of this 30S RNA is distinct from mRNA poly(A) polymerase. While the human SRP RNA 3 adenylating enzyme in the HeLa cell extract adenylated human SRP or Alu RNAs, the yeast adenylating enzyme did not adenylate the human SRP or Alu RNAs in vitro; these data indicate species specificity for this adenylating enzyme.     

Pepsin fragmentation of botulinum type E neurotoxin: Isolation and characterization of 112, 48, 46, and 16 kD fragments

Controlled digestion of 150 kD single chain botulinum type E neurotoxin with pepsin atpH 6.0 produced 112, 48, 46, and 16 kD fragments. These were chromatographically purified; their locations in the 1300 amino acid residue long neurotoxin were determined by identifying the amino terminal 10 residues of 112 and 48 kD fragments, 50 residues of 46 kD fragment, and 59 residues of 16 kD fragment. The 48 and 112 kD fragments contain the N-terminal segment of the neurotoxin (i.e., residue no. 1 to 425 and 1 to 990, respectively), the 46 kD fragment corresponds to 407 residues of the C-terminal region, and the 16 kD fragment contains the 140 residues from a segment nearer to the C-terminus. The 48 kD fragment is similar to the 50 kD N-terminal light chain of the 150 kD dichain neurotoxin, which is generated by tryptic cleavage of the 150 kD single chain neurotoxin, and is separated from the 100 kD C-terminal heavy chain by dithiothreitol (DTT) reduction of an intrachain disulfide bond in the presence of 2 M urea (Sathyamoorthy and DasGupta,J. Biol. Chem. 260, 10461, 1985). The pepsin-generated 48 kD fragment, unlike the light chain, was isolated without exposure to DTT and urea. The single chain 112 kD fragment following trypsin digestion yielded 48 and 60 kD fragments that were separable after DTT reduction of the intrachain disulfide which links them. The N-terminal residues of the smaller fragment were identical to that of the single chain 150 kD neurotoxin; the single chain 112 kD fragment is therefore the neurotoxin minus the 50 kD C-terminal half of the heavy chain. The biological activities of the 48 and 112 kD fragments can be demonstrated in permeabilized PC12 cells (Lomnethet al., J. Neurochem. 57, 1413, 1991); they inhibit norepinephrine release.     

Coccidia of Brazilian edentates: Eimeria cyclopei n.sp. from the silky anteater,Cyclopes didactylus (Linn.) and Eimeria choloepi n.sp. from the two-toed sloth,Choloepus didactylus (Linn.)

Summary Eimeria cyclopei n.sp. is described from the silky anteater, Cyclopes didactylus, from Pará State, north Brazil. Undifferentiated oocysts, passed in the faeces, complete sporulation in seven days at 26 to 28°C. Oocysts are ellipsoidal to sub-spherical, with a mean size of 28.1 × 23.6 m: the wall is 1.5 to 2.0 m thick, apparently with an outer thin, colourless membrane and two inner, thicker, striated and yellowish layers. There is no micropyle, oocyst residuum or polar body. The mean measurements of sporocysts are 19.0 × 9.0 m, and they are slightly asymmetrical, elongate pear-shape, with a plug-shaped Steida body projecting beyond the end of the sporocyst. Sporozoites are as long as or longer than the sporocysts: The sporocyst residuum is scattered between sporozoites in younger specimens and becomes condensed into rounded mass in older ones. The endogenous stages occur in the epithelial cells of the ileum, on the lumenal side of the host-cell nucleus. Uninucleate meront, microgamont and macrogamont precursors are recognizable morphologically. Mature meronts are 20.0 × 15.7 m some produce 12 to 20 merozoites which are 8.7 × 2.0 m, and others 10 to 26 merozoites which are 11.4 × 2.0 to 15.0 × 3.0 m. Mature microgamonts which are 27.5 × 24.1 m, produce from 150 to 170 microgametes of 7.1 × 1.0 m: microgametes have two flagella of unequal length. Mature macrogamonts are 28.4 × 24.5 m Eimeria choloepi n.sp. is recorded from the two-toed sloth, Choloepus didactylus, from the same area of Brazil. Undifferentiated oocysts, passed in the faeces, complete sporulation in 23 days at 26 to 28°C. Oocysts with a mean size of 23.0 × 20.3 m, have a wall 2.0 to 2.5 m thick which is composed of two thick, yellowish and striated outer layers and a delicate, colourless inner one. There is no micropyle, oocyst residuum or polar granule. Mature sporocysts with a mean size of 11.3 × 7.1 m, are ellipsoidal to egg-shaped and have a poorly developed Steida body. The sporocyst residuum is composed of a small number of large globules: The sporozoites are longer than the sporocyst and strongly recurved. The endogenous stages occur in epithelial cells of the ileum, on the lumenal side of the host-cell nucleus. Dimorphic meronts produce 8 to 18 merozoites which are either 13.0 × 2.0 m or 13.0 × 3.0 m. Microgamonts produce 50 to 80 microgametes of 8.0 × 1.0 m. Mature macrogamonts are 18.3 × 17.9 m. ac]19820212     

Efficient secretion of human lysozyme from the yeast, <Emphasis Type="Italic">Kluyveromyces lactis</Emphasis>

Efficient secretion of human lysozyme from the yeast, Kluyveromyces lactis, was achieved by using more stable vectors in the order of S11 replication origin-containing episomal vector < full-length K. lactis plasmid pKD1-containing vector < centromeric vector < chromosome-integrated vectors. Cells containing a PGK (phosphoglycerate kinase) promoter-driven integration vector grown in non-selective rich medium achieved the highest level of secretion, 100 g lysozyme secretion ml ^–1 culture: this level was 10-fold higher than that achieved by episomal vectors. An additional copy of the protein disulfide isomerase gene further facilitated the secretion.     

Lipase-mediated homotopic and heterotopic double resolutions of a planar chiral organometallic alcohol

Summary (±)-Tricarbonyl ⁶-3-methylbenzyl alcohol)chromium was resolved to of 100%e.e. and of 92%e.e. by lipase-catalyzed transesterifications arranged in homotopic and heterotopic double resolutions.     

Carbon and nitrogen stable isotope ratios of deposit-feeding polychaetes in the Nanakita River Estuary, Japan

Two types of deposit-feeding polychaetes, Neanthes japonica and Notomastus sp., and their surrounding sediments were collected from the Nanakita River Estuary and a small brackish lagoon (Gamõ Lagoon) in northeastern Japan. The samples were examined using stable isotope analysis to assess the site specific feeding mode of the animals and their trophic status. N. japonica is a surface deposit-feeder and Notomastus sp. is a subsurface deposit-feeder. In the estuary, the sedimentary ⁵N tended to become isotopically heavier from the upper estuary (2.0 3.9) to the river mouth (4.3 6.2), while sedimentary organic ¹³C constant value (–26.8 –24.4, average –25.6) throughout the river estuary. The ¹³C values of N. japonica were similar to those of the surrounding sediment in the upper estuary, whereas in the lower estuary, N. japonica had a heavier ¹³C value than the surrounding sediment. The ¹³C and dg ¹⁵N values indicated that the carbon, but not the nitrogen, of N. japonica was derived from upland plants in the upper estuary. In the lower estuary, a significant fraction of carbon of N. japonica was derived from phytoplankton. Notomastus sp. exhibited heavier ¹³C values than the surrounding surface sediment throughout the estuary and had heavier ¹³C values than N. japonica in the same location. These results suggest selective utilization of sedimentary carbon by those animals following bacterial processing and subsequent fractionation. The difference in ¹⁵N between sedimentary organics and corresponding polychaetes was 5 ± 1 and rather higher than 3.4 ± 1.1 expected for normal trophic effects in other animals.     

Coral growth in high-nutrient,low-pH seawater: a case study of corals cultured at the Waikiki Aquarium,Honolulu, Hawaii

Fifty-seven species of hermatypic corals have been maintained and grown in high-nutrient seawater at the Waikiki Aquarium, Honolulu, Hawaii. In this study we document the chemical conditions of aquarium water in terms of dissolved nutrients and carbon. Aquarium water is characterized by concentrations of inorganic nutrients that are high relative to most natural reef ecosystems: SiO₃ 200 M; PO₄ 0.6 M; NO₃ 5 M; NH₄ 2 M. In contrast, concentrations of organic nutrients are lower than most tropical surface ocean waters: DOP 0.1 M and DON 4 M. The incoming well-water servicing the facility has low pH, crating over-saturation of carbon dioxide. The coral communities in aquaria took up inorganic nutrients and released organic nutrients. Rates of nutrient uptake into aquaria coral communities were similar to nutrient uptake by natural reef communities. Coral growth rates were near the upper rates reported from the field, demonstrating corals can and do flourish in relatively high-nutrient water. The growth of corals does not appear to be inhibited at concentrations of nitrogen up to 5 M. Statements implying that corals can only grow in low nutrient oligotrophic seawater are therefore oversimplifications of processes that govern growth of these organisms. Some basic guidelines are given for maintenance of coral communities in aquaria.     

Heterogeneity of calcium compartmentation: Electron probe analysis of renal tubules

Summary The objective of this study has been to determine the intracellular localization of calcium in cryofixed, cryosectioned suspensions of kidney proximal tubules using quantitative electron probe X-ray microanalysis. Two populations of cells have been identified: 1) Viable cells, representing the majority of cells probed, are defined by their relatively normal K/Na concentration ratio of 41. Their measured Ca content is 4.1±1.4 (sem) mmol/kg dry wt in the cytoplasm and 3.1 ± 1.1 mmol/kg dry wt in the mitochondria, or an average cell calcium content of 3.8 mmol/kg dry wt. 2) Nonviable cells, defined by the presence of dense inclusions in their mitochondria and a K/Na concentration ratio of 1. The Ca content is 15±2 mmol/kg dry wt in the cytoplasm and 685±139 mmol/kg dry wt in the mitochondria of such cells. Assuming 25 to 30% of the cell volume is mitochondrial, the overall calcium content of such nonviable cells is 210 mmol/kg dry wt. The presence of these inclusions in 4 to 5% of the cells would account for the average total Ca content measured in perchloric acid extracts of isolated proximal tubule suspensions ( 18 nmol/mg protein or 12.6 mmol/kg dry wt). Whole kidney tissues display a large variability in toal Ca content (4.5 to 18 nmol/mg protein, or 3.4 to 13.5 mmol/kg dry wt), which could be accounted for by inclusion in 0 to 4% of the cells. The electron probe X-ray microanalysis (EPXMA) data conclusively demonstrate that thein situ mitochondrial Ca content of viable cells from the kidney, proximal tubule is low and support the idea that mitochondrial Ca may regulate dehydrogenase activity but probably does not normally control cytosolic free Ca.     

Subunit distribution of calcium-binding sites in Lumbricus terrestris hemoglobin

The giant, 3.6-MDa hexagonal bilayer hemoglobin (Hb) of Lumbricus terrestris consist of twelve 213-kDa globin subassemblies, each comprised of three disulfide-bonded trimers and three monomer globin chains, tethered to a central scaffolding of 36–42 linkers L1–L4 (24–32 kDa). It is known to contain 50–80 Ca and 2–4 Cu and Zn; the latter are thought to be responsible for the superoxide dismutase activity of the Hb. Total reflection X-ray fluorescence spectrometry was used to determine the Ca, Cu, and Zn contents of the Hb dissociated at pH 2.2, the globin dodecamer subassembly, and linker subunits L2 and L4. Although the dissociated Hb retained 20 Ca²⁺ and all the Cu and Zn, the globin subassembly had 0.4 to 3 Ca²⁺, depending on the method of isolation, and only traces of Cu and Zn. The linkers L2 and L4, isolated by reversed-phase high-pressure liquid chromatography at pH 2.2, had 1 Ca per mole and very little Cu and Zn. Electrospray ionization mass spectrometry of linker L3 at pH 2.2 and at neutral pH demonstrated avid binding of 1 Ca²⁺ and additional weaker binding of 7 Ca²⁺ in the presence of added Ca²⁺. Based on these and previous results which document the heterogeneous nature of the Ca²⁺-binding sites in Lumbricus Hb, we propose three classes of Ca²⁺-binding sites with affinities increasing in the following order: (i) a large number of sites (>100) with affinities lower than EDTA associated with linker L3 and dodecamer subassembly, (ii) 30 sites with affinities higher than EDTA occurring within the cysteine-rich domains of linker L3 and dodecamer subassembly, and (iii) 25 very high affinity sites associated with the linker subunits L1, L2, and L4. It is likely that the low-affinity type (i) sites are the ones involved in the effects of 1–100 mM Group IIA cations on Lumbricus Hb structure and function, namely increased stability of its quaternary structure and increased affinity and cooperativity of its oxygen binding.     

Stable isotope and radiocarbon compositions of methane emitted from tropical rice paddies and swamps in Southern Thailand

Stable isotopes (¹³C, D) and radiocarbon weremeasured in methane bubbles emitted from rice paddies and swamps in southernThailand. Methane emitted from the Thai rice paddies was enriched in¹³C (mean ¹³C; –51.5 ±7.1 and–56.5 ± 4.6 for mineral soil and peat soil paddies,respectively)relative to the reported mean value of methane from temperate rice paddies(– 63 ± 5). Large seasonal variation was observed in¹³C(32) in the rice paddies, whereas variationinD was much more smaller (20), indicating that variation in¹³C is due mainly to changes in methane production pathways.Values of ¹³C were lower in swamps (–66.1 ±5.1)than in rice paddies. The calculated contribution of acetate fermentation from¹³C value was greater in rice paddies (mineral soils:62–81%, peat soils: 57–73%) than in swamps (27–42%). Din methane from Thai rice paddies (–324± 7 (n=46)) isrelativelyhigher than those from 14 stations in Japanese rice paddies ranging from–362 ± 5 (Mito: n=2) to –322 ± 8(Okinawa: n=3), due tohigher D in floodwaters. ¹⁴C content in methane produced fromThai rice paddies (127±1 pMC) show higher ¹⁴Cactivity compared with previous work in paddy fields and those from Thai swamps(110±2 pMC).     

Evidence for two modes of Ca2+ entry following muscarinic stimulation of a human salivary epithelial cell line

Summary We have investigated muscarinic receptor-operated Ca²⁺ mobilization in a salivary epithelial cell line, HSG-PA, using an experimental approach which allows independent evaluation of intracellular Ca²⁺ release and extracellular Ca²⁺ entry. The carbachol (Cch) dose response of intracellular Ca²⁺ release indicates the involvement of a single, relatively low-affinity, muscarinic receptor site (K _0.510 or 30 m, depending on the method for [Ca²⁺] _i determination). However, similar data for Ca²⁺ entry indicate the involvement of two Cch sites, one consistent with that associated with Ca²⁺ release and a second higher affinity site withK _0.52.5 m. In addition, the Ca²⁺ entry response observed at lower concentrations of Cch (2.5 m) was completely inhibited by membrane depolarization induced with high K⁺ (>55mm) or gramicidin D (1 m), while membrane depolarization had little or no effect on Ca²⁺ entry induced by 100 m Cch. Another muscarinic agonist, oxotremorine-M (100 m; Oxo-M), like Cch, also induced an increase in the [Ca²⁺] _i of HSG-PA cells (from 72±2 to 104±5nm). This response was profoundly blocked (75%) by the inorganic Ca²⁺ channel blocker La³⁺ (25–50 m) suggesting that Oxo-M primarily mobilizes Ca²⁺ in these cells by increasing Ca²⁺ entry. Organic Ca²⁺ channel blockers (verapamil or diltiazem at 10 m, nifedipine at 1 m), had no effect on this response. The Oxo-M induced Ca²⁺ mobilization response, like that observed at lower doses of Cch, was markedly inhibited (70–90%) by membrane depolarization (high K⁺ or gramicidin D). At 100 m Cch the formation of inositol trisphosphate (IP₃) was increased 55% above basal levels. A low concentration of carbachol (1 m) elicited a smaller change in IP₃ formation (25%), similar to that seen with 100 m Oxo-M (20%). Taken together, these results suggest that there are two modes of muscarinic receptor-induced Ca²⁺ entry in HSG-PA cells. One is associated with IP₃ formation and intracellular Ca²⁺ release and is independent of membrane potential; the other is less dependent on IP₃ formation and intracellular Ca²⁺ release and is modulated by membrane potential. This latter pathway may exhibit voltage-dependent gating.     

Conditions for high frequency embryogenesis from orange (Citrus sinensis Osb.) protoplasts

Using Trovita orange (Citrus sinensis Osb.) protoplasts isolated from 6-year-old nucellar callus, the effects of protoplast density and mannitol concentration on cell divisions and embryoid formation were examined.Somatic embryogenesis in nearly direct manner was observed only at a combination of low cell densities (4×10⁴/ml) and low mannitol concentrations (0.4 M). Two alternatives to achieve high frequency embryogenesis (70%) were to either dilute the cells to lower densities, or to do serial transfers of cells to fresh medium.Orange protoplasts (cells) showed embryogenic potential, and repression of embryogenesis occurred when protoplasts were cultured at a high density and/or under high osmotic pressure.     

Synthesis of nanophase hydroxyapatite by a <Emphasis Type="Italic">Serratia</Emphasis> sp. from waste-water containing inorganic phosphate

Synthesis of nanophase hydroxyapatite (HA) on a bacterial surface was achieved at the expense of CaCl₂ and inorganic phosphate (Pi). After initial nucleation, calcium was precipitated on and around the cells as calcium phosphate at the expense of inorganic phosphate in the challenge solution, with no precipitation in cell-free controls. HA was also biomanufactured using inorganic phosphate ions scavenged from a phosphate-containing waste-water. With additional Ca²⁺, the concentration of phosphate was decreased from 0.27 (25ppm) to 0.02m (2ppm) in the waste-water. Crystals of calcium phosphate manufactured by the cells were located by scanning electron microscopy (SEM) and identified as HA by X-ray powder diffraction, with an average crystal size calculated as 25nm. Possible application of bioHA as a biomaterial and implications for one-step `waste-into product' are discussed.     

An analysis of flash-induced electrical transients of a BLM containing chloroplast lamella extracts

Summary The electrical transients produced by chloroplast bilayer lipid membranes (Chl-BLM) from flash excitation are seen to result from three photocurrents and a discharge current. Each of the three photo-initiated charge transports in Chl-BLM (designated as Components A, B and C) exhibits an action spectrum similar to chlorophyll absorption spectra. The fast components (A and B), which are induced by electron acceptors such as Fe⁺³, have rise-times of 3 sec and 20 msec, and occur in TLM (thin lipid membranes, i.e., colored membranes up to 1 thick) as well as in BLM. Component C is induced by a transmembrane pH difference or applied voltage, has a rise-time of 1 sec, and occurs only in BLM. Component C is associated with exciton dissociation and proton transport. The mobility of the Component A current carriers in TLM is estimated to be about 1×10^–2 cm²/volt sec, and are, hence,electronic. The photovoltage waveforms are described by equations developed, which consider Component A as being caused by a direct charge separation proportional to the illumination intensity (within 0.5 sec), and Components B and C being caused by two types of exciton processes which cause charge transport after the illumination period.     

Absolute measurement of cell expansion in plant cell suspension cultures

A method is described for the measurement of intracellular volume (V_i) in cell cultures. In principle, any stable compound that neither penetrates the plasma membrane nor binds to the cells can be used to trace the total extracellular (apoplastic) volume and hence to estimate the intracellular volume. No suitable coloured or UV-absorbing compound could be found among those tested; the main problems were binding to the cell surface and/or instability in the medium. However, [¹⁴C]mannitol was an acceptable apoplastic marker, by use of which we showed that 21–47% of total packed cell volume (PCV) was intracellular, and 14–33% of total settled cell volume (SCV) was intracellular. Therefore, measurements of PCV and SCV misrepresent cell expansion to a variable extent. Cultures of Acer, Rosa, Spinacia and Zea achieved final symplastic volumes of only 9, 14, 6 and 6%, respectively, of the total suspension culture volume.     

A Marine Plant (Spartina Anglica) Invades Widely Varying Habitats: Potential Mechanisms of Invasion and Control

We report on the habitat dependent invasion and control pattern of the English cordgrass, Spartina anglica C. E. Hubbard, in Puget Sound, Washington. In 36 years, the plant has successfully invaded 73 sites, affecting 3311 ha of marine intertidal habitat, which if allowed to solidly fill, would equal 400ha. Invasion and control both depend on habitat type. Mudflats and low salinity marshes have significantly more solid area of S. anglica than do high salinity marshes and cobble beaches. Control efforts since 1997 have resulted in a 13% decline of the grass. We find that high salinity marshes have the greatest decline ( 70%), low salinity marshes have the lowest decline ( 10%), and mudflat ( 29%) and cobble beaches ( 21%) have intermediate losses. We hypothesize that invasion success and control are dependent on a relatively complex interplay between habitat physical conditions and species interactions.     

Comparative studies on cellular resistance of bivalves from marine and brackish waters

Summary 1. The cellular resistance of representatives from four euryhaline poikilosmotic bivalves caught in Büsum (North Sea, 30 S), Kieler Förde (Belt Sea, 15 S), and Tvärminne (Gulf of Finland, 6 S) has been tested. All experiments were performed in October.2. According to their cellular salinity rangesMacoma baltica andMytilus edulis are more euryhaline thanMya arenaria andCardium edule.3. The cellular heat resistance decreases in specimens from the North Sea in the following order:Cardium, Mya, Macoma, Mytilus. Among the representatives collected near Tvärminne,Macoma has the highest heat resistance.4. The cellular freezing resistance in specimens from the North Sea is highest inMytilus. The bivalves of the Gulf of Finland practically lack resistance to freezing.5. In localities of decreased salinity the cellular resistance of these bivalves to a dilution of the external medium is somewhat increased, but simultaneously the cellular resistance to other environmental factors, such as heat, freezing and high salinity, decreases unspecifically.

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Vergleichende Untersuchungen über zelluläre Resistenz bei Muscheln aus Meer- und Brackwasser

Kurzfassung An vier euryhalinen poikilosmotischen Muschelarten aus Büsum (Nord-seeküste, 30 S), der Kieler Förde Beltsee, 15 S) und Tvärminne (Finnischer Meerbusen, 6 S), wurden zur gleichen Jahreszeit (Herbst) vergleichende Untersuchungen über die zellulären Resistenzgrenzen durchgeführt. Auf Grund ihrer zellulären Salzgehaltsbereiche sindMacoma baltica undMytilus edulis euryhaliner alsMya arenaria undCardium edule. Die zelluläre Hitzeresistenz nimmt bei den Individuen aus der Nordsee in der Reihenfolge:Cardium, Mya, Macoma, Mytilus ab. Bei Exemplaren aus Tvärminne ist die zelluläre Hitzeresistenz vonMacoma am größten. Die zelluläre Gefrierresistenz ist unter den Muscheln aus der Nordsee am größten, fehlt dagegen praktisch bei den Tieren aus dem Finnischen Meerbusen. Bei verringertem Salzgehalt des Fundortwassers ist die zelluläre Resistenz der untersuchten Muscheln gegenüber Verdünnung des Außenmediums jeweils etwas erhöht, gleichzeitig nimmt die zelluläre Resistenz gegenüuber anderen Außenfaktoren wie Hitze, Frost und hohen Salzkonzentrationen unspezifisch ab.

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Dedicated to Professor Dr.Friedrich Krüger on his 65^th birthday, August 18, 1967.     

Laboratory culture studies of Trichodesmium isolated from the Great Barrier Reef Lagoon, Australia

Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR 40–50molquantam^–2s^–1). N₂ fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2–0.3day^–1 and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR 5–120molquantam^–2s^–1) with the maximum growth occurring at 40–50molquantam^–2s^–1. These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45nM. No active growth was observed with the 4.5nM Fe addition.