Nucleic acid-like structures III. Oligomerization of 3′-deoxyadenosine 2′,5′-diphosphoimidazolide

Summary The activated dimonophosphate of 3-deoxyadenosine (cordycepin) undergoes oligomerization to produce a new family of pyrophosphate-linked oligomers in which the average repeating unit involves a nine-atom structural group. The presence of a poly(U) template increase the relative yields of higher oligomers, although the template-free reaction is itself extremely efficient.For the previous paper in this series see Schwartz et al. (1987)     

Oligomerization of deoxynucleoside-bisphosphate dimers: Template and linkage specificity

Evidence is presented that a poly(U) template selectively favors the oligomerization of the activated, 3–5 pyrophosphate-linked dimer pdAppdAp, in comparison with the 3–3 and 5–5 linked dimers. In the absence of poly(U), the 5–5linked dimer is the most reactive, and chains are formed which are more than 60 monomer units in length.Nucleic Acid-Like Structures V. For the previous paper in this series see Visscher and Schwartz (1988).     

Search for polythionates in cultures of Chromatium vinosum after sulfide incubation

Cultures of Chromatium vinosum, devoid of sulfur globules, were supplemented with sulfide and incubated under anoxic conditions in the light. The concentrations of sulfide, polysulfides, thiosulfate, polythionates and elemental sulfur (sulfur rings) were monitored for 3 days by ion-chromatography and reversed-phase HPLC. While sulfide disappeared rapidly, thiosulfate and elemental sulfur (S₆, S₇ S₈ rings) were formed. After sulfide depletion, the concentration of thiosulfate decreased fairly rapidly, but elemental sulfur was oxidized very slowly to sulfate. Neither polysulfides (S _x ^2– ), polythionates (S_nO ₆ ^2– , n=4–6), nor other polysulfur compounds could be detected, which is in accordance with the fact that sulfide-grown cells were able to oxidize polysulfide without lag. The nature of the intracellular sulfur globules is discussed.     

Lysosomal hydrolases in calf thyroid

1. Two acid phosphatases (β-glycerophosphatase and phenylphosphatase), acid β-glucuronidase and cathepsin were demonstrated in the 0·25m-sucrose homogenates from whole calf thyroid tissue and from isolated calf thyroid cells. 2. The main kinetic characters of these enzymes were studied. 3. All these acid hydrolases are partially sedimentable and display a latency that is unmasked by treatment with Triton X-100 and on dilution in hypo-osmotic media. It is concluded that these acid hydrolases belong to the lysosomes.     

Demethylation of dimethylsulfoniopropionate to 3-mercaptopropionate by an aerobic marine bacterium.

A bacterium, strain BIS-6, that grew aerobically on dimethylsulfoniopropionate (DMSP) was isolated from an intertidal mud sample. Strain BIS-6 quantitatively demethylated DMSP and 3-methiolpropionate to 3-mercaptopropionate. Strain BIS-6 was a versatile methylotroph growing on the osmolytes DMSP and glycine betaine and their methylated degradation products (dimethyl glycine, sarcosine, methylamines, and dimethyl sulfide.     

Organic Thiols as Organolithotrophic Substrates for Growth of Phototrophic Bacteria

Rhodopseudomonas sp. strain BB1, isolated from a coastal marine sediment, immediately metabolized mercaptomalate when grown on mercaptomalate. Sulfide was detected as an intermediate. Extracts of cells grown on mercaptomalate converted mercaptomalate or 3-mercaptopropionate to equimolar amounts of sulfide and either fumarate or acrylate, respectively. Rhodopseudomonas sp. strain BB1 gave higher growth yields on mercaptomalate than on sulfide or malate, consistent with metabolism of the carbon chain of the thiol and the liberated sulfide; i.e., the organic thiol was an organolithotrophic substrate. In contrast, Thiocapsa roseopersicina, isolated previously from a marine microbial mat, had similar growth yields on sulfide, mercaptomalate, or 3-mercaptopropionate, with fumarate or acrylate accumulation from the thiols. T. roseopersicina did not grow photoorganotrophically on fumarate or acrylate, and the thiols were only a source of sulfide for photolithoautotrophic growth.     

Volume regulation by flounder red blood cells in anisotonic media

The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation.     

Phytoplankton primary production and nutrients in the Oosterschelde (The Netherlands) during the pre-barrier period 1980–1984

Phytoplankton primary production, nutrient concentrations and turbidity were monitored at three stations in the Oosterschelde during 1980–1984 as part of an ecosystem study.From comparisons of dissolved nutrient ratios with the nutrient requirements of phytoplankton, and of ambient nutrient concentrations with half-saturation constants for nutrient uptake by natural phytoplankton populations it was concluded that silicate was a limiting nutrient for diatoms after the spring bloom until the end of the summer. Dissolved inorganic nitrogen and phosphate were not considered to be limiting to phytoplankton growth.In general, the phytoplankton growing season started during the first fortnight of April and ended at the end of September. Column production in the whole Oosterschelde varied between 201 and 540 g C m^–2 yr^–1 and was, on average, 25% higher in the western part than in the eastern part. Basin production in the Oosterschelde varied between 120 and 466 g C m^–2 yr^–1 and was, on average, 55% higher in the western part than in the eastern part; this difference could be explained by differences in the ratio of euphotic depth to mean depth of the compartments.Estimated carbon-specific growth rates in the eastern part varied between < 0.1 and 3 d^–1 and in the western part between < 0.1 and 1 d^–1. This difference could be explained by the great differences in depth of the compartments. Carbon-specific growth rates are discussed in relation to phytoplankton loss rates. It is suggested that in the eastern part sedimentation must be an important sink for phytoplankton.Communication no. 473 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.