Laboratory investigations on the survival of marine bacteriophages in raw and treated seawater

Laboratory investigations were performed to gain insight into the mechanisms which govern the survival of marine bacteriophages in nature. Samples collected in 1988 to 1990 at station “Kabeltonne” near Helgoland were used raw, membrane-filtered (0.15μm), and/or after inverse filtration through 10 μm-mesh gauze to reduce or increase live and dead particles. The development of natural or artificial bacterial populations and the survival of 2 to 10 distinguishable strains of test phage were followed during incubation at 20°C. The results obtained with most test phages point to the predominant role of indigenous bacteria for marine phage inactivation which was generally enhanced by sample managements leading to improved growth of bacteria. The virucidal properties of the samples differed greatly in total strength as well as in the changes taking place during incubation, the latter resulting in conspicuously differing inactivation curves. Generally, phage inactivation was slow during the first 2 to 3 days of incubation, followed by a period of very rapid inactivation which usually coincided with the die-away of colony-forming bacteria. This period lasted either only a few days or until the concentration of test phage was reduced to (near) zero. While the inactivation of most test phage is assumedly caused by proteolytic enzymes released during the die-away of bacteria, the survivability of one test phage (H7/2) was also markedly influenced by the bacteria sensitive to it. Survival rates of the test phages in the laboratory tests were generally of the same order of magnitude as those recently observed with natural phage populations.     

Abiotic edaphic factors affecting the growth of a threatened North American Sunflower, Helianthus paradoxus (Asteraceae)

This study evaluated the relationships among soil moisture, soil salinity, and soil oxygen on the growth of Helianthus paradoxus (Asteraceae), a threatened inland salt marsh species of western North America. The study was conducted in large growth boxes (1×2×0.3 m) tilted at an angle to achieve a saturated to dry water gradient similar to that found in the marsh. This experimental design allowed the evaluation of major abiotic factors (soil moisture and soil salinity) which have been shown to be potentially important for this species, while removing major biotic factors, such as competition from other community dominants. Maximum aboveground biomass occurred in the middle rows of the boxes, where surface soil water was reduced and subsurface soil water was intermediate in the gradient. Regression analyses indicated that H. paradoxus would grow best where surface soil water is approximately 5%, subsurface soil water ranges from 20 to 30%, and where surface soil salinity is less than 0.5 g kg⁻¹. Edaphic variables, particularly soil moisture and soil salinity, affect the growth of H. paradoxus. Data presented here suggest that the survival of this species depends on maintenance of the hydrologic regime.     

Purification of soluble guanylate cyclase enzyme from human platelets

Soluble guanylate cyclase enzyme was purified from human platelets. The soluble fraction of the lysed platelets was sequentially chromatographed over DEAE-sepharose, GTP-agarose and HPLC size-exclusion columns. About 0.1 mg of purified enzyme could be obtained from 2000 ml of platelet rich plasma. The purified enzyme had the specific activity of 205 nmoles cGMP/mg/min with Mn2+ as cofactor. The enzyme eluted at the 160,000 daltons position from the size-exclusion column. Electrophoresis in the presence of sodium dodecyl sulfate under reducing conditions revealed two subunits of 83,000 and 71,000 daltons respectively.     

Effectiveness of chemical mutagenesis in multiple damage to one or both strands of plasmid DNA

Methods for site-directed multiple modification of DNA have been developed and used for modification of either one or two strands of plasmid DNA. Plasmid DNAs modified in the region of the tet gene were transformed into Escherichia coli cells and Tet colonies were screened. It was shown that multiple lesions in one DNA strand performed using either N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or sodium bisulfite were effectively repaired in the cell by error-free mechanism. In contrast, modification of two DNA strands led to induction of mutations. The efficiency of mutagenesis in the case of modification of a local region of one DNA strand with sodium bisulfite and modification of the other strand with MNNG was 1.1-7.9%. Mutations were analysed by restriction mapping and sequencing. All of them were G----A transitions.