Evidence for Na+/H+ antiport inMethanospirillum Hungatei

The growth and methane formation ofMethanospirillum hungatei were inhibited by an inhibitor of Na⁺/H⁺ antiport amiloride. After addition of NaCl or LiCl, when the cells had a lower intracellular pH and were deenergized, they extruded protons into the external medium. The acidification of the external medium was stimulated by protonophores and inhibited by amiloride. These findings suggest the existence of an Na⁺/H⁺ antiport in the cytoplasmic membrane ofM. hungatei and its role in the energetics of methanogenic bacteria.     

Microphotometric determination of structure-bound oxidoreductase activities avoiding nothing-dehydrogenase artefacts: succinate dehydrogenase

 A tetrazolium-based microphotometric method has been devised for the determination of structure-bound dehydrogenase activities with correction for nothing-dehydrogenase artefacts. The method is based on the microphotometric recording of maximum reaction rates in a simple incubation chamber and consists of two successive measurements on the same section, the first in the absence and the second in the presence of the substrate. Following the first measurement, the substrate-free medium is quickly exchanged with the substrate-containing medium and a second measurement is taken. Subtraction of the first from the second reaction rate yields the enzyme activity corrected for nothing-dehydrogenase. Measurements of succinate dehydrogenase (SDH) in skeletal muscle fibres, liver, cardiac atrium and ventricle demonstrate the feasibility of the method. Measurements on the extensor digitorum longus muscle of rat reveal a range of up to fivefold differences in SDH activity within the fibre population of this muscle. Accepted: 11 April 1997     

Occurrence ofEnterococcus spp. in waters

We studied 630 bacterial strains isolated from surface waters and determined as enterococci on the basis of their growth on Slanetz-Bartley agar in typical colonies. The strains were tested and characterized by several key conventional tests for basic differentiation of enterococci and by commercial test kits. We identified 135 strains ofE. fœcium (21%), 115E. fœcalis (18%), 30E. mundtii (5%), 27E. hirae (4%), 22E. casseliflavus (3%), 21E. gallinarum (3%), 17E. durans-E. hirae complex (3%), 5E. durans (1%), and 1 strain ofE. avium. 150 strains were classified only asEnterococcus sp. (25%) and 107 strains (17%) isolated from Slanetz-Bartley agar were not enterococci. We found that the non-enterococcal group consisted of other Gram-positive cocci and Gram-positive and Gram-negative rods. Based on the identification we tried to find a relation between taxonomic position of isolated strains and their colony morphology on Slanetz-Bartley agar. Out of the total of 523 identified enterococci, 345 strains (66%) formed purple colonies, 136 red colonies (26%), 37 pink colonies (7%) and 5 cream colored colonies (1%). There was no correlation among the color, size or colony morphology and the taxonomic characterization of enterococcal strains.     

Vergleichend-anatomische Untersuchung einer interglazialen Konifere

Ohne Zusammenfassung     

Thermal melting and circular dichroism of DNA complexes with (Lys-Ala-Ala)10 and (Lys-Ala-Ala)n: effect of polypeptide chain length

DNA complexes with polypeptides (Lys-Ala-Ala)₁)] and (Lys-Ala-Ala)₃₄ have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)₁₀ DNA differed substantially from those of (Lys-Ala-Ala)₃₄ prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with T_m increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with T_m values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)₁₀-DNA system but a slow redistribution of (Lys-Ala-Ala)₃₄ on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding.