Bacteriophage and the Toxigenicity of <Emphasis Type="Italic">Clostridium botulinum</Emphasis> Type D

THE data of Inoue and Iida^1,2 strongly suggest that bacteriophage is involved in the toxigenicity of Clostridium botulinum types C and D. They were able to recover toxigenic isolates from nontoxigenic cultures incubated in broth containing filtrates of the toxigenic strains (Stockholm strain of type C and strain 1873 of type D). Lysis was observed in the cultures, but plaques were not demonstrated on solid medium. The change from hontoxigenicity to toxigenicity in C. botulinum type C strain 468C has been shown³ to require the active and continued participation of a specific bacteriophage designated CEβ.     

Relations Between Indoleacetic Acid, Calcium Ions and Ethylene in the Regulation of Growth and Cell Wall Composition in Picea abies

Effects of indoleacetic acid, calcium ions and ethylene on thegrowth of and deposition of different cell wall fractions inthe hypocotyl of Norway spruce (Picea abies (L.) Karst.) seedlingswere investigated. Indoleacetic acid progressively stimulated cellulose depositionas the amount of added Ca²⁺ increased. In contrast, indoleaceticacid promoted lignification and the deposition of non-cellulosicpolysaccharides only in the absence of added Ca²⁺ . When Ca²⁺was added, the indoleacetic acid effect disappeared. Similarly,indoleacetic acid promoted non-cellulosic polysaccharide depositiononly in the absence of ethylene. At increasing ethylene levelsthe effect of indoleacetic acid on non-cellulosic polysaccharidedeposition disappeared and indoleacetic acid instead promotedcellulose deposition. The response to indoleacetic acid depended on the Ca²⁺ concentrationand on the rate of ethylene production. The relationship betweenindoleacetic acid and Ca²⁺ seemed complex, but clearly indoleaceticacid could partially overcome a Ca²⁺ deficiency. The resultssuggest that ethylene may be a factor of particular importancefor the type of polysaccharide deposition during cell wall formation. Key words: Calcium, cell wall, conifers, ethylene, indoleacetic acid     

The effects of selection,drift and genetic variation on life‐history trait divergence among insular populations of natterjack toad,Bufo calamita

Although loss of genetic variation is frequently assumed to be associated with loss of adaptive potential, only few studies have examined adaptation in populations with little genetic variation. On the Swedish west coast, the northern fringe populations of the natterjack toad Bufo calamita inhabit an atypical habitat consisting of offshore rock islands. There are strong among‐population differences in the amount of neutral genetic variation, making this system suitable for studies on mechanisms of trait divergence along a gradient of within‐population genetic variation. In this study, we examined the mechanisms of population divergence using Q_ST–F_ST comparisons and correlations between quantitative and neutral genetic variation. Our results suggest drift or weak stabilizing selection across the six populations included in this study, as indicated by low Q_ST–F_ST values, lack of significant population × temperature interactions and lack of significant differences among the islands in breeding pond size. The six populations included in this study differed in both neutral and quantitative genetic variation. Also, the correlations between neutral and quantitative genetic variation tended to be positive, however, the relatively small number of populations prevents any strong conclusions based on these correlations. Contrary to the majority of Q_ST–F_ST comparisons, our results suggest drift or weak stabilizing selection across the examined populations. Furthermore, the low heritability of fitness‐related traits may limit evolutionary responses in some of the populations.     

Effects of Calcium Ion Concentration on Cel Wall Synthesis

Cuttings of 6-week-old Norway spruce (Picea abies (L.) Karst.)seedlings were placed in liquid media containing various concentrationsof Ca²⁺. Cytoplasmic concentrations of Ca²⁺ were manipulatedusing the ionophore A 23 187. The effects of Ca²⁺ concentrationson the deposition of total cell wall material as well as onthe deposition of cellulose, lignin, and non-cellulosic polysaccharidesin the hypocotyls were investigated. At low concentrations ofCa²⁺ wall deposition was reduced, mainly as a result of theinhibition of lignin and non-cellulosic polysaccharide deposition.High concentrations of Ca²⁺ stimulated non-cellulosic polysaccharideand lignin deposition, whereas cellulose deposition was almosttotally inhibited. Key words: Conifers, calcium, cell wall, lignin, cellulose