Phage A25-mediated transfer induction of a prophage in Streptococcus pyogenes

Summary The group A streptococcal strain 56188 used as standard donor in transduction with the virulent phage A25 is lysogenic for a phage called P56188. By using specific antiphage sera it is shown that A25 lysates obtained from 56188 contain a fraction of about 10^-4 phenotypically A25 but genotypically P56188 particles. A25-mediated transduction of prophage P56188 is measured by scoring plaques produced by transfer induction on 5004, a lysogenic strain unable to support the growth of A25. Data are obtained suggesting that A25 can also transduce a prophage carried by strain T25₃.Prophage P5004 present in 5004 is found to interfere with the propagation of A25 but does not seem to exert its action by directing extensive degradation of A25 DNA. Lysogenization of SM27 with P5004 leads to dramatically decreased burst sizes of A25, associated with the loss of its ability to plaque on this strain. Furthermore, P5004 lysogens of SM27 yield fewer streptomycin resistant transductants than their parent but gain the ability to serve as donors in A25-mediated transduction. A comparison of the burst size and the yield of transducing particles of A25 on various lysogenic and nonlysogenic hosts suggests that interfering with A25 growth is a widespread property of streptococcal prophages, which might favour processes leading to the formation of transducing A25 particles.     

Regulation des photosynthetischen Elektronentransports zwischen Photosystem II und Photosystem I

Synchronkulturen einzelliger Grünalgen stellen ein ausgezeichnetes Untersuchungsmaterial zum Studium von Änderungen im Photosyntheseapparat ohne Anwendung externer Einflüsse dar. Vorausgegangene Untersuchungen legen es nahe, den begrenzenden Faktor für die Photosynthesekapazität im Elektronentransport zwischen PS II und PS I zu suchen. Die Regulation des Elektronentransportes zwischen PS'II und PS I während der Entwicklungszyklen von Scenedesmus und Chlamydomonas ist Gegenstand der vorliegenden Untersuchungen. Messungen der Poolgrößen des Plastochinons und der Cytochrome ergaben während der Entwicklungszyklen größere Differenzen für Chlamydomonas als für Scenedesmus. Jedoch waren die Differenzen nicht groß genug, um die Schwankungen in der Photosynthesekapazität zu erklären. Aus den Messungen konnte indirekt geschlossen werden, daß die Poolgröße des Quenchers Q während der Entwicklungszyklen konstant bleibt. Experimente mit den Photosynthesehemmstoffen DCMU und DBMIB an ganzen Zellen und photosynthetisch aktiven Partikeln führten zu dem Schluß, daß die Reoxidationskapazität von Plastochinon den geschwindigkeitsbestimmenden Schritt und somit die Regulation des nichtzyklischen Elektronentransports darstellt. Die Möglichkeit, daß während der Abnahme des nichtzyklischen Elektronentransports die Kapazität von PS I für zusätzliche zyklische Photophosphorylierung genutzt wird, wird diskutiert. Wir danken Herrn Prof. Dr. A. Trebst für die freundliche Überlassung von DBMIB und der Deutschen Forschungsgemeinschaft für apparative Unterstützung.     

Population Genetics of LEBISTES (POECILIA) RETICULATUS Peters (Poeciliidae; Pisces). I. Effects of Radiation-Induced Mutations on the Segregation Ratio in Postirradiation F2

Wild-type germ cells of the viviparous fish, Lebistes (Poecilia) reticulatus, were irradiated in the stages of oogonia, spermatogonia or spermatozoa with 1000 R of X rays at a dose-rate of 200-220 R/min. The grown-up fish were mated after irradiation or sham treatment to unirradiated mutant fish homozygous for three recessive gene loci, causing albinism, lack of yellow and reddish pigmentation ("blue" constitution), and diminution of the size of melanophores ("blond" constitution). As compared to the control series, the phenotypic segregation ratios in the adult F(2) generation after irradiation was changed significantly in favour of wild-type and blue fish, whereas the proportion of albinotic, blond and "white" (= blond + blue) guppies was lowered. This unidirectional effect in postirradiation F(2) was greatest after exposure of spermatozoa with 2 x 500 R (24 hr apart), followed by single doses of 1000 R to spermatogonia and oogonia. These results were explained in terms of a synergistic interaction of recessive radiation-induced mutations in the heterozygous state with those genotypes of the guppy which affect the formation of melanophoric patterns and the synthesis of melanins.     

Biosynthesis of plastoquinone and β-carotene in isolated chloroplasts

Intact, isolated spinach chloroplasts incorporated ¹⁴C from ¹⁴CO₂ into plastoquinone and β-carotene under photosynthetic conditions. Addition of unlabelled l-tyrosine, p-hydroxyphenylpyruvate, or homogentisate increased the incorporation of ¹⁴C into plastoquinone, but decreased that into β-carotene.     

Transient expression of chimaeric genes in dividing and non-dividing cereal protoplasts after PEG-induced DNA uptake

Transient expression of chimaeric genes (neomycin phosphotransferase fused to four different promoters) was detected in suspension culture derived protoplasts of maize, barley and rice, in mesophyll protoplasts of maize, rice, rye, and root protoplasts of maize. The introduction and expression of foreign genes could be performed with both dividing and non-dividing protoplasts by applying the PEG transformation method. The significance of this method for the functional analysis of genes was demonstrated by the differential expression of a regulated gene in protoplasts of different tissues in agreement with its expression in the donor tissue.Abreviations PEG polyethylene glycol - NPT neomycin phosphotransferase - 2,4-D 2,4-dichlorophenoxyacetic acid - caseinh. caseinhydrolysate     

Heterogeneity of the α-globin gene defects in German α-thalassemia affected families

Summary Analysis of -thalassemia syndromes in several German families revealed DNA deletion as well as nondeletion forms as the molecular basis for the defects. Thus, the -thalassemia haplotype was identified as the (–)^3.7 rightward deletion form, and the region of the putative recombination process generating such a deletion was further characterized. In addition three different ° haplotypes, (--)^MED, (--)^>26, and ()^T, could be detected using -and -globin gene-specific probes.     

Incorporation of shikimate and other precursors into aromatic amino acids and prenylquinones of isolated spinach chloroplasts

Under conditions of photosynthesis, shikimate-[1,6-¹⁴C] and D,L-tyrosine-[β-¹⁴C] were incorporated into the aromatic amino acids Phe, Tyr and Trp, and the prenylquinone and α-tocopherol by intact spinach chloroplasts. This might indicate the presence of enzymes of shikimate pathway in chloroplasts.     

The development of structure and function in chloroplasts of greening mutants of Scenedesmus IV. Blue light-dependent carbohydrate and protein metabolism

Pigment mutant C-2A' of Scenedesmus obliquus forms only tracesof chlorophyll when grown heterotrophically in the dark. Thechloroplast shows pre-thylakoid structures and a high Contentof starch grains. Illumination causes a sequence of reactionsleading, finally, to chloroplasts with normal thylakoids andan efficiently functioning photosynthetic apparatus. Upon illumination the respiration of the cells is enhanced,starch is degraded and protein is synthesized. The newly-formedprotein in turn is used for formation of enzyme(s) leading tothe synthesis of -aminolevulinic acid, of structural proteinsin the thylakoid membranes and finally to the chlorophyll holochrome.Most of the newly-synthesized protein becomes part of the thylakoidmembranes. All these processes are strictly blue light-dependent. The blue light phenomena can be separated into two groups onthe basis of small wavelength shifts and of their energy requirement.Enhancement of respiration and starch degradation are saturatedat low energy (0.4 w/m² whereas the subsequent protein synthesisand following processes are saturated at high energy (100 w/m²) From the wavelength dependence of the reactions we conclude,in accordance with other authors, that flavoproteins are theprimary photoreceptors. The possibility that the primary lowenergy process might excite a flavoprotein which in turn causesa conformational change in its apoprotein, and that the highenergy process might present a direct energy transduction viaa flavoprotein is discussed. (Received May 10, 1978; )     

Primary structure of the Klebsiella serotype 16 capsular polysaccharide

The primary structure of the Klebsiella serotype 16 capsular polysaccharide consists of tetrasaccharide repeating-units comprising a/ar3)-α-D-Glcp-(1/ar4)β-D-GlcAp-(1/ar4)-α-L-Fucp-(1/ar chain with a β-D-Galp-(1→ branch at position 4 of the D-glucosyl residue.     

Nucleotide sequence of the mitochondrial structural genes for cysteine-tRNA and histidine-tRNA of yeast.

We have determined the nucleotide sequence of a segment of Saccharomyces cerevisiae mtDNA that contains the structural genes for a cysteine-tRNA and a histidine-tRNA. The genes are approximately 85 bp apart, they do not contain intervening sequences or sequences coding for the 3'-CCA terminus and they are surrounded by nearly pure AT segments. The tRNAs deduced are very AT-rich, 74 and 75 nucleotides long, respectively, and contain one or more unusual features not found in tRNAs from other sources.