Uptake of DNA has been examined in the naturally competent cyanobacterium, Synechocystis sp. Pasteur Culture Collection (PCC) 6803. This bacterium is easily transformed by exogenously offered, ...homologous as well as heterologous DNA. During uptake, the DNA is converted from double stranded to single stranded form. A Ca‐dependent nuclease, located in the cytoplasmic membrane, probably processes the DNA offered for uptake and converts it into single stranded form. The cyanobacterial DNA‐uptake process is discussed in comparison to respective phenomena in other bacteria.
La méthode prosopographique, mise au point par des historiens de Rome au xixe siècle, s’attache à la constitution de notices individuelles fondées sur des renseignements biographiques de toutes ...sortes à propos de personnes ayant des liens entre elles. L’analyse comparée de l’ensemble des notices, à partir du matériel réuni, classé et interprété, permet d’établir les points communs et particularités, en vue d’une synthèse d’histoire générale. Cette méthode a contribué, dès ses origines, au renouvellement de nos connaissances de l’empire romain. Les diverses contributions de ce symposium international, célébrant l’activité scientifique de Janine Desmulliez, professeur émérite d’Histoire du christianisme à Lille 3, se présentent comme la première synthèse de ce type, à portée méthodologique et historiographique, fondée sur des recherches originales, d’éminents prosopographes comme de jeunes chercheurs, abordant sur la longue durée de multiples aspects de la société romaine d’empire, païenne et chrétienne. Des empereurs aux gouverneurs de provinces, des prêtres et dévots païens aux évêques et pères de l’Église chrétienne, ce sont autant d’éléments constitutifs de la société romaine d’empire qui sont éclairés par l’analyse prosopographique des données disponibles, sa méthode rigoureuse et ses résultats assurés. Ce volume illustre la fécondité de recherches entreprises dont la seule légitimité est de faire progresser l’histoire sociale du monde romain, cette « vie des autres », ce miroir de l’humanité qu’évoque Ségolène Demougin en conclusion.
The chicken Ig lambda light chain locus is composed of a single V gene closely linked (1.8 kb) to a single J‐C unit in its natural configuration. In mice transgenic for this locus, the transgene ...becomes rearranged in B cells and to a much lesser extent in T cells. Modifications were introduced in the transgene in order to characterize elements which target the recombinase to the Ig loci. In the absence of either the promoter or the enhancer located 3′ of C lambda, rearrangement of the transgene is reduced 20‐ to 100‐fold. Moreover, rearrangement is increased 5‐fold when the DNA segment between V lambda and J lambda (‘Uo segment’), which is deleted during the joining process, is replaced by a neutral DNA segment of equal length. The Uo segment behaved as a strong transcriptional silencer when tested in a CAT assay in vitro. Control transgenic mice harbouring only the two 3 bp mutations that introduced restriction sites at both ends of the Uo segment to allow for its replacement were also analysed. Rearrangement was reduced 10‐ to 100‐fold in B cells from such transgenic lines. A model is proposed whereby the sites of these two mutations would function by counteracting transiently the repressing effect of the silencer, thus giving access of the chicken light chain locus to the recombinase.
The DNA encoding the subunits of the ATP synthase (F
1F
o) of
Streptomyces lividans 66 strain 1326 was identified using oligodeoxyribonucleotide probes derived from the N-terminal sequence of subunit ...γ of the F
1 complex. The complete nucleotide sequence of the operon was determined. The
atp operon contains nine genes,
atpIBEFHAGDC, encoding the eight structural components of the ATP synthase complex and the i protein, a polypeptide of unknown function. The gene order found is identical to that in other non-photosynthetic eubacteria. The determination of the N-terminal amino acid (aa) sequences of the F
1 subunits α, β, γ, δ and ε allowed us to identify the translational start points and to define the primary structures of the proteins. The aa sequence deduced for subunit δ revealed an N-terminal extension of about 90 aa, which is not present in any δ subunit or OSCP (oligomycin sensitivity-conferral protein) of other species studied so far. The phylogenetic relationship of eu- and archaebacteria was investigated using sequencing data of the highly conserved β subunit of different ATP synthases including that of
S. lividans. The calculations revealed that
S. lividans β does not form a phylogenetic group together with the Gram
+ taxa of low G+C contents, but is more closely related to the β subunit of Rhodobacteria.
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