Characterization of Desulfovibrio giganteus sp. nov., a sulfate-reducing bacterium isolated from a brackish coastal lagoon

In the course of ecological studies in Berre Lagoon, a mediterranean brackish coastal lagoon (Marseille, France), a new slightly halophilic sulfate-reducing bacterium was isolated from anoxic sediments enriched with lactate plus sulfate, and cysteine-HCL as reductant. Because of its morphology and the incomplete oxidation of organic substrates, the isolated strain 8601 was assigned to the genus #Desulfovibrio, resembling #Desulfovibrio gigas. However, it differed from this species in some morphological and physiological characteristics : only one polar flagellum the utilization of methanol, isopropanol, glycerol and cysteine as energy source. Therefore a new species #Desulfovibrio giganteus$ is described. (Résumé d'auteur

Taxonomic rearrangements of the genera Thiocapsa and Amoebobacter on the basis of 16S rDNA sequence analyses and description of Thiolamprovum gen. nov.

Complete nucleotide sequences of the 16S rDNAs were determined from Thiocapsa and Amoebobacter species, including all available type strains and some additional isolates. The distance-matrix analysis and the dendrogram for estimating the genetic relationships revealed that the investigated strains were found in two major clusters within the Chromatiaceae. One cluster comprises all Amoebobacter species, Thiocapsa roseopersicina and several isolates related to Thiocapsa roseopersicina. Representatives of the species Amoebobacter roseus, Amoebobacter pendens and Thiocapsa roseopersicina, the so called ‘Thiocapsa roseopersicina group’, are very closely related, justifying their inclusion into one genus, Thiocapsa, for which an emended description is presented. Amoebobacter purpureus and Amoebobacter pedioformis formed two separate lines of descent with less than 93% (89·6–92·9%) similarity to strains of the ‘Thiocapsa roseopersicina group’. Therefore, they will be considered as two separate genera. As a consequence, an emended description is presented for the genus Amoebobacter, with Amoebobacter purpureus as the new type species and A. pedioformis is transferred to Thiolamprovum pedioforme gen. nov., comb. nov. Two species, Thiocapsa pfennigii and Thiocapsa halophila, which have been classified with the genus Thiocapsa because of their morphological properties, were found within another major cluster of the Chromatiaceae and are only distantly phylogenetically related to the first cluster with 88·4–90·6% and 90·4–92·2% sequence similarity, respectively

Marichromatium bheemlicum sp. nov., a non-diazotrophic photosynthetic gammaproteobacterium from a marine aquaculture pond

A rod-shaped, phototrophic, purple sulfur bacterium, strain JA124(T), was isolated in pure culture from a marine aquaculture pond, located near Bhimunipatnam, in a medium that contained 3 % NaCl (w/v). Strain JA124(T) is a Gram-negative, motile rod with a single polar flagellum. Strain JA124(T) has a requirement for NaCl, with optimum growth at 1.5-8.5 %, and tolerates up to 11 % NaCl. Intracellular photosynthetic membranes are of the vesicular type. Bacteriochlorophyll a and probably carotenoids of the spirilloxanthin series are present as photosynthetic pigments. Strain JA124(T) was able to utilize sulfide, sulfate, thiosulfate, sulfite, thioglycollate and cysteine as sulfur sources. Strain JA124(T) was able to grow photolithoautotrophically, photolithoheterotrophically and photo-organoheterotrophically. Chemotrophic and fermentative growth could not be demonstrated. Strain JA124(T) lacks diazotrophic growth and acetylene reduction activity. Pyridoxal phosphate is required for growth. During growth on reduced sulfur sources as electron donors, sulfur is deposited intermediately as a number of small granules within the cell. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA124(T) clusters with species of the genus Marichromatium belonging to the class Gammaproteobacteria. The highest sequence similarities of strain JA124(T) were found with the type strains of Marichromatium indicum (98 %), Marichromatium purpuratum (95 %) and Marichromatium gracile (93 %). However, DNA-DNA hybridization with Marichromatium indicum DSM 15907(T) revealed relatedness of only 65 % with strain JA124(T). The DNA base composition of strain JA124(T) was 67 mol% G+C (by HPLC). Based on 16S rRNA gene sequence analysis, morphological and physiological characteristics and DNA-DNA hybridization studies, strain JA124(T) (=ATCC BAA-1316(T)=JCM 13911(T)) is sufficiently different from other Marichromatium species to merit its description as the type strain of a novel species, Marichromatium bheemlicum sp. nov

The In Vivo Role of the RP-Mdm2-p53 Pathway in Signaling Oncogenic Stress Induced by pRb Inactivation and Ras Overexpression

The Mdm2-p53 tumor suppression pathway plays a vital role in regulating cellular homeostasis by integrating a variety of stressors and eliciting effects on cell growth and proliferation. Recent studies have demonstrated an in vivo signaling pathway mediated by ribosomal protein (RP)-Mdm2 interaction that responds to ribosome biogenesis stress and evokes a protective p53 reaction. It has been shown that mice harboring a Cys-to-Phe mutation in the zinc finger of Mdm2 that specifically disrupts RP L11-Mdm2 binding are prone to accelerated lymphomagenesis in an oncogenic c-Myc driven mouse model of Burkitt's lymphoma. Because most oncogenes when upregulated simultaneously promote both cellular growth and proliferation, it therefore stands to reason that the RP-Mdm2-p53 pathway might also be essential in response to oncogenes other than c-Myc. Using genetically engineered mice, we now show that disruption of the RP-Mdm2-p53 pathway by an Mdm2C305F mutation does not accelerate prostatic tumorigenesis induced by inactivation of the pRb family proteins (pRb/p107/p130). In contrast, loss of p19Arf greatly accelerates the progression of prostate cancer induced by inhibition of pRb family proteins. Moreover, using ectopically expressed oncogenic H-Ras we demonstrate that p53 response remains intact in the Mdm2C305F mutant MEF cells. Thus, unlike the p19Arf-Mdm2-p53 pathway, which is considered a general oncogenic response pathway, the RP-Mdm2-p53 pathway appears to specifically suppress tumorigenesis induced by oncogenic c-Myc

Numération et approche qualitative des populations bactériennes des lagunes aménagées de Certes (Arcachon). I. Bactéries hétérotrophés aérobies

Numeration, biomass, distribution within time, some physiological characters and a taxonomical outline, with a standardized micro method, of aerobic hétérotrophie bacteria isolated from sediments an waters, from fishponds of "Domaine de Certes" (Arcachon) from june 1977 to may 1978 are described. Number of hétérotrophie bacteria evolved in a significant way, according to seasons, and bacterial biomass is higher in the sediments than in the waters. Metabolic or physiological differences (proteolysis, denitrification) appeared among populations due to the origin of sediments. Moreover the qualitative study pointed out taxonomical units as Bacillus associated to seasons, or Agrobacterium associated to vegetable detritical sediments.La numération, la biomasse, la distribution dans le temps, quelques caractères physiologiques et une ébauche taxonomique des bactéries hétérotrophes aérobies isolées des sédiments et des eaux lagunaires des réservoirs à poissons du domaine de Certes (Arcachon) de juin 77 à mai 78 sont décrits. Le nombre de bactéries hétérotrophes évolue d'une façon significative suivant les saisons et la biomasse bactérienne est plus élevée dans les sédiments que dans les eaux. Des différences métaboliques ou physiologiques (protéolyse, dénitrification) sont apparues au sein des populations en fonction de l'origine des sédiments. De plus, l'étude qualitative fait ressortir des unités taxonomiques telles que Bacillus associé aux saisons ou Agrobacterium associé à un sédiment détritique végétal