The Arthrobacter arilaitensis Re117 Genome Sequence Reveals Its Genetic Adaptation to the Surface of Cheese

Arthrobacter arilaitensis is one of the major bacterial species found at the surface of cheeses, especially in smear-ripened cheeses, where it contributes to the typical colour, flavour and texture properties of the final product. The A. arilaitensis Re117 genome is composed of a 3,859,257 bp chromosome and two plasmids of 50,407 and 8,528 bp. The chromosome shares large regions of synteny with the chromosomes of three environmental Arthrobacter strains for which genome sequences are available: A. aurescens TC1, A. chlorophenolicus A6 and Arthrobacter sp. FB24. In contrast however, 4.92% of the A. arilaitensis chromosome is composed of ISs elements, a portion that is at least 15 fold higher than for the other Arthrobacter strains. Comparative genomic analyses reveal an extensive loss of genes associated with catabolic activities, presumably as a result of adaptation to the properties of the cheese surface habitat. Like the environmental Arthrobacter strains, A. arilaitensis Re117 is well-equipped with enzymes required for the catabolism of major carbon substrates present at cheese surfaces such as fatty acids, amino acids and lactic acid. However, A. arilaitensis has several specificities which seem to be linked to its adaptation to its particular niche. These include the ability to catabolize D-galactonate, a high number of glycine betaine and related osmolyte transporters, two siderophore biosynthesis gene clusters and a high number of Fe3+/siderophore transport systems. In model cheese experiments, addition of small amounts of iron strongly stimulated the growth of A. arilaitensis, indicating that cheese is a highly iron-restricted medium. We suggest that there is a strong selective pressure at the surface of cheese for strains with efficient iron acquisition and salt-tolerance systems together with abilities to catabolize substrates such as lactic acid, lipids and amino acids

The Complete Genome Sequence of Cupriavidus metallidurans Strain CH34, a Master Survivalist in Harsh and Anthropogenic Environments

Many bacteria in the environment have adapted to the presence of toxic heavy metals. Over the last 30 years, this heavy metal tolerance was the subject of extensive research. The bacterium Cupriavidus metallidurans strain CH34, originally isolated by us in 1976 from a metal processing factory, is considered a major model organism in this field because it withstands milli-molar range concentrations of over 20 different heavy metal ions. This tolerance is mostly achieved by rapid ion efflux but also by metal-complexation and -reduction. We present here the full genome sequence of strain CH34 and the manual annotation of all its genes. The genome of C. metallidurans CH34 is composed of two large circular chromosomes CHR1 and CHR2 of, respectively, 3,928,089 bp and 2,580,084 bp, and two megaplasmids pMOL28 and pMOL30 of, respectively, 171,459 bp and 233,720 bp in size. At least 25 loci for heavy-metal resistance (HMR) are distributed over the four replicons. Approximately 67% of the 6,717 coding sequences (CDSs) present in the CH34 genome could be assigned a putative function, and 9.1% (611 genes) appear to be unique to this strain. One out of five proteins is associated with either transport or transcription while the relay of environmental stimuli is governed by more than 600 signal transduction systems. The CH34 genome is most similar to the genomes of other Cupriavidus strains by correspondence between the respective CHR1 replicons but also displays similarity to the genomes of more distantly related species as a result of gene transfer and through the presence of large genomic islands. The presence of at least 57 IS elements and 19 transposons and the ability to take in and express foreign genes indicates a very dynamic and complex genome shaped by evolutionary forces. The genome data show that C. metallidurans CH34 is particularly well equipped to live in extreme conditions and anthropogenic environments that are rich in metals

Isolement d'une communaute microbienne degradant l'acide 2,4-dichlorophenoxyacetique a partir d'un sol de Dijon. Caracterisations cinetique et genetique des souches impliquees

*INRA Laboratoire de Microbiologie des Sols BP 86510 21065 Dijon cedex(FRA) Diffusion du document : INRA Laboratoire de Microbiologie des Sols BP 86510 21065 Dijon cedex(FRA) Diplôme : Dr. d'Universit

Isolement d'une communaute microbienne degradant l'acide 2,4-dichlorophenoxyacetique a partir d'un sol de Dijon. Caracterisations cinetique et genetique des souches impliquees

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 83784 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Caractérisation taxonomique et dynamique de la flore bactérienne de surface de munsters (rôle antagoniste d'isolats corynéformes issus de la flore résiliente contre Listeria)

PARIS-AgroParisTech Centre Paris (751052302) / SudocSudocFranceF

Gene tfd from the 2,4-D degrading bacteria Alcaligenes paradoxus TV1 could be used as probe for the research of soil microorganisms able to degrade this herbicide

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An approach to freshwater cyanobacterial production and excretion : tentative application of a deterministic model

49 ref.International audienceThe rates of photosynthesis, respiration and carbon excretion by the cyanobacteriumOscillatoria rubescens D.C. were estimated at a range of light intensities between 0 and 60 μE m−2 s−1 (μmol photon m−2 s−1) using the14C method. A model of the evolution of cell carbon concentration based on the Hobsonet al. (1976) equations and taking excretion into account is presented. This model predicts that the sum of respiration and excretion rates increases more rapidly with light than the rate of photosynthesis and therefore maximum growth of theO. rubescens strain under study should be obtained at low light intensities, approximately 20 μE m−2 s−1 . Light rapidly increases the excretion rate and so induces a deficit in the carbon balance of the cell. In addition, the simultaneous increase in respiration rate, possibly due to photorespiration, contributes to carbon depletion at high irradiances. Thus, this model explains some of our observations, particularly the fact that growth is saturated at lower light intensities than photosynthesis.Nous avons estimé les taux de photosynthèse, de respiration et d'excrétion carboné chez Oscillatoria rubescens D.C. sous une gamme de conditions d'éclairement comprise entre 0 et 60 μE m−1 s−1 grâce à l'emploi de la méthode au14C. Un modèle d'évolution du carbone chez la cyanobactérie s'appuyant sur les équations de Hobsonet al. (1976) et prenant en compte la respiration et l'excrétion cellulaire est présenté. Ce modèle prévoit que la somme des taux de respiration et d'excrétion doit croître plus rapidement avec la lumière que le taux de photosynthèse. Il montre par ailleurs que la croissance maximale de la souche étudiée d'O. rubescens doit être trouvée à faible intensité lumineuse, environ 20 μE m−2 s−1. La lumière semble provoquer un accroissement rapide du taux d'excrétion et provoquer ainsi un deficit au niveau du bilan carboné de la cellule. De plus, l'accroissement simultané du taux de respiration probablement du à l'apparition de la photorespiration contribue à l'épuisement du carbone cellulaire aux fortes intensités lumineuses. Ainsi, ce modèle explique certaines de nos observations expérimentales et particulièrement le fait que la croissance est saturée à de plus faibles intensités lumineuses que la photosynthèse

Assessing side effects of micropolluants on the soil microflora

91 ref.International audienc

Amplification of putative chlorocatechol dioxygenase gene fragments from alphaand beta-proteobacteria

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