We sequenced nearly complete small-subunit rRNAs of 54 reference strains belonging to the genera Kbrio, Photobacterium, Aeromonas, and Plesiomonas. We then performed a phylogenetic analysis by comparing the sequences which we obtained with all other known sequences for bacteria belonging to the gamma subgroup of the Proteobacteh (thus providing a data base consisting of 70 sequences for the genera investigated), using methods such as neighbor joining, maximum likelihood, and maximum parsimony, as well as bootstrap, to assess the robustness of each topology. Our results confirmed that the family V?riomceae should include only Photobacterium and Kbrio species (but not Hbrio marinus); that Aeromonas species deserve family rank; and that Plesiomonas shigebides is linked to the family Enterobacterheae. The genera Vdrio, Photobacterium, Aeromonas, and Pleswmonas, together with the family Enterobactkrheae, the family Pasteurekeae, and probably the genus Alteromonas, form a robust monophyletic unit within the gamma 3 subgroup of the Proteokteria.rRNA oligomer cataloging (18, 37, 43), DNA-DNA and RNA-DNA hybridization (3,6,18,32), and 5s rRNA sequencing (15,27,28) have been used previously to study the genera Vibrio, Photobacterium, Aeromonas, and Plesiomonas. Smallsubunit rRNA oligomer catalogs have revealed that these genera, along with the family Enterobacteriaceae, form a branch of the gamma 3 subdivision of the purple bacteria (43). More recently, inter-and intrageneric relationships have been determined by using small-subunit rRNA sequences of Vibrio strains (nearly complete sequences for 10 species [ 141 and partial sequences for Vibrio and Photobacterium species [23]) and Aeromonas strains (10 species), as well as Plesiomonas shigelloides (29). From a taxonomic point of view, broad general agreement has been reached between classification based on a molecular approach and classical classification derived from physiological comparisons and numerical taxonomy. The results of genetic studies suggested, however, that the family Vibrionaceae should include only the genera Vibrio and Photobacterium (9,16,41,42), that the genus Aeromonas should be placed in a different family, the Aeromonadaceae, and that Plesiomonas shigelloides is more closely related to the family Enterobacteriaceae than to the family Vibrionaceae (6, 12, 18, 27, 43).Comparisons of small-subunit rRNA sequences are more informative than either analyses of 5s rRNA sequences or analyses of small-subunit rRNA oligomer catalogs. However, the results of studies in which workers used small-subunit rRNA sequences, which for many species were either not determined or were only partially determined, have left some questions unanswered. Also, the phylogenetic methods used previously to analyze relationships often have not included any estimate of the robustness of the results. Under these conditions, the phylogenetic relationships of all of these species were uncertain. In this study, we sequenced 54 strains and combined our data with previously published seque...

We describe a new species on the basis of phenotypic characteristics and the results of an analysis of small-subunit rRNA sequences. Three strains of this organism were isolated from a culture of the toxinproducing dinoflagellate Prorocentrum Zima. These bacteria are gram-negative, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37°C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase, P-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growth. They grow only when glucose, trehalose, saccharose, fructose, maltose, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketogluconate, glutamate, or shikimate is present as a sole carbon source. The three strains have identical small-subunit rRNA sequences. A phylogenetic analysis of these sequences revealed that these bacteria belong to the alpha subdivision of the Proteobacteria and that they form a distinct and robust monophyletic group with Roseobacter denitrifcans and Roseobacter Zitoralis. This result and the general phenotypic characteristics of the organisms place them in the genus Roseobacter, although they do not produce bacteriochlorophyll a, in contrast to previously described Roseobacter species. On the basis of the phenotypic and genetic similarities of these strains, we assigned them to a single species, for which the name Roseobacter algicola is proposed. The type strain is R. algicola FF3 (= ATCC 51440).The genus Roseobacter was created to comprise two bacterial species, Roseobacter denitriJicans and Roseobacter litoralis, which have been isolated from the surfaces of green seaweeds but not from seawater; these aerobic, pink-pigmented bacteria contain bacteriochlorophyll a (16,17). The genus Roseobacter differs phenotypically from the closely related genus Elythrobacter in carotenoid composition, bacteriochlorophyll-protein complex composition, and cell shape (16).Three bacterial strains that were isolated recently from a culture of the toxin-producing dinoflagellate Prorocentrum lima have been shown to produce okadaic acid (14). In this paper we show that on the basis of the results of a phenotypic examination and phylogenetic analyses of small-subunit rRNA these bacteria should be included in the genus Roseobacter, although none of the strains produces bacteriochlorophyll a. All of the data suggest that these three strains belong to the same new species, for which we propose the name Roseobacter algicola; strain FF3 (= ATCC 51440) is the type strain of this species. MATERIALS AND METHODSBacterial strains and growth conditions. Roseobacter algicola ML4, FF2, and FF3T (T = type strain) (14) were isolated f...

No abstract

Fractalkine displays features that distinguishes it from the other chemokines. In particular, besides its chemoattractant action it promotes, under physiologic flow, the rapid capture and the firm adhesion of a subset of leukocytes or intervenes in the neuron/microglia interaction. This study verified that indeed the human

The adaptation of enteric bacteria in seawater has previously been described in terms of nutrient starvation. In the present paper, we bring experimental arguments suggesting that survival of these microorganisms could also depend on their ability to overcome the effects of osmotic stress. We analyzed the influence of osmoregulatory mechanisms (potassium transport, transport and accumulation of organic osmolytes) on the survival of Escherichia coli in seawater microcosms by using mutants lacking components of the osmotic stress response. Long-term protection was afforded to cells by growth in a medium whose osmotic pressure was increased by either NaCl, LiCl, or saccharose. Achievement of the protection state depended at least partly on osmoregulatory mechanisms, but differed when these were activated or induced during prior growth or in resting cells suspended in phosphate buffer or in seawater. When achieved during growth, K+ transport, glycine-betaine (GBT) synthesis or transport, and trehalose synthesis helped increase the ability to survive in seawater. Protection by GBT was also obtained with resting cells in a phosphate buffer at high osmotic pressure. However, when added only to the seawater, GBT did not change the survival ability of cells no matter what their osmoregulation potential. These results showed that the survival of E. coli cells in seawater depends, at least partly, on whether they possess certain genes which enable them to regulate osmotic pressure and whether they can be stimulated to express those genes before or after their release into the environment. This expression requires nutrients as the substrates from which the corresponding gene products are made.

Prostaglandins (PGs) are important mediators of bone response to growth factors, hormones, inflammation, or mechanical strains. In this study, we show that in MG63 osteosarcoma cells, prostaglandin E 2 (PGE 2 ) produces the opening of a large conductance Ca 2؉ -dependent K ؉ channel (BK). This PGE 2 -mediated channel opening induces the recruitment of various tyrosine-phosphorylated proteins on the hSlo ␣-subunit of BK. Because the C-terminal domain of hSlo encompasses an immunoreceptor tyrosine-based activation motif (ITAM), we show that the Syk nonreceptor tyrosine kinase, reported yet to be expressed mainly in hematopoietic cells, is expressed also in osteoblastic cells, and recruited on this ITAM after a PGE 2 -induced docking/activation process. We show that Syk/hSlo association is dependent of an upstream Src-related tyrosine kinase activity, in accord with the classical two-step model described for immune receptors.

Background and aims: Fractalkine, a chemokine that presents as both a secreted and a membrane-anchored form, has been described as having tumour-suppressive activities in standard subcutaneous models. Here, we investigate the antitumour effect of fractalkine, in its three molecular forms, in two orthotopic models of metastatic colon cancer (liver and lung) and in the standard subcutaneous model. Methods: We have developed models of skin tumours, liver and pulmonary metastasis and compared the extent of tumour development between C26 colon cancer cells expressing either the native, the soluble, the membrane-bound fractalkine or none. Results: The native fractalkine exhibits the strongest antitumour effect, reducing the tumour size by 93% in the skin and by 99% in the orthotopic models (p,0.0001). Its overall effect results from a critical balance between the activity of the secreted and the membrane-bound forms, balance that is itself dependent on the target tissue. In the skin, both molecular variants reduce tumour development by 66% (p,0.01). In contrast, the liver and lung metastases are only significantly reduced by the soluble form (by 96%, p,0.002) whereas the membrane-bound variant exerts a barely significant effect in the liver (p = 0.049) and promotes tumour growth in the lungs. Moreover, we show a significant difference in the contribution of the infiltrating leukocytes to the tumour-suppressive activity of fractalkine between the standard and the orthotopic models. Conclusions: Fractalkine expression by C26 tumour cells drastically reduces their metastatic potential in the two physiological target organs. Both molecular forms contribute to its antitumour potential but exhibit differential effects on tumour development depending on the target tissue.

No abstract