Oligotrophy and pelagic marine bacteria:Facts and fiction

Oligotrophy, or the inability of bacterial cells to propagate at elevated nutrient concentrations, is a controversial phenomenon in microbiology. The exact cause of the unculturability of many indigenous marine bacteria on standard laboratory media has still not been resolved. Unfortunately the physiology of such cells is difficult to investigate as long as high cell density cultures cannot be obtained. An extensive evaluation of experiments relating to oligotrophy and the cultivation of marine bacteria is presented in this review. When incorporating the findings of studies performed with molecular biological methods, the picture emerges that indigenous marine bacteria can be cultivated under certain conditions and that the 'oligotrophic way of life' is a transient characteristic. Although strong generalisations should not be made with respect to a biological system as diverse as the world's oceans, it should be anticipated that cells with unique physiological characteristics appear to exist in the oceanic system. When combining conventional physiological approaches with molecular biological techniques it is feasible to unveil the phenotypes that go with the encountered genotypes. In view of the enormous complexity of the oceanic system this will prove an ambitious, yet resourceful undertaking

Carbohydrates in the North Sea during spring blooms of <i>Phaeocystis</i>: a specific fingerprint

Regional and temporal variation in the composition of water-soluble carbohydrates from Phaeocystis colonies sampled in the southern North Sea was small during spring 1994, except for a high variability in the contribution of glucose. Glucose is universally present in storage products of microalgae; the relative constancy of the carbohydrate pattern of the other monosaccharides suggests that these are part of the more refractory colony mucus. In all Phaeocystis samples arabinose dominated, followed by xylose (Belgian coast) or galactose and mannose (Dutch coast). Rhamnose, glucuronate and O-methylated sugars were present in lower amounts. The latter, always present in samples containing Phaeocystis, may be typical for North Sea strains. The sugar patterns we report here differ from those presented in the literature concerning Phaeocystis-derived material, and also from the sugar fingerprint in the preceding diatom bloom. The Phaeocystis mucus apparently behaves as particulate matter since it was retained on filters of over 1 um. This characteristic together with its refractory nature, typical of 'transparent exopolymer particles' (TEPs), must have consequences for the heterotrophic microbial community in terms of adherence and substrate availability

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

High acrylate concentrations in the mucus of Phaeocystis globosa colonies

Acrylate produced from dimethylsulphoniopropionate (DMSP) by Phaeocystis has been claimed to inhibit bacterial growth. However, the concentrations of acrylate measured in seawater during Phaeocystis blooms are not high enough to expect inhibition of bacterial growth. In this study, the total acrylate in Phaeocystis cultures free from bacteria was measured. The concentration found in the exponential phase of growth was similar (0.1 to 1.0 mu M) to earlier field reports, but the amount found in the stationary phase of growth was much higher (1 to 4 mu M). Acrylate in cultures, as well as in field samples. was found to be located in the mucous layer of the colony. 'Microscale' concentrations in that layer were more than 1000-fold higher (1.3 to 6.5 mM) than the total concentration found in the unfractionated culture. Such high concentrations could have an antimicrobial effect. However, acrylate appears to be adsorbed to the mucus and may be inaccessible to bacteria. including those that consume acrylate. As soon as the colonies started to decay, acrylate was released into the surrounding environment, and since it is not detected in bloom samples, it is apparently consumed by bacteria

Vi er stolt, men inte nøjd. Erfaringer fra velferdsteknologiprosjektet i Skien kommune

Skien kommune har pilotert GPS og ulike trygghetsteknologier, både for hjemmeboende og på institusjon, som en del av oppdraget i Nasjonalt velferdsteknologiprogram. Prosjektet tok utgangspunkt i etablert kunnskap knyttet til bruk av lokaliseringsteknologi og ulike trygghetsteknologier for hjemmeboende, og kommunen har gjennom systematisk arbeid i tjenesten etablert egne erfaringer og praksisnær kunnskap som et godt fundament for å implementere ulike løsninger i tjenesten. SINTEF har vært forskningspartner i innovasjonsarbeidet og har bidratt med kunnskap og erfaringer knyttet til teknologi og tjeneste. Kommunen har fått veiledning knyttet til bruk av ulike velferdstekologiske løsninger og fått hjelp til å gjennomføre tjenesteinnovasjonsprosesser. SINTEF har videre tilrettelagt for kartlegging og forståelse av brukerbehov og har innhentet erfaringer fra de ulike teknologipilotene underveis. Det er også gjennomført en effektstudie knyttet til bruk av lokaliseringsteknologi og mobile trygghetsalarmer og utviklet tjenestemodeller for responssentertjenesten. Prosjektet har også beskrevet ulike gevinster for bruk av trygghetsteknologi, både for hjemmeboende og på institusjon. Erfaringene fra prosjektet i viser at trygghetsteknologi kan møte behov hos brukerne og gi bedre og mer effektive tjenester for kommunen

Mammographic sensitivity as a function of tumor size: A novelestimation based on population-based screening data.

Instead of a single value for mammographic sensitivity, a sensitivity function based on tumor size more realistically reflects mammography’s detection capability. Because previous models may have overestimated size-specific sensitivity, we aimed to provide a novel approach to improve sensitivity estimation as a function of tumor size. Using aggregated data on interval and screen-detected cancers, observed tumor sizes were back-calculated to the time of screening using an exponential tumor growth model and a follow-up time of 4 years. From the observed number of detected cancers and an estimation of the number of false-negative cancers, a model for the sensitivity as a function of tumor size was determined. A univariate sensitivity analysis was conducted by varying follow-up time and tumor volume doubling time (TVDT). A systematic review was conducted for external validation of the sensitivity model