Viral degradation of marine bacterial exopolysaccharides.

The identification of the mechanisms by which marine dissolved organic matter (DOM) is produced and regenerated is critical to develop robust prediction of ocean carbon cycling. Polysaccharides represent one of the main constituents of marine DOM and their degradation is mainly attributed to polysaccharidases derived from bacteria. Here, we report that marine viruses can depolymerize the exopolysaccharides (EPS) excreted by their hosts using five bacteriophages that infect the notable EPS producer, Cobetia marina DSMZ 4741. Degradation monitorings as assessed by gel electrophoresis and size exclusion chromatography showed that four out of five phages carry structural enzymes that depolymerize purified solution of Cobetia marina EPS. The depolymerization patterns suggest that these putative polysaccharidases are constitutive, endo-acting and functionally diverse. Viral adsorption kinetics indicate that the presence of these enzymes provides a significant advantage for phages to adsorb onto their hosts upon intense EPS production conditions. The experimental demonstration that marine phages can display polysaccharidases active on bacterial EPS lead us to question whether viruses could also contribute to the degradation of marine DOM and modify its bioavailability. Considering the prominence of phages in the ocean, such studies may unveil an important microbial process that affects the marine carbon cycle.

Two viruses, MCV1 and MCV2, which infect Marinitoga bacteria isolated from deep-sea hydrothermal vents: functional and genomic analysis.

Viruses represent a driving force in the evolution of microorganisms including those thriving in extreme environments. However, our knowledge of the viral diversity associated to microorganisms inhabiting the deep-sea hydrothermal vents remains limited. The phylum of Thermotogae, including thermophilic bacteria, is well represented in this environment. Only one virus was described in this phylum, MPV1 carried by Marinitoga piezophila. In this study, we report on the functional and genomic characterization of two new bacterioviruses that infect bacteria from the Marinitoga genus. Marinitoga camini virus 1 and 2 (MCV1 and MCV2) are temperate siphoviruses with a linear dsDNA genome of 53.4 kb and 50.5 kb respectively. Here, we present a comparative genomic analysis of the MCV1 and MCV2 viral genomes with that of MPV1. The results indicate that even if the host strains come from geographically distant sites, their genomes share numerous similarities. Interestingly, heavy metals did not induce viral production, instead the host of MCV1 produced membrane vesicles. This study highlights interaction of mobile genetic elements (MGE) with their hosts and the importance of including hosts-MGEs' relationships in ecological studies.

Interplay between the genetic clades of Micromonas and their viruses in the Western English Channel.

The genus Micromonas comprises distinct genetic clades that commonly dominate eukaryotic phytoplankton community from polar to tropical waters. This phytoplankter is also recurrently infected by abundant and genetically diverse prasinoviruses. Here we report on the interplay between prasinoviruses and Micromonas with regard to the genetic diversity of this host. For 1 year, we monitored the abundance of three clades of Micromonas and their viruses in the Western English Channel, both in the environment using clade-specific probes and flow cytometry, and in the laboratory using clonal strains of Micromonas clades to assay for their viruses by plaque-forming units. We showed that the seasonal fluctuations of Micromonas clades were closely mirrored by the abundance of their corresponding viruses, indicating that the members of Micromonas genus are susceptible to viral infection, regardless of their genetic affiliation. The characterization of 45 viral isolates revealed that Micromonas clades are attacked by specific virus populations, which exhibit distinctive clade specificity, life strategies and genetic diversity. However, some viruses can also cross-infect different host clades, suggesting a mechanism of horizontal gene transfer within the Micromonas genus. This study provides novel insights into the impact of viral infection for the ecology and evolution of the prominent phytoplankter Micromonas.

Genomic and functional analysis of Vibrio phage SIO-2 reveals novel insights into ecology and evolution of marine siphoviruses.

We report on a genomic and functional analysis of a novel marine siphovirus, the Vibrio phage SIO-2. This phage is lytic for related Vibrio species of great ecological interest including the broadly antagonistic bacterium Vibrio sp. SWAT3 as well as notable members of the Harveyi clade (V.harveyi ATTC BAA-1116 and V.campbellii ATCC 25920). Vibrio phage SIO-2 has a circularly permuted genome of 80598 bp, which displays unusual features. This genome is larger than that of most known siphoviruses and only 38 of the 116 predicted proteins had homologues in databases. Another divergence is manifest by the origin of core genes, most of which share robust similarities with unrelated viruses and bacteria spanning a wide range of phyla. These core genes are arranged in the same order as in most bacteriophages but they are unusually interspaced at two places with insertions of DNA comprising a high density of uncharacterized genes. The acquisition of these DNA inserts is associated with morphological variation of SIO-2 capsid, which assembles as a large (80 nm) shell with a novel T=12 symmetry. These atypical structural features confer on SIO-2 a remarkable stability to a variety of physical, chemical and environmental factors. Given this high level of functional and genomic novelty, SIO-2 emerges as a model of considerable interest in ecological and evolutionary studies.

Characterization of different viruses infecting the marine harmful algal bloom species Phaeocystis globosa.

Twelve lytic viruses (PgV) infecting the marine unicellular eukaryotic harmful algal bloom species Phaeocystis globosa were isolated from the southern North Sea in 2000-2001 and partially characterized. All PgV isolates shared common phenotypic features with other algal viruses belonging to the family Phycodnaviridae and could be categorized in four different groups. Two main groups (PgV Group I and II) were discriminated based on particle size (150 and 100 nm respectively), genome size (466 and 177 kb) and structural protein composition. The lytic cycle showed a latent period of 10 h for PgV Group I and latent periods of 12 h and 16 h for PgV Group IIA and IIB. Host specificity and temperature sensitivity finally defined a fourth group (PgV Group IIC). Our results imply that viral infection plays an important role not only in P. globosa dynamics but also in the diversity of both host and virus community.

Adjuvant treatment with high dose medroxyprogesterone acetate in node-negative early breast cancer. A 3-year interim report on a randomized trial (I).

After initial surgery, 240 pre-, peri- or postmenopausal patients with early node-negative breast carcinoma were randomized to receive either no hormone therapy or adjuvant therapy with medroxyprogesterone acetate at high dosage (HD-MPA; 500 mg IM per day times 28 or 500 mg intramuscularly (i.m.) 5 days a week for 5 weeks then 500 mg i.m. twice weekly for the 5 following months. After a median follow-up time of 3 years, relapse-free survival and overall survival appeared significantly improved in the HD-MPA arm. Side effects were tolerable.

Improvement of hematological and general tolerance to CMF by high-dose medroxyprogesterone acetate (HD-MPA) adjuvant treatment for primary node positive breast cancer (analysis of 100 patients).

In a prospective randomized trial comparing CMF to CMF + HD-MPA for primary node positive breast cancer patients, the authors evidenced clear improvement of hematological tolerance (especially of WBC - granulocytes counts) to chemotherapy in the group receiving also hormonotherapy. The design of the trial allowed to give the patients overall high doses of CMF therapy in both arms; in the group receiving HD-MPA significantly higher doses of CMF could be administered (96.3-97.8% for CMF + HD-MPA treated patients vs 89.7-91.1% for CMF alone treated patients). The menopausal status did not influence the results.

[Scintigraphy of biliary system (author's transl)]. / La scintigraphie des voies biliaires.

Hepatobiliary functional scintigraphy (HBFS) using 99m Tc-labeled Diethyl-IDA was tested in 84 patients suffering from various hepatic and bile duct disorders. The investigated pathologies were: gall bladder dysfunction, parital bile duct obstruction, total obstruction, hepatocellular disease, cirrhosis and drug induced cholostastis. The diagnosis accuracy of the method was found to be 95 %, and the method proved to be useful for guiding the clinician in selecting those additional investigation techniques most apt to define the etiology of the pathological condition accurately. In conclusion, the non-invasive character of the technique, its usefulness even in the presence of elevated bilirubin levels and the information yielded by HBFS make it a method of choice to be placed in the beginning of the test series liver or duct patients are submitted to.

[Intestinal tolerance in mice after low dose rate 60CO irradiation. Implications for radiotherapy]. / Tolérance de l'intestin de la souris à une irradiation par 60Co à faible débit. Implications en radiothérapie.

Influence of absorbed dose rate has been studied in BALB/c mice for early intestinal tolerance. After selective abdominal irradiation, LD50 at 5.5 days increases from 12.36 to 20.22 and 21.79 Gy when dose rate decreases from 0.61 to 0.054 and 0.026 Gy/mn. LD50 at 6.5 days increases from 12.05 to 19.22 and 21.58 Gy respectively. The LD50 ratios are then 1.6 and 1.8 for both endpoints. After total body irradiation. LD50 at 5.5 days increases from 9.92 to 15.20and 16.83 Gy when dose rate decreases from 0.56 to 0.049 and 0.024 Gy/mn. The corresponding LD50 ratios, i.e. 1.5 and 1.7, are then similar to the former ones. Increase of LD50 when decreasing dose rate is in agreement with that expected taking into account only repair of sublethal lesions, for the generally accepted cellular models.