A daily study of the diatom spring bloom at Roscoff (France) in 1985. III. Free amino acids composition studied by HPLC analysis

The growth of a natural phytoplankton population was studiedduring a monospecific spring bloom of the diatom Rhizosoleniadelicatula at Roscoff (western English Channel). Direct examinationof the intracellular pool of 19 free amino acids (FAA) was usedas an index of the physiological status of the cells. TotalFAA in the particulate matter shows a general decrease duringthe bloom, and FAA cell content varies from 200 mM 1 cell volume^–1to 10 mM at the time of maximum biomass. FAA-N/particulate Nis <3% during the study, slightly decreasing at the timeof maximum biomass. Individual free amino acids appear reliablefor the development of the diatom biomass and good indicatorsof the growing population. At maximum biomass, major compoundsare glutamic acid (30.8 mol%), glutamine (11.7%), alanine (9.9%),isoleucine (6.6%) and lysine (6.4%). Serine, glycine, arginineand aspartic acid appear also as major components during otherperiods of the study. We suggest that the observed changes arean indication of the physiological state of the cells duringthe bloom. In particular glutamine (GLN), glutamic acid (GLU)and the GLN/GLU ratio allow the metabolic evolution of the naturalpopulation to be characterized. GLN is strictly linked to theliving biomass (Chla) while GLU is present at high percentagethroughout the study. The ecological significance of ß-alanine(BALA) is also revealed during this study, being strongly correlatedto degraded matter represented by phaeopigments. These resultsdemonstrate the validity of using individual free amino acidsas an aid in understanding the physiological status of algaein natural bloom conditions.     

La pollution des Baies de Morlaix et de Lannion par les hydrocarbures de l' “Amoco Cadiz”: Répartition sur les fonds et évolution

Distribution of hydrocarbons from the “Amoco Cadiz” oil spill in sublittoral sediments, north of Brittany. The quantitative distribution of hydrocarbons in the sublittoral sediments, north of Brittany (France), was followed and recorded for the first year after the spill (March, 1978). Following preliminary observations in spring of 1978, 250 stations were sampled in August from the Bay of Lannion to Portsall at water depths down to 70 m. Subsequently, 40 stations were studied at three-month intervals. During the summer of 1978, the widest polluted sublittoral areas were localised in the Bays of Morlaix and Lannion down to depths of about 30 m and even deeper in some places. In these two bays, the distribution of hydrocarbons showed: (1) deposition near the coasts hit by the slicks, mostly after adsorption by fine sedimentary particles; (2) redistribution of particulate and adsorbed oil towards low hydrodynamic energy areas favourable to deposition of fine particles. In autumn and winter, the coarse sediments became progressively less polluted. Oil, often in significant quantities, remained or was reconcentrated in the fine sediments of the inner bay parts. Consequently, the hydrodynamic structure ot the area (waves, tidal currents) has played an important role in the deposition and redistribution of the hydrocarbons on sublittoral bottoms.      

Physiological Responses to Stress Conditions and Barophilic Behavior of the Hyperthermophilic Vent Archaeon Pyrococcus abyssi

The physiology of the deep-sea hyperthermophilic, anaerobic vent archaeon Pyrococcus abyssi, originating from the Fiji Basin at a depth of 2,000 m, was studied under diverse conditions. The emphasis of these studies lay in the growth and survival of this archaeon under the different conditions present in the natural habitat. Incubation under in situ pressure (20 MPa) and at 40 MPa increased the maximal and minimal growth temperatures by 4(deg)C. In situ pressure enhanced survival at a lethal high temperature (106 to 112(deg)C) relative to that at low pressure (0.3 MPa). The whole-cell protein profile, analyzed by one-dimensional sodium dodecyl sulfate gel electrophoresis, did not change in cultures grown under low or high pressure at optimal and minimal growth temperatures, but several changes were observed at the maximal growth temperature under in situ pressure. The complex lipid pattern of P. abyssi grown under in situ and 0.1- to 0.5-MPa pressures at different temperatures was analyzed by thin-layer chromatography. The phospholipids became more complex at a low growth temperature at both pressures but their profiles were not superimposable; fewer differences were observed in the core lipids. The polar lipids were composed of only one phospholipid in cells grown under in situ pressure at high temperatures. Survival in the presence of oxygen and under starvation conditions was examined. Oxygen was toxic to P. abyssi at growth range temperature, but the strain survived for several weeks at 4(deg)C. The strain was not affected by starvation in a minimal medium for at least 1 month at 4(deg)C and only minimally affected at 95(deg)C for several days. Cells were more resistant to oxygen in starvation medium. A drastic change in protein profile, depending on incubation time, was observed in cells when starved at growth temperature.     

The initiation of Phaeocystis colonies

This study was designed to elucidate the sequence of eventsthat leads to the formation of new colonies of Phaeocystis sp.(strain PCC 540) starting from single cells released from maturecolonies. Colonies were first isolated by filtration onto a10 µm mesh. Colonial cells were then liberated by shakingand inoculated into individual culture wells containing mediumwith a PO₄^2– concentration of {small tilde}1 µM.Cell size and shape were determined daily by image analysis,while chlorophyll and DNA distributions were estimated by flowcytometry. Released cells were non-flagellated and mostly locatedin the G₁ phase of the cell cycle. They developed flagella andup to 90% became motile within 24 h. Swarmers lost motilityrapidly, became elongated, began to cycle again, excreted amucilaginous compound and divided leading to new colonies withina few days. During this reproducible process, no change of ploidycould be observed. Colonies initially adhered to the bottomof culture wells. Frequent mixing drastically reduced the fractionof colonies produced and their volume. High initial PO₄^2–concentrations (5 µM) delayed colony appearance, whereaslow concentrations (0.3 µM) prevented colony formation.The two main conclusions of this study are: (i) under favorableconditions ({small tilde}1 µM PO₄^2– no mixing),a large percentage of released colonial cells give back coloniesafter going through a flagellated stage; (ii) sexuality doesnot appear to be involved in this process. ¹Present address: CREMA BP 5, F-17137 L'Houmeau, France     

Specifically depleted spleen cell populations recover responsiveness by a concomitant unrelated delayed hypersensitivity reaction.

Spleen cells from nonimmunized CBA mice were specifically depleted of cells able to react spontaneously to pigeon erythrocytes (PRBC) by the formation of either rosettes (RFC) or hemolytic plaques (PFC). Spontaneous RFC were eliminated by centrifugation on a Ficoll-Isopaque gradient whereas spontaneous PFC were removed by filtration through a PRBC-coated column. RFC-depleted populations transferred into lethally irradiated syngeneic recipients and stimulated with PRBC failed to develop any significant response during the first 7 days after transfer but developed a definite anti-PRBC reaction on the eighth day. PFC- depleted populations remained unresponsive to PRBC throughout the 12-day observation period. When the spleen cells were taken from mice whose skin had been painted with picryl (trinitrophenyl, TNP) chloride 12–15 days before and the recipients of cell populations depleted of anti-PRBC were challenged with picryl chloride and stimulated with PRBC, they recovered the responsiveness to PRBC in an accelerated fashion. Under these conditions both anti-PRBC and anti-TNP RFC and PFC were found, and some cells simultaneously reacting to both PRBC and TNP were also detected.     

Numerical taxonomic study of thermophilic Bacillus isolated from three geographically separated deep-sea hydrothermal vents

Abstract: A numerical taxonomic study has been carried out with 80 strains, newly isolated, from three geographically separated deep-sea hydrothermal vents (Mid-Atlantic Ridge, Guaymas Basin and Lau Basin) and eleven thermophilic reference strains representing 11 Bacillus species. The deep-sea isolates were all halotolerant spore-forming rods and grew aerobically above 65°C. Results from unweighted average linkage cluster analysis of a similarity matrix derived from the simple matching coefficient, showed formation of nine major phena, which were defined at the 83% similarity level or above. Seven phena were composed exclusively of strains isolated from the same site (4 from Mid-Atlantic Ridge, 1 from Guaymas Basin and 2 from Lau Basin). The majority of the Lau Basin isolates clustered with 6 of the reference strains in one phenon, while isolates from Mid-Atlantic Ridge and Guaymas Basin were found separated from this phenon at the 69% similarity level. The other reference strains showed less than 69% similarity with the deep-sea isolates.     

MORPHOLOGY,PLOIDY, PIGMENT COMPOSITION,AND GENOME SIZE OF CULTURED STRAINS OF PHAEOCYSTIS (PRYMNESIOPHYCEAE)1

We examined cell morphology, ploidy level, cell size, pigment composition, and genome size in 16 cultured strains of Phaeocystis Lagerheim. Two strains originated from the Antarctic, 3 from the tropical Western Atlantic, and 11 from temperate regions (Eastern Atlantic, English Channel, North Sea, and Mediterranean Sea). Thirteen strains made colonies morphologically similar to P. glo-bosa Scherffel, whereas three never formed colonies under any circumstances. Five-rayed star-like structures with filaments were observed in 11 strains. In several strains, two ploidy levels were observed, one (haploid) linked to flagellates and one (diploid) linked to colonies. Cell size did not appear to be a very good criterion for distinguishing strains since size distributions overlapped. Pigment analysis by reversed-phase-high-performance liquid chroma-tography allowed the strains to be grouped into three clusters that differed from each other mainly by the relative proportions of three carotenoids: fucoxanthin, 19′-hex-anoyloxyfucoxanthin, and diadinoxanthin. All strains contained low levels of 19′-butanoyloxyfucoxanthin. Differences in genome size measured by flow cytometry delimited at least five groups. On the basis of both pigment composition and genome size, six clusters were defined, one corresponding to an Antarctic species (possibly P. antarc-tica), one to P. globosa, and the rest probably to several yet-undescribed species or subspecies. Two main conclusions emerge from this study. First, the taxonomy of the genus Phaeocystis needs to be clarified through a combination of morphological, biochemical, and molecular studies. Second, sexuality is a prevalent phenomenon in Phaeocystis, but controls of the sexual cycle are most likely strain-dependent.     

Presence of Hydrogenophilus thermoluteolus DNA in accretion ice in the subglacial Lake Vostok, Antarctica, assessed using rrs, cbb and hox

The 3561 m Vostok ice core sample originating from the subglacial Lake Vostok accretion (frozen lake water) ice with sediment inclusions was thoroughly studied by various means to confirm the presence of the thermophile bacterium Hydrogenophilus thermoluteolus reported earlier in the 3607 m accretion ice sample. PCR and molecular-phylogenetic analyses performed in two independent laboratories were made using different 16S rRNA gene (rrs) targeted primers. As a result, rrs-targeted PCR permitted to recover several very closely related clones with a small genetic distance to Hydrogenophilus thermoluteolus (< 1%). In addition, RubisCO (cbbL or rbcL) and NiFe-Hydrogenase (hoxV or hupL) targeted PCR have also allowed to recover sequences highly related to Hydrogenophilus thermoluteolus. All these results point to the presence of thermophilic chemoautotrophic microorganisms in Lake Vostok accretion ice. They presumably originate from deep faults in the bedrock cavity containing the lake in which episodes of seismotectonic activity would release debris along with microbial cells.     

On the mechanism of early recovery of specifically depleted lymphoid cell populations by nonspecific activation of T cells.

Specific depletion from normal CBA mouse spleen cells of those bound on pigeon erythrocyte (PRBC) immunoabsorbent columns before transfer of the depleted population into irradiated syngeneic recipients resulted in elimination of the anti-PRBC responsiveness as assessed by rosette (RFC) and hemolytic plaque (PFC) formation. The anti-sheep erythrocyte (SRBC) responses of cell populations treated in the same manner remained unimpaired. When, however, these populations were stimulated with both PRBC and muramyl dipeptide (MDP), an early recovery of specific anti-PRBC responsiveness was produced. PFC response in particular, suddenly increased between the fourth and fifth day after transfer and stimulation thus exhibiting a doubling time of only 4 to 6 hr. This effect of MDP was T-cell dependent since treatment of the depleted population with anti-θ antigen serum and complement hindered early recovery. Depleted populations stimulated with PRBC alone resumed their T-dependent RFC (but not PFC) responsiveness after the eighth day. In spite of the existence of these educated T cells, a second stimulation on the tenth day with PRBC was unable to elicit a specific PFC response. On the other hand stimulation with MDP alone on the day of cell transfer (Day 0) followed by stimulation with PRBC on Day 10 resulted in a specific PFC response on Day 15. Thus, MDP appeared to do more than simply promote education of T cells by antigen. In vitro cultures of depleted populations also recovered their specific reactivity when stimulated by antigen and MDP.