A total of 94 vertical profiles of size-fractionated chlorophyll a concentration and primary production rate were obtained along a meridional transect from the United Kingdom to the Falkland Islands (50°N to 50°S) during 4 cruises carried out in April and October 1996 and in April and October 1997. This data set allowed us to characterize the patterns of phytoplankton size-structure and productivity in temperate, oligotrophic, upwelling and equatorial regions. On average, picophytoplankton (0.2 to 2 µm) accounted for 56 and 71% of the total integrated carbon (C) fixation and autotrophic biomass, respectively. Enhanced biomass and productivity contributions by nano-and microplankton took place in the temperate regions and in the upwelling area off Mauritania. Small (< 2 µm in diameter) phytoplankton cells should not be regarded as a background, relatively invariant component of the microbial community, given that most of the latitudinal variability in total photoautotrophic biomass and production was driven by changes in the picophytoplankton. In temperate regions and in the upwelling area off Mauritania, small (< 2 µm) and large (> 2 µm) phytoplankton accounted for a proportion of total biomass that was similar to their shares of productivity. In the oligotrophic and equatorial regions, in contrast, large phytoplankton tended to account for a fraction of the total production that was significantly higher than their share of the biomass. We found that the equatorial upwelling causes an increase in phytoplankton biomass and productivity without altering the typical size structure found in less productive regions such as the subtropical gyres. In the oligotrophic ocean, significant changes in C fixation rates take place without accompanying variations in the magnitude of the phytoplankton standing stocks or the size structure of the microbial community.KEY WORDS: Size distribution · Phytoplankton · Chlorophyll · Primary production · Plankton food webs · Atlantic Ocean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 216: [43][44][45][46][47][48][49][50][51][52][53][54][55][56] 2001 which determine the magnitude of different C pathways (i.e. size structure of primary production and coupling between production and grazing) are, in turn, under hydrodynamical control (Legendre & Rassoulzadegan 1996).Numerous studies have been carried out in which size-fractionated chlorophyll concentration and primary production are simultaneously quantified in particular geographical areas (see reviews in Tremblay & Legendre 1994, Legendre & Rassoulzadegan 1996. The majority of these observations, however, have been made in coastal and/or temperate environments, with relatively little attention given to tropical and subtropical open-ocean environments. In the tropical and subtropical Atlantic Ocean, only a few studies have dealt with the distribution of size-fractionated phytoplankton (i.e. Platt et al. 1983, Malone et al. 1993, Jochem & Zeitzschel 1993, and these have not c...

Abstract-The mean (ϮSE) depth-integrated gross production (P) of 2,600 Ϯ 271 mg O 2 m Ϫ2 d Ϫ1 derived from a compilation of data from nine cruises conducted between 1991-2000 in the subtropical NE Atlantic was found to be significantly lower (t-test, P ϭ 0.005, N ϭ 33) than the mean (ϮSE) community respiration (R) of 3,821. Two-thirds of the stations investigated were heterotrophic, and the P/R ratio of the communities tended to increase as P increased, such that communities where P Ͻ 3,000 mg O 2 m Ϫ2 d Ϫ1 tended to be heterotrophic. The tendency for R to exceed P (P/R Ͻ 1.0) was statistically significant (Wilcoxon ranked sign test, P Ͻ 0.05) in the upper and deep layers of the photic zone, with an overall balance between P and R at intermediate depths. These results provide evidence that the subtropical NE Atlantic is a heterotrophic ecosystem, where planktonic communities respire more organic carbon than they produce, thereby acting as net sources of CO 2 .

The oligotrophic waters of the Subtropical Gyres cover > 60% of the total ocean surface and contribute > 30% of the global marine carbon fixation. Despite apparently uniform growth conditions over broad areas, primary production in these regions exhibits a remarkable degree of variability. In this study of 34 stations in the North and South Atlantic Subtropical Gyres, we found a 20-fold variation (from 18 to 362 mg C m -2 d -1 ) in water-column-integrated primary production rate (∫PP), while chlorophyll biomass only varied by a factor of 3. The changes in productivity were not associated with variations in incident surface irradiance, chlorophyll concentration, phytoplankton C biomass or phytoplankton size structure. The rate of nutrient supply to the euphotic layer, as estimated from variations in the depth of nitracline, appeared as the most relevant environmental factor in explaining the observed variability in ∫PP. We found significant changes in the composition of the picophytoplankton community across the range of measured productivities. The relative biomass contribution of Synechococcus spp. and the picoeukaryotes tended to increase with increasing ∫PP, whereas the opposite was true for Prochlorococcus spp. Across the wide range of measured primary productivity rates, the persistent dominance of picophytoplankton indicates that the microbial loop and the microbial food web continued to be the most important trophic pathways. Our observations of the oligotrophic ocean reflect a dynamic ecosystem where the microbial community responds to environmental forcing with significant changes in biological rates rather than trophic organization.

Heterotrophic bacteria play a major role in organic matter cycling in the ocean. Although the high abundances and relatively fast growth rates of coastal surface bacterioplankton make them suitable sentinels of global change, past analyses have largely overlooked this functional group. Here, time series analysis of a decade of monthly observations in temperate Atlantic coastal waters revealed strong seasonal patterns in the abundance, size and biomass of the ubiquitous flow-cytometric groups of low (LNA) and high nucleic acid (HNA) content bacteria. Over this relatively short period, we also found that bacterioplankton cells were significantly smaller, a trend that is consistent with the hypothesized temperature-driven decrease in body size. Although decadal cell shrinking was observed for both groups, it was only LNA cells that were strongly coherent, with ecological theories linking temperature, abundance and individual size on both the seasonal and interannual scale. We explain this finding because, relative to their HNA counterparts, marine LNA bacteria are less diverse, dominated by members of the SAR11 clade. Temperature manipulation experiments in 2012 confirmed a direct effect of warming on bacterial size. Concurrent with rising temperatures in spring, significant decadal trends of increasing standing stocks (3% per year) accompanied by decreasing mean cell size (−1% per year) suggest a major shift in community structure, with a larger contribution of LNA bacteria to total biomass. The increasing prevalence of these typically oligotrophic taxa may severely impact marine food webs and carbon fluxes by an overall decrease in the efficiency of the biological pump.

No abstract

BackgroundSpecific antibodies are likely to be present before S. pneumoniae infection. We explored cefditoren (CDN) total and free values of serum concentrations exceeding the MIC (t>MIC) related to efficacy in a mice sepsis model, and the effect of specific gammaglobulins on in-vitro phagocytosis and in-vivo efficacy.Methodology/Principal FindingsWe used three pneumococcal isolates (serotype, MIC of CDN): Strain 1 (6B, 1 µg/ml), Strain 2 (19F, 2 µg/ml) and Strain 3 (23F, 4 µg/ml). Hyperimmune serum (HS) was obtained from mice immunized with heat-inactivated strains. In-vitro, phagocytosis by HS diluted 1/10 in presence/absence of sub-inhibitory concentrations was measured by flow cytometry including fluorescent bacteria and a neutrophil cell line. In-vivo dose-ranging experiments with HS (dilutions 1/2–1/16) and CDN (6.25 mg/kg–100 mg/kg tid for 48 h) were performed to determine the minimal protective dilution/dose (highest survival) and the non-protective highest dilution/dose (highest mortality: HS-np dilution and CDN-np dose) over 7 days. Efficacy of CDN-np in animals pre-immunized with HS-np (combined strategy) was explored and blood bacterial clearance determined. The CDN measured protein binding was 86.9%. In-vitro, CDN significantly increased phagocytosis (vs. HS 1/10). In non pre-immunized animals, t>MIC values for CDN of ≈35% (total) and ≈19% (free) were associated with 100% survival. Significant differences in survival were found between HS-np alone (≤20%) or CDN-np alone (≤20%) vs. the combined strategy (90%, 60% and 60% for Stains 1, 2 and 3), with t>MIC (total/free) of 22.8%/14.3%, 26.8%/16.0%, and 22.4%/12.7% for Strains 1, 2 and 3, respectively. Prior to the second dose (8 h), median bacterial counts were significantly lower in animals surviving vs. dead at day 7.Conclusions/SignificanceIn mice (CDN protein binding similar to humans) total t>MIC values of ≈35% (≈19% free) were efficacious, with a decrease in the required values in pre-immunized animals. This reinforces that immunoprotection to overcome resistance may provide lifesaving strategies.

Polycyclic aromatic hydrocarbons (PAH; naphthalene, anthracene and phenanthrene) degrading microbial consortium C2PL05 was obtained from a sandy soil chronically exposed to petroleum products, collected from a petrochemical complex in Puertollano (Ciudad Real, Spain). The consortium C2PL05 was highly efficient degrading completely naphthalene, phenanthrene and anthracene in around 18 days of cultivation. The toxicity (Microtox method) generated by the PAH and by the intermediate metabolites was reduced to levels close to non-toxic in almost 40 days of cultivation. The identified bacteria from the contaminated soil belonged to gamma-proteobacteria and could be include in Enterobacter and Pseudomonas genus. DGGE analysis revealed uncultured Stenotrophomonas ribotypes as a possible PAH degrader in the microbial consortium. The present work shows the potential use of these microorganisms and the total consortium for the bioremediation of PAH polluted areas since the biodegradation of these chemicals takes place along with a significant decrease in toxicity.

Daptomycin exhibited rapid bactericidal activity against the strains of the three Gram-positive species tested, regardless of resistance phenotype or the presence of physiological concentrations of albumin.