Arbuscular mycorrhiza infection enhances the growth response of Lolium perenne to elevated atmospheric pCO(2)

Elevated atmospheric pCO(2) increases the C-availability for plants and thus leads to a comparable increase in plant biomass production and nutrient demand. Arbuscular mycorrhizal fungi (AMF) are considered to play an important role in the nutrient uptake of plants as well as to be a significant C-sink. Therefore, an increased colonization of plant roots by AMF is expected under elevated atmospheric pCO(2). To test these hypotheses, Lolium perenne L. plants were grown from seeds in a growth chamber in pots containing a silica sand/soil mixture for 9 weeks with and without inoculation with Glomus intraradices (Schenck and Smith). The growth response of plants at two different levels of N fertilization (1.5 or 4.5 mM) combined with ambient (35 Pa) and elevated atmospheric pCO(2) (60 Pa) was compared. The inoculation with G. intraradices, the elevated atmospheric pCO(2) and the high N fertilization treatment all led to an increased plant biomass production of 16%, 20% and 49%, respectively. AMF colonization and high N fertilization increased the plant growth response to elevated atmospheric pCO(2); the plant growth response to high N fertilization was also increased by AMF colonization. The root/shoot ratio was reduced by high N fertilization or elevated atmospheric pCO(2), but was not affected by AMF colonization. The unchanged specific leaf area indicated that if AMF colonization represented an increased C-sink, this was fully covered by the plant. Elevated atmospheric pCO(2) strongly increased AMF colonization (60%) while the high N fertilization had a slightly negative effect. AMF colonization neither improved the N nor P nutrition status, but led to an improved total P uptake. The results underline the importance of AMF for the response of grassland ecosystems to elevated atmospheric pCO(2).     

Paralytic shellfish toxins or spirolides? The role of environmental and genetic factors in toxin production of the Alexandrium ostenfeldii complex

Dinoflagellates of the Alexandrium ostenfeldii complex (A. ostenfeldii, A. peruvianum) are capable of producing different types of neurotoxins: paralytic shellfish toxins (PSTs), spirolides and gymnodimines, depending on the strain and its geographic origin. While Atlantic and Mediterranean strains have been reported to produce spirolides, strains originating from the brackish Baltic Sea produce PSTs. Some North Sea, USA and New Zealand strains contain both toxins. Causes for such intraspecific variability in toxin production are unknown. We investigated whether salinity affects toxin production and growth rate of 5 A. ostenfeldii/peruvianum strains with brackish water (Baltic Sea) or oceanic (NE Atlantic) origin. The strains were grown until stationary phase at 7 salinities (6–35), and their growth and toxin production was monitored. Presence of saxitoxin (STX) genes (sxtA1 and sxtA4 motifs) in each strain was also analyzed. Salinity significantly affected both growth rate and toxicity of the individual strains but did not change their major toxin profile. The two Baltic Sea strains exhibited growth at salinities 6–25 and consistently produced gonyautoxin (GTX) 2, GTX3 and STX. The two North Sea strains grew at salinities 20–35 and produced mainly 20-methyl spirolide G (20mG), whereas the strain originating from the northern coast of Ireland was able to grow at salinities 15–35, only producing 13-desmethyl spirolide C (13dmC). The effects of salinity on total cellular toxin concentration and distribution of toxin analogs were strain-specific. Both saxitoxin gene motifs were present in the Baltic Sea strains, whereas the 2 North Sea strains lacked sxtA4, and the Irish strain lacked both motifs. Thus sxtA4 only seems to be specific for PST producing strains. The results show that toxin profiles of A. ostenfeldii/peruvianum strains are predetermined and the production of either spirolides or PSTs cannot be induced by salinity changes. However, changes in salinity may lead to changed growth rates, total cellular toxin concentrations as well as relative distribution of the different PST and spirolide analogs, thus affecting the actual toxicity of A. ostenfeldii/peruvianum populations.     

Morphology, phylogenetic position, and ecophysiology of Alexandrium ostenfeldii (Dinophyceae) from the Bohai Sea, China

Alexandrium ostenfeldii is a potentially toxic dinoflagellate that often occurs in coastal areas at high latitudes.Here we report the presence of A.ostenfeldii in the Bohai Sea,China,for the first time.The vegetative cells ofA.ostenfeldii are characterized by a narrow first apical plate and a large ventral pore located on the anterior right side.Partial large subunit sequence comparison revealed that the Chinese strain differs from the Finnish strains at only three positions,and from A.peruvianum of Spain at five positions.Maximum parsimony analysis revealed that A.ostenfeldii from China and Finland and A.peruvianum from Spain grouped together.They were the nearest sister group to a clade with A.ostenfeldii from New Zealand,Europe,and North America.In culture,growth did not occur at temperatures below 9 ℃ and occurred at salinities between 7 and 27 psu.It took 10-20 days for newly formed cysts to mature at 20 ℃.Lower temperature delayed germination,but the germination rate exceeded 90％ at temperatures from 12 to 24 ℃.No germination occurred below 9 ℃ after 1 month of incubation.The Chinese strain ofA.ostenfeldii produced neither spirolides nor paralytic shellfish poisoning toxins.     

Morphology,phylogenetic position and ecophysiology of Alexandrium ostenfeldii (Dinophyceae) from the Bohai Sea,China

Alexandrium ostenfeldii is a potentially toxic dinoflagellate that often occurs in coastal areas at high latitudes. Here we report the presence of A. ostenfeldii in the Bohai Sea, China, for the first time. The vegetative cells of A. ostenfeldii are characterized by a narrow first apical plate and a large ventral pore located on the anterior right side. Partial large subunit sequence comparison revealed that the Chinese strain differs from the Finnish strains at only three positions, and from A. peruvianum of Spain at five positions. Maximum parsimony analysis revealed that A. ostenfeldii from China and Finland and A. peruvianum from Spain grouped together. They were the nearest sister group to a clade with A. ostenfeldii from New Zealand, Europe, and North America. In culture, growth did not occur at temperatures below 9 °C and occurred at salinities between 7 and 27 psu. It took 10–20 days for newly formed cysts to mature at 20 °C. Lower temperature delayed germination, but the germination rate exceeded 90% at temperatures from 12 to 24 °C. No germination occurred below 9 °C after 1 month of incubation. The Chinese strain of A. ostenfeldii produced neither spirolides nor paralytic shellfish poisoning toxins.     

冬小麦旺盛生长期间CO2浓度升高对根际呼吸的影响

依托FACE（free air carbon dioxide enrichment）技术平台,利用阻断根法,采用H6400红外气体分析仪（IRGA）-田间原位测定的方法,研究了大气CO2浓度升高和不同氮肥水平对水稻／小麦轮作制中冬小麦旺盛生长期间根际呼吸的影响。结果表明,在整个测定期间,大气CO2浓度升高增强了根际呼吸速率,提高了根际呼吸排放量。在高N和低N处理中,高CO2浓度下的根际呼吸总排放量分别比Ambient极显著增加117．0％和90．8％。根际呼吸速率在孕穗初期达到最大值;使根际呼吸在土壤呼吸中的比重由24．5％（LN）～26．7（HN）提高到39．8％（LN）～47．1％（HN）。CO2浓度升高与氮肥用量对根际呼吸产生交互效应。表明大气CO2浓度升高将加快土壤向大气的CO2排放,结果将有助于评价未来高CO2浓度背景下农田生态系统土壤碳的固定潜力。     

The study of Salmonellaenteritidis growth kinetics using Rapid Automated Bacterial Impedance Technique

In order to study strain-specific differences in their growth behaviour at different, and particularly lower, temperatures, generation times for 45 strains of Salmonella enteritidis isolated from food were determined impedimetrically over a temperature range from 7 to 42 °C. In practical terms, 7 °C is the minimum requirement for Salm. enteritidis growth, and generation time variability increases markedly as this temperature is reached. Reports in the literature describing psychrotrophic behaviour and multiplication at lower temperatures cannot be confirmed. Generation time variability increased as temperature moved away from the optimal range with variation coefficients tending to rise as temperature fell. The great variability of multiplication parameters near the growth limit found in Salm. enteritidis may also be a characteristic of other bacterial species. It is therefore imperative to commence studies on larger numbers of strains to allow prediction of their behaviour at lower temperatures.     

Field and culture studies of species of Gelidium (Gelidiales,Rhodophyta) from their northern limit of distribution in Europe

Two species of Gelidium, provisionally referred to as G. pusillum and G. latifolium, are included in the Scandinavian flora and reach their northern limit of distribution on the Norwegian west coast. Small frond sizes due to adverse growth conditions, extreme phenotypic variability and lack of sexual reproduction make identification of specimens very difficult. Both species were isolated into unialgal culture and were compared with cultured strains referable to G. pusillum from Ireland and France. Temperature and salinity requirements and tolerance ranges were determined and discussed in view of distribution along the Norwegian coast. Little or no growth occurs below 9 °C, corresponding to a northern summer growth limit. On the Norwegian Skagerrak coast, low winter temperature rather than reduced salinity is the limiting factor.     

Metabolic capacity of Bacillus cereus strains ATCC 14579 and ATCC 10987 interlinked with comparative genomics

Bacillus cereus is an important food-borne pathogen and spoilage organism. In this study, numerous phenotypes and the genomes of B. cereus strains ATCC 14579 and ATCC 10987 were analysed to compare their metabolic capacity and stress resistance potential. The growth performance of the two strains was assessed for nearly 2000 phenotypes, including use of nutrient sources, performance in acid and basic environments, osmo-tolerance and antibiotic resistance. Several food-relevant phenotypic differences were found between ATCC 14579 and ATCC 10987, such as differences in utilization of carbohydrates, peptides, amino acids and ammonia. Subsequently, the genomes of both strains were analysed with INPARANOID to search for strain-specific open reading frames (ORFs). B. cereus ATCC 14579 and ATCC 10987 were found to harbour 983 and 1360 strain-specific ORFs respectively. The strain-specific phenotypic features were interlinked with corresponding genetic features and for several phenotypic differences a related strain-specific genetic feature could be identified. In conclusion, the combination of phenotypic data with strain-specific genomic differences has led to detailed insight into the performance of the two B. cereus strains, and may supply indicators for the performance of these bacteria in different environments and ecological niches.     

Combined effects of temperature and salinity on growth rates of germlings of threeFucus species from iceland,helgoland and the north adriatic sea

The growth rate of germlings of threeFucus species (F. distichus subsp.edentatus from Iceland,F. vesiculosus from Helgoland, North Sea, andF. virsoides from the North Adriatic Sea) has been investigated under different temperature and salinity conditions. The highest growth rate and the maximum elongation factor were found at 9° C forF. distichus; in the other two species growth increased with increasing temperature. Growth decreases with dilution in the three species under consideration. A rather low tolerance to dilution was observed inF. vesiculosus germlings. In view of the overall distribution of the latter species the opposite was expected. It seems likely, however, that susceptible strains have developed at Helgoland, where salinity rarely drops below 30.     

Effect of carbon dioxide on growth of Pseudomonas fluorescens.

In minimal medium at 30 degrees C, growth of Pseudomonas fluorescens was stimulated when the pressure (p) of CO2 in solution was 100 mm of Hg, but at higher concentrations the growth rate declined linearly with increasing pCO2. All concentrations of CO2 were inhibitory for growth in complex medium, and at 30 degrees C the maximum degree of inhibition was attained when pCO2 was 250 mm of Hg. The degree of inhibition at a constant pCO2 in solution increased with decreasing temperature. The degree of inhibition was directly proportional to temperature for growth in complex medium, but not in minimal medium. The inhibition of cell respiration by CO2 was the same whether cells had been grown in air or in the presence of CO2, indicating that adaptive enzyme synthesis does not occur in response to CO2.     

Effect of carbon dioxide on growth of Pseudomonas fluorescens.

In minimal medium at 30 degrees C, growth of Pseudomonas fluorescens was stimulated when the pressure (p) of CO2 in solution was 100 mm of Hg, but at higher concentrations the growth rate declined linearly with increasing pCO2. All concentrations of CO2 were inhibitory for growth in complex medium, and at 30 degrees C the maximum degree of inhibition was attained when pCO2 was 250 mm of Hg. The degree of inhibition at a constant pCO2 in solution increased with decreasing temperature. The degree of inhibition was directly proportional to temperature for growth in complex medium, but not in minimal medium. The inhibition of cell respiration by CO2 was the same whether cells had been grown in air or in the presence of CO2, indicating that adaptive enzyme synthesis does not occur in response to CO2.     

The North Atlantic Oscillation forcing through the last 2000 years: Spatial variability as revealed by high-resolution marine diatom records from N and SW Europe

The Tagus pro-delta (Portuguese Margin) and the Skagerrak (NE of the North Sea) are two marine systems controlled by atmospheric changes, which at present are mainly determined by fluctuations of the North Atlantic Oscillation (NAO). On the basis of diatom records from marine sediment cores, environmental changes (primary productivity and salinity) are reconstructed for the last 2000 years for both regions. These sites are investigated focusing on the regional response to changing NAO forcing.Both studied sites are characterized by sedimentation rates in the order of 0.12 cm/year and 0.47 cm/year for the most recent deposits off the Tagus pro-delta, allowing high-resolution paleoceanographic reconstructions (8.3 and 2.1 years represented per sample). The last 2000 years are a period covering in Europe the historical climatic periods known as the Dark Ages (DA), the Medieval Warm Period (MWP) and the Little Ice Age (LIA). In the Skagerrak, the cold periods of the DA and LIA are marked by diatom dissolution stages, whereas at the Tagus pro-delta, the DA were associated with increased diatom production and possible upwelling and the onset of the LIA corresponded to enhanced flow of the Tagus River. During the MWP, better diatom preservation in the Skagerrak, related to stronger advection of salty Atlantic waters, is paralleled by dominant upwelling conditions at the Tagus pro-delta. The two most intense upwelling periods at the Tagus pro-delta, at ∼ AD 600 and ∼ AD 900, correspond to a dissolution stage and a slight change in salinity in the Skagerrak, respectively.Although the comparison of the two study sites suggests a common forcing such as the NAO, the different inferred behaviors for each main climatic period in each region demonstrate that the NAO by its own is not sufficient to explain the climatic variability at a regional scale.     

On the allelochemical potency of the marine dinoflagellate Alexandrium ostenfeldii against heterotrophic and autotrophic protists

Three strains of the marine dinoflagellate Alexandrium ostenfeldiiof different geographic origin were tested for their short-termdeleterious effects on a diversity of marine protists. All A.ostenfeldii strains were capable of eliciting an apparent allelochemicalresponse, but the various protistan target species were differentiallyaffected. Protists that were negatively affected by exposureto cells of A. ostenfeldii and associated extracellular metabolitescomprised both autotrophs (Rhodomonas sp., Dunaliella salina,Thalassiosira weissflogii) and heterotrophs (Oxyrrhis marina,Amphidinium crassum, Rimostrombidium caudatum). Observed effectsincluded immobilisation (e.g. of O. marina), morphological changes(e.g. in D. salina) and/or aberrant behaviour (e.g. of R. caudatum),mainly as preliminary stages of cell lysis. Immobilization andlytic effects against O. marina were strongly dependent on A.ostenfeldii cell concentrations. Effects also differed substantiallyamong strains and different batch cultures of the same strain.Values of EC₅₀, defined as the A. ostenfeldii cell concentrationcausing lysis of 50% of O. marina cells, ranged from 0.3 to1.9 x 10³ mL^–1, depending on the A. ostenfeldii strain.The autotrophic dinoflagellate Scrippsiella trochoidea reactedto exposure to A. ostenfeldii cells by formation of temporary(ecdysal) cysts, whereas, in contrast, the flagellates Emilianiahuxleyi and Prymnesium parvum and the ciliate Strombidium sp.were relatively refractory or even unaffected. As long as cellsdid not lyse, the fluorescence yield of target autotrophs, estimatedby pulse-amplitude modulation fluorometry, did not significantlychange during the first 3 h of incubation, suggesting that allelochemicalsproduced by A. ostenfeldii caused no short-term negative effectson the photosynthetic apparatus. Overall, the allelochemicalresponses of target species showed no obvious relationship tocell quota or extracellular concentrations of either toxic macrocyclicimines (spirolides) or tetrahydropurine neurotoxins (saxitoxinand analogues) produced by various strains of A. ostenfeldii.Instead, the potency of A. ostenfeldii, eliciting immobilizationand lytic species-specific responses in potential predatorsand competitors, is consistent with the existence of an allelochemicalmechanism unrelated to the bioactivity of known phycotoxinsof the genus Alexandrium.     

Biocomplexity in Populations of European Anchovy in the Adriatic Sea

The sustained exploitation of marine populations requires an understanding of a species'' adaptive seascape so that populations can track environmental changes from short- and long-term climate cycles and from human development. The analysis of the distributions of genetic markers among populations, together with correlates of life-history and environmental variability, can provide insights into the extent of adaptive variation. Here, we examined genetic variability among populations of mature European anchovies (n = 531) in the Adriatic (13 samples) and Tyrrhenian seas (2 samples) with neutral and putative non-neutral microsatellite loci. These genetic markers failed to confirm the occurrence of two anchovy species in the Adriatic Sea, as previously postulated. However, we found fine-scale population structure in the Adriatic, especially in northern areas, that was associated with four of the 13 environmental variables tested. Geographic gradients in sea temperature, salinity and dissolved oxygen appear to drive adaptive differences in spawning time and early larval development among populations. Resolving adaptive seascapes in Adriatic anchovies provides a means to understand mechanisms underpinning local adaptation and a basis for optimizing exploitation strategies for sustainable harvests.     

Environmental Optima for Seven Strains of Pseudochattonella (Dictyochophyceae,Heterokonta)

The ichthyotoxic flagellate Pseudochattonella has formed recurrent blooms in the North Sea, Skagerrak and Kattegat since 1998. Five strains of Pseudochattonella farcimen and two strains of P. verruculosa were examined in an assay comparing the light response of specific growth rates over a range of temperatures and salinities to get further knowledge on the autecology of members of this genus. Temperature optima were lower in P. farcimen (9°C–15°C) than in P. verruculosa (12°C–20°C). P. farcimen also showed a somewhat lower salinity optimum (18–26) than P. verruculosa (20–32). All strains showed light‐dependent growth responses reaching saturation between 18 and 52 μmol · photons · m^?2 · s^?1 at optimal temperature and salinity conditions. Compensation point estimates ranged from 4.2 to 15 μmol · photons · m^?2 · s^?1. Loss rates increased with temperature and were lowest at salinities close to optimal growth conditions. Blooms of P. farcimen have been recorded in nature under conditions more similar to those minimizing loss rates rather than those maximizing growth rates in our culture study.     

Warming temperatures and smaller body sizes: synchronous changes in growth of North Sea fishes

Decreasing body size has been proposed as a universal response to increasing temperatures. The physiology behind the response is well established for ectotherms inhabiting aquatic environments: as higher temperatures decrease the aerobic capacity, individuals with smaller body sizes have a reduced risk of oxygen deprivation. However, empirical evidence of this response at the scale of communities and ecosystems is lacking for marine fish species. Here, we show that over a 40‐year period six of eight commercial fish species in the North Sea examined underwent concomitant reductions in asymptotic body size with the synchronous component of the total variability coinciding with a 1–2 °C increase in water temperature. Smaller body sizes decreased the yield‐per‐recruit of these stocks by an average of 23%. Although it is not possible to ascribe these phenotypic changes unequivocally to temperature, four aspects support this interpretation: (i) the synchronous trend was detected across species varying in their life history and life style; (ii) the decrease coincided with the period of increasing temperature; (iii) the direction of the phenotypic change is consistent with physiological knowledge; and (iv) no cross‐species synchrony was detected in other species‐specific factors potentially impacting growth. Our findings support a recent model‐derived prediction that fish size will shrink in response to climate‐induced changes in temperature and oxygen. The smaller body sizes being projected for the future are already detectable in the North Sea.     

Characterization of hybridoma cell responses to elevated pCO(2) and osmolality: intracellular pH, cell size, apoptosis, and metabolism.

CO(2) partial pressure (pCO(2)) in industrial cell culture reactors may reach 150-200 mm Hg, which can significantly inhibit cell growth and recombinant protein production. The inhibitory effects of elevated pCO(2) at constant pH are due to a combination of the increases in pCO(2) and [HCO(-) (3)], per se, and the associated increase in osmolality. To decouple the effects of pCO(2) and osmolality, low-salt basal media have been used to compensate for this associated increase in osmolality. Under control conditions (40 mm Hg-320 mOsm/kg), hybridoma cell growth and metabolism was similar in DMEM:F12 with 2% fetal bovine serum and serum-free HB GRO. In both media, pCO(2) and osmolality made dose-dependent contributions to the inhibition of hybridoma cell growth and synergized to more extensively inhibit growth when combined. Elevated osmolality was associated with increased apoptosis. In contrast, elevated pCO(2) did not increase apoptotic cell death. Specific antibody production also increased with osmolality although not with pCO(2). In an effort to understand the mechanisms through which elevated pCO(2) and osmolality affect hybridoma cells, glucose metabolism, glutamine metabolism, intracellular pH (pHi), and cell size were monitored in batch cultures. Elevated pCO(2) (with or without osmolality compensation) inhibited glycolysis in a dose-dependent fashion in both media. Osmolality had little effect on glycolysis. On the other hand, elevated pCO(2) alone had no effect on glutamine metabolism, whereas elevated osmolality increased glutamine uptake. Hybridoma mean pHi was approximately 0.2 pH units lower than control at 140 mm Hg pCO(2) (with or without osmolality compensation) but further increases in pCO(2) did not further decrease pHi. Osmolality had little effect on pHi. Cell size was smaller than control at elevated pCO(2) at 320 mOsm/kg, and greater than control in hyperosmotic conditions at 40 mm Hg.     

Effects of CO2 and osmolality on hybridoma cells: growth, metabolism and monoclonal antibody production

CO2 partial pressure (pCO2) in industrial cell culture reactors may reach 150–200 mm Hg, which can significantly inhibit cell growth and recombinant protein production. Due to equilibrium with bicarbonate, increased pCO2 at constant pH results in a proportional increase in osmolality. Hybridoma AB2-143.2 cell growth rate decreased with increasing pCO2 in well-plate culture, with a 45% decrease at 195 mm Hg with partial osmolality compensation (to 361 mOsm kg- 1). Inhibition was more extensive without osmolality compensation, with a 63% decrease in growth rate at 195 mm Hg and 415 mOsm kg-1. Also, the hybridoma death rate increased with increasing pCO2, with 31- and 64-fold increases at 250 mm Hg pCO2 for 401 and 469 mOsm kg- 1, respectively. The specific glucose consumption and lactate production rates were 40–50% lower at 140 mm Hg pCO2. However, there was little further inhibition of glycolysis at higher pCO2. The specific antibody production rate was not significantly affected by pCO2 or osmolality within the range tested. Hybridomas were also exposed to elevated pCO2 in continuous culture. The viable cell density decreased by 25–40% at 140 mm Hg. In contrast to the well-plate cultures, the death rate was lower at the new steady state at 140 mm Hg. This was probably due to higher residual nutrient and lower byproduct levels at the lower cell density (at the same dilution rate), and was associated with increased cell-specific glucose and oxygen uptake. Thus, the apparent effects of pCO2 may vary with the culture system. VMdZ and RK contributed equally to the results in this article. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of elevated dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum on D-glucose and L-lactate

The effect of increased dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum was studied with continuous turbidostatic cultures. The carbon sources were either l-lactate or d-glucose. To increase the dissolved carbon dioxide concentration the carbon dioxide partial pressure of the inlet gas stream pCO2,IN was increased stepwise from 0.0003 bar (air) up to 0.79 bar, while the oxygen partial pressure of the inlet gas stream was kept constant at 0.21 bar. For each resulting carbon dioxide partial pressure pCO2 the maximum specific growth rate mu(max) was determined from the feed rate resulting from the turbidostatic control. On d-glucose and pCO2 up to 0.26 bar, mu(max) was mostly constant around 0.58 h(-1). Higher pCO2 led to a slight decrease of mu(max). On l-lactate mu(max) increased gradually with increasing carbon dioxide partial pressures from 0.37 h(-1) under aeration with air to a maximum value of 0.47 h(-1) at a pCO2 of 0.26 bar. At very high pCO2 (0.81 bar) mu(max) decreased down to 0.35 h(-1) independent of the carbon source.