Combined physical,chemical and biological factors shape Alexandrium ostenfeldii blooms in The Netherlands

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations. Since 2012, dense Alexandrium ostenfeldii blooms (up to 4500 cells mL⁻¹) have recurred annually in a creek located in the southwest of the Netherlands, an area characterized by intense agriculture and aquaculture. We investigated how physical, chemical and biological factors influenced A. ostenfeldii bloom dynamics over three consecutive years (2013–2015). Overall, we found a decrease in the magnitude of the bloom over the years that could largely be linked to changing weather conditions during summer. More specifically, low salinities due to excessive rainfall and increased wind speed corresponded to a delayed A. ostenfeldii bloom with reduced population densities in 2015. Within each year, highest population densities generally corresponded to high temperatures, low DIN:DIP ratios and low grazer densities. Together, our results demonstrate an important role of nutrient availability, absence of grazing, and particularly of the physical environment on the magnitude and duration of A. ostenfeldii blooms. Our results suggest that predicted changes in the physical environment may enhance bloom development in future coastal waters and embayments.     

An alternative infrared spectroscopy assay for the quantification of polysaccharides in bacterial samples

The ability of bacteria to produce extracellular polysaccharides has been regarded as an indication of biofilm-forming capacity. Therefore, the determination of the sugar content in bacterial samples becomes a significant parameter. The colorimetric methods currently used are rather sensitive to the nature of the sugars and therefore require knowledge of the sugar types present in the samples. Unfortunately, the types of sugars present in bacteria are generally unknown and often composed of a complex mixture. In this article, we propose an alternative method based on Fourier transform infrared (FTIR) spectroscopy for the estimation of the total sugar content in bacterial samples. The method is based on a systematic treatment of FTIR spectra obtained from dried bacteria samples. It is assumed that the total sugar amount can be estimated from the area of characteristic bands between 970 and 1182 cm(-1). In parallel, the amide II band (1560-1530 cm(-1)) associated with proteins, or the C-H stretching region (2820-3020 cm(-1)) associated with the biomass, can be used for normalization purposes. Therefore, the ratio of the band area in the sugar window over that of the amide II or C-H stretching can be used to report the sugar content in bacterial samples. This method has been validated on model bacterial mixtures containing sugars, proteins, and DNA. Results with real bacterial samples are also provided and show conclusively that increased sugar contents in biofilms can be identified. The proposed FTIR approach requires minimal sample preparation and a single acquisition, is rapid, and may be applied to any kind of bacterial growth.     

Heterotrophic bacterial and viral dynamics in Arctic freshwaters: results from a field study and nutrient-temperature manipulation experiments

Heterotrophic bacterial and viral concentrations (range, 0.7 × 10⁴ to 206.2 × 10⁴ ml⁻¹ and 0.05 × 10⁶ to 128.9 × 10⁶ ml⁻¹, respectively) were determined in several Arctic freshwater environments, including lakes and glacial ecosystems (78.55°N, 11.56°E). Our bacteria and virus results mirrored trends seen in temperate lakes, with an average virus-to-bacteria ratio (VBR) of 13 (range, 7.3–25.2) and viral concentrations and DOC positively correlated with bacterial concentrations (R = 0.964, P < 0.01 and R = 0.813, P < 0.05, respectively). Lysogenic bacteria, determined by induction with Mitomycin C, were not detected in any of the investigated Arctic freshwater environments. Nutrient-addition experiments at in situ and at elevated temperatures were performed to elucidate the factors which influenced the bacterial growth and the virus–bacteria interactions in Arctic freshwaters. Our results suggest that multiple limiting factors interacted and constrained bacterial growth. Bacterial concentrations and doubling times increased at elevated temperatures and appeared to be co-stimulated by phosphorus and carbon. However, viral concentrations showed a lack of response to nutrient addition thus indicating an uncoupling between bacteria and viruses in the experiment.     

Detection of bioterror agents in air samples using real-time PCR

Aims:  To use real-time PCR for the detection of bacterial bioterror agents in a liquid air sample containing potential airborne interferences, including bacteria, without the need for DNA extraction.
Methods and Results:  Bacteria in air were isolated after passive sedimentation onto R2A agar plates and characterized by 16S rRNA sequencing. Real-time PCR was used to identify different bacterial bioterror agents in an artificial air sample consisting of a liquid air sample and a mixture of miscellaneous airborne bacteria showing different colony morphology on R2A agar plates. No time-consuming DNA extraction was performed. Specifically designed fluorescent hybridization probes were used for identification.
Conclusions:  Fourteen different bacterial genera were classified by 16S rRNA gene sequencing of selected bacterial colonies showing growth on R2A agar plates. Real-time PCR amplification of all the bacterial bioterror agents was successfully obtained in the artificial air sample containing commonly found airborne bacteria and other potential airborne PCR interferences.
Significance and Impact of the Study:  Bacterial bioterror agents can be detected within 1 h in a liquid air sample containing a variety of commonly found airborne bacteria using real-time PCR. Airborne viable bacteria at Kjeller (Norway) were classified to the genera level using 16S rRNA gene sequencing.     

Climate change and heat-related mortality in six cities Part 1: model construction and validation

Heat waves are expected to increase in frequency and magnitude with climate change. The first part of a study to produce projections of the effect of future climate change on heat-related mortality is presented. Separate city-specific empirical statistical models that quantify significant relationships between summer daily maximum temperature (T _max) and daily heat-related deaths are constructed from historical data for six cities: Boston, Budapest, Dallas, Lisbon, London, and Sydney. ‘Threshold temperatures’ above which heat-related deaths begin to occur are identified. The results demonstrate significantly lower thresholds in ‘cooler’ cities exhibiting lower mean summer temperatures than in ‘warmer’ cities exhibiting higher mean summer temperatures. Analysis of individual ‘heat waves’ illustrates that a greater proportion of mortality is due to mortality displacement in cities with less sensitive temperature–mortality relationships than in those with more sensitive relationships, and that mortality displacement is no longer a feature more than 12 days after the end of the heat wave. Validation techniques through residual and correlation analyses of modelled and observed values and comparisons with other studies indicate that the observed temperature–mortality relationships are represented well by each of the models. The models can therefore be used with confidence to examine future heat-related deaths under various climate change scenarios for the respective cities (presented in Part 2).     

大鼠肠内容物细菌基因组DNA提取方法的比较

目的比较两种肠内容物前处理和两种提取方法对清洁级SD大鼠肠内容物细菌基因组DNA提取效率。方法分别选用PBS多次离心漂洗、液氮破细胞两种前处理方法和酚/氯仿抽提、试剂盒过柱法两种提取方法进行组合分析,对4份肠内容物和16份含金黄色葡萄球菌肠内容物进行随机提取。结果大鼠肠内容物细菌基因组DNA含量和纯度测定结果显示,与PBS反复离心相比,液氮研磨前处理能显著提高大鼠肠内容物基因组DNA。荧光定量PCR表明,液氮研磨前处理较PBS反复离心能更好地收集细菌基因组DNA,其Ct值最低。结论研究结果表明,采用液氮研磨试剂盒法在大鼠肠内容物DNA提取中是较为优良的方法,该方法为建立实验动物中微生物的定量PCR检测方法打下了基础。     

Influence of abiotic factors on bacterial proliferation and anoxic survival of the sea mussel Mytilus edulis L.

The effect of several abiotic factors (salinity, temperature and pH) on bacterial proliferation and survival time of the sea mussel Mytilus edulis L. were studied under anoxic incubations. In addition, the presence in the incubation media of ammonium and the volatile fatty acids propionate and acetate, both excreted fermentation products of the bivalve, was tested.Anoxic incubations with seawater diluted with demineralised water showed at the lowest salinity (50% seawater, SW) a significant increase in the capacity of M. edulis to survive anoxia as compared to both 75% SW and control [100% SW, corresponding to 32 practical salinity units (psu)]. Formation of biotic sulphide and ammonium occurred in all incubations. However, bacterial proliferation was postponed by 2-3 days at lowest salinity and accordingly, concentrations of both compounds were lower. Anoxic survival profiles of mussels collected from different habitats in the Dutch Scheldt area, characterised by differences in salinity (range from 17 to 31 psu), corresponded with the above salinity effect. Walsoorden mussels (17 psu) showed the longest (P<0.001) survival time under anoxia (LT₅₀=17.2 days) as compared with Paulina (27 psu) and Wemeldinge (31 psu) mussels (LT₅₀=12.8 and 9.8 days, respectively). Condition index (ratio of soft body weight to shell volume) was not correlated with anoxic survival time in untreated mussels, although this was clearly the case when the antibiotic chloramphenicol was added to the anoxic seawater.Acidification of the anoxic incubation medium had a positive effect on survival time. LT₅₀ values significantly (P<0.001) increased from 10.2 days at pH 8.1 to 11.6 and 11.5 days at pH 7.3 and 6.5, respectively. Biotic sulphide and ammonium accumulation as well as bacterial numbers were significantly lower at pH 7.3 and 6.5 as compared with pH 8.1. Anoxic incubations at 10 °C (LT₅₀=12.0 days) strongly increased survival time as compared to 18 °C (LT₅₀=5.9 days). The benefit of antibiotic addition was also stronger at lower temperature (10 °C).Addition of both propionate and acetate (0.5 mM) displayed no effect on mortality of mussels under anoxia, but ammonium (0.5 mM) caused a negative effect (P<0.001). Biotic sulphide and ammonium concentrations measured in both volatile fatty acid incubations were lower than the control situation, as well as total bacterial numbers.This study shows that environmental factors play a significant role in determining the course of bacterial infection and death of bivalves exposed to anoxia.     

茶园生态边界层结构及其变化规律

对茶园生态边界层的垂直结构特征及其变化规律的研究表明,茶园冠层的枝叶密集,叶片垂直分布集中。在晴天,由于茶树生理活动的影响,使得温度和湿度垂直分布形成明显的逆温层和正的湿度梯度,在叶片分布层附近达到最大值,向上向下减小,并随天气条件和时间变化而有所不同。生态实体是叶片分布层中生物体与环境之间相互作用而形成的具有特殊生态功能的实体,在较大的尺度上,以独特的生态功能与其周围环境进行物能交换和信息传递。     

我国西南地区风速变化及其影响因素

基于110个台站日风速观测资料,对我国西南地区1969—2009年风速时空变化及其影响因素进行研究,结果表明:1969—2009年西南地区平均风速以0.24 m s-110a-1的速率显著降低,其中1969—2000年平均风速以0.37 m s-110a-1速率降低,而2001—2009年却以0.55 m s-110a-1的速率升高,各季节、非季风和季风期风速变化趋势与年序列相似。空间分布上,1969—2009年风速降低台站主要位于高海拔区,降低幅度呈现西高东低趋势。1969—2000年风速降低台站主要位于西藏高原、横断山区和云南高原。2001—2009年风速增加台站主要位于云南高原、横断山区和四川盆地。风速这种变化趋势一方面受大气环流影响,西风环流和季风环流风速的减弱可能是2000年之前风速降低的重要原因,而纬向风的加强则对2000年以来风速增强有重要贡献。另一方面,区域变暖是风速降低的关键诱因。     

Climate change feedbacks to microbial decomposition in boreal soils

Boreal ecosystems store 10–20 % of global soil carbon and may warm by 4–7 °C over the next century. Higher temperatures could increase the activity of boreal decomposers and indirectly affect decomposition through other ecosystem feedbacks. For example, permafrost melting will likely alleviate constraints on microbial decomposition and lead to greater soil CO₂ emissions. However, wet boreal ecosystems underlain by permafrost are often CH₄ sources, and permafrost thaw could ultimately result in drier soils that consume CH₄, thereby offsetting some of the greenhouse warming potential of soil CO₂ emissions. Climate change is also likely to increase winter precipitation and snow depth in boreal regions, which may stimulate decomposition by moderating soil temperatures under the snowpack. As temperatures and evapotranspiration increase in the boreal zone, fires may become more frequent, leading to additional permafrost loss from burned ecosystems. Although post-fire decomposition could also increase due to higher soil temperatures, reductions in microbial biomass and activity may attenuate this response. Other feedbacks such as soil drying, increased nutrient mineralization, and plant species shifts are either weak or uncertain. We conclude that strong positive feedbacks to decomposition will likely depend on permafrost thaw, and that climate feedbacks will probably be weak or negative in boreal ecosystems without permafrost. However, warming manipulations should be conducted in a broader range of boreal systems to validate these predictions.     

California Multivariate Ocean Climate Indicator (MOCI) and marine ecosystem dynamics

Marine ecosystems are complex adaptive systems with physical and biological processes operating on multiple spatial and temporal scales. Here, we present an operational regional indicator for California's continental shelf system and investigate its skill in predicting a variety of biological responses across trophic levels. This updated Multivariate Ocean Climate Indicator (MOCI) version 2 includes data that are readily available from the Internet so the indicator can be automatically updated and shared regularly. MOCIv.2 is a simplified version of MOCIv.1, but it captures ocean-climate variability similarly. MOCIv.2 illustrates all major ENSO events that occurred over the past 25 years as well as the phasing and magnitude of the most recent North Pacific marine heat wave, dubbed ‘The Blob’. It also shows differences in the magnitude and timing of ocean-climate variability in different regions off California. MOCIv.2 has skill in nowcasting marine ecosystem dynamics, from zooplankton to top predators, and therefore may be useful in establishing bio-physical relationships important to ecosystem-based fisheries and wildlife management in California.     

Relationships of fungal spore concentrations in the air and meteorological factors

High concentrations of airborne fungal spores are associated with human health concerns. Environmental variables, such as temperature and moisture, can influence growth and reproduction in fungi and airborne spore concentrations can fluctuate seasonally. However, we do not understand how long-term changes in climate affect fungal abundance in the air. Here, we sampled annually (at peak season, in September, over a 20-yr period) for airborne fungal spores in two North American cities (New York and Toronto), and related fungal abundance to local variation in climate. We found that at both locations, the total precipitation during the 2- month period prior to sampling (Jul.–Aug.) was negatively related to observed fungal spore concentrations. Considering that climate predictions for these two regions indicate an increase in drought events in summer, we expect airborne fungal concentrations to increase in future years, potentially exacerbating human health concerns.     

鱼池生态系统中影响浮游细菌生长制约因素的研究

从溶解有机质及营养盐对细菌生长、细菌利用和矿化营养物质的影响,细菌捕食者和水温对细菌生长的影响等方面就鱼池生态系内影响细菌生长的主要制约因素进行研究。结果表明,向池水中添加P明显促进了细菌的生长和对C、N素的吸收,而添加C和N对细菌数量增长和营养物质吸收的作用不明显,但添加N明显增强了细菌对有机N的矿化能力,表明原池水中C、N供应充足,而无机磷限制了细菌的生长和对营养物质的利用;捕食组的细菌生长速率最低,比对照组减少6.26%-15.4%,且增长结束后细菌数量下降较其它组显著;池塘水体的原有细菌丰度,试验培养中细菌增长数量和生长速率在温度较高的季节也较高,温度升高促进了细菌生长,减弱捕食对细菌生长的负作用。     

Development of species-specific primers for detection of Streptococcus mutans in mixed bacterial samples

Streptococcus mutans is the major microbial pathogen associated with dental caries in children. The objectives of this study were to design and evaluate species-specific primers for the identification of S. mutans. Validation of the best primer set, Sm479F/R, was performed using seven S. mutans reference strains, 48 ATCC non-S. mutans strains, 92 S. mutans clinical isolates, DNA samples of S. mutans-Streptococcus sobrinus or S. mutans-Streptococcus sanguinis, and mixed bacterial DNA of saliva samples from 33 18-month-old children. All of the S. mutans samples tested positive, and no PCR products were amplified from members of the other streptococci or nonstreptococci strains examined. The lowest detection level for PCR was 10(-2) ng of S. mutans DNA (c. 4.6 x 10(3) copies) in the test samples. The results of this study suggest that the Sm479F/R primer pair is highly specific and sensitive for identification of S. mutans in either purified or mixed DNA samples.     

渤海三湾表层水域细菌群落结构多样性及其环境因子分析

【背景】近海生态系统的可持续发展是目前人们关注的重大问题之一,河口输出以及人类活动干扰对渤海近岸环境有着重要的影响。【目的】选取2015年夏季渤海湾、辽东湾、莱州湾3个断面12个站位表层水样品,探究渤海三湾细菌群落结构多样性。【方法】提取3个断面水环境样品DNA,利用Illumina Hi Seq高通量测序技术对样品进行测序分析,比较3个断面的细菌群落结构多样性差异。【结果】根据多样性指数和稀释曲线结果发现,3个断面的微生物多样性有着明显的差别,多样性依次为莱州湾渤海湾辽东湾。分析3个断面中占优势地位的主要类群,渤海湾断面中变形杆菌门(Proteobacteria)所占比例为39.8%,拟杆菌门(Bacteroidetes)占25.7%,蓝细菌门(Cyanobacteria)占22.4%,放线菌门(Actinobacteria)占5.85%,浮霉菌门(Planctomycetes)占4.38%;辽东湾断面各类群所占比例依次为变形杆菌门(Proteobacteria)37.8%,拟杆菌门(Bacteroidetes) 25.7%,蓝细菌门(Cyanobacteria) 17.8%,放线菌门(Actinobacteria) 10.4%,浮霉菌门(Planctomycetes)5.64%;莱州湾断面主要类群所占比例为(Proteobacteria)59.0%,拟杆菌门(Bacteroidetes)17.5%,蓝细菌门(Cyanobacteria)8.2%,放线菌门(Actinobacteria)7.88%。通过主成分分析和热图相关性分析发现环境因子对微生物群落组成和多样性分布有显著的影响,通过Manteltest统计分析,其中硝酸盐的作用尤为显著。【结论】渤海三湾微生物多样性非常丰富且存在较大的差异,莱州湾种群结构最复杂且物种最丰富,渤海湾和辽东湾次之,多样性分布与环境因子和空间分布有一定的相关性,该研究将为进一步保护海洋微生物多样性和生态开发提供一定的理论基础。     

The effect of temperature on bacterial degradation of EDTA in pH-auxostat

The effect of temperature on the maximum specific growth rate and the cell yield was studied during cultivation of two bacterial strains (LPM-4 and Pseudomonas sp. LPM-410) on EDTA under unlimited cell growth conditions in a pH-auxostat. Both strains displayed linear dependence of reciprocal biomass yield against reciprocal specific growth rate, from which the values of rate of substrate expenditure for cell maintenance and the “maximum” yield (i.e., hypothetical yield without cell maintenance processes) were estimated. Analysis of the maximum yield values based on mass–energy balance theory suggested that oxidation of the carboxylic acid side chains of EDTA by a monooxygenase had zero or low energetic efficiency. An Arrhenius equation with different values of Arrhenius parameters within different temperature ranges gave a good fit with the temperature dependence of both growth rate and biomass yield. Specific growth rates of both strains showed a more pronounced temperature dependence than did the cell yields. A possible kinetic mechanism was suggested which might be responsible for the modes of the temperature dependences of specific growth rate and yield that were found. The mechanism is based on a hypothetical key substance governing the metabolic flows, which is formed in a zero-order reaction and destroyed in a first-order reaction, both rate constants depending on temperature according to the Arrhenius law.     

Climate and plant distribution at global and local scales

This paper investigates, with predictive models, the utility of ecophysiological responses to climate as predictors of plant distribution. At the global scale responses to extreme minimum temperatures and to the hydrological budget effectively predict the distribution limits of the major vegetation types of the World. A minimum temperature of -15°C, for example, appears critical in controlling the poleward spread of vegetation that is dominated by evergreen broadleaved species; however, the presence or absence of more frost resistant species, such as those that are deciduous broadleaved, is not obviously explained in terms of extremes of climate. In such cases, predicting the competitive relationships between species is necessary and dependent on the climatic sensitivity of population dynamics.We are grateful to Hans de Kroon for discussions on the application of matrices to ecology.     

Some factors influencing the sensitivity of body temperature to activity in neonates

In adult humans, core temperature is influenced by activity; the sensitivity of core temperature to such effects shows a phase dependence and is also influenced by the environment and whether the individual is asleep or awake. We have investigated if similar effects are evident in neonates, in whom thermoregulation and the circadian rhythm of core temperature are not fully developed. Eleven full-term, healthy babies were studied singly (light 07:00-19:00) at 2 days of age and again 4 weeks after birth; between these times, they were tended routinely on a communal ward. On study days, 10-minute recordings were made of rectal and skin (abdominal) temperature, heart rate (HR), and behavioral state. Sensitivities of the temperatures to activity (“arousal”) were assessed throughout the 24h by measuring the gradient of (temperature/HR). Sensitivities measured at 01:00, 05:00, 09:00, 13:00,17:00, and 21:00 were used as dependent variables in stepwise regression and linear regression analyses, with “subjects” “light versus dark”, “behavioral state”, and “difference between time of measurement and the acrophase of the endogenous component of the temperature rhythm” (ignoring sign) as possible predictors. (Acrophases of the temperature rhythms had been estimated from 24h data purified using the behavioral state record.) Light versus dark acted as a significant predictor of the sensitivity of rectal temperature to arousal on day 2 and week 4, the sensitivity increasing in the light, and there was limited evidence for behavioral state acting as a predictor on day 2. Neither factor was a significant predictor when the sensitivity of the babies' skin temperatures to arousal was investigated. There was also some evidence that the difference between the time of measurement and the temperature acrophase acted as a predictor of sensitivity to arousal in both rectal (day 2) and skin (week 4) temperature, with larger differences decreasing the sensitivity. These results indicate that there are masking effects on body temperature due to arousal in neonates, the size of which depends on both internal and external factors. However, this sensitivity of temperature to arousal shows differences from the sensitivity of temperature to physical activity in both adult humans and adult mice. One possible explanation of this result is that temperature regulation and the circadian system are not fully developed in humans at this age. (Chronobiology International, 17(5), 679-692, 2000)     

Relative importance of biotic and abiotic factors affecting bacterial abundance in Lake Biwa: an empirical analysis

To determine the relative importance of factors affecting bacterial abundance in Lake Biwa, correlation and multiple regression analyses were performed with relevant biotic and abiotic variables. Data used in the analyses were collected weekly from April 1997 to June 1998 at a pelagic site in the north basin. The bacterial abundance ranged from 1 to 7 × 10⁶ cells ml⁻¹, and its spatio-temporal pattern was virtually identical to that in previous studies conducted 12–15 years ago. In the surface layer (0–12.5 m), bacterial abundance was significantly correlated with water temperature and with protozoan and metazoan grazers, but not with chlorophyll a and nutrient concentrations. The results suggest that loss factors rather than growth factors are more important in determining bacterial abundance in this lake. However, grazing effects on bacterial abundance differed among zooplankton. Bacterial abundance correlated negatively with phagotrophic nanoflagellates (PNF) and Daphnia, but positively with Eodiaptomus. Thus, PNF and Daphnia act to reduce the bacterial abundance, while Eodiaptomus acts to stimulate. In contrast, these biotic factors did not explain changes in bacterial abundance in the middle (12.5–25 m) and deep (>25 m) layers. Instead, the bacterial abundance in the deep layer was highly correlated with vertical mixing regimes, suggesting that bacterial abundance was directly or indirectly affected by abiotic factors. These results indicate that bacterial abundance in Lake Biwa was regulated by different factors at different depths. Received: February 8, 2000 / Accepted: August 29, 2000     

鼎湖山马尾松径向生长动态与气候因子的关系

Dendroclimatology method was used to study the relationship between ring index of Pinus massoniana and three climate factors in Dinghushan,South China.The ring indices were negatively correlated with the average tem-perature in June,August and September,and positively correlated with the average temperature of March,whereas no statistically significant correlation was found with monthly precipitation,showing that high summer temperature could limit the radial growth of the species,Meanwhile,tree ring indices showed a strong positive correlation with the relative humidity of April June,August,September,October and November,and also with the average humidity of the whole year,indicating that atmospheric moisture could not fully satisfy the growth of Pinus massoniana despite of abundant rainfall,The possible impact of climate change on the growth of Pinus massoniana was discussed accordingly.