Comparison of growth,acidification and productivity of pure and mixed cultures of Streptococcus salivarius subsp. thermophilus 404 and Lactobacillus delbrueckii subsp. bulgaricus 398

Pure and mixed controlled-pH batch cultures of Streptococcus salivarius subsp. thermophilus 404 and Lactobacillus delbrueckii subsp. bulgaricus 398 have been conducted. The characteristics of growth and acidification and the productivity of the cultures were compared. During the mixed cultures, the growth characteristics revealed a pronounced stimulation of S. thermophilus whereas L. bulgaricus metabolism was not significantly improved. The final total population was 1.4 to 4.9 higher than in pure cultures. The acidification characteristics were not enhanced by the mixed culture conditions. The productivity of mixed cultures was 1.7 to 2.4 times higher as compared to an equivalent mixing of pure cultures.Correspondence to: C. Béal     

黄河三角洲刺槐白蜡混交对土壤细菌群落结构及多样性的影响

为探讨黄河三角洲刺槐白蜡混交对土壤细菌群落结构及多样性的影响,通过高通量测序技术分析比较了刺槐白蜡混交林及刺槐纯林、白蜡纯林土壤细菌群落结构及多样性。结果表明:(1)混交林与两种纯林土壤细菌群落共36门。酸杆菌门、变形菌门、放线菌门(相对丰度大于10%)为刺槐白蜡混交林与两种纯林土壤中共有的优势菌群;硝化螺旋菌门为刺槐纯林土壤中的优势菌群。不同人工林土壤中各门细菌相对丰度差异显著。(2)混交改变了土壤细菌群落结构,提高了细菌多样性。刺槐白蜡混交林土壤细菌物种数、Chao1指数、Shannon指数分别为1934.5、2629.1、9.1,显著高于两种纯林。(3)相关性分析表明,土壤含水量与放线菌门细菌呈显著正相关;pH与芽单胞菌门细菌呈极显著正相关,与酸杆菌门细菌呈显著负相关。细菌多样性与土壤含水量呈显著正相关,与速效钾、有机质含量呈显著负相关。研究表明,刺槐白蜡混交林土壤细菌群落结构与两种纯林之间有一定差异,多样性差异显著,刺槐白蜡混交改变细菌群落结构,提高细菌多样性。     

木麻黄纯林及其混交林对土壤剖面理化性质的影响

为明确混交林对木麻黄林地土壤肥力的改善作用,该文选取海南岛北部滨海沙地木麻黄纯林、木麻黄-琼崖海棠混交林、木麻黄-大叶相思混交林3种林分类型,通过采集土壤剖面样品,分析腐殖质层、0～100 cm土壤各层次的理化性质、分布特征及其林分间差异。结果表明：(1)与纯林相比,木麻黄-琼崖海棠混交林可显著提高腐殖质层以及20～40 cm土壤层pH,增幅分别为6.11%和5.97%。(2)与纯林相比,木麻黄-琼崖海棠混交林和木麻黄-大叶相思混交林均可显著提高各层土壤的有机碳和全氮含量,有机碳含量增幅分别为69.8%～358.3%和90.2%～908.3%,全氮含量增幅分别为44.1%～160.7%和31.4%～210.7%;另外,木麻黄-琼崖海棠混交林还可显著提高0～100 cm各土层的全磷含量,增幅为20.8%～39.6%,而木麻黄-大叶相思混交林可显著提高20～100 cm各土层的全磷含量,增幅为25.0%～39.6%;木麻黄-大叶相思混交林对腐殖质层速效养分的改善效果较好,而两种混交林均可显著提高各土层的速效钾含量。(3)方差分析表明,林分类型和土层深度对林下有机碳、全氮、全磷、有效磷、硝态...     

Bioleaching of chalcopyrite by pure and mixed cultures of Acidithiobacillus spp. and Leptospirillum ferriphilum

Bioleaching is an economical method for the recovery of metals that requires low investment and operation costs. Furthermore, it is generally more environmentally friendly than many physicochemical metal extraction processes. The bioleaching of chalcopyrite in shake flasks was investigated with pure and mixed cultures of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus, and Leptospirillum ferriphilum. The mixed cultures containing both iron- and sulfur-oxidizing bacteria were more efficient than the pure culture alone. The presence of sulfur-oxidizing bacteria positively increased the dissolution rate and the percentage recovery of copper from chalcopyrite. Mixed cultures consisting of moderately thermophilic L. ferriphilum and A. caldus leached chalcopyrite more effectively than mesophilic A. ferrooxidans pure and mixed cultures. The decrease of the chalcopyrite dissolution rate in leaching systems containing A. ferrooxidans after 12–16 days coincided with the formation of jarosite precipitation as a passivation layer on the mineral surface during bioleaching. Low pH significantly reduces jarosite formation in pure and mixed cultures of L. ferriphilum and A. caldus.     

单种及混合种植对花叶芦竹铅积累量的影响

该研究采用盆栽试验法,选取石菖蒲、水生鸢尾、美人蕉、花叶芦竹为试验材料,将石菖蒲、水生鸢尾、美人蕉与花叶芦竹混种,用花叶芦竹单种作为对照,研究了混种对花叶芦竹生物量、根冠比以及铅积累量的影响。结果表明:(1)在不同浓度铅污染处理下,与花叶芦竹单种相比,混种模式增加了花叶芦竹的根冠比,且随着铅污染浓度的增加,表现出先上升后下降的趋势。(2)在单种和混种模式下花叶芦竹体内和土壤内的铅含量均表现出明显的浓度积聚效应;在混种模式下植物体内和土壤内的铅含量明显低于单种模式,且与单种模式之间的差异性显著(P<0.05)。(3)在高浓度铅污染处理下,单种和混种模式的花叶芦竹铅转运系数均大于1,而富集系数则表现为在低浓度和高浓度铅污染处理下均大于1;在美人蕉+花叶芦竹的混种模式中,花叶芦竹的地上部分和地下部分的铅富集系数达到最大。因此,我们认为美人蕉+花叶芦竹混种模式,显著提高了花叶芦竹的生物量和根冠比,并对铅污染土壤的净化效果最佳。     

Fermentation behaviour of controlled mixed and sequential cultures of Candida cantarellii and Saccharomyces cerevisiae wine yeasts

Behaviour of Candida cantarellii and Saccharomyces cerevisiae strains during the fermentation of Syrah grape must using pure, mixed and sequential yeast cultures was studied. Different kinds of inocula have been tested according to the type of culture. Inocula proportions used in mixed C. cantarellii and S. cerevisiae strains reflect the population levels in natural grape microbiota. Biomass evolution of both strains was analysed in relation to different byproduct levels. Saccharomyces cerevisiae overcame C. cantarellii in the different co-culture assays at 48 h of fermentation. The final concentration of ethanol was similar in mixed and both sequential tests and higher (from 7.8 to 10.6%) than in S. cerevisiae pure culture. In mixed and sequential cultures, the glycerol content of the final products was 44.3 to 52.8% higher than the one obtained with pure S. cerevisiae fermentation. Wine analytical profiles of experiments that involved S. cerevisiae and C. cantarellii strains differed from the pure ones mainly in acetoin, propanol and succinic acid contents. From an enological point of view, analysed byproducts are relevant. Considering this, mixed assay and the inoculation of S. cerevisiae after 3 days of pure C. cantarellii fermentation appear to be the more appropriate options to develop the particular characteristics of Syrah wines. This revised version was published online in July 2006 with corrections to the Cover Date.     

副溶血性弧菌-霍乱弧菌混合生物被膜形成过程研究

【目的】研究副溶血性弧菌(Vibrioparahaemolyticus,VP)和霍乱弧菌(Vibriocholera,VC)混合生物被膜的形成过程。【方法】在4、8、12、24、36、48、60、72 h测定单独条件下VP、VC及其混合后生物被膜的形成情况,通过结晶紫染色法、平板菌落计数法、测定胞外多糖、胞外蛋白,通过荧光原位杂交(FISH)观察混合生物被膜形成。【结果】虽然形成的混合生物被膜量介于VC和VP之间,但混合生物被膜在形成过程中,成熟期后生物被膜量的变化较小,对环境的抗性增强。混合生物被膜中拥有更多的活菌,混合生物被膜形成过程中胞外蛋白和胞外多糖的变化体现出其可能在对抵御不适应环境中起重要作用,通过FISH可观察到不同时期生物被膜的变化过程。【结论】VC与VP共同形成生物被膜的过程中,混合生物被膜总量虽然减少,但混合生物被膜中拥有更多的活菌,这可能引起更大的危害。研究混合生物被膜形成过程中被膜的变化,可为有害生物被膜的控制提供基础。     

混合生物结皮对土壤养分的影响与群落结构之关联——以黄土丘陵区的生物结皮为例

自然条件下生物结皮是藻、藓及地衣等结皮类型以不同比例组成的混合群落,显著影响土壤养分含量,目前混合生物结皮对土壤养分的影响与其群落结构的关系尚不清楚,限制了混合生物结皮土壤养分的评估。为此,研究通过测定单一组成的藻结皮、藓结皮以及80%藻+20%藓、60%藻+40%藓、40%藻+60%藓和20%藻+80%藓4个不同藻藓比例的混合生物结皮土壤有机碳、全氮、全磷、速效磷、铵态氮和硝态氮含量,研究了混合生物结皮土壤养分与其群落结构之间的关联。结果显示：(1)藓结皮层土壤有机碳、全氮、速效磷、铵态氮和硝态氮含量显著高于藻结皮,分别高出166.4%、77.2%、55.1%、56.2%和42.2%。(2)藻藓混合生物结皮土壤有机碳、全氮、速效磷和铵态氮含量与组成和盖度等结构特征有关,可以通过单一类型生物结皮土壤养分含量与盖度加权预测混合生物结皮土壤养分储量。(3)混合生物结皮土壤有机碳、全氮、速效磷和铵态氮储量实测值(x)与预测值(y)拟合的线性函数分别为y=0.97x、y=0.96x、y=1.18x和y=0.92x。(4)混合生物结皮对全磷和硝态氮含量的影响与群落结构无关。生物结皮对下层0—5 ...     

Production of lactic acid from date juice extract with free cells of single and mixed cultures of Lactobacillus casei and Lactococcus lactis

The production of lactic acid from date juice by single and mixed cultures of Lactobacillus casei and Lactococcus lactis was investigated. In the present conditions, the highest concentration of lactic acid (60.3 g l⁻¹) was obtained in the mixed culture system while in single culture fermentations of Lactobacillus casei or Lactococcus lactis, the maximum concentration of lactic acid was 53 and 46 g l⁻¹, respectively. In the case of single Lactobacillus casei or Lactococcus lactis, the total percentage of glucose and fructose utilized were 82.2; 94.4% and 93.8; 60.3%, respectively, whereas in the case of mixed culture, the total percentage of glucose and fructose were 96 and 100%, respectively. These results showed that the mixed culture system gave better results than single cultures regarding lactic acid concentration, and sugar consumption.     

Changes in the antibiotic production by co-culture of Rhizopus peka P8 and Bacillus subtilis IFO3335

The co-culture of Bacillus subtilis IFO 3335 with Rhizopus peka P8 or Rhizopus oligosporus P12 in liquid medium was found to increase production of antibiotic activity and to alter the spectrum of activity relative to the pure cultures. However, a mixed culture of Rhizopus arrhizus P7 and Rhizopus oryzae P17 did not produce antibiotic activity. The concentration, ratio, and time of addition of B. subtilis to the R. peka culture was found to influence antibiotic yields. Solid-state fermentations using mixed cultures of R. peka and B. subtilis were investigated. The growth of Escherichia coli IFO 3792 as a target bacterium was inhibited by the mixed culture. These results suggest the possibility of biopreservation of fermented foods by novel co-culture systems.     

Effects of environmental settings on MTBE removal for a mixed culture and its monoculture isolation

A mixed culture was utilized to evaluate methyl tert-butyl ether (MTBE) removal under various conditions and to isolate a MTBE-degrading pure culture. The results showed that high MTBE removal efficiencies can be reached even in the presence of other substrates. The biodegradation sequence of the target compounds by the mixed culture, in order of removal rate, was toluene, ethyl benzene, p-xylene, benzene, MTBE, ethyl ether, tert-amyl methyl ether, and ethyl tert-butyl ether. In addition, preincubation of the mixed cultures with benzene and toluene showed no negative effect on MTBE removal; on the contrary, it could even increase the degradation rate of MTBE. The kinetic behavior showed that the maximum specific growth rate and the saturation constant of the mixed culture degrading MTBE are 0.000778 h⁻¹ and 0.029 mg l⁻¹, respectively. However, a high MTBE concentration (60 mg l⁻¹) was slightly inhibiting to the growth of the mixed culture. The pure culture isolated from the enrichments in the bubble-air bioreactor showed better efficiency in MTBE removal than the mixed culture; whereas, tert-butyl alcohol was formed as a metabolic intermediate during the breakdown of MTBE.     

Degradation of BTEX compounds in liquid media and in peat biofilters

A mixed culture, enriched from Sphagnum peat moss, contaminated with gasoline vapours, degraded individual and mixed components of BTEX (benzene, toluene, ethylbenzene, xylene). Complete degradation of radiolabelled toluene by the mixed culture was observed in mineralisation studies. Individual isolates from a mixed culture containingPseudomonas maltophilia, P. testosteroni andP. putida biotype A exhibited contrasting BTEX degradation patterns. WhileP. putida biotype A degraded all of the BTEX compounds,P. maltophilia andP. testosteroni, appeared unable to degrade benzene and xylenes, respectively. When the peat, inoculated with the mixed culture, was used as a biofilter (6.2 cm diameter ×93 cm length) for degradation of toluene and ethylbenzene vapours, percentage removal efficiencies were 99 and 85, respectively. When the capacity of the biofilter to degrade a combination of BTEX compounds was evaluated, percentage removal efficiencies for toluene, ethylbenzene,p-xylene,o-xylene and benzene were 99, 85, 82, 80 and 78, respectively. The importance of using the mixed culture as an inoculum in the biofilter was established and also the relationship between contaminated vapour flow rate and percentage removal efficiency.     

Growth Response and Modifications of Organic Nitrogen Compounds in Pure and Mixed Cultures of Lactic Acid Bacteria from Wine

The interactions between the proteolytic X₂L strain of Oenococcus oeni and the non-proteolytic 12p strain of Pediococcus pentosaceus were assayed. The characteristics of cell growth, protein degradation, and amino acid production of both strains were determined in pure and mixed cultures. O. oeni showed poor cell growth and greater ability in the release of amino acids to the extracellular medium, whereas P. pentosaceus showed a higher yield in cell production with a decrease in the amino acid concentration in the medium. P. pentosaceus especially consumed essential amino acids for growth, and O. oeni released several of the essential amino acids important for growth of P. pentosaceus. In the mixed culture, mutualism was observed. The higher activity of the proteolytic system of O. oeni in mixed culture produced an increase in cell growth and in the amount of essential amino acids released. These findings provide new knowledge about the metabolic interactions between lactic acid bacteria isolated from wine when proteins are degraded in mixed bacterial populations.     

Regeneration and coexistence of two Abies species dominating subalpine forests in central Japan

Summary The mechanism of coexistence of the dominant firs Abies veitchii and A. mariesii is described in relation to regeneration patterns for climax subalpine forests of the northern Yatsugatake Mountains, central Honshu, Japan. Two mature stand types, pure conifer stands of Abies spp., and mixed stands of Abies spp. and hardwoods (mainly the birch Betula ermanii), are distinguished. Pure stands are likely to show simultaneous decay, followed by evenaged regeneration of stand-floor seedlings (<20 cm tall), Rapidly growing A. veitchii dominates over A. mariesii in this type of regeneration, which is occasionally invaded by light-demanding Betula. In constrast, mixed stands degenerate rather slowly, followed by the regeneration of Abies from the bank of suppressed saplings (>20 cm tall), which persist only in mixed stands. The more shade-tolerant A. mariesii is supeior in this type of regeneration, while Betula does not succeed, and mixed stands change to pure stands with time. The fact that two patterns of Abies regeneration occur in a certain ratio in the forest is what enables the two Abies species to coexist. A simple dynamical system model supports this conclusion.     

不同水淹下狗牙根-牛鞭草混作对植株生物量的影响

了解狗牙根(Cynodon dactylon)和牛鞭草(Hemarthria altissima)在不同水淹地区较优的种植方式对退化湿地的植被修复具有重要意义。设置4种不同水分条件,即对照组(CK)、水淹与干旱交替组(FD)、土壤表面水淹组(FL)和全淹组(SM),4种不同的植株密度(每盆分别种植1,2,4株或12株)和2种不同的种植方式(单作和混作),研究两物种在不同水淹条件下以不同方式和密度种植时的生物量变化。结果表明,水分、种植密度和种植方式均显著影响两物种的地上生物量和总生物量(P0.05)。CK和FD条件下,以中、高密度混作的狗牙根地上生物量和总生物量与单作相比显著下降(P0.05),牛鞭草在混作方式下的生物量与单作相比有了一定提高,其中在高密度混作情况下其生物量得到显著提高(P0.05)。在FL条件下,与单作相比,中、低密度混作的狗牙根和牛鞭草生物量均具有一定的上升。全淹条件下以中、低密度混作对狗牙根地上生物量和总生物量具有显著的促进作用(P0.05),对牛鞭草无显著差异(P0.05),高密度混作方式则对两物种生物量均无显著影响(P0.05)。随着水淹程度的增加,混作对狗牙根产生的生长抑制影响逐渐减弱。在长期浅水淹的地区,采取中、低密度混作将更有利于牛鞭草和狗牙根的长期共存。在较低海拔的全淹地区,采取高密度的牛鞭草-狗牙根混作方式将是更为理想的选择。     

Growth and survival ofAzospirillum brasilense andArthrobacter giacomelloi in binary continuous culture

Summary Azospirillum brasilense andArthrobacter giacomelloi were grown in single and mixed succinate-limited continuous cultures at a partial oxygen pressure of 0.01atm. Growth, viability and survival during nutrient starvation were examined at various dilution rates. At D=0.05 h^–1, K_s values for succinate consumed were calculated.Arthrobacter giacomelloi viability was inversely related to dilution rate whereasAzo. brasilense was directly related. Slightly lower values of viability were obtained in mixed culture, but the ratio between the microorganisms was constant. The survival ofArth. giacomelloi in single culture decreased with increasing growth rate while survival ofAzo. brasilense was directly related to dilution rate. Acetylene reduction activity was generally very low in both single and mixed cultures. Respiration rate was also determined and the mixed culture showed an oxygen uptake rate higher than that of single cultures.Research work supported by CNR, Italy. Special grant I.P.R.A. Sub-project 1. Paper N. 317.     

桥山栎林群落结构特征与物种多样性相关关系分析

为了解森林群落结构特征与物种多样性之间的相关关系,以黄土高原桥山林区典型麻栎纯林、麻栎阔叶混交林和麻栎油松混交林为研究对象,调查分析了群落结构特征,计算物种重要值及物种多样性,并进行了冗余分析,结果表明:(1)麻栎油松混交林主要以乔木层胸径、树高、枝下高等最高;麻栎阔叶混交林以灌木层盖度、地径、冠幅、高度等最高;麻栎纯林以草本地径、草本盖度及草本冠幅最高。(2) 3种类型林分乔木层重要值最高的均为麻栎(Quercus acutissima),灌木层为狼牙刺(Sophora viciifolia)、南蛇藤(Celastrus orbiculatus)、胡枝子(Lespedeza bicolor),草本层为苔草(Carex tristachya)。(3)麻栎油松混交林乔、灌层物种多样性较高,麻栎阔叶混交林以草本层物种多样性最高。(4)不同类型麻栎林群落结构特征与物种多样性关系有差异。松栎混交林中,对物种多样性影响最大的为乔木胸径、新稍长及灌木高度;麻栎阔叶混交林对物种多样性影响最大的为灌木层高度及冠幅;麻栎纯林中,对物种多样性影响最大的为乔木胸径。(5)麻栎油松混交林、麻栎阔叶混交林的胸径、树高、物种多样较麻栎纯林高,具有较高木材生产能力和生态防护功能,是未来森林经营培育的方向。     

Community Comparison and Determinant Analysis of Understory Vegetation in Six Plantations in South China

Plantations cover large areas in many countries, and the enhancement of plantation biodiversity is an increasingly important ecological concern. Many studies have demonstrated that overstory composition is important because it influences understory regeneration. To compare the understory vegetation and analyze its determinant factors, six typical plantations in South China were investigated: Acacia mangium plantation, Schima superba plantation, Eucalyptus citriodora plantation, E. exserta plantation, mixed‐coniferous plantation, and mixed native species plantation. The results show that native species plantations shaded out more grasses and herbs than exotic species plantations, mixed‐species plantations recruited more understory species than monoculture plantations, the leguminous species plantation had higher soil nitrogen than nonleguminous species plantations, and understory vegetation in the mixed‐coniferous plantation was similar to that of mixed, native broadleaf species plantation. Although light is the crucial environmental factor affecting the understory community and diversity among the 14 measured factors, other environmental variables such as soil nutrients and soil moisture are also important.     

Temporal variation of competition and facilitation in mixed species forests in Central Europe

Facilitation, reduced competition or increased competition can arise in mixed stands and become essential to the performance of these stands when compared to pure stands. Facilitation and over‐yielding are widely held to prevail on poor sites, whereas neutral interactions or competition, leading to under‐yielding of mixed versus pure stands, can occur on fertile sites. While previous studies have focused on the spatial variation of mixing effects, we examine the temporal variation of facilitation and competition and its effect on growth. The study is based on tree ring measurement on cores from increment borings from 559 trees of Norway spruce (Picea abies [L.] Karst.), European beech (Fagus sylvatica [L.]) and sessile oak (Quercus petraea (Matt.) Liebl.) in southern Germany, half of which were in pure stands and half in adjacent mixed stands. Mean basal area growth indices were calculated from tree ring measurements for pure and mixed stands for every species and site. The temporal variation, with positive correlations between species‐specific growth indices during periods of low growth and neutral or negative correlations during periods of high growth, is more distinct in mixed than in neighbouring pure stands. We provide evidence that years with low growth trigger over‐yielding of trees in mixed as opposed to pure stands, while years with high growth lead to under‐yielding. We discuss the relevance of the results in terms of advancing our understanding and modelling of mixed stands, extension of the stress gradient hypothesis, and the performance of mixed versus pure stands in the face of climate change.     

炉渣与生物炭施加对稻田土壤产甲烷菌群落结构的影响

为了了解废弃物施加处理影响稻田甲烷排放通量的微生物学机制,对稻田分别进行炉渣、生物炭单一施加和混合施加处理,分析施加处理条件下早、晚稻拔节期稻田土壤的理化性质,并采用PCR-RFLP技术及克隆测序对稻田土壤中的产甲烷菌群落组成多样性及其结构进行分析。研究结果表明:早稻拔节期,混施处理显著提高土壤盐度和pH;晚稻拔节期,混施处理显著提高土壤盐度,炉渣和混施处理显著提高pH。香农-威纳指数(H')和辛普森指数(D)显示:炉渣、生物炭和混施处理提高了稻田土壤产甲烷菌的多样性。群落组成分析结果表明:稻田土壤产甲烷菌主要含有甲烷微菌目(Methanomicrobiales)、甲烷杆菌目(Methanobacteriales)、甲烷八叠球菌目(Methanosarcinales)、甲烷球菌目(Methanococcales)、甲烷胞菌目(Methanocellales)和Methanomassiliicoccales等6大类群,其中甲烷微菌目(Methanomicrobiales)为优势类群。从属水平的群落结构来看,与对照相比,3种施加处理均降低了早稻土壤Methanomassiliicoccus相对丰度;生物炭处理还降低了Methanosarcina相对丰度。初步认为Methanomassiliicoccus和Methanosarcina这2个菌属与CH_4排放量减少密切相关。