The in vitro effect of manuka honeys on growth and adherence of oral bacteria

Honey has been used since ancient times and more recently, for the healing of wounds and against infectious diseases. The aim of our study was to investigate the effect of two manuka honeys showing different potencies of their antibacterial activity, on potentially pathogenic oral bacteria. The antimicrobial activity was examined by determining the MIC and MBC using the macro dilution broth technique. The effect on the adherence was tested on growing cells of Streptococcus mutans on a glass surface and on a multi-species biofilm grown on saliva-coated hydroxyapatite discs. As expected, the antibacterial activity of manuka 1 (with higher potency of antibacterial activity) was the most important. The two tested honeys weakly inhibited the adherence of S.mutans cells to a glass surface at sub-MIC concentration. Manuka 1 showed a total inhibition of multi-species biofilm at the concentration of 200 μg/ml manuka 2 inhibited biofilm formation weakly at the concentration of 200 μg/ml but firmly at the concentration of 500 μg/ml. Our findings suggest that manuka honeys might be able to reduce oral pathogens within dental plaque. These two honeys appear to be able to control dental biofilm deposit.     

西南不同岩性混合小流域化学风化特征

岩石化学风化影响着全球碳循环和气候变化,化学风化速率的估算及控制因素一直是研究的热点。为探究不同岩性混合小流域内化学风化速率及影响因素,于2018年9月对印江河流域、石阡河流域及余庆河流域采集河水样品并分析水化学特征。结果表明:河水的总溶解性固体(TDS)平均值为244 mg·L^-1,高于世界河流平均值(100 mg·L^-1);TDS值的空间差异显示,岩性分布不同导致离子浓度的明显变化。流域中的优势阴阳离子分别为HCO₃^-和Ca²⁺,表明流域碳酸盐岩风化对河水水化学组成起主导作用;通过正演模型解析不同端元(大气、人为、硅酸盐岩和碳酸盐岩)对河流中总溶解阳离子贡献发现,支流中碳酸盐岩贡献变化明显(55.0%～93.9%),空间差异主要受岩性影响;印江河、石阡河和余庆河的硅酸盐岩风化速率分别为4.4、2.8和2.5 t·km^-2·a^-1,相应的CO₂消耗速率为45×10³、18×10^3...     

Use of strontium isotopes and foliar K content to estimate weathering of biotite induced by pine seedlings colonised by ectomycorrhizal fungi from two different soils

Pinus sylvestris seedlings, colonised by ectomycorrhizal (EM) fungi from either of two different soils (untreated forest soil and a limed soil from a clear cut area), were grown with or without biotite as a source of K. The biotite was naturally enriched in ⁸⁷Sr and the ratio of ⁸⁷Sr/ ⁸⁶Sr in the plant biomass was estimated and used as a marker for biotite weathering and compared to estimates of weathering based on foliar content of K. Different nutrient regimes were used to expose the seedlings to deficiencies of K with and without an application of nitrogen (NH₄NO₃) in excess of seedling demand. The seedlings were grown for 220 days and the elemental composition of the shoots were analysed at harvest. The EM colonisation was followed by analysing the concentration of ergosterol in the roots and the soils. Bacterial activity of the soil was estimated by the thymidine incorporation technique. The concentration of organic acids in the soil solution was measured in the soil in which seedlings colonised by EM fungi from the untreated forest soil were grown. It was found that seedlings colonised by EM fungi from untreated forest soil had taken up more K in treatments with biotite addition compared to seedlings colonised by EM fungi from the limed forest soil (p<0.05). Seedlings from untreated forest soil had larger shoots and contained more K when grown with biotite compared to KCl as K source, indicating that biotite had a stimulatory effect on the growth of these seedlings which was not related to K uptake. Seedlings from the limed soil, on the other hand, had similar foliar K content when grown with either biotite or KCl as K source. The larger uptake of K in seedlings from untreated forest soil was not an effect of a more developed EM colonisation of the roots since seedlings from the limed soil had a higher ergosterol concentration both in the soil and in the roots. Nutrient regimes had no significant influence on the total uptake of K but the ⁸⁷Sr/ ⁸⁶Sr isotope ratio in the plant biomass indicated that seedlings grown with excess nitrogen supply had taken up proportionally less Sr from the biotite (1.8% of total Sr content) compared to seedlings grown with a moderate nitrogen supply (5.0%). Furthermore, seedlings grown with excess nitrogen supply had a reduced fungal colonisation of roots and soil and bacterial activity was lower in these soils. The ⁸⁷Sr/ ⁸⁶Sr ratio in the plant biomass was positively correlated with fungal colonisation of the roots (r ²=0.98), which may indicate that the fungus was involved in releasing Sr from the biotite. Uptake of K from biotite was not related to the amount of organic acids in the soil solution. Oxalic acid was positively related to the amount of ergosterol in the root, suggesting that oxalic acid in the soil solution originates from the EM symbionts. The accuracy of the estimations of biotite weathering based on K uptake by the seedlings in comparison with the ⁸⁷Sr/⁸⁶Sr isotope ratio measured in the shoots is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of material properties and photocatalysis on phototrophic growth in multi-year roof weathering

Phototrophic growth on roofs leads to weathering and impacts their appearance. Roof tiles with various properties are available (natural clay, engobed, varnished or coated with photocatalytic TiO₂). The aim of this study was to examine the influence of materials on the development of phototrophic biofilms. Roof tiles were weathered in six climatic regions in Germany for several years. Phototrophic biomass was periodically determined by PAM-fluorometry, image analysis, and visual evaluation. Roof tiles of natural clay were the most heavily infested, while black varnished roof tiles were hardly covered with any phototrophs. This colonisation pattern was compared to water availability on roof tiles surfaces. In contrast to rough natural clay, varnished black tiles accumulated less water, dried quickly, and were rather resistant to phototrophs. The photocatalytic coating was not effective against phototrophic growth. Materials with appropriate properties may prevent phototrophic growth without biocides through reduced water absorption capacities and by avoiding radiation protected structures.     

Suppression of common root pathogens by helper bacteria and ectomycorrhizal fungi in vitro

 Root pathogens cause considerable loss of tree seedlings in nurseries and are generally difficult to control using conventional methods. Inoculation with ectomycorrhizal fungi may provide some suppression of pathogens. Bacteria (so-called mycorrhization helper bacteria) have been isolated that stimulate mycorrhiza formation on seedling roots and enhance seedling growth; however, their role in pathogen inhibition has not been explored. Four strains of helper bacteria were inoculated together with the ectomycorrhizal fungal species Laccaria bicolor, L. proxima and Suillus granulatus on culture plates to determine inhibition of the pathogens Fusarium oxysporum and Cylindrocarpon sp. Buffered medium was used to rule out acidification of the medium as a mechanism of inhibition. None of the ectomycorrhizal fungal species alone inhibited the growth of Fusarium but all showed slight inhibition of Cylindrocarpon growth. Helper bacterium strain MB3 (Bacillus subtilis) was effective in inhibiting both pathogens and, when inoculated with either L. proxima or S. granulatus, inhibition of Fusarium growth was enhanced over MB3 alone. With Cylindrocarpon, however, only S. granulatus inoculated along with MB3 showed enhanced inhibition over MB3 alone. The other three bacterial strains had little effect on the growth of Fusarium or Cylindrocarpon. More research is necessary to determine if these inhibitory effects are reproducible in situ. Accepted: 23 October 1996     

细菌群体感应及其在食品变质中的作用

食品相关细菌引起的生物被膜形成和食品变质是食品工业中的重大问题。研究表明细菌群体感应(Quorum sensing,QS)与被膜形成、食品腐败变质密切相关。重点对细菌产生的各种QS信号分子及其在被膜形成的作用和被膜在食品工业中的重要性做了介绍。QS信号分子与食品变质密切相关,故对QS抑制剂作为新型食品防腐剂以延长储存期限及加强食品安全的前景进行了概述。     

Effect of organic and inorganic nitrogen sources on endogenous polyamines and growth of ectomycorrhizal fungi in pure culture

 The abilities of three ectomycorrhizal fungi, Paxillus involutus, Suillus variegatus and Lactarius rufus, to utilize organic and inorganic nitrogen sources were determined by measuring the growth and endogenous free polyamines (putrescine, spermidine and spermine) of pure culture mycelium. Differences were found in the utilization of the nitrogen sources and in the polyamine concentrations between the fungal species and between isolates of L. rufus. All the fungi grew well on ammonium and on several amino acids. Endogenous polyamine levels varied with the nitrogen source. Spermidine was commonly the most abundant polyamine; however, more putrescine than spermidine was found in P. involutus growing on inorganic nitrogen or arginine. Low amounts of spermine were found in S. variegatus and some samples of L. rufus. None or only a trace of spermine was found in P. involutus mycelium. In all fungi, putrescine concentrations were higher with ammonium than with the nitrate treatment. The total nitrogen content of peat did not determine the ability of L. rufus strains isolated from peatland forest sites to utilize organic nitrogen. Accepted: 27 November 1998     

Impact of Douglas-fir and Scots pine seedlings on plagioclase weathering under acidic conditions

The weathering of soil minerals in forest ecosystems increases nutrient availability for the trees. The rate of such weathering and its relative contribution to forest tree nutrition, is a major issue when evaluating present and potential forest stand productivity and sustainability. The current paper examines the weathering rate of plagioclase with and without Douglas-fir or Scots pine seedlings, in a laboratory experiment at pH 3–4 and 25 °C. All nutrients, with the exception of Ca, were supplied in sufficient amounts in a nutrient solution. The objective of the experiment was to evaluate the potential of trees to mobilise Ca from the mineral plagioclase that contained 12% of Ca. Amounts of nutrients supplied in the nutrient solution, amounts accumulated in the living tissue of the seedlings and amounts leached from the experimental vessels, were measured. A weathering balance, accounting for leached + accumulated − supplied amounts, was established. Bio-induced weathering, defined as the weathering increase in the presence of trees, relative to the weathering rate without trees (geochemical weathering; control vessels), under the present experimental conditions, explained on average, 40% of total weathering (biological + geochemical). These conditions appeared more beneficial to Scots pine (higher relative growth rate, higher Ca incorporation) than to Douglas-fir.     

苦参提取物对口腔主要致龋细菌作用的实验研究

目的 观察苦参提取物对口腔主要致龋细菌及其生物膜生长、黏附、产酸和产糖的影响,探寻其防龋作用机制。方法 将苦参提取物按照二倍梯度稀释法测定最低抑菌浓度,0.5 g/L氯己定为阳性对照,不含药液组为阴性对照组;采用紫外分光光度计测定细菌黏附能力;通过生物膜结晶紫染色法测定生物膜抑制浓度和生物膜清除浓度;通过ΔpH法和苯酚‒硫酸法分别测定细菌的产酸和合成水不溶性胞外多糖情况。结果 苦参提取物对口腔主要致龋细菌的最低抑菌浓度均为4 g/L;在4 g/L时,对变形链球菌、远缘链球菌、血链球菌、粘性放线菌和内氏放线菌黏附抑制率分别为（77.6%±1.2%）、（66.7%±1.8%）、（60.68%±2.9%）、（79.8%±1.2%）和（85.1%±1.3%）。2 g/L时能够显著抑制浮游菌产酸及合成水不溶性胞外多糖能力。4 g/L时对变形链球菌、远缘链球菌、血链球菌、粘性放线菌、内氏放线菌和嗜酸乳杆菌生物膜形成抑制率分别为（87.5%±1.3%）、（85.4%±0.5%）、（89.0%±0.3%）、（77.2%±0.7%）、（87.4%±1.1%）和（80.4%±1.3%）;并对以上细菌生物膜的最低清除浓度分别为16、16、16、16、8和8 g/L。苦参提取物在50%的最小生物膜清除浓度下对单菌生物膜的产酸和合成水不溶性细胞外多糖的抑制率分别为67.5%~94.1%和42.3%~60.0%。结论 苦参提取物能够抑制口腔主要致龋细菌浮游和生物膜状态下的生长、黏附、产酸和产糖,其有望成为一种龋齿预防制剂。     

The effect of pretransplant inoculation with VA mycorrhizal fungi on the subsequent growth of leeks in the field

Summary Leek plants were preinoculated with a mixed inoculum ofGlomus caledonium, Glomus fasciculatum andGlomus sp., and transplanted to Dazomet disinfected and untreated field plots of moderate P deficiency. Successive harvests were made until 99 days after transplanting. Preinoculated leeks attained marketable weights 25 days earlier than uninoculated leeks from untreated soil and their final dry matter yields were 5.7 and 1.5 times as high as those of uninoculated leeks from disinfected and untreated soil, respectively. Phosphorus concentration in preinoculated leeks remained highest for at least 22 and 75 days after transplanting in untreated and disinfected soil, respectively. Preinoculation had a similar, although smaller, influence on Cu and Zn concentrations. Infection levels produced by introduced and indigenous VA endophytes in leeks reached plateaus of 90% and 40%, respectively, 47 days after transplanting. It is concluded that VAM is essential to leeks grown in moderately P deficient soils, and the potential for inoculating seedlings in commercial leek production is discussed.     

The effect of light on growth and sporulation of certain fungi

Summary The response of the fungi investigated to duration of exposure to light varies with the variation in the light intensity employed. Using relatively low intensity light (160 and/or 300 foot candles/inch²), the growth ofMyrothecium verrucaria &Pestalotia gracilis was not affected by the increase in the time of light exposure, while that ofPleurotus ostreatus was checked. Fruiting under the same conditions was hastened on exposure to light. Under higher light intensity (950 foot candles/inch²), growth ofMyrothecium was not affected, while that ofPestalotia andPleurotus decreased as the daily period of exposure to light increased. Pleurotus cultures exposed continuously to light showed practically no growth, and combined addition of malt and yeast extracts had a noticeable growth promoting effect on cultures exposed continuously to light, but not significantly on those kept in the dark. This was explained by assuming the presence in malt and yeast extracts of light sensitive growth promoting substances. The effect of light on growth ofPleurotus was found to be concerned with both cell mechanism and medium: light probably inhibits inside the cell the synthesis of one or more substances essential for growth and at the same time it favors the breakdown in the medium of one or more substances required for growth.     

飞机草挥发油的化学组成及其对植物、真菌和昆虫生长的影响

飞机草挥发油对5种植物幼苗生长有显著的抑制作用,受抑制的大小排序为黑麦草＞白菜＞萝卜＞四季豆＞水稻．中等浓度(800mg·L-1)飞机草挥发油对水稻稻温病菌的抑制作用最强,对长春花疫病菌的抑制作用次之,对香蕉枯萎病菌的抑制作用最弱;其抑茵串分别为61．40％、29．27％和14．44％．10-20μl·株^-1的飞机草挥发油对小菜峨和黄曲条跳甲有显著的驱避产卵作用．经GC／MS,飞机草挥发油的化学成分主要是萜类化合物,如反式—石竹烯(16．58％)、δ—杜松烯(15．85％)、α—可巴烯(11．58％)、氧化石竹烯(9．63％)、大根香叶烯(4．96％)和α—Lu草烯(4．32％)。     

鲍曼不动杆菌生物被膜形成和菌体形态变化的研究

目的观察鲍曼不动杆菌能否以生物被膜菌的方式存在。方法采用平板改良法,分别于24h、2d、3d、5d和7d五个时间点,用扫描电镜观察硅胶膜上是否有鲍曼不动杆菌附着并形成生物被膜。结果鲍曼不动杆菌可以生物被膜菌的方式存在,第3天时在硅胶膜上生物被膜成熟。同时发现细菌形态在被膜形成后发生改变。结论鲍曼不动杆菌可以生物被膜菌的形式存在。     

化肥磷酸二铵对花背蟾蜍蝌蚪发育的影响

目的为了探究化肥磷酸二铵对两栖类幼体发育的影响。方法以花背蟾蜍(Bufo raddei)蝌蚪为研究对象,用化肥磷酸二铵(DAP)进行染毒培育,并依据Gosner(1960)分期标准,将蝌蚪分为G0实验组和G20实验组,分别暴露于浓度为0.045g/L、0.135g/L、0.225g/L的DAP水溶液中,直至蝌蚪完成变态发育,并对孵化率、死亡率、畸形率以及发育时程等参数进行统计分析。结果随着化肥DAP浓度的升高,孵化率逐渐下降,但对照组与各侵染组之间均无显著性差异;侵染组蝌蚪死亡率均高于对照组,均呈极显著性差异(P0.01),且G20侵染组明显高于G0侵染组;蝌蚪畸形可分为四大类,侵染组蝌蚪畸形率均高于对照组,且均呈极显著性差异(P0.01),畸形率随着DAP浓度的升高而增加;完成变态发育所用时程,侵染组明显长于对照组。结论化肥磷酸二铵对蝌蚪发育具有显著影响及损伤。     

Influence of climatypes of Scots pine on certain chemical and microbiological characteristics of soils

By using multivariate statistical analysis, the influence of Scots pine climatypes on a set of chemical and microbiological properties of soil, i.e., soil C/N, C_mic/C_org, and C_mic/N_mic, was revealed in a series of long-term (ca. 30 years) field experiments, which were carried out according to the same scheme under contrasting environmental and soil conditions of Siberian forestries.     

The effect of the chemical environment on interactions in groups of crayfish

Most of our knowledge of social behaviour in crustaceans stems from observations of pairs of animals engaged in conflict. Less consideration has been given to the dynamics of group behaviour. We investigated whether chemical signals affect the dynamic of groups of Cherax destructor. Animals were exposed to odours collected from male, female, moulted or dominant crayfish, or from fish. We observed agonistic encounters in the group during a 15 min period after the introduction of the odour. There was a decrease in threat behaviours when the male odour was added. We conclude from this that an olfactory stimulus can affect the dynamic of group interactions and the results suggest that the outcome is likely to be different from that obtained with paired or single individuals.