Characterization of actinomycetes isolated from the indoor air of the church of Saint Katherine Monastery, Egypt

Actinomycetes were isolated from the indoor air of the church of Saint Katherin Monastery during different visiting hours. Fifty air samples collected over one year by using automated air sampler were plated on four different media. The low nutrient-content medium 1/10 SC was significantly effective in recovery of actinomycetes compared to the other formula of rich media. Average counts of bacteria, actinomycetes and fungi were 487, 65 and 90 cfu/m³, respectively. Fifty-six morphologically different actinomycetes isolates were recovered during this study assigned into five different genera, in addition to three unidentified isolates. Tentative identification of the isolates indicated predominance of genus Streptomyces, representing 59% of the isolates. Isolates were screened for resistance to 11 antibiotics, antimicrobial activities towards seven microbial strains, Growth on 12 different carbon source, acid production and pigmentation. About 77% of actinomycete isolates were resistant to the antibiotics with different resistance patterns. 12.5% of the airborne actinomycetes exhibited antinmicrobial activities. The isolates showed wide variation in carbon source usage. Forty percent of the isolates were able to utilize all tested carbon sources while 80% were acid producers. Melanin production was produced by 34% of the isolates. While 45% of the isolates were able to produce other diffusible pigments, the majority of the pigments were brown in color however; yellow, orange and green pigments were produced by a number of isolates. The impact of these activities on the historical objects of the church and the tourist’s health is discussed.     

Phenotypic plasticity of a cooperative behaviour in bacteria

There is strong evidence that natural selection can favour phenotypic plasticity as a mechanism to maximize fitness in animals. Here, we aim to investigate phenotypic plasticity of a cooperative trait in bacteria – the production of an iron‐scavenging molecule (pyoverdin) by Pseudomonas aeruginosa. Pyoverdin production is metabolically costly to the individual cell, but provides a benefit to the local group and can potentially be exploited by nonpyoverdin‐producing cheats. Here, we subject bacteria to changes in the social environment in media with different iron availabilities and test whether cells can adjust pyoverdin production in response to these changes. We found that pyoverdin production per cell significantly decreased at higher cell densities and increased in the presence of cheats. This phenotypic plasticity significantly influenced the costs and benefits of cooperation. Specifically, the investment of resources into pyoverdin production was reduced in iron‐rich environments and at high cell densities, but increased under iron limitation, and when pyoverdin was exploited by cheats. Our study demonstrates that phenotypic plasticity in a cooperative trait as a response to changes in the environment occurs in even the simplest of organisms, a bacterium.     

一株可同时降解多种高环PAHs的丝状真菌——宛氏拟青霉(Paecilomyces variotii)

采用液体培养的方法,分离纯化了丝状真菌宛氏拟青霉(Paecilomyces variotii)并研究了其对苯并[a]蒽、苯并[a]芘、苯并[b]荧蒽、苯并[k]荧蒽、茚并[1,2,3-cd]芘的降解效果.结果表明:接种处理30 d,该菌株对混合体系中5种PAHs的降解率为16.1%～24.6%,而对单一体系中的降解率为10.4%～33.3%;同时,对单一与混合体系中PAHs的降解作用存在一定差异,苯并[k]荧蒽和苯并[b]荧蒽在单一体系中降解率增大,而其他种类的则减小.本研究结果为高环多环芳烃共代谢机理研究和多环芳烃复合污染水土环境的生物修复提供了一种新的种质资源.     

Effects of post-fire conditions on soil respiration in boreal forests with special reference to Northeast China forests

Forest fires frequently occur in boreal forests,and their effects on forest ecosystems are often significant in terms of carbon flux related to climate changes.Soil respiration is the second largest carbon flux in boreal forests and the change in soil respiration is not negligible.Environmental factors controlling the soil respiration,for example,soil temperature,are altered by such fires.The abnormal increase in soil temperature has an important negative effect on soil microbes by reducing their activities or even by killing them directly with strong heat.On the other hand,although vegetation is directly disturbed by fires,the indirect changes in soil respiration are followed by changes in root activities and soil microbes.However,there is very limited information on soil respiration in the forests of Northeast China.This review,by combining what is known about fire influence on soil respiration in boreal forests from previous studies of post-fire effects on soil conditions,soil microbes,and forest regeneration,presents possible scenarios of the impact of anticipated post-fire changes in forest soil respiration in Northeast China.     

母婴间菌群传递的研究进展

肠道菌群的结构对婴儿肠道系统发育及免疫系统构建具有重要的影响,研究表明最初的婴儿肠道菌群在母亲子宫内就已经存在并受分娩方式和喂养方式的影响。本研究从母亲怀孕、分娩、喂养三个阶段综述母婴间的菌群传递,为母婴间菌群传递机制及婴儿肠道菌群对其免疫系统构建的影响提供一定的理论依据。     

混合菌群发酵秸秆合成菌体蛋白及其动力学分析

混合菌群发酵秸秆可有效提高秸秆纤维的降解率及菌体蛋白的转化率,对拓广蛋白饲料来源、减少环境污染起到积极的作用。本研究以小麦秸秆为原料,在纤维素酶水解预处理的基础上,以米曲霉作为先导菌,进一步分解残留的粗纤维,为后期发酵提供充足的碳源。根据不同微生物的代谢特征和协同机理,试验确定了发酵阶段混合菌群的组成为:米曲霉、产朊假丝酵母和枯草芽胞杆菌;接种顺序为:先接种米曲霉,再接种产朊假丝酵母,最后接种枯草芽胞杆菌。正交试验表明,影响发酵主要因素的主次顺序为:秸秆与麸皮配比>接种比例>发酵时间>接种量>发酵温度;发酵的最适条件为:米曲霉的接种量2.5%,发酵12h后接入5%的产朊假丝酵母,继续发酵8h后接入2.5%的枯草芽胞杆菌,发酵温度为28℃,秸秆与麸皮的配比为4∶1,尿素添加量为1.2%;结合动力学分析,将混合菌群的发酵时间优化为35h,发酵产物中粗蛋白含量由原来的5.47%提高到25%左右。对最适发酵条件下的动力学过程进行了探讨,建立了以Logistic方程为基础的数学模型和动力学方程。本研究表明,混合菌群发酵秸秆提高了发酵产物中的粗蛋白含量。动力学分析对于了解发酵机理、掌握整个发酵过程中混合菌群生长的动态变化、优化发酵工艺具有重要的指导意义。     

一株具有脱胶功能大麻内生真菌的分离和鉴定

采用组织块法对大麻(Cannabis sativa)根、茎、叶等组织中的内生真菌进行分离,利用平板透明圈法筛选具有脱胶功能的菌株,对获得的脱胶菌菌株进行形态学鉴定和分子生物学鉴定。结果表明:(1)从大麻根、茎、叶的组织部位共分离得到内生真菌16株,茎部分离到9株真菌,叶部5株,根部2株。(2)编号为DM6的内生真菌具有较强的果胶分解能力,其透明圈直径为2.49cm。(3)形态学鉴定发现,内生真菌DM6不能产生孢子,菌丝较为粗壮、分支较少、有明显的隔;分子学鉴定表明,内生真菌DM6与Phoma aliena(KC311486)序列的相似性最高,为99%,并且在系统发育树上位于同一分支上。因而内生真菌DM6可以鉴定为茎点霉属一种(Phomasp.)。     

动物及其肠道菌群的协同进化研究

动物自身合成一些关键营养物质的能力缺失,转而依赖体内的共生物来完成相应功能,如动物体内共生细菌能帮助宿主从食物中提取营养物质,并能合成一些关键代谢反应的化合物。结合国内外在动物及其肠道菌群的协同进化的研究进展,从三个方面进行了归纳:(1)动物及其肠道微生物组成与功能的协同进化研究;(2)动物行为与肠道微生物的关系;(3)共生肠道微生物在人类或动物自身消化食物、营养获取、健康和疾病方面发挥的重要作用。