Impact of a native Streptomyces flavovirens from mushroom compost on green mold control and yield of Agaricus bisporus

ABSTRACT

Thirty-five actinobacterial isolates, obtained from button mushroom (Agaricus bisporus) substrates (i.e., compost in different phases of composting, black peat or casing layer) in Serbia in 2014–2016 were tested in vitro against the causal agents of green mold in cultivated mushroom. Out of six most promising isolates, A06 induced 42.4% in vitro growth inhibition of Trichoderma harzianum T54, and 27.6% inhibition of T. aggressivum f. europaeum T77. The novel strain A06 was identified as Streptomyces flavovirens based on macroscopic and cultural characteristics and 16S rDNA sequence and used in mushroom growing room experiments. Actinobacteria had no negative influence on mycelial growth of the cultivated mushroom in compost in situ. Isolate S. flavovirens A06 enhanced mushroom yield significantly, up to 31.5%. The A06 isolate was more efficient in enhancing yield after inoculation with the compost mold T. aggressivum (26.1%), compared to casing mold T. harzianum (8%). Considering disease incidence, actinobacteria significantly prevented green mold in compost caused by T. aggressivum (6.8%). However, fungicide prochloraz-Mn had a more significant role in reducing symptoms of casing mold, T. harzianum, in comparison with actinobacteria (24.2 and 11.8%, respectively). No significant differences between efficacies of S. flavovirens A06 and the fungicide prochloraz-Mn against T. aggressivum were revealed. These results imply that S. flavovirens A06 can be used to increase mushroom yield and contribute to disease control against the aggressive compost green mold disease caused by Trichoderma aggressivum.     

Hormesis-like growth and photosynthetic physiology of marine diatom Phaeodactylum tricornutum Bohlin exposed to polystyrene microplastics

• Polystyrene microplastic caused hormesis-like effects in Phaeodactylum tricornutum. • Low concentration of microplastic promoted growth, otherwise the opposite was true. • The change trends of pigment contents were opposite at two initial algae densities. • The chlorophyll fluorescence parameters were more sensitive at low algae density. The effects of pristine polystyrene microplastics (pMPs) without any pretreatment at different concentrations (0, 10, 20, 50, and 100 mg/L) on Phaeodactylum tricornutum Bohlin at two initial algae densities (10⁵ and 10⁶ cells/mL) were assessed in this study. Hormesis-like effects were found when microalgae grew with pMPs. The results showed that pMPs inhibited microalgae growth under a high concentration of microplastics tolerated by individual algal cell (low initial algae density) (up to −80.18±9.71%) but promoted growth when the situation was opposite (up to 15.27±3.66%). The contents of photosynthetic pigments including chlorophyll a, chlorophyll c and carotenoids showed resistance to pMPs stress under a low initial algae density and increased with time, but the opposite was true under a high initial algae density. Compared with the low initial algae density group, Qp received less inhibition, and NPQ (heat dissipation) also decreased under the high initial algae density. Under the low initial algae density, OJIP parameters such as S_m, N, Area, Pi Abs, ѱ_o, φ_Eo, TRo/RC and ETo/RC were more perturbed initially and returned to the levels of the control group (without pMPs) over time, but they remained stable throughout the experiment at high initial algae density. These results show that microplastics in the marine environment may have different toxic effects on P. tricornutum at different growth stages, which is of great significance for understanding the impact of microplastics on marine microalgae and aquatic ecosystems.     

农户视角下台湾农业技术在大陆扩散影响因素分析——以广东韶关粤台农业合作试验区兰花种植业为例

以广东韶关粤台农业合作试验区兰花种植业为例,基于农户视角,构建三个维度下7个外因潜在变量,利用问卷调查数据,通过结构方程模型对台湾农业（兰花）技术扩散效果（内因潜在变量）的影响因素进行了分析。结果表明:农户社会网络与主观规范因素、农户对台湾农业的认知因素、台湾农业特点因素、台湾农业技术服务特点因素及基础条件因素等对兰花技术扩散效果具有显著正向影响,相应假设通过检验;农户创业特征及政策环境等两个因素对兰花技术扩散效果的影响不显著,相应假设未通过检验;试验区特殊的地域文化在促进兰花技术扩散的同时,也带来了一些消极影响;试验区应结合当地实际情况,根据兰花技术扩散的影响因素,制定合理的兰花产业发展对策。     

克雷伯氏菌生产絮凝剂M-C11的培养优化及其在污泥脱水中的应用

从活性污泥中筛选分离得到可产生微生物絮凝剂的克雷伯氏菌C11,对微生物絮凝剂M-C11的培养基碳源、氮源、无机盐等条件进行优化.探讨将微生物絮凝剂应用于活性污泥脱水时,pH、CaCl2投加量、M-C11投加量等因素对污泥脱水效果的影响,并与常规化学絮凝剂的调理效果对比分析.结果表明,絮凝剂M-C11生产的最优培养条件:30 g·L-1葡萄糖、2g·L-1NaNO3、0.5 g·L-1MgSO4分别作培养基碳源、氮源、无机盐,在37℃,150 r·min-1振荡培养48 h,絮凝活性高达91.70%.M-C11在pH为4~8、温度为20~60℃的范围内具有良好的絮凝稳定性.克雷伯氏菌产絮凝剂M-C11应用于调理污泥脱水,在pH为6、3 mL M-C11、4 mL CaCl2(1%)的最佳投加组合下,调理后污泥比阻(SRF)和含水率分别由原泥的11.64×1012m·kg-1和98.86%,降低至4.66×1012m·kg-1和83.74%,调理后的污泥脱水效果显著优于硫酸铝、聚合氯化铝(PAC)等无机絮凝剂.微生物絮凝剂具有成本低廉、易生物降解、无二次污染等优点,且对污泥pH、盐度等条件具有良好的适应性,可作为新型高效的污泥脱水调理剂.     

以污水厂二沉污泥为种泥培养颗粒污泥的研究

在自制生物反应器中,以天津市纪庄子污水处理厂二沉池回流污泥为种泥,通过控制系统的运行条件成功培养出了好氧颗粒污泥,并研究了其除污性能。试验结果表明：该好氧颗粒污泥具有良好的沉降性及生物活性,并具有良好的除污效果和硝化脱氮能力,对COD、NIV—N的去除率可达到90％、80％以上,达到国标GB18918—2002一级排放标准。     

放射性废水处理中吸附铀的优势藻种筛选

随着核工业的发展,含铀放射性废水的产生量越来越大,必须进行妥善处理与处置.微藻吸附技术是近年来放射性废水处理领域的研究热点,而获得吸附铀的优势藻种则是该技术得以研究和应用的基础.从工程应用的角度出发确定了筛选原则,并针对11株备选藻种进行了优势藻种筛选工作.栅藻LX1对铀的吸附容量最大,为40.7 mg·g~(-1);在m BG11培养基(模拟城镇污水处理厂污染物排放一级A标准的氮磷浓度限值)中的生物质产量较高,为0.32 g·L~(-1);生长进入稳定期后的沉降性能较好,沉降率为45.3%.综上,在本研究范围内,栅藻LX1为放射性废水处理中吸附铀的优势藻种.     

海洋微藻对游离氨基酸的利用特性研究

分别以4种游离氨基酸——丙氨酸、甘氨酸、谷氨酸和天冬氨酸为唯一氮源,采用实验室一次性培养的方法,研究典型赤潮藻——东海原甲藻(Prorocentrum donghaiense)、球形棕囊藻(Phaeoecystis globosa)和米氏凯伦藻(Karenia mikimotoi)及常见种类中肋骨条藻(Skeletonema costatum)的生长特性、光合特征及对氨基酸的吸收动力学特征,以无机氮源硝氮、氨氮作为对照.研究结果表明,在无菌条件下,东海原甲藻和球形棕囊藻可以利用多种游离氨基酸快速生长,而米氏凯伦藻和中肋骨条藻在以游离氨基酸为唯一氮源条件下不能维持生长.东海原甲藻和球形棕囊藻在丙氨酸中的生长速率最高,天冬氨酸和谷氨酸次之,甘氨酸最低.氨基酸处理组的Fv/Fm值在培养后期降幅小、降速慢,且高于无机氮处理组.东海原甲藻和球形棕囊藻对丙氨酸的最大吸收速率和半饱和常数分别为3.32、0.41pmol·cell-1·h-1和6.99和20.54pmol·L-1.因此,海洋微藻对游离氨基酸的吸收利用具有显著的种间差异,东海原甲藻和球形棕囊藻具有更广的氮营养生态位,在近海有机污染不断加剧的背景下,更容易形成优势甚至暴发赤潮.     

环境因子对红胞藻JZB-2降解海水中对二甲苯的影响

前期研究分离得到一种隐藻门微藻—红胞藻(Rhodomonas sp. JZB-2),能够快速生物降解海水中的PX.为了判断该微藻用于PX污染海域生物修复所需的适宜条件,依次研究4种环境因子(海水pH值、温度、盐度和光强)对该微藻生长及其降解PX的影响.结果表明:各因子均对红胞藻JZB-2生长及其降解PX产生较大影响.pH 7.0～8.5时微藻生长最快,但是最有利于PX降解的pH值为7.0.微藻生长适宜盐度为14～35,而PX降解速率最大值出现在盐度35时.温度20～30℃时最有利于微藻生长,而PX降解的最适温度为30℃.光强的影响比较特别,在光照条件下,微藻在200～400μmol/(m²·s)时生长较快,但是PX降解速率在800μmol/(m²·s)时最大;黑暗条件下微藻无法生长却仍能快速降解PX,这有利于泄漏事故海域生物修复在阴雨天气和夜间正常进行.研究结果将为红胞藻JZB-2在污染海域的合理应用提供依据.     

现代农业发展过程中土壤肥力资源合理利用的思考与对策

土壤是农业生产的重要基础,也是人类赖以生存的保障,其不仅关系食物安全供应,而且直接影响生态环境。土壤肥力是发展现代农业的重要支撑,其有效的培育涉及多学科与多专业,需要系统创新与联合攻关,如今人们对土壤肥力的认识已经从农业生产向环境安全、资源利用、生态健康及全球变化等方向转变与提升。本文从土肥长期定位研究、土壤肥力培育技术、现代农业发展等方面阐述内在关系及其特点,同时分析了现代土壤学研究领域所面临的重要挑战与发展趋势,并提出若干建议与对策。     

海洋微藻脲酶活性测定方法的实验研究

为进一步了解海洋微藻对尿素的吸收和利用机制,揭示水体尿素浓度升高对近海浮游植物群落演替的潜在影响及对近海有害藻类水华(HABs)形成的促进作用,对海洋微藻脲酶活性的测定方法进行了研究.以典型赤潮藻东海原甲藻为实验材料,在Peers方法的基础上,探讨了失活处理时间、提取液pH值、酶促反应温度以及微藻生长阶段对脲酶活性的影响.结果表明,失活处理时间、提取液pH值、酶促反应温度以及微藻所处的生长阶段都对微藻的脲酶活性具有显著影响.海洋微藻脲酶活性的最佳测定条件为:100℃下失活处理时间 > 2min;提取液pH值7.9;反应温度应与微藻生长温度一致;指数生长初期的藻体具有较高的酶活,而平台期后酶活趋于稳定.