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Investigating the effects of Bacillus subtilis endospore surface reactivity on low-temperature aqueous geochemical systems.

機(jī)譯：研究枯草芽孢桿菌內(nèi)生孢子表面反應(yīng)性對低溫含水地球化學(xué)系統(tǒng)的影響。

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Microbes are a ubiquitous component in water-rock systems including ground and surface waters, soils, mid-ocean ridge hydrothermal systems, and deep sedimentary basins. Microbial envelopes provide complex organic surfaces that serve as a physical interface between cellular and geochemical processes and thus represent a confluence of the bio-, hydro- and litho-spheres. As an intrinsic component in water-rock systems, microbes have the capacity to influence geochemical cycling in their surroundings through surface mediated pathways. This dissertation utilizes Bacillus subtilis endospores, a metabolically dormant cell type, to isolate and quantify the effects of bacterial endospore surfaces on low-temperature aqueous geochemical processes including ion adsorption and silicate weathering rates.;Chapter 2 outlines novel methods describing B. subtilis endospore growth and harvesting as well as a quality control technique enabling quantification of endospore harvest purity using bright-field and fluorescence microscopy imaging in conjunction with automated cell counting software. The resultant average endospore purity was 88 +/- 11% (1sigma error, n=22) with a median value of 93%.;Chapter 3 couples potentiometric titration and isothermal titration calorimetry (ITC) analyses to quantify B. subtilis endospore-proton adsorption. We modeled the potentiometric titration and ITC data using four- and five-site non-electrostatic surface complexation models (NE-SCM). Log Ks and site concentrations describing endospore surface protonation are statistically equivalent to B. subtilis cell surface protonation constants while enthalpies are more exothermic. The thermodynamic parameters defined in this study provide insight on molecular scale spore surface protonation reactions and provide a robust chemical framework for modeling and predicting endospore-metal adsorption behavior in systems not directly studied in the lab.;Chapter 4 investigates the B. subtilis endospore adsorption capacity of two major elements: magnesium (Mg) and silica (Si). We measure Mg and Si adsorption as a function of solution pH, adsorbate to adsorbent ratio and in systems containing both Mg and Si. NE-SCMs described in Chapter 3 provide a framework for modeling endospore-Mg. Mg adsorption to the endospore surface increases with increasing pH, adsorbent to adsorbate ratio and high concentrations of total Si. Si adsorption was negligible under all conditions studied. These findings suggest direct endospore-Mg adsorption is more likely to influence geochemical processes than endospore- Si adsorption.;In Chapter 5, B. subtilis endospores are used to isolate and quantify the effects of bacterial surface reactivity on the rate of forsterite (Mg2SiO4) dissolution at circumneutral pH. Assays utilizing homogeneous and dialysis bound mineral powder compare the influence of direct, spore-mineral and indirect, spore-ion interactions on forsterite dissolution rate. We show that endospore surface reactivity enhances forsterite dissolution rates through both direct and indirect pathways and as a function of endospore concentration.
機(jī)譯：微生物是水-巖石系統(tǒng)（包括地下水和地表水，土壤，中洋脊熱液系統(tǒng)和深層沉積盆地）中普遍存在的成分。微生物包膜提供了復(fù)雜的有機(jī)表面，可充當(dāng)細(xì)胞和地球化學(xué)過程之間的物理界面，因此代表了生物，水和巖石圈的融合。作為水-巖石系統(tǒng)中的固有成分，微生物具有通過表面介導(dǎo)的途徑影響其周圍環(huán)境中地球化學(xué)循環(huán)的能力。本文利用代謝休眠細(xì)胞類型的枯草芽孢桿菌內(nèi)生孢子來分離和定量細(xì)菌內(nèi)生孢子表面對低溫水化地球化學(xué)過程的影響，包括離子吸附和硅酸鹽風(fēng)化速率。第二章概述了描述枯草芽孢桿菌內(nèi)生孢子生長的新方法。采收以及質(zhì)量控制技術(shù)，可以使用明場和熒光顯微鏡成像結(jié)合自動細(xì)胞計數(shù)軟件對內(nèi)生孢子采收純度進(jìn)行定量。得到的平均內(nèi)生孢子純度為88 +/- 11％（1sigma誤差，n = 22），中值為93％.;第3章結(jié)合了電位滴定和等溫滴定量熱法（ITC）分析來定量枯草芽孢桿菌的內(nèi)生孢子質(zhì)子吸附。我們使用四和五位非靜電表面絡(luò)合模型（NE-SCM）對電位滴定和ITC數(shù)據(jù)進(jìn)行建模。 Log Ks和描述內(nèi)生孢子表面質(zhì)子化的位點濃度在統(tǒng)計學(xué)上等同于枯草芽孢桿菌細(xì)胞表面質(zhì)子化常數(shù)，而焓更容易放熱。這項研究中定義的熱力學(xué)參數(shù)提供了對分子尺度的孢子表面質(zhì)子化反應(yīng)的了解，并為在實驗室中未直接研究的系統(tǒng)中建模和預(yù)測內(nèi)生孢子-金屬吸附行為提供了強(qiáng)大的化學(xué)框架。第4章研究枯草芽孢桿菌內(nèi)生孢子的吸附兩種主要元素的容量：鎂（Mg）和二氧化硅（Si）。我們根據(jù)溶液pH值，被吸附物與吸附劑的比率以及同時包含Mg和Si的系統(tǒng)來測量Mg和Si的吸附。第3章中描述的NE-SCM提供了一個建模孢子內(nèi)鎂的框架。隨著pH值，吸附劑與被吸附物的比率以及高濃度的總Si的吸附，鎂對內(nèi)生孢子表面的吸附增加。在所有研究條件下，Si的吸附量均可以忽略不計。這些發(fā)現(xiàn)表明直接的內(nèi)生孢子Mg吸附比內(nèi)生孢子Si吸附更可能影響地球化學(xué)過程。;在第5章中，枯草芽孢桿菌內(nèi)生孢子用于分離和定量細(xì)菌表面反應(yīng)性對鎂橄欖石（Mg2SiO4）速率的影響在環(huán)境pH下溶解。利用均質(zhì)和滲析結(jié)合的礦物粉末進(jìn)行的分析比較了直接，孢子礦物和間接孢子離子相互作用對鎂橄欖石溶解速率的影響。我們表明，內(nèi)生孢子表面反應(yīng)性通過直接和間接途徑以及作為內(nèi)生孢子濃度的函數(shù)增強(qiáng)了鎂橄欖石的溶出速率。

著錄項

  • 作者

    Harrold, Zoe R.;

  • 作者單位

    University of Washington.;

  • 授予單位 University of Washington.;
  • 學(xué)科 Geobiology.;Geochemistry.;Microbiology.
  • 學(xué)位 Ph.D.
  • 年度 2014
  • 頁碼 155 p.
  • 總頁數(shù) 155
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類
  • 關(guān)鍵詞

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