Name: preventing contamination in microbiology labs
Uploaded: 2023-04-30T06:35:10.000Z
Duration: 10 min 48 s
Channel: JoVE

K12 Standards

new-york-state-science-learning-standards

New York State Science Learning Standards

High School

Life Science

interdependent-relationships-in-ecosystems

Interdependent Relationships in Ecosystems

HS-LS2-2.

aseptic-technique-in-environmental-science

Aseptic Technique in Environmental Science

1. 无菌操作的准备工作
<ol>
	<li>获取并穿戴以下个人防护装备（PPE）：实验服、无破损或孔洞的乳胶或丁腈手套，以及护目镜（图1）。若需使用明火，为安全起见，请将长发束起。 
	<img alt="实验安全设备，包括实验台上用于实验防护的实验服、护目镜和手套。" src="/files/ftp_upload/10040/10040fig1.jpg" data-altupdatedat="1761830439000" data-alt="Figure 1"> 
	图1：个人防护装备：实验服、乳胶手套和护目镜。</li>
	<li>无菌操作技术的另一个重要方面是正确灭菌和储存将在实验中使用的培养基/试剂。通过称取适量干燥基础粉末，并将其加入规定体积的去离子水中，配制液体肉汤培养基（例如，胰蛋白胨大豆肉汤）和基于琼脂的培养基（例如，R2A）。</li>
	<li>对于液体肉汤培养基，将粉末置于加热板上以低温加热溶解，并将液体分装至玻璃螺旋盖瓶中（每瓶100 mL）或玻璃螺旋盖试管中（每管10 mL）。使用磁力搅拌子，在加热板搅拌器上搅拌琼脂培养基，直至粉末完全溶解。</li>
	<li>在容器上贴上高压灭菌指示胶带，并按照制造商说明进行高压灭菌处理（例如，121 °C 下维持20分钟）（图2和图3）。注意，高压灭菌胶带上的条纹颜色应由白色（灭菌前）变为黑色（灭菌后）。尽管颜色变化通常表明灭菌成功，但仍可使用芽孢条检测工具进行无菌验证，以确认高压灭菌效果。 
	<img alt="锥形瓶密封过程、实验设置、实验室研究、橙色手套、液体样品。" src="/files/ftp_upload/10040/10040fig2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 2"> 
	图2：将高压灭菌指示胶带贴附于物品表面。 
	<img alt="装有棕色化学溶液的锥形瓶，放置于深色背景上，用于实验室合成实验。" src="/files/ftp_upload/10040/10040fig3.jpg" data-altupdatedat="1761830439000" data-alt="Figure 3"> 
	图3：注意高压灭菌胶带上的条纹颜色由白色（灭菌前）变为黑色（灭菌后）。</li>
	<li>将液体肉汤冷却至室温，随后可在室温下保存，或于4 °C 冷藏保存。</li>
	<li>将琼脂培养基容器置于约50 °C 的水浴中冷却。冷却后，可将培养基倒入无菌培养皿中。待其冷却凝固后，按照制造商规定的温度条件集中储存。</li>
	<li>某些类型的培养基因高温会破坏关键成分而无法进行高压灭菌。此类培养基需采用真空过滤系统，通过0.22 µm 滤膜进行过滤除菌，随后在适当温度下储存。</li>
	<li>在实验台操作前，使用合适的消毒液（例如，500 ppm 次氯酸钠溶液）对台面进行消毒，以降低污染物从工作表面传播至培养物或无菌培养基的风险。</li>
	<li>为建立无菌区域，打开本生灯。用于灭菌金属接种环的最佳火焰类型为强烈的蓝色火焰，其中心应可见清晰的蓝色内锥（图4）。 
	<img alt="本生灯产生蓝色火焰，用于实验室实验中的加热与燃烧。" src="/files/ftp_upload/10040/10040fig4.jpg" data-altupdatedat="1761830439000" data-alt="Figure 4"> 
	图4：将细菌从一个显示培养物生长的培养皿转移至另一个含有琼脂培养基但未接种的培养皿。</li>
	<li>缓慢将接种环通过火焰最热的部分（蓝色内锥尖端），使其烧至通红，以实现彻底灭菌。</li>
</ol>
2. 细菌转移：从一个培养皿到另一个培养皿
<ol>
	<li>一种常见的细菌转移场景是将已培养分离物生长的培养皿中的细菌，转移到另一个含有基于琼脂的培养基的无菌培养皿中。</li>
	<li>开始时，轻轻打开含有纯细菌培养物的培养皿，将灼烧灭菌后仍处于高温状态的接种环轻触琼脂表面。</li>
	<li>使用冷却后的接种环从培养皿表面挑取一个单一菌落，然后关闭培养皿。</li>
	<li>使用含有培养基的新鲜培养皿进行划线分离操作，操作时将皿盖微微打开。</li>
	<li>在进行每一区段的划线分离（每皿共3个区段）之前，均需用火焰对接种环进行灭菌。在完成最后一次划线后，也应立即对接种环进行火焰灭菌，以防止实验台面污染，并考虑到实验室中其他人员后续可能使用或接触接种环。</li>
	<li>将划线后的培养皿放入恒温培养箱中，过夜培养。</li>
</ol>
3. 细菌转移：从肉汤培养物到培养皿
<ol>
	<li>另一种细菌转移的情景是从表现出生长的液体培养物（通常通过浑浊现象观察到）转移到含有培养基的无菌培养皿中。</li>
	<li>取下装有纯细菌培养物的试管（或烧瓶）的瓶盖，并将容器开口处通过火焰最热部分2-3次。为防止污染，切勿将瓶盖放置在实验台面上。</li>
	<li>小心地将已灭菌的接种环插入试管/烧瓶中，并在接触液体培养物之前，轻轻触碰容器内壁以冷却接种环。</li>
	<li>取一环液体培养物（图5），并立即盖上瓶盖。 
	<img alt="显微镜图像：毛发结构，聚焦于毛干和毛小皮。" src="/files/ftp_upload/10040/10040fig5.jpg" data-altupdatedat="1761830439000" data-alt="图5"> 
	图5：一环液体培养物。</li>
	<li>使用含有培养基的新鲜培养皿，将皿盖略微打开，进行划线分离操作。</li>
	<li>每段划线（每皿共3段）操作前，均需将接种环进行火焰灭菌。在完成最后一次划线后，也应立即对接种环进行火焰灭菌，以防止实验台面污染，并为实验室中后续使用接种环的人员提供安全考虑。</li>
	<li>将已完成划线的培养皿放入培养箱中，过夜培养以促进菌落生长。</li>
</ol>
4. 细菌转移：从长有菌落的培养皿到无菌液体培养基
<ol>
	<li>第三种细菌转移场景是从含有分离培养物的培养皿转移到含有无菌液体培养基的试管/烧瓶中。</li>
	<li>轻轻打开含有纯细菌培养物的培养皿，通过将灼热的接种环轻触琼脂表面以冷却。</li>
	<li>使用已冷却的接种环从培养皿表面挑取一个孤立菌落，并关闭培养皿。</li>
	<li>取下含有无菌液体培养基的试管（或烧瓶）的盖子，并将容器口在火焰最热部分通过2至3次。为防止污染，切勿将盖子放置在实验台面上。</li>
	<li>小心地将挑出的菌落放入液体培养基中，并轻轻搅动接种环以释放细菌。立即重新盖上盖子。</li>
	<li>对接种环进行火焰灭菌，以防止对实验台面造成污染，并考虑到实验室其他人员后续可能使用这些接种环。</li>
	<li>将烧瓶放入培养箱中过夜培养。</li>
	<li>次日从培养箱中取出烧瓶，进行梯度稀释以定量测定菌液浓度。</li>
	<li>将系列稀释液接种至琼脂糖培养基平板上，并将平板过夜培养。</li>
	<li>次日取出平板，观察是否存在任何污染。</li>
</ol>
5. 细菌转接：从肉汤培养物到无菌液体培养基
<ol>
	<li>第四种细菌转移场景是从处于生长状态的液体培养物转移到含有无菌液体培养基的试管或烧瓶中。</li>
	<li>取下装有纯细菌培养物的试管（或烧瓶）的瓶盖，将容器口通过火焰最热部分两次。为防止污染，切勿将瓶盖放置在实验台面上。</li>
	<li>小心地将接种环 lowered 放入试管/烧瓶中，并在插入液体培养物之前，轻轻接触容器壁以冷却接种环。</li>
	<li>吸取一环液体培养物后，立即盖上瓶盖。</li>
	<li>取下装有无菌液体培养基的试管（或烧瓶）的瓶盖，并将容器口通过火焰最热部分两次。 为防止污染，切勿将瓶盖放置在实验台面上。</li>
	<li>小心地将含有培养物的接种环放入无菌液体培养基中，轻轻搅动接种环以释放细菌，然后立即盖上瓶盖。</li>
	<li>对接种环进行火焰灭菌（图6），以防止实验台面污染，并考虑到实验室中其他后续使用接种环的人员。 
	<img alt="本生灯火焰测试，用于实验室光谱发射分析的光谱学实验。" src="/files/ftp_upload/10040/10040fig6.jpg" data-altupdatedat="1761830439000" data-alt="图6"> 
	图6：接种环在本生灯火焰中灭菌时烧至通红。</li>
	<li>将烧瓶放入培养箱中，过夜培养。</li>
	<li>次日从培养箱中取出烧瓶，进行系列稀释以定量测定菌液浓度。</li>
	<li>将系列稀释液涂布于琼脂糖培养基平板上，并将平板过夜培养。</li>
	<li>次日取出平板，观察是否存在污染。</li>
</ol>

除了使用本生灯外，还可以在称为层流罩的专用工作台中维持无菌工作环境，层流罩利用定向气流和过滤器来保持无菌状态。
环境微生物学家在野外采样以及在实验室中处理培养基、试剂和培养分离物时，正确使用无菌技术至关重要。&#160; 野外操作中无菌技术不当可能导致微生物从技术人员转移到关键环境样品中，或造成微生物在不同样品之间的交叉污染。此类事件在微生物生态学研究中尤为重要，例如在试图鉴定和比较特定生物群落中可能存在的细菌和真菌种群时。样品污染可能导致数据完整性的丧失。无菌技术对于维持来自野外采样的实验室培养分离物，或来自已建立的微生物和细胞培养保藏库的分离物同样至关重要。实验室若需“清理”或替换受污染的培养物，尤其是一些来自独特环境的稀有分离物，所需投入的时间、人力和经济成本可能极高，甚至无法承受，因为某些分离物可能是不可替代的。

环境科学中的无菌技术

来源：亚利桑那大学 Ian Pepper 博士和 Charles Gerba 博士实验室 
示范作者：Luisa Ikner
无菌技术是环境微生物学领域广泛采用的一项基本技能，需要在实验室内保持专注与实践的平衡。正确使用无菌技术可降低试剂、培养基和环境样品被细菌或真菌污染的可能性。无菌技术对于确保数据完整性以及维持可能包含极为稀有且难以培养的分离株的菌种库纯度也至关重要。实验室环境中的污染源包括空气中的微生物（包括附着在灰尘和纤维颗粒上的微生物）、存在于实验台表面、未灭菌玻璃器皿或设备上的微生物，以及来自研究人员身体和头发的微生物。使用无菌技术也是一种安全措施，可降低微生物向研究人员传播的风险，这在处理病原体时尤为重要。

该操作的结果展示了正确的无菌技术和不正确的无菌技术之间的差异。图7展示了倾注琼脂糖平板时因无菌操作不当而导致的污染情况（上方平板：无菌培养基；下方平板：受污染的培养基）。
<img alt="培养皿培养；显示在琼脂平板上菌落形成的真菌生长实验装置。" src="/files/ftp_upload/10040/10040fig7.jpg" data-altupdatedat="1761830439000" data-alt="Figure 7"> 
图7：倾注琼脂平板时因无菌操作技术不当可能导致的污染。 上方平板：无菌培养基；下方平板：受污染的培养基。

来源：亚利桑那大学 Ian Pepper 博士与 Charles Gerba 博士实验室  
演示作者：Luisa Ikner  
无菌技术是一种……

无菌技术是微生物学中的一项基本技能，在环境研究中具有至关重要的应用。如果微生物培养物被污染，实验室需要投入的时间、人力和经济成本来“清理”或替换这些培养物可能会非常高昂，甚至难以承受，尤其是一些来自独特环境的稀有分离株，某些样品可能无法替代。正确使用无菌技术可降低试剂、培养基和环境样品被细菌和真菌污染的可能性，同时避免样品之间的交叉污染。这也是一种安全措施，可减少微生物向实验人员传播的风险，尤其是在处理病原体时尤为重要。本视频将介绍无菌操作的基本原理；维持试剂和培养物无菌状态的几种重要技术；最后还将介绍这些技术在环境科学中的一些应用。使用无菌技术的目的是创建并维持一个无菌的工作环境、设备和试剂，以最大限度地减少生物样本的污染。常见的污染源包括空气中的微生物、存在于实验台或设备上的微生物，以及研究人员的头发、身体和衣物上的微生物。去除或防止实验室污染主要依赖两类试剂：消毒化学品和热处理。在进行无菌操作前，通常使用70%乙醇和稀释漂白剂等溶液对实验设备、工作台面及实验人员的手套进行消毒。同时，工具、玻璃器皿和液体培养基上的微生物可通过高压灭菌器中的高温高压蒸汽进行热灭杀，高压灭菌器是一种利用高温加压蒸汽对内部物品进行灭菌的密闭装置。此外，用于涂布平板的玻璃棒和金属接种环等工具，可使用本生灯等火焰源进行火焰灭菌。使用火焰源也是建立无菌工作环境的最常见方法之一。火焰产生的热量会引起空气对流，形成上升气流，将燃烧器周围区域的空气中的污染物带走，从而形成一个“无菌区域”，用于开展无菌实验操作。现在您已经了解了无菌技术的原理及其重要性，接下来我们将介绍如何建立无菌工作环境、配制无菌培养基，以及在不同培养条件下无菌转移细菌的操作流程。在开始无菌操作之前，实验人员必须穿戴适当的个人防护装备（PPE）。其目的不仅是防止实验人员污染样品和实验室培养物，同时也防止潜在的致病微生物传播给实验人员。PPE 包括实验服、手套和安全护目镜。下一步是正确灭菌并储存用于培养微生物样品的培养基。首先，称取适量的固体培养基组分，并将其加入制造商指定体积的液体溶剂（如去离子水）中，置于可高压灭菌的容器内。加入一个磁力搅拌子，将容器放在加热搅拌器上，通过低温加热并搅拌使固体培养基组分充分溶解。关闭培养基容器。如果使用带螺旋盖的玻璃容器，请勿将盖子完全拧紧，因为在高压灭菌加热过程中，容器内的空气会膨胀，需要排出。若气体无法排出，可能导致容器破裂。在容器上贴一条高压灭菌指示胶带，并根据制造商的说明对培养基进行高压灭菌，例如 121 °C 下灭菌 20 分钟。高压灭菌后，检查灭菌指示胶带上的条纹是否变为黑色，以确认已达到适当的灭菌温度。对于液体培养基，让其冷却至室温，并根据需要在室温或冷藏条件下储存。对于基于琼脂的固体培养基，让其冷却至约 50 °C，然后倒入无菌培养皿中。待琼脂冷却并凝固后，于适当的温度下储存。对于因含有热敏成分而无法进行高压灭菌的培养基，需使用 0.22-µm 滤膜进行过滤除菌。微生物学工作中的一项核心技术是在不同培养基（包括固体和液体）之间无菌转移细菌培养物。实验开始前，需用消毒剂清洁实验台表面，以降低污染培养物或无菌培养基的风险。转移细菌培养物通常使用一种称为接种环的工具，该工具在使用前需通过火焰加热进行灭菌。打开火源。将接种环缓慢通过火焰尖端，直至接种环烧至通红。若要从固体琼脂平板上转移细菌菌落，需将培养皿轻轻打开一条缝隙，将灼热的接种环轻轻触碰琼脂表面无菌落的区域，以避免高温杀死细菌。用接种环刮取单个菌落后，立即盖上培养皿。从液体培养基中转移细菌时，先打开培养容器的盖子。为防止污染，避免将盖子直接放在实验台上。将容器口在火焰最热部位通过2-3次。然后，小心地将已灭菌的接种环接触容器内壁，待其冷却后再插入液体培养物中。取一环培养物后，立即盖上盖子。将获得的细菌转移至无菌培养基时，取下装有无菌肉汤的容器盖，将容器开口在火焰上通过2-3次。然后，小心地将接种环插入培养基中，轻轻振荡以释放细菌。立即盖上盖子。使用后对接种环进行灭菌处理。若将细菌转移至无菌琼脂平板，先打开一个含有未接种琼脂的新培养皿的皿盖。用接种环蘸取细菌培养物，在琼脂表面的一个区域来回划线。对接种环进行灭菌，并通过接触琼脂上无菌的部分冷却接种环，然后以与第一道划线呈钝角的方向在琼脂上进行第二次划线，注意前1-2次划线需与第一道划线相交，但后续划线应避免接触第一道划线。重复灭菌与划线操作两次。关闭培养皿，并对接种环进行灭菌。接种后，应将肉汤或琼脂平板置于该微生物最适生长温度下培养，以获得可存活的培养物。在固体培养基上，前两区划线覆盖的琼脂表面会形成细菌菌苔或连续的菌带，而最终划线区域应获得单个菌落。无菌操作技术不当会导致平板上生长霉菌及其他污染物。在涉及环境微生物样本的许多实验中，无菌技术至关重要。本研究中，研究人员从常见的土壤细菌节杆菌（Arthrobacter）中分离出噬菌体，即能够感染细菌的病毒。首先在无菌条件下培养节杆菌菌种。随后将土壤样品在噬菌体缓冲液中洗涤并过滤，将所得噬菌体溶液与细菌培养物混合，并接种至琼脂平板上。平板上会形成细菌菌苔，但在病毒已感染并杀死细菌的位置会出现透明区域，即“噬斑”。随后可从这些噬斑中纯化噬菌体以进行进一步研究。除了使用本生灯外，无菌工作环境还可以通过一种称为层流罩的专用工作台来维持，层流罩利用定向气流和过滤器来保持无菌状态。在此，科研人员在层流罩中操作，从水样中分离潜在的致病性细菌和病毒。随后将这些分离物与阿米巴原虫共同培养。由于阿米巴原虫通常会摄取或“吞噬”细菌，因此任何能够抵抗阿米巴消化并在其中存活的细菌，也可能在人体细胞中保持活性并引发疾病。最后，无菌条件使得能够深入研究生态机制，例如豆科植物根瘤的形成——这种充满细菌的器官可将大气中的氮“固定”为氨，供植物生长利用。研究人员在此处使用带有切口的培养皿和植物生长培养基，构建了用于研究结瘤过程的“微宇宙”系统，将幼苗放入其中，并接种可形成根瘤的根瘤菌。超净工作台提供的无菌环境可防止其他细菌或真菌对培养物造成污染。您刚刚观看了 JoVE 关于环境科学中无菌技术的视频。现在，您应该理解了无菌工作条件的重要性；如何无菌地进行微生物学实验；以及无菌技术在环境研究中的一些应用。一如既往，感谢观看！

Education

教育

JoVE Science Education

Environmental Sciences

环境科学

Environmental Microbiology

环境微生物学

无菌技术在环境科学中

preventing contamination in microbiology labs

Aseptic technique helps prevent contamination in environmental microbiology labs. It is a careful lab skill that takes practice and attention. When used correctly, it lowers the chance that bacteria or fungi will contaminate reagents, culture media, or environmental samples.

This technique also protects data quality. Keeping samples and cultures clean helps preserve the purity of culture libraries, including rare isolates that are difficult to grow. In this way, aseptic technique supports reliable results in environmental science labs.

Contamination can come from several places in the lab. Airborne microorganisms can ride on dust and lint particles. Microbes can also be present on the lab bench, on unsterilized glassware or equipment, and on the body or hair of the researcher.

Aseptic technique is also a safety measure. It reduces the chance that microorganisms will be passed to researchers, which matters even more when working with pathogens.

Preventing Contamination in Microbiology Labs

preventing-contamination-in-microbiology-labs

determination of moisture content in soil

determination-of-moisture-content-in-soil

Soil Pore Space and Water Content

Soil pore space holds water and air. Soil moisture content is the amount of water present in soil. This water sits in the spaces between soil aggregates and inside the aggregates themselves. These spaces are called inter-aggregate pore space and intra-aggregate pore space. In normal soil, pore space is usually filled by air, water, or both. If the pores contain only air, the soil is completely dry. If the pores are filled with water, the soil is saturated.

aseptic technique in environmental science

Aseptic technique helps prevent contamination in environmental microbiology labs. It is a careful lab skill that takes practice and attention. When used correctly, it lowers the chance that bacteria or fungi will contaminate reagents, culture media, or environmental samples. This technique also protects data quality. Keeping samples and cultures clean helps preserve the purity of culture libraries, including rare isolates that are difficult to grow. In this way, aseptic technique supports...

gram staining of bacteria from environmental sources

gram-staining-of-bacteria-from-environmental-sources

Visualizing Environmental Bacteria with Gram Stain

Gram staining helps scientists visualize bacteria collected from environmental sources. It is a fast, practical method for sorting culturable bacterial populations of interest. For environmental microbiologists, this can be useful whether the sample comes from a known isolate in the lab or from soil or water collected in the field. Environmental microbiology includes many kinds of research, from bench-scale work to field sampling. Soil and water samples often contain unknown bacterial...

visualizing soil microorganisms via the contact slide assay and microscopy

visualizing-soil-microorganisms-via-contact-slide-assay

Soil Life, Microbes, and the Rhizosphere

Soil is the thin layer at Earth’s surface that supports life. It contains both abiotic factors, which are nonliving parts, and biotic factors, which are living or once-living parts. The abiotic portion includes inorganic particles of different sizes and shapes that help determine soil texture. The biotic portion of soil includes plant residues, roots, organic matter, and microorganisms. Soil is especially rich in microbes. One gram of soil can contain large numbers of bacteria, actinomycetes,...

filamentous fungi

Fungi in Soil and Nutrient Cycling

Fungi are heterotrophic eukaryotic organisms that play an important role in soil. With the exception of yeasts, they are aerobic, which means they use oxygen. They are abundant in surface soils and help break down organic matter and some organic contaminants. These organisms also support nutrient cycling in the environment. White rot fungi, such as Phanerochaete chrysosporium, are a well-known example. They can degrade aromatics, which are ring-shaped organic compounds found in many materials.

community dna extraction from bacterial colonies

community-dna-extraction-from-bacterial-colonies

Soil Microbe Study Using Community DNA

Community DNA from soil helps scientists study microbial communities without relying only on culture tests. Traditional methods use dilution and plating on selective or differential media, or they use direct count assays. Direct counts show the total number of bacteria present, but they do not show how many populations are in the community or how diverse those populations are. Plate counts can measure total culturable bacteria or selected culturable groups. That makes them useful for comparing...

detecting environmental microorganisms with the polymerase chain reaction and gel electrophoresis

detecting-environmental-microorganisms-with-polymerase-chain-reaction

PCR for Tracking Microbes in Soil and Water

PCR is used to track microorganisms in soil, water, and air samples by detecting their DNA. The technique copies a specific DNA segment, which helps identify target microbes at the species, strain, and serovar or pathovar level. It can also help describe whole microbial communities in a sample. Culture-based methods are still used to detect microorganisms in environmental samples. These methods grow microbes on special media in the lab. They are useful, but they can miss microbes that are...

rna analysis of environmental samples using rt-pcr

rna-analysis-of-environmental-samples-using-rt-pcr

RT-PCR for Detecting RNA in Samples

RT-PCR is used to detect RNA in environmental samples by first converting RNA into DNA. It follows the same temperature-cycling steps as conventional PCR, but it begins with ribonucleic acid (RNA) instead of deoxyribonucleic acid (DNA). The RNA is turned into complementary DNA, or cDNA, so DNA-based tools can be used to study it. This method is important for finding RNA-based organisms in soil, water, and agricultural samples. Many viruses in the environment use RNA as their genetic material.

quantifying environmental microorganisms and viruses using qpcr

quantifying-environmental-microorganisms-and-viruses-using-qpcr

qPCR for Detecting Waterborne Viruses

Quantitative polymerase chain reaction (qPCR), also called real-time PCR, is a molecular method used to measure microorganisms in environmental samples. It helps researchers estimate how much microbial material is present, including disease-causing pathogens. This makes qPCR useful in environmental microbiology when samples need accurate counts. Before qPCR, scientists mainly relied on culture-based methods to quantify microbes. Those methods can be difficult to use with environmental samples.

water quality analysis via indicator organisms

water-quality-analysis-via-indicator-organisms

Indicator Organisms for Safe Water Testing

Water quality analysis can use indicator organisms to check for contamination in a fast and practical way. It helps monitor pollutants, nutrients, pathogens, and other substances that can affect water as a resource. When water is affected by human activity, its integrity can change. Fecal contamination is especially important because it can introduce microbial pathogens. These pathogens can threaten plant, animal, and human health and lead to disease or illness. As water demand increases and...

isolation of fecal bacteria from water samples by filtration

isolation-of-fecal-bacteria-from-water-samples-by-filtration

Coliform Testing in Water Safety Monitoring

Coliform testing helps monitor water safety in agricultural, recreational, and domestic settings. It is used because contaminated water can spread waterborne disease to people and animals. The microorganisms linked to these outbreaks include parasites, bacteria, and viruses. They are shed in high numbers in the feces of infected hosts. Infection can then spread by the fecal-oral route when a person ingests contaminated water. Testing every possible pathogen in water is not practical or...

detection of bacteriophages in environmental samples

detection-of-bacteriophages-in-environmental-samples

Bacteriophages and Coliphages in Wastewater

Bacteriophages are viruses that infect bacteria, and coliphages are the ones that infect coliform bacteria. These viruses can be found wherever coliform bacteria are present. The page focuses on how these phages relate to environmental samples, especially domestic wastewater. Viruses are a special group of biological entities that can infect both eukaryotic and prokaryotic organisms. They are obligate parasites, which means they must use a host cell to make more virus particles. They have no...

culturing and enumerating bacteria from soil samples

culturing-and-enumerating-bacteria-from-soil-samples

Soil Bacteria and Actinomycete Plating

Soil bacteria can be counted and grown using dilution and plating methods. Surface soils contain inorganic and organic particles that form secondary aggregates. The spaces between these aggregates hold air and water. That mix creates a good habitat for bacteria, and soil often contains more than 1 million bacteria per gram. Bacteria are the simplest microorganisms and are known as prokaryotes. A special group within this group is the actinomycetes. Actinomycetes are bacteria with a filamentous...

bacterial growth curve analysis and its environmental applications

bacterial-growth-curve-analysis-and-its-environmental-applications

Tracking Bacterial Growth in Pure Culture

Bacterial growth in pure culture shows how one species increases under controlled laboratory conditions. Pure culture means that only one type of bacterium is being studied. Because bacteria grow quickly, their cell numbers can rise sharply in a short time. Scientists measure how the bacterial population changes over time to create a growth curve. This curve helps show the rate of growth for the isolate being tested. It is a useful way to study bacteria in the lab instead of mixing many...

algae enumeration via culturable methodology

algae-enumeration-via-culturable-methodology

Counting Algae in Soil and Water Samples

Algae can be counted in soil and water samples using a culture-based most probable number (MPN) method. These microorganisms share one key trait: they contain photosynthetic pigments. The method helps measure algae that may grow in swimming pools, surface waters, and soils. Algae can create problems in lakes and reservoirs when blooms release toxins. They are also important in biofuel research because some species are being explored as energy sources. Blue-green algae are actually bacteria...

environmental microbiology

本系列介绍了环境中微生物群落及其在生态系统中的作用;同时也探讨了研究环境微生物学的常用方法。

Learn how aseptic technique helps prevent contamination in environmental microbiology labs, protect culture purity, and improve safety when working with microbes.

Preventing Contamination in Microbiology Labs | JoVE K12

Natural Selection and Evolution

HS-LS4-5.

Overview

Principles of Aseptic Technique

Preparation for Aseptic Work

Aseptic Transfer of Bacteria Between Liquid Media and Petri Plates

Applications

Summary

What is Central Tendency?

Descriptive statistics describe or summarize relevant characteristics of a sample and aid in the analysis of data of interest. When analyzing large ...

Arithmetic Mean

The arithmetic mean is the most commonly used measure of the central tendency of a data set. It is defined as the sum of all the elements constituting the ...

Geometric Mean

The mean is a measure of the central tendency of a data set. In some data sets, the data is inherently multiplicative, and the arithmetic mean is not ...

Harmonic Mean

The arithmetic mean is usually skewed towards the larger values in the data set. Therefore, to avoid this inherent bias towards smaller values, the ...

Trimmed Mean

While measuring the mean of a data set, care needs to be taken when associating the mean to its central tendency. The same goes for the arithmetic mean, ...

Weighted Mean

While taking the arithmetic, geometric, or harmonic mean of a sample data set, equal importance is assigned to all the data points. However, all the ...

Root Mean Square

If in an experiment, data values have a probability of being both positive and negative, neither the arithmetic mean, the geometric mean, nor the harmonic ...

What is a Mode?

The mode is one of the commonly used measures of a central tendency. It is defined as the most frequent value in a data set.
There can be more than one ...

Median

Besides mean, the median is a widely used measure of central tendency. Typically, median is defined as the central or middle value of a data set, measured ...

Multiple Bar Graph

As the name suggests, a multiple bar graph is the same as a bar graph but has multiple bars to depict relationships between different data values. One can ...

Pareto Chart

A Pareto chart is a bar graph or a combination of both line and bar graphs. The bar lengths represent the individual values or the frequency, while the ...

Pie Chart

A pie chart (or a pie graph) is a circular graphical chart or a pictorial representation of categorical data. It is divided into slices of pie each ...

Community Diversity

Populations do not live in isolation; thus, every population interacts with others in certain ways. These interactions give rise to a network of ...

What is Biodiversity?

Biodiversity describes the variety of living things at multiple organizational levels: genetic, species and ecosystem diversity. Species diversity ...

Measuring Biodiversity

Diverse ecosystems are important for the health of the planet and our survival as humans; it is therefore incredibly important for us to understand and ...

Quadrats and Transects Preparation
ExpandStart by tying a knot at the beginning, end and every 5 feet of six 20-foot pieces of rope.
Then, identify three ...

Quadrats and Transects
ExpandIn this activity, you will be using quadrats along transect lines to take biodiversity measurements of the plant species in ...

What are Populations and Communities?

Populations are groups of individuals of the same species that inhabit a shared environment. Communities include multiple co-existing, interacting ...

What is an Ecosystem?

Overview

An ecosystem is the interaction between all abiotic and biotic factors in an environment and can be classified as terrestrial or aquatic. ...

Population Growth

Population Models
An ecological population is a group of individuals of a single species living in an area at the same time. To persist, a population must ...

Species Distribution and Biogeography

Species Distribution

Biogeography is the study of species distribution across geographic space and the processes that shape these distributions. This ...

Threats to Biodiversity

There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species ...

What is Conservation Biology?

Conservation biology is a scientific field that focuses on the preservation of biodiversity in order to protect ecosystems while meeting the needs of the ...

Algae Enumeration via Culturable Methodology

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Bradley Schmitz
Algae are a highly ...

an-introduction-to-the-chick-gallus-gallus-domesticus

An Introduction to the Chick: Gallus gallus domesticus

The chicken embryo (Gallus gallus domesticus) is an extremely valuable model organism for research in developmental biology, in part because most of their ...

an-introduction-to-the-laboratory-mouse-mus-musculus

An Introduction to the Laboratory Mouse: Mus musculus

Mice (Mus musculus) are an important research tool for modeling human disease progression and development in the lab. Despite differences in their size ...

an-introduction-to-the-zebrafish-danio-rerio

An Introduction to the Zebrafish: Danio rerio

Zebrafish (Danio rerio) are small freshwater fish that are used as model organisms for biomedical research. The many strengths of these fish include their ...

determination-of-nox-in-automobile-exhaust-using-uv-vis-spectroscopy

Determination Of NOx in Automobile Exhaust Using UV-VIS Spectroscopy

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
In the troposphere, ozone is naturally formed when sunlight splits nitrogen ...

analysis-of-earthworm-populations-in-soil

Analysis of Earthworm Populations in Soil

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Using mustard, Lumbricus terrestris earthworm populations can be sampled ...

Dissolved Oxygen in Surface Water

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Dissolved oxygen (DO) measurements calculate the amount of gaseous oxygen ...

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Aseptic technique is a ...

Drosophila Maintenance

Drosophila melanogaster, commonly known as fruit flies, are a frequently used model organism for life science research. Although starting a collection of ...

Bacterial Growth Curve Analysis and its Environmental Applications

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Bacteria are among the most ...

drosophila-melanogaster-embryo-and-larva-harvesting-and-preparation

Drosophila melanogaster Embryo and Larva Harvesting and Preparation

Drosophila melanogaster embryos and larvae are easy to manipulate and develop rapidly by mechanisms that are analogous to other organisms, including ...

Bacterial Transformation: Electroporation

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA.  In nature, transformation can occur in certain types of bacteria.  In ...

Filamentous Fungi

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Bradley Schmitz
Fungi are heterotrophic ...

bacterial-transformation-the-heat-shock-method

Bacterial Transformation: The Heat Shock Method

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of ...

Introduction to the Spectrophotometer

The spectrophotometer is a routinely used instrument in scientific research.  Spectrophotometry is the quantitative measurement of how much a chemical ...

Basic Mouse Care and Maintenance

Mice (Mus musculus) are small rodents that breed and sexually mature quickly, making them perfectly suited to generating large animal colonies for ...

Isolation of Fecal Bacteria from Water Samples by Filtration

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
The quality of water destined ...

C. elegans Maintenance

Ceanorhabditis elegans has been, and is still, used to great success as a model organism for studying a variety of developmental, genetic, molecular and ...

lead-analysis-of-soil-using-atomic-absorption-spectroscopy

Lead Analysis of Soil Using Atomic Absorption Spectroscopy

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
Lead occurs naturally in soil, in levels ranging from 10-50 ppm. However, ...

Culturing and Enumerating Bacteria from Soil Samples

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Authors: Bradley Schmitz and Luisa Ikner
Surface ...

Measuring Tropospheric Ozone

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Ozone is a form of elemental oxygen (O3), a molecule of three oxygen atoms ...

Detection of Bacteriophages in Environmental Samples

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Alex Wassimi
Viruses are a unique group of ...

Nutrients in Aquatic Ecosystems

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
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Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
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Preventing Contamination in Microbiology Labs

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