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Cell Wall: The outermost layer of a cell in most Plants; Bacteria; Fungi; and Algae. The cell wall is usually a rigid structure that lies external to the Cell membrane, and provides a protective barrier against physical or chemical agents.

Cell Structure- Concept

JoVE 10587


Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, multicellular organisms like elephants and giant redwood trees. In the mid 19th century, the Cell Theory was proposed to define a cell, which states:

Every living organism is made up of one or more cells.
The cells…

 Lab Bio

Tonicity in Plants

JoVE 10703

Tonicity describes the capacity of a cell to lose or gain water. It depends on the quantity of solute that does not penetrate the membrane. Tonicity delimits the magnitude and direction of osmosis and results in three possible scenarios that alter the volume of a cell: hypertonicity, hypotonicity, and isotonicity. Due to differences in structure and physiology, tonicity of plant cells is different from that of animal cells in some scenarios. Unlike animal cells, plants thrive when there is more water in their surrounding extracellular environment compared to their cytoplasmic interior. In hypotonic environments, water enters the cell via osmosis and causes it to swell because there is a higher concentration of solutes inside plant cells than outside. The force, that is generated when an influx of water causes the plasma membrane to push against the cell wall, is called turgor pressure. In contrast to animal cells, plant cells have rigid cell walls that limit the osmosis-induced expansion of the plasma membrane. By limiting expansion, the cell wall prevents the cell from bursting and causes plants to stiffen (i.e., become turgid). Turgidity allows plants to hold themselves upright instead of wilting. Plants wilt if they cannot take up sufficient water. In such a scenario, their extracellular surrounding becomes hypertonic, causing water to leave the

 Core: Membranes and Cellular Transport

Antibiotic Selection

JoVE 10807

Researchers use antibiotic resistance genes to identify bacteria that possess a plasmid containing their gene of interest. Antibiotic resistance naturally occurs when a spontaneous DNA mutation creates changes in bacterial genes that eliminate antibiotic activity. Bacteria can share these new resistance genes with their offspring and other bacteria. The overuse and misuse of antibiotics have created a public health crisis, as resistant and multi-resistant bacteria continue to develop. Antibiotics, such as penicillin, are drugs that kill or stop bacterial growth. Bacteria that naturally or artificially acquired antibiotic resistance genes do not respond to antibiotics. Scientists exploit this by designing plasmids—small, self-replicating pieces of DNA—that carry both an antibiotic resistance gene and a gene of interest. Antibiotic resistance is an integral part of DNA cloning that allows a researcher to identify cells that absorbed a DNA of interest. The researcher’s DNA of interest is introduced into bacterial cells using a process called transformation. Bacterial transformation involves temporarily creating small holes in the bacterial cell wall to permit the uptake of external DNA such as a plasmid. Only some bacterial cells absorb new DNA. Since the plasmid includes both the DNA of interest and a gene that confers resistance to a spe

 Core: Biotechnology

Microbial and Fungal Diversity- Concept

JoVE 10601

Bacteria and fungi are two highly diverse groups of organisms that can have significant beneficial or detrimental impacts on human health. For this reason, it is important to understand and distinguish between individual species of these groups. As you will recall, biological taxonomists group organisms based on their phylogenetic relatedness. The three domains of life, Bacteria, Archaea, and…

 Lab Bio

Diffusion and Osmosis- Concept

JoVE 10622

Cell Membranes and Diffusion

In order to function, cells are required to move materials in and out of their cytoplasm via their cell membranes. These membranes are semipermeable, meaning that certain molecules are allowed to pass through, but not others. This movement of molecules is mediated by the phospholipid bilayer and its embedded proteins, some of which act as transport channels…

 Lab Bio

Microscopy and Staining: Gram, Capsule, and Endospore Staining

JoVE 10513

Source: Rhiannon M. LeVeque1, Natalia Martin1, Andrew J. Van Alst1, and Victor J. DiRita1
1 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America

Bacteria are diverse microorganisms found nearly everywhere on Earth. Many properties help distinguish them from…


Prokaryotic Cells

JoVE 10690

Prokaryotes are small unicellular organisms in the domains Archaea and Bacteria. Bacteria include many common organisms such as Salmonella and Escherichia coli, while the Archaea include extremophiles that live in harsh environments, such as volcanic springs.

Like eukaryotic cells, all prokaryotic cells are surrounded by a plasma membrane and have DNA that contains the genetic instructions, cytoplasm that fills the interior of the cell, and ribosomes that synthesize proteins. However, unlike eukaryotic cells, prokaryotes lack a nucleus or other membrane-bound intracellular organelles. Their cellular components generally float freely within the cytoplasm, although their DNA—usually consisting of a single, circular chromosome—is clustered within a region called the nucleoid. Inside the cytoplasm, many prokaryotes have small circular pieces of DNA called plasmids. These are distinct from the chromosomal DNA in the nucleoid and tend to have just a few genes—such as genes for antibiotic resistance. Plasmids are self-replicating and can be transmitted between prokaryotes. Most prokaryotes have a cell wall made of peptidoglycan that lies outside of their plasma membrane, which physically protects the cell and helps it maintain osmotic pressure in different environments. Many prokaryotes also have a sticky capsule layer that covers

 Core: Cell Structure and Function

Mitosis and Cytokinesis

JoVE 10762

In eukaryotic cells, the cell's cycle—the division cycle—is divided into distinct, coordinated cellular processes that include cell growth, DNA replication/chromosome duplication, chromosome distribution to daughter cells, and finally, cell division. The cell cycle is tightly regulated by its regulatory systems as well as extracellular signals that affect cell proliferation. The processes of the cell cycle occur over approximately 24 hours (in typical human cells) and in two major distinguishable stages. The first stage is DNA replication, during the S phase of interphase. The second stage is the mitotic (M) phase, which involves the separation of the duplicated chromosomes into two new nuclei (mitosis) and cytoplasmic division (cytokinesis). The two phases are separated by intervals (G1 and G2 gaps), during which the cell prepares for replication and division. Mitosis can be divided into five distinct stages—prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis, which begins during anaphase or telophase (depending on the cell), is part of the M phase, but not part of mitosis. As the cell enters mitosis, its replicated chromosomes begin to condense and become visible as threadlike structures with the aid of proteins known as condensins. The mitotic spindle apparatus b

 Core: Cell Cycle and Division

Contact-dependent Signaling

JoVE 10715

Contact-dependent signaling uses specialized cytoplasmic channels between cells that allow the flow of small molecules between them. In animal cells, these channels are called gap junctions. In plants, they are known as plasmodesmata.

Gap junctions form when two hemichannels, or connexons, join; one connexon from one cell coupling to a connexon of an adjacent cell. Each cell’s connexon is formed from six proteins creating a circular channel. There are over 20 different types of these proteins, or connexins, so there is substantial variation in how they come together as connexons and as gap junctions. Connexins have four transmembrane subunits with both their N- and C-terminus endings located intracellularly. The C-terminus has multiple phosphorylation sites so it can be activated by numerous different kinases- further adding to gap junction variety. Depending on the activating kinase, and the C-terminal amino acid residues of connexins that are phosphorylated, gap junctions can be partially or fully opened. This selectively allows small molecules to flow from one cell into another. A gap junction may also exclude by electrochemical charge. The selectivity of gap junctions allows a single cell to coordinate a complex multicellular response. However, some toxic molecules, matching the size and electrochemical preference of the gap junction, can also p

 Core: Cell Signaling

Bacterial Transformation: Electroporation

JoVE 5060

The term “transformation” refers cellular ingestion of foreign DNA. In nature, transformation can occur in certain types of bacteria. In molecular biology, however, transformation is artificially induced through the creation of pores in the bacterial cell walls. Bacterial cells that are able to take up DNA from the environment are called competent cells. Electrocompetent…

 Basic Methods in Cellular and Molecular Biology

Plasmid Purification

JoVE 5062

Plasmid purification is a technique used to isolate and purify plasmid DNA from genomic DNA, proteins, ribosomes, and the bacterial cell wall. A plasmid is a small, circular, double-stranded DNA that is used as a carrier of specific DNA molecules. When introduced into a host organism via transformation, a plasmid will be replicated, creating numerous copies of the DNA fragment under…

 Basic Methods in Cellular and Molecular Biology

Dehydration Synthesis

JoVE 10681

Dehydration synthesis is the chemical process in which two molecules are covalently linked together with the release of a water molecule. Many physiologically important compounds are formed by dehydration synthesis, for example, complex carbohydrates, proteins, DNA, and RNA.

Sugar molecules can be covalently linked together by dehydration synthesis, also called condensation reaction. The resulting stable bond is called a glycosidic bond. To form the bond, a hydroxyl (-OH) group from one reactant and a hydrogen atom from the other form water, while the remaining oxygen links the two compounds. For each additional bond that is formed, another molecule of water is released, literally dehydrating the reactants. For example, individual glucose molecules (monomers) can undergo repeated dehydration synthesis to create a long chain or branched compound. Such a compound, with repeating identical or similar subunits, is called a polymer. Given the diverse set of sugar monomers, and variation in the location of the linkage, a virtually unlimited number of sugar polymers can be built. Plants produce simple carbohydrates from carbon dioxide and water in a process called photosynthesis. Plants store the resulting sugars (i.e., energy) as starch, a polysaccharide that is created from glucose molecules by dehydration synthesis. Cellulose is likewise buil

 Core: Macromolecules


JoVE 10672

Adhesion occurs when one type of molecule is attracted to a different kind of molecule. Water exhibits adhesive properties in the presence of polar surfaces—like glass or cellulose in plants. Regarding glass, the positively charged hydrogen molecules in water are more attracted to the negatively charged oxygen molecules in the silica than to the oxygen in neighboring water molecules. Capillary action is a result of water’s adhesive tendencies. When a narrow glass tube is inserted into water, the water molecules bind to the tube surface, and the water level inside the tube rises. The smaller the tube diameter, the farther the water rises, because more water molecules are exposed to the glass surface. Capillary action continues as long as the adhesive force is greater than the pull of gravity. Plants use the adhesion of capillary action and cohesion between water molecules to move water up from the roots to the leaves. In plants, xylem vessels consist of long, narrow cells called tracheary elements, which transport water. Because water molecules have an attraction to cellulose, they cling to the xylem cell wall. Cohesive forces between water molecules also attract the water molecules to each other. Together, these forces of adhesion and cohesion create a column of water molecules that gradually moves up the xylem vessels.

 Core: Chemistry of Life

Yeast Reproduction

JoVE 5097

Saccharomyces cerevisiae is a species of yeast that is an extremely valuable model organism. Importantly, S. cerevisiae is a unicellular eukaryote that undergoes many of the same biological processes as humans. This video provides an introduction to the yeast cell cycle, and explains how S. cerevisiae reproduces both asexually and sexually Yeast reproduce asexually …

 Biology I

An Introduction to Saccharomyces cerevisiae

JoVE 5081

Saccharomyces cerevisiae (commonly known as baker’s yeast) is a single-celled eukaryote that is frequently used in scientific research. S. cerevisiae is an attractive model organism due to the fact that its genome has been sequenced, its genetics are easily manipulated, and it is very easy to maintain in the lab. Because many yeast proteins are similar in sequence and function…

 Biology I

Yeast Maintenance

JoVE 5095

Research performed in the yeast Saccharomyces cerevisiae has significantly improved our understanding of important cellular phenomona such as regulation of the cell cycle, aging, and cell death. The many benefits of working with S. cerevisiae include the facts that they are inexpensive to grow in the lab and that many ready-to-use strains are now commercially available. Nevertheless,…

 Biology I

Bacterial Transformation: The Heat Shock Method

JoVE 5059

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of bacteria. In molecular biology, transformation is artificially reproduced in the lab via the creation of pores in bacterial cell membranes. Bacterial cells that are able to take up DNA from the environment are called competent cells. In the…

 Basic Methods in Cellular and Molecular Biology

Gram Staining of Bacteria from Environmental Sources

JoVE 10092

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

The spectrum of research in environmental microbiology is broad in scope and application potential. Whether the work is bench-scale with known bacterial isolates, or in the field collecting soil or water samples…

 Environmental Microbiology

Binary Fission

JoVE 10759

Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the Archaea and Bacteria domains reproduce using binary fission, in which a parent cell splits into two parts that can each grow to the size of the original parent cell. This asexual method of reproduction produces cells that are all genetically identical. Though its speed varies among species, binary fission is generally rapid and can yield staggering growth. In the amount of time it takes bacterial cells to undergo binary fission, the number of cells in the bacterial culture doubles. Thus, this period is the doubling time. For example, Escherichia coli cells typically divide every 20 minutes. Bacterial growth, however, is limited by factors including nutrient and space availability. Thus, binary fission occurs at much lower rates in bacterial cultures that have encountered a growth-limiting factor (i.e., entered a stationary growth phase). In addition to organisms in the Archaea and Bacteria domains, some organelles in eukaryotic cells also reproduce via binary fission. Mitochondria, for example, divide by prokaryotic binary fission. This process requires the division of mitochondrial proteins and DNA.

 Core: Cell Cycle and Division

Yeast Transformation and Cloning

JoVE 5083

S. cerevisiae are unicellular eukaryotes that are a commonly-used model organism in biological research. In the course of their work, yeast researchers rely upon the fundamental technique of transformation (the uptake of foreign DNA by the cell) to control gene expression, induce genetic deletions, express recombinant proteins, and label subcellular structures.


 Biology I

Tests on Wood

JoVE 10422

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA

Wood is a ubiquitous material that has been used in construction from the earliest times. Wood is a renewable, sustainable material with great aesthetic value. Today, there are probably more buildings constructed with wood than any…

 Structural Engineering

Isolating Nucleic Acids from Yeast

JoVE 5096

One of the many advantages to using yeast as a model system is that large quantities of biomacromolecules, including nucleic acids (DNA and RNA), can be purified from the cultured cells.

This video will address the steps required to carry out nucleic acid extraction. We will begin by briefly outlining the growth and harvest, and lysis of yeast cells, which are the initial steps…

 Biology I

Community DNA Extraction from Bacterial Colonies

JoVE 10218

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

Traditional methods of analysis for microbial communities within soils have usually involved either cultural assays utilizing dilution and plating methodology on selective and differential media or direct count assays.…

 Environmental Microbiology

Bacterial Transformation- Concept

JoVE 10573


In early 20th century, pneumonia was accountable for a large portion of infectious disease deaths1. In order to develop an effective vaccine against pneumonia, Frederick Griffith set out to study two different strains of the Streptococcus pneumoniae: a non-virulent strain with a rough appearance (R-strain) and a virulent strain with a smooth appearance…

 Lab Bio

Lytic Cycle of Bacteriophages

JoVE 10823

Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication cycle, the phage uses the bacterium’s cellular machinery to make proteins that are critical for the phage’s replication and dispersal. Some of these proteins cause the host cell to take in water and burst, or lyse, after phage replication is complete, releasing hundreds of phages that can infect new bacterial cells. Since the early 20th century, researchers have recognized the potential value of lytic bacteriophages in combating bacterial infections in crops, humans, and agricultural animals. Because each type of phage can infect and lyse only specific types of bacteria, phages represent a highly specific form of anti-bacterial treatment. This quality stands in contrast to the familiar antibiotic drugs that we often take for bacterial infections, which are typically broad-spectrum treatments that kill both pathogenic and beneficial bacteria. The w

 Core: Viruses

Diffusion and Osmosis - Prep Student

JoVE 10563

Preparation of Solutions for the Agar Cube Experiment
IMPORTANT: Wear gloves, goggles, and appropriate personal protective equipment – chemicals can be hazardous at high concentrations.
For the diffusion indicator solution, weigh out 1 g of phenolphthalein and add it to a beaker containing 100 mL of 95% ethanol.
To make the basic…

 Lab Bio

Bacterial Transformation

JoVE 10982

In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.

Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that produced pathogenic offspring. Griffith concluded that the non-pathogenic strain received something from the dead pathogenic strain that transformed it into the pathogenic strain; he called this the transforming principle. At the time of Griffith’s studies, there was heated debate surrounding the identity of the genetic material. Much early evidence implicated proteins as the hereditary molecules. Griffith’s experiments on bacterial transformation provided some of the earliest data demonstrating that DNA is the genetic material. Bacteria incorporate external DNA through transformation. Transformation occurs naturally but is also induced in laboratories—often to clone DNA. To clone a specific gene, scientists can insert the gene into a plasmid, a circular DNA molecule that can independently replicate. The plasmid often contains an antibio

 Core: DNA Structure and Function

Biofuels: Producing Ethanol from Cellulosic Material

JoVE 10014

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

In this experiment, cellulosic material (such as corn stalks, leaves, grasses, etc.) will be used as a feedstock for the production of ethanol. The cellulosic material is first pretreated (ground and heated), digested with enzymes, and then fermented with…

 Environmental Science

Microbial and Fungal Diversity - Prep Student

JoVE 10638

Nutrient Agar and Bacterial Culture Plate Preparation
Add 23 g of nutrient agar to a 2,000 mL beaker containing 1 L of distilled water 4 – 5 days before the activity.
Place the beaker on a hotplate and set the hotplate to high, stirring the mixture with a stirring rod.
When the agar has dissolved into the water, use a hot pad to…

 Lab Bio

Using a pH Meter

JoVE 5500

Source: Laboratory of Dr. Zhongqi He - United States Department of Agriculture

Acids and bases are substances capable of donating protons (H+) and hydroxide ions (OH-), respectively. They are two extremes that describe chemicals. Mixing acids and bases can cancel out or neutralize their extreme effects. A substance that is neither acidic…

 General Chemistry

The Colonization of Land

JoVE 11016

Changes in the environment of the early Earth drove the evolution of organisms. As prokaryotic organisms in the oceans began to photosynthesize, they produced oxygen. Eventually, oxygen saturated the oceans and entered the air, resulting in an increase in atmospheric oxygen concentration, known as the oxygen revolution approximately 2.3 billion years ago. Therefore, organisms that could use oxygen for cellular respiration had an advantage. More than 1.5 years ago, eukaryotic cells and multicellular organisms also began to appear. Initially, all of these species were restricted to the oceans of Earth. The first organisms to live on land were photosynthetic prokaryotes that inhabited moist environments near ocean shores. Despite the lack of water, terrestrial environments offered an abundance of sunlight and carbon dioxide for photosynthesis. Around 500 million years ago, the ancestors of nowadays plants were able to colonize drier environments, but they required adaptations to prevent dehydration. They developed methods for reproduction that did not depend on water and protected their embryos from drying out. These early plants furthermore evolved a vascular system that included roots to acquire water and nutrients and a shoot to obtain sunlight and carbon dioxide. Plants and fungi appear to have colonized land at the same time. Their coevolution onto land

 Core: Evolutionary History

Inducible, Cell Type-Specific Expression in Arabidopsis thaliana Through LhGR-Mediated Trans-Activation

1Department of Developmental Physiology, Centre for Organismal Studies (COS) Heidelberg, 2Department of Cell Biology, Centre for Organismal Studies (COS) Heidelberg, 3Department of Stem Cell Biology, Centre for Organismal Studies (COS) Heidelberg

JoVE 59394


Human Pluripotent Stem Cell Based Developmental Toxicity Assays for Chemical Safety Screening and Systems Biology Data Generation

1Center of Physiology and Pathophysiology, Institute of Neurophysiology, University of Cologne, 2Department of Biology, University of Konstanz, 3Department of Statistics, Technical University of Dortmund, 4Leibniz Research Centre for Working Environment and Human Factors, Technical University of Dortmund

JoVE 52333

 Developmental Biology

Deciphering and Imaging Pathogenesis and Cording of Mycobacterium abscessus in Zebrafish Embryos

1Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS, UMR 535, Université Montpellier, 2Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé, CNRS, FRE 3689, Université Montpellier, 3Unité de Formation et de Recherche des Sciences de la Santé, EA3647-EPIM, Université Versailles St Quentin

JoVE 53130

 Immunology and Infection

Antibody Binding Specificity for Kappa (Vκ) Light Chain-containing Human (IgM) Antibodies: Polysialic Acid (PSA) Attached to NCAM as a Case Study

1Department of Neurology, Mayo Clinic, 2Mayo Clinic Center for Multiple Sclerosis and Autoimmune Neurology, Mayo Clinic, 3Center for Regenerative Medicine, Neuroregeneration, Mayo Clinic, 4Division of Neonatal Medicine, Mayo Clinic, 5Department of Pediatric and Adolescent Medicine, Mayo Clinic

JoVE 54139

 Immunology and Infection
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