Bacteria engineered to act as genetic clocks flash in synchrony. Here, a "supernova" burst in a colony of coupled genetic clocks just after reaching critical cell density. Superimposed: A diagram from the notebook of Christiaan Huygens, who first characterized synchronized oscillators in the 17th century.

The nucleus of a human fibroblast cell with chromatin—a substance made up of DNA and proteins—shown in various colors. Fibroblasts are one of the most common types of cells in mammalian connective tissue, and they play a key role in wound healing and tissue repair. This image was captured using Stochastic Optical Reconstruction Microscopy (STORM).

Related to images 6887 and 6893.

Luciferase-based imaging enables visualization and quantification of internal organs and transplanted cells in live adult zebrafish. In this image, a cardiac muscle-restricted promoter drives firefly luciferase expression. This is the lateral and overhead (Bottom) view.
For imagery of the overhead view go to 3557.
For imagery of the lateral view go to 3558.
For more information about the illumated area go to 3559.

The proteasome is a critical multiprotein complex in the cell that breaks down and recycles proteins that have become damaged or are no longer needed. This movie shows how a protein substrate (red) is bound through its ubiquitin chain (blue) to one of the ubiquitin receptors of the proteasome (Rpn10, yellow). The substrate's flexible engagement region then gets engaged by the AAA+ motor of the proteasome (cyan), which initiates mechanical pulling, unfolding and movement of the protein into the proteasome's interior for cleavage into shorter protein pieces called peptides. During movement of the substrate, its ubiquitin modification gets cleaved off by the deubiquitinase Rpn11 (green), which sits directly above the entrance to the AAA+ motor pore and acts as a gatekeeper to ensure efficient ubiquitin removal, a prerequisite for fast protein breakdown by the 26S proteasome. Related to image 3763.

The cells shown here are fibroblasts, one of the most common cells in mammalian connective tissue. These particular cells were taken from a mouse embryo. Scientists used them to test the power of a new microscopy technique that offers vivid views of the inside of a cell. The DNA within the nucleus (blue), mitochondria (green), and actin filaments in the cellular skeleton (red) are clearly visible.

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.

Industrious V. cholerae bacteria (yellow) tend to thrive in denser biofilms (left) while moochers (red) thrive in weaker biofilms (right). More information about the research behind this image can be found in a Biomedical Beat Blog posting from February 2014.

Animation for the cisternae maturation model of Golgi transport.

Xenopus laevis, the African clawed frog, has long been used as a model organism for studying embryonic development. In this image, RNA encoding the transcription factor Sox 7 (dark blue) is shown to predominate at the vegetal pole, the yolk-rich portion, of a Xenopus laevis frog egg. Sox 7 protein is important to the regulation of embryonic development.

The receptor is shown bound to a partial inverse agonist, carazolol.

Ionic and covalent bonds hold molecules, like sodium chloride and chlorine gas, together. Hydrogen bonds among molecules, notably involving water, also play an important role in biology. See image 2519 for an unlabeled version of this illustration. Featured in The Chemistry of Health.

A cell in metaphase during mitosis: The copied chromosomes align in the middle of the spindle. Mitosis is responsible for growth and development, as well as for replacing injured or worn out cells throughout the body. For simplicity, mitosis is illustrated here with only six chromosomes.

The green spots in this mouse brain are cells labeled with Calling Cards, a technology that records molecular events in brain cells as they mature. Understanding these processes during healthy development can guide further research into what goes wrong in cases of neuropsychiatric disorders. Also fluorescently labeled in this image are neurons (red) and nuclei (blue). Calling Cards and its application are described in the Cell paper “Self-Reporting Transposons Enable Simultaneous Readout of Gene Expression and Transcription Factor Binding in Single Cells” by Moudgil et al.; and the Proceedings of the National Academy of Sciences paper “A viral toolkit for recording transcription factor–DNA interactions in live mouse tissues” by Cammack et al. The technology was also featured in the NIH Director’s Blog post The Amazing Brain: Tracking Molecular Events with Calling Cards.

Related to video

Merged fluorescent images of symmetrically (left) or asymmetrically (right) elongating HeLa cells at the end of early anaphase (magenta) and late anaphase (green). Chromosomes and cortical actin are visualized by expressing mCherry-histone H2B and Lifeact-mCherry. Scale bar, 10µm. See the PubMed abstract of this research.

How far and fast an infectious disease spreads across a community depends on many factors, including transportation. These U.S. maps, developed as part of an international study to simulate and analyze disease spread, chart daily commuting patterns. They show where commuters live (top) and where they travel for work (bottom). Green represents the fewest number of people whereas orange, brown, and white depict the most. Such information enables researchers and policymakers to visualize how an outbreak in one area can spread quickly across a geographic region.

Two cells over a 2-hour period. The one on the bottom left goes through programmed cell death, also known as apoptosis. The one on the top right goes through cell division, also called mitosis. This video was captured using a confocal microscope.

Normal mice, like the B6 breed pictured on the left, develop scars when their ears are pierced. The Murphy Roths Large (MRL) mice pictured on the right can grow back lost ear tissue thanks to an inactive version of the p21 gene. When researchers knocked out that same gene in other mouse breeds, their ears also healed completely without scarring. Journal Article: Clark, L.D., Clark, R.K. and Heber-Katz, E. 1998. A new murine model for mammalian wound repair and regeneration. Clin Immunol Immunopathol 88: 35-45.

Mycobacterium tuberculosis, the bacterium that causes tuberculosis, has infected one-quarter of the world's population and causes more than one million deaths each year, according to the World Health Organization.

A mouse liver glows after being tagged with specially designed infrared-fluorescent protein (IFP). Since its discovery in 1962, green fluorescent protein (GFP) has become an invaluable resource in biomedical imaging. But because of its short wavelength, the light that makes GFP glow doesn't penetrate far in whole animals. So University of California, San Diego cell biologist Roger Tsien--who shared the 2008 Nobel Prize in chemistry for groundbreaking work with GFP--made infrared-fluorescent proteins (IFPs) that shine under longer-wavelength light, allowing whole-body imaging in small animals.

Various views of a mouse brain that was genetically modified so that subpopulations of its neurons glow. Researchers often study mice because they share many genes with people and can shed light on biological processes, development, and diseases in humans.

This video was captured using a light sheet microscope.

Related to images 6929 and 6930.

A study published in March 2012 used cryo-electron microscopy to determine the structure of the DNA replication origin recognition complex (ORC), a semi-circular, protein complex (yellow) that recognizes and binds DNA to start the replication process. The ORC appears to wrap around and bend approximately 70 base pairs of double stranded DNA (red and blue). Also shown is the protein Cdc6 (green), which is also involved in the initiation of DNA replication. The video shows the structure from different angles. See related image 3597.

La sepsis o septicemia es la respuesta fulminante y extrema del cuerpo a una infección. En los Estados Unidos, más de 1.7 millones de personas contraen sepsis cada año. Sin un tratamiento rápido, la sepsis puede provocar daño de los tejidos, insuficiencia orgánica y muerte. El NIGMS apoya a muchos investigadores en su trabajo para mejorar el diagnóstico y el tratamiento de la sepsis.

Vea 6536 para la versión en inglés de esta infografía.

DNA encodes RNA, which encodes protein. DNA is transcribed to make messenger RNA (mRNA). The mRNA sequence (dark red strand) is complementary to the DNA sequence (blue strand). On ribosomes, transfer RNA (tRNA) reads three nucleotides at a time in mRNA to bring together the amino acids that link up to make a protein. See image 2549 for a numbered version of this illustration and 2547 for an unlabeled version. Featured in The New Genetics.

The green spots in this mouse brain are cells labeled with Calling Cards, a technology that records molecular events in brain cells as they mature. Understanding these processes during healthy development can guide further research into what goes wrong in cases of neuropsychiatric disorders. Also fluorescently labeled in this video are neurons (red) and nuclei (blue). Calling Cards and its application are described in the Cell paper “Self-Reporting Transposons Enable Simultaneous Readout of Gene Expression and Transcription Factor Binding in Single Cells” by Moudgil et al.; and the Proceedings of the National Academy of Sciences paper “A viral toolkit for recording transcription factor–DNA interactions in live mouse tissues” by Cammack et al. This video was created for the NIH Director’s Blog post The Amazing Brain: Tracking Molecular Events with Calling Cards.

Related to image 6780.

Stained glomeruli in the kidney. The kidney is an essential organ responsible for disposing wastes from the body and for maintaining healthy ion levels in the blood. It works like a purifier by pulling break-down products of metabolism, such as urea and ammonium, from the bloodstream for excretion in urine. The glomerulus is a structure that helps filter the waste compounds from the blood. It consists of a network of capillaries enclosed within a Bowman's capsule of a nephron, which is the structure in which ions exit or re-enter the blood in the kidney.

A light microscope image of a cell from the endosperm of an African globe lily (Scadoxus katherinae). This is one frame of a time-lapse sequence that shows cell division in action. The lily is considered a good organism for studying cell division because its chromosomes are much thicker and easier to see than human ones. Staining shows microtubules in red and chromosomes in blue. Here, condensed chromosomes are clearly visible and lined up.

Related to images 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, and 1019.

By attaching fluorescent proteins to the genetic circuit responsible for B. subtilis's stress response, researchers can observe the cells' pulses as green flashes. This video shows flashing cells as they multiply over the course of more than 12 hours. In response to a stressful environment like one lacking food, B. subtilis activates a large set of genes that help it respond to the hardship. Instead of leaving those genes on as previously thought, researchers discovered that the bacteria flip the genes on and off, increasing the frequency of these pulses with increasing stress. See entry 3253 for a related still image.

Kinases are enzymes that add phosphate groups (red-yellow structures) to proteins (green), assigning the proteins a code. In this reaction, an intermediate molecule called ATP (adenosine triphosphate) donates a phosphate group from itself, becoming ADP (adenosine diphosphate). See image 2535 for a labeled version of this illustration. Featured in Medicines By Design.

Hippocampal neuron in culture. Dendrites are green, dendritic spines are red and DNA in cell's nucleus is blue. Image is featured on Biomedical Beat blog post Anesthesia and Brain Cells: A Temporary Disruption?

A light microscope image of a cell from the endosperm of an African globe lily (Scadoxus katherinae). This is one frame of a time-lapse sequence that shows cell division in action. The lily is considered a good organism for studying cell division because its chromosomes are much thicker and easier to see than human ones. Staining shows microtubules in red and chromosomes in blue.

Related to images 1010, 1011, 1013, 1014, 1015, 1016, 1017, 1018, 1019, and 1021.

The brain sections are treated with fluorescent antibodies specific to a particular protein and visualized using serial electron microscopy (SEM).

Gene transcription is a process by which information encoded in DNA is transcribed into RNA. It's essential for all life and requires the activity of proteins, called transcription factors, that detect where in a DNA strand transcription should start. In eukaryotes (i.e., those that have a nucleus and mitochondria), a protein complex comprising 14 different proteins is responsible for sniffing out transcription start sites and starting the process. This complex represents the core machinery to which an enzyme, named RNA polymerase, can bind to and read the DNA and transcribe it to RNA. Scientists have used cryo-electron microscopy (cryo-EM) to visualize the TFIID-RNA polymerase-DNA complex in unprecedented detail. This animation shows the different TFIID components as they contact DNA and recruit the RNA polymerase for gene transcription.

To learn more about the research that has shed new light on gene transcription, see this news release from Berkeley Lab.

Related to image 3766.

A crystal of rabbit GPDA protein created for X-ray crystallography, which can reveal detailed, three-dimensional protein structures.

The TRPA1 protein is responsible for the burn you feel when you taste a bite of sushi topped with wasabi. Known therefore informally as the "wasabi receptor," this protein forms pores in the membranes of nerve cells that sense tastes or odors. Pungent chemicals like wasabi or mustard oil cause the pores to open, which then triggers a tingling or burn on our tongue. This receptor also produces feelings of pain in response to chemicals produced within our own bodies when our tissues are damaged or inflamed. Researchers used cryo-EM to reveal the structure of the wasabi receptor at a resolution of about 4 angstroms (a credit card is about 8 million angstroms thick). This detailed structure can help scientists understand both how we feel pain and how we can limit it by developing therapies to block the receptor. For more on cryo-EM see the blog post Cryo-Electron Microscopy Reveals Molecules in Ever Greater Detail.

This image results from a research project to visualize which regions of the adult fruit fly (Drosophila) brain derive from each neural stem cell. First, researchers collected several thousand fruit fly larvae and fluorescently stained a random stem cell in the brain of each. The idea was to create a population of larvae in which each of the 100 or so neural stem cells was labeled at least once. When the larvae grew to adults, the researchers examined the flies’ brains using confocal microscopy. With this technique, the part of a fly’s brain that derived from a single, labeled stem cell “lights up. The scientists photographed each brain and digitally colorized its lit-up area. By combining thousands of such photos, they created a three-dimensional, color-coded map that shows which part of the Drosophila brain comes from each of its ~100 neural stem cells. In other words, each colored region shows which neurons are the progeny or “clones” of a single stem cell. This work established a hierarchical structure as well as nomenclature for the neurons in the Drosophila brain. Further research will relate functions to structures of the brain.

Related to image 5868 and video 5843

This illustration shows vesicle traffic inside a cell. The double membrane that bounds the nucleus flows into the ribosome-studded rough endoplasmic reticulum (purple), where membrane-embedded proteins are manufactured. Proteins are processed and lipids are manufactured in the smooth endoplasmic reticulum (blue) and Golgi apparatus (green). Vesicles that fuse with the cell membrane release their contents outside the cell. The cell can also take in material from outside by having vesicles pinch off from the cell membrane.

Cells walk along body surfaces via tiny "feet," called focal adhesions, that connect with the extracellular matrix. See image 2503 for a labeled version of this illustration.

Here, a human HeLa cell (a type of immortal cell line used in laboratory experiments) is undergoing cell division. They come from cervical cancer cells that were obtained in 1951 from Henrietta Lacks, a patient at the Johns Hopkins Hospital. The final stage of division, called cytokinesis, occurs after the genomes—shown in yellow—have split into two new daughter cells. The myosin II is a motor protein shown in blue, and the actin filaments, which are types of protein that support cell structure, are shown in red.

X-ray co-crystal structure of Src kinase bound to a DNA-templated macrocycle inhibitor. Related to images 3413, 3414, 3415, 3416, 3417, and 3419.

Cells move forward with lamellipodia and filopodia supported by networks and bundles of actin filaments. Proper, controlled cell movement is a complex process. Recent research has shown that an actin-polymerizing factor called the Arp2/3 complex is the key component of the actin polymerization engine that drives amoeboid cell motility. ARPC3, a component of the Arp2/3 complex, plays a critical role in actin nucleation. In this photo, the ARPC3+/+ fibroblast cells were fixed and stained with Alexa 546 phalloidin for F-actin (red) and DAPI to visualize the nucleus (blue). ARPC3+/+ fibroblast cells with lamellipodia leading edge. Related to images 3328, 3329, 3330, 3331, and 3333.

These neurons were derived from human embryonic stem cells. The neural cell bodies with axonal projections are visible in red, and the nuclei in blue. Some of the neurons have become dopaminergic neurons (yellow), the type that degenerate in people with Parkinson's disease. Image and caption information courtesy of the California Institute for Regenerative Medicine. Related to images 3270 and 3271.

The receptor is shown bound to an inverse agonist, doxepin.

The three fibers of the cytoskeleton--microtubules in blue, intermediate filaments in red, and actin in green--play countless roles in the cell.

The enzyme CCP is found in the mitochondria of baker’s yeast. Scientists study the chemical reactions that CCP triggers, which involve a water molecule, iron, and oxygen. This structure was determined using an X-ray free electron laser.

When we walk, muscles and nerves interact in intricate ways. This simulation, which is based on data from a six-foot-tall man, shows these interactions.

Like a building supported by a steel frame, a cell contains its own sturdy internal scaffolding made up of proteins, including microtubules. Researchers studying snapshots of microtubules have proposed a model for how these structural elements shorten and lengthen, allowing a cell to move, divide, or change shape. This picture shows an intermediate step in the model: Smaller building blocks called tubulins peel back from the microtubule in thin strips. Knowing the operations of the internal scaffolding will enhance our basic understanding of cellular processes.

This illustration shows, in simplified terms, how the CRISPR-Cas9 system can be used as a gene-editing tool. The CRISPR system has two components joined together: a finely tuned targeting device (a small strand of RNA programmed to look for a specific DNA sequence) and a strong cutting device (an enzyme called Cas9 that can cut through a double strand of DNA). In this frame (3 of 4), the Cas9 enzyme cuts both strands of the DNA.

For an explanation and overview of the CRISPR-Cas9 system, see the iBiology video, and find the full CRIPSR illustration here.

Many researchers use the mouse (Mus musculus) as a model organism to study mammalian biology. Mice carry out practically all the same life processes as humans and, because of their small size and short generation times, are easily raised in labs. Scientists studying a certain cellular activity or disease can choose from tens of thousands of specially bred strains of mice to select those prone to developing certain tumors, neurological diseases, metabolic disorders, premature aging, or other conditions.

Multicellular yeast called snowflake yeast that researchers created through many generations of directed evolution from unicellular yeast. Here, the researchers visualized nuclei in orange to help them study changes in how the yeast cells divided. Cell walls are shown in blue. This image was captured using spinning disk confocal microscopy.

Related to images 6969 and 6970.

C. elegans, a tiny roundworm, with a ribosomal protein glowing red and muscle fibers glowing green. Researchers used these worms to study a molecular pathway that affects aging. The ribosomal protein is involved in protein translation and may play a role in dietary restriction-induced longevity. Image created using confocal microscopy.
View group of roundworms here 6582.
View closeup of roundworms here 6583.

The image visualizes a part of the yeast molecular interaction network. The lines in the network represent connections among genes (shown as little dots) and different-colored networks indicate subnetworks, for instance, those in specific locations or pathways in the cell. Researchers use gene or protein expression data to build these networks; the network shown here was visualized with a program called Cytoscape. By following changes in the architectures of these networks in response to altered environmental conditions, scientists can home in on those genes that become central "hubs" (highly connected genes), for example, when a cell encounters stress. They can then further investigate the precise role of these genes to uncover how a cell's molecular machinery deals with stress or other factors. Related to images 3730 and 3733.