Bacteria are simple microorganisms. A single one of these life forms is called a “bacterium”. Each bacterium is a single cell, which reproduces by growing and splitting in half. Bacteria are so small that it would take a million to cover the head of a pin. To see one you would need a microscope able to magnify by at least 100 times. Unlike viruses, bacteria can live on their own outside of another life form, under certain conditions. They are found everywhere and most of them do not cause disease. Some types of bacteria prefer to live inside humans. Many of these are harmless, some are good for us, and some can cause harmful infections. Bacteria can be killed with medications called antibiotics.
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DNA is short for deoxyribonucleic acid, found in every living cell. It is made up of segments called “genes”, which determine the structure and function of each organism. DNA is organized into chromosomes, which are like strings of genes. Humans have 23 pairs of chromosomes.

Enzymes are proteins that speed up some of the chemical reactions that take place in living things.

Gastritis is irritation or inflammation of the stomach lining. The stomach lining contains cells that produce acid and enzymes that help break down food, and mucus to protect the stomach lining from acid. When the stomach lining is inflamed, it may produce either too much or too little acid, enzymes, and mucus.

Gastritis can be acute or chronic. Acute gastritis is an initial reaction to something that irritates the stomach lining. Acute gastritis is short-term and stops when the irritant is gone. If the irritant does not go away, gastritis can become chronic and last a long time. People who have gastritis may experience pain or discomfort in the upper abdomen, but many people with gastritis do not have any symptoms. H. pylori infection causes many cases of chronic gastritis, but there are other causes as well.
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Gene refers to a unit of DNA that contains information required to build and maintain an organism’s cells. Genes also pass traits from parents to offspring. Most genes contain the code for making a specific protein.

Helicobacter pylori (H. pylori) are bacteria that infect the stomach lining. Chronic infection with H. pylori occurs when the bacteria live in the stomach for a long time. For further information, see the ‘Learn about H. pylori’ section of the CANHelp Working Group website.

Infection occurs when tiny life forms called microorganisms, like bacteria or viruses, live in the body’s tissues. Usually your body’s immune system protects you from infections. Sometimes you feel sick when microorganisms harm the tissue or because of inflammation that results from your immune response (your body’s attempt to protect you).

Inflammation occurs in the tissues of living things as a response to harm from germs, injury, or irritants. Inflammation is an attempt to remove the harm and initiate healing. During inflammation, fluid containing protective cells migrates to the injured or irritated tissue. When the cause of inflammation persists, the inflammation will persist and can harm the tissue. During chronic inflammation, the tissue is both destroyed and healed at the same time.

Microorganisms are tiny life forms that are so small they can only be seen under a microscope.

Peptic ulcer refers to a sore in the lining of the stomach or duodenum (the beginning of the small intestine). Peptic ulcers often cause abdominal pain, which can be severe. In some cases, people do not feel discomfort. Peptic ulcers usually require treatment to heal. Many cases of peptic ulcer are caused by H. pylori infection. Medications such as aspirin and ibuprofen are another common cause. Stress or eating spicy food can make ulcer symptoms worse. Smoking and drinking alcohol can also worsen ulcers and prevent healing.

Phylogenetics is the study of how closely related organisms are based on their DNA sequences.

Proteins are large molecules made up of building blocks called amino acids that are linked in a specific order. Proteins are fundamental components of all living cells and are required for proper tissue and organ structure, function, and regulation.

Risk is the probability of an event occurring during a specified time period. Disease risk is the probability that someone will get a particular disease during a specified time period.

Risk Factor refers to a factor that increases or decreases a particular risk. Risk factors for a particular disease are factors that influence the risk of that disease. Sometimes factors that decrease risk are called protective factors rather than risk factors.

Species can be defined as a group of organisms that can interbreed and produce fertile offspring. A bacterial species, such as H. pylori, can be thought of as a group of bacteria that look and act the same at a surface level. Bacterial species are further classified into types, known as strains, based on distinct genetic traits.

Stomach cancer includes any type of cancer located in the stomach, an organ found in the upper part of the abdomen, just below the ribs. The stomach is part of the body’s digestive system; it produces acid and enzymes that break down food before passing it to the intestine. Cancer is a broad term for diseases that involve the multiplication and uncontrollable growth of cells. Cancer cells do not perform their regular functions and they can damage nearby tissues or spread to other parts of the body.
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Strains are types or variants of species characterized by distinct patterns of genes or DNA sequences.

Virus refers to a microorganism smaller than bacteria. Viruses can only be seen with special microscopes capable of magnifying thousands of times. Viruses cannot reproduce outside of other living cells. There are many different types of viruses, and each type infects specific cells of humans, other animals, or larger microorganisms such as bacteria. Viruses enter living cells and use the cell’s “machinery” to reproduce; they typically break the cell open, killing it, to release new viruses. This is how they cause disease. Viruses cannot be killed with antibiotics, unlike bacteria.