Cancer

Probing H. pylori cancer protein

Infection with the stomach-dwelling bacterium Helicobacter pylori— particularly strains producing the oncoprotein CagA—is a strong risk factor for gastric cancer.

Medications

When medicine makes patients sicker

Despite the jackhammerlike rhythm of a mechanical ventilator, Alicia Moreno had dozed off in a chair by her 1-year-old's hospital bed, when a doctor woke her with some bad news: The common stool softener her son, Anderson, ...

Diseases, Conditions, Syndromes

How cholera bacteria make people so sick

The enormous adaptability of the cholera bacterium explains why it is able to claim so many victims. Professor Ariane Briegel from the Leiden Institute of Biology has now discovered that this adaptability is due to rapid ...

Medical research

Sugar targets gut microbe linked to lean and healthy people

Sugar can silence a key protein required for colonization by a gut bacterium associated with lean and healthy individuals, according to a new Yale study published the week of Dec. 17 in the journal Proceedings of the National ...

Pediatrics

Stopping superbugs with friendly microbes

Newborn Baby Jane in Sacramento, California, might have access to the best, most modern medical care, but she's likely missing something else: Friendly gut microbes. Uniquely adapted to human breast milk, these microbes provide ...

Immunology

Immunity connects gut bacteria and aging

Over the years, researchers have learned that the different populations of bacteria that inhabit the gut have significant effects on body functions, including the immune system. The populations of gut bacteria are sometimes ...

Diseases, Conditions, Syndromes

Experimental vaccine shows promise in preventing TB

(HealthDay)—Tuberculosis remains the most lethal of infectious diseases worldwide, killing more than 1.6 million people a year. But researchers say a new vaccine might prevent half of full-blown illnesses in infected people ...

Diseases, Conditions, Syndromes

Responding to cholera before it strikes

Research by University of Maryland microbiologist Rita Colwell is enabling a new British-led international aid effort to predict and stop potential epidemics of the disease cholera before they happen.

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Bacteria

Actinobacteria (high-G+C) Firmicutes (low-G+C) Tenericutes (no wall)

Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Deinococcus-Thermus Fusobacteria Gemmatimonadetes Nitrospirae Proteobacteria Spirochaetes Synergistetes

Acidobacteria Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Dictyoglomi Fibrobacteres Planctomycetes Thermodesulfobacteria Thermotogae

The bacteria [bækˈtɪərɪə] (help·info) (singular: bacterium)[α] are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth, forming much of the world's biomass. Bacteria are vital in recycling nutrients, with many steps in nutrient cycles depending on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. However, most bacteria have not been characterized, and only about half of the phyla of bacteria have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

There are approximately ten times as many bacterial cells in the human flora of bacteria as there are human cells in the body, with large numbers of bacteria on the skin and as gut flora. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and a few are beneficial. However, a few species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy and bubonic plague. The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people a year, mostly in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and in agriculture, so antibiotic resistance is becoming common. In industry, bacteria are important in sewage treatment, the production of cheese and yoghurt through fermentation, as well as in biotechnology, and the manufacture of antibiotics and other chemicals.

Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved independently from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea.

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