Endocrinology

What Is Bacteria? What Are Bacteria?

The word bacteria is the plural of bacterium. Grammatically the headline should just say "What are bacteria?" The incorrect usage has been included in the headline to remind readers that it is wrong - and hopefully help correct an increasingly common mistake in the English language. Bacteria are tiny living beings (microorganisms) - they are neither plants nor animals - they belong to a group all by themselves. Bacteria are tiny single-cell microorganisms, usually a few micrometers in length that normally exist together in millions. A gram of soil typically contains about 40 million bacterial cells. A milliliter of fresh water usually holds about one million bacterial cells. Planet Earth is estimated to hold at least 5 nonillion bacteria. Scientists say that much of Earth"s biomass is made up of bacteria. 5 nonillion = 5,000,000,000,000,000,000,000,000,000,000 (or 5x1030) (Nonillion = 30 zeros in USA English. In British English it equals 54 zeros. This text uses the American meaning) Bacteria come in three main shapes: Visit our specialized news sections Biology / Biochemistry News Infectious Diseases / Bacteria / Viruses News Tropical Diseases News Bioterrorism News *Spherical (like a ball) These are usually the simplest ones. Bacteria shaped like this are called cocci (singular coccus). *Rod shaped These are known as bacilli (singular bacillus). Some of the rod-shaped bacteria are curved; these are known as vibrio. *Spiral These known are as spirilla (singular spirillus). If their coil is very tight they are known as spirochetes. There are many variations within each shape group. This is a file from Wikimedia Commons Bacteria are found everywhere Bacteria can be found in: *Soil *Radioactive waste *Water *Plants *Animals *Deep in the earth"s crust *Organic material *Arctic ice *Glaciers *Hot springs *The stratosphere (between 6 to 30 miles up in the atmosphere) *Ocean depths - they have been found deep in ocean canyons and trenches over 32,800 feet (10,000 meters) deep. They live in total darkness by thermal vents at incredible pressure. They make their own food by oxidizing sulfur that oozes from deep inside the earth. Scientists who specialize in bacteria - bacteriologists - say bacteria are found absolutely everywhere except for places that humans have sterilized. Even the most unlikely places where temperatures may be extreme, or where there may be a high concentration of toxic chemicals have bacteria - these are known as extremophiles (an extremophile is any organism adapted to living in conditions of extreme temperature, pressure, or/and chemical concentrations) - these bacteria can survive where no other organism can. The cells of bacteria A bacterial cell differs somewhat from the cell of a plant or animal. Bacterial cells have no nucleus and other organelles (sub-units within a cell with a specific function) bound by a membrane, except for ribosomes. Bacteria have pili, flagella, and a cell capsule (most of them), unlike animal or plant cells. An organism without a nucleus is called a prokaryote. A bacterial cell includes: *Basal body - this anchors the base of the flagellum, allowing it to rotate. *Capsule - a layer on the outside of the cell wall. Some bacteria don"t have a capsule. *Cell wall - a thin layer (membrane) outside the plasma membrane, and within the capsule. *DNA (Deoxyribonucleic acid) - contains all the genetic instructions used in the development and functioning of the bacterium. It is inside the cytoplasm. *Cytoplasm - a gelatinous substance inside the plasma membrane. Genetic material and ribosomes lie inside. *Flagellum - this is used for movement; to propel the cell. Some bacterial cells have more than one. *Pili (singular: pilus) - these spikes allow the cell to stick to surfaces and transfer genetic material to other cells. A study revealed that pili are involved in causing traveler"s diarrhea. *Plasma membrane - it generates energy and transports chemicals. Substances can pass through the membrane (permeable). It is located within the cell wall. *Ribosomes - this is where protein is made (synthesized). Ribosomes are small organelles made up of RNA-rich granules. This is a file from Wikimedia Commons The origins and evolution of bacteria Modern bacteria"s ancestors - single-celled microorganisms - appeared on earth about 4 billion years ago. Scientists say they were the first life forms on Earth. For the following 3 billion years all life forms on Earth were microscopic in size, and included two dominant ones: 1. Bacteria, and 2. Archaea (classified as bacteria, but genetically and metabolically different from all other known bacteria). There are fossils of bacteria. However, because their form and structure (morphology) are not distinctive it is virtually impossible to date them, making it extremely hard to study the process of bacterial evolution with any degree of accuracy. However, with the help of gene sequences, it is now possible to know that bacteria diverged from their original archaeal/eukaryotic ancestry (Eukaryotic = pertaining to an eukaryotice; a single-celled or multicellular organism whose cells contain a distinct membrane-bound nucleus). Archaea is bacteria"s most recent common ancestor - it was most likely hyperthermophile, an organism that thrived in extremely hot environments, approximately 2.5 - 3.2 billion years ago. Bacteria were also involved in the divergence of archaea and eukaryotes. Eukaryotes came from a very early bacteria which had an endosymbiotic association (when an organism lives within the body or cells of another organism) with the predecessors of eukaryotes cells, which were probably related to the Archaea. Biologists say that some algae probably originated from later endosymbiotic relationships. Put simply - bacteria were the first organisms to appear on earth, about 4 billion years ago. Our oldest known fossils are of bacteria-like organisms. A short history of bacteriology Some people had suggested thousands of years ago that something too small for the naked eye to see may be the cause of disease. Over the hundreds of years that followed various theories were given. It was not until 1676 that bacteria were properly identified as microorganisms. Below is a short synopsis of some of the most famous scientists/microbiologists in history: *Marcus Terentius Varro (Roman - 116 BC-27 BC) - a prolific author. He suggested that disease may be caused by miniscule animals that floated in the air. He is admired by many scientists today for his anticipation of microbiology (the study of microorganisms and their effects on other living organisms) and epidemiology (the study of the causes, distribution, and control of disease in populations). He believed marshy places should be avoided during building work because they might contain insects too small for the eye to see that entered the body through the mouth and nostrils and cause diseases. Interesting articles What are antibiotics? How do antibiotics work? What is MRSA? Why is MRSA a concern? What are genes? What is pneumonia? What is food poisoning? What is gastroenteritis? What is typhoid? *Hippocrates (c 460-377 BC) - a physician, considered one of the most outstanding figures in the history of medicine. He was the first physician to separate medicine from superstition. He said disease was not a punishment meted out by gods, but rather a result of lifestyle, diet and environmental factors. However, Hippocrates" theories on diseases being an imbalance of the four humors present in the human body, caused by miasmas - vapors from rotting vegetables or bodies, polluted rivers and marshy places - were slightly wider of the mark than we know about today. *Jacobo Forli and Alexandro Benedetti (Italian c. 14th/15th century) - they said it was not possible to get ill just by breathing in the air. They said particles that floated in the air may cause disease if they were breathed in. Nevertheless, the Miasma Theory persevered for a long time, right from the first century through to about 1500, when the Germ Theory started to develop: *Antonie van Leeuwenhoek (Dutch 1632-1723) - he handcrafted single-lens microscopes himself, with which he saw what he called animalcules in 1676 (to be called bacteria 162 years later). In a series of letters to the Royal Society (England) he published his findings. He is commonly known as the father of microbiology and considered to be the first microbiologist. *Christian Gottfried Ehrenberg (German 1795-1876) - one of the most famous and prolific scientists during the nineteenth century, introduced the term bacterium in 1838. *Louis Pasteur (French - 1822 - 1895) - a remarkable chemist who became famous for many breakthroughs in the causes and preventions of disease. He created the first vaccine for rabies. Pasteur demonstrated in 1859 that the fermentation process is caused by the growth of microorganisms, and not spontaneous generation. He and Robert Kich, said that diseases were caused by germs (The Germ Theory). *Robert Koch (German - 1843-1910) - a brilliant physician/researcher who was awarded the Nobel Prize in 1905 after he proved The Germ Theory. *Paul Ehrlich (German - 1854-1915) - a scientist who became a world authority in immunology. He invented the term chemotherapy. He developed the first antibiotic (Salvarsan) and used it to cure syphilis. He was awarded the Nobel Prize in 1908 for his research on immunology. He pioneered the use of stains to detect bacteria. *Carl Woese (American - 1928-) - currently professor of microbiology at the University of Illinois at Urbana-Champaign. His work recognized that archaea evolved along a separate line from bacteria. Metabolism - How do bacteria feed themselves? Bacteria feed themselves in a variety of ways. *Heterotrophic bacteria (or just heterotrophs) - these eat other organisms. Most of them are saprobes, they absorb dead organic material,

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