![]() ![]() ![]() ![]() Bacteria that create their own energy, fueled by light or through chemical reactions, are autotrophs.Ĭapsule - Some species of bacteria have a third protective covering, a capsule made up of polysaccharides (complex carbohydrates). This includes species that are found in decaying material as well as those that utilize fermentation or respiration. Bacteria that have to consume and break down complex organic compounds are heterotrophs. The second way of grouping them is by how they obtain their energy. Facultative aneraobes prefer oxygen, but can live without it. Anerobic bacteria can't tolerate gaseous oxygen at all and die when exposed to it. Aerobic bacteria require oxygen for their health and existence and will die without it. They can be divided into three types based on their response to gaseous oxygen. There are two different ways of grouping bacteria. The discovery that some bacteria produced compounds lethal to other bacteria led to the development of antibiotics, which revolutionized the field of medicine. Most notably, a number of scientists around the world made contributions to the field of microbial ecology, showing that bacteria were essential to food webs and for the overall health of the Earth's ecosystems. ![]() The twentieth century saw numerous advances in bacteriology, indicating their diversity, ancient lineage, and general importance. During the nineteenth century, the French scientist Louis Pasteur and the German physician Robert Koch demonstrated the role of bacteria as pathogens (causing disease). In the late 1600s, Antoni van Leeuwenhoek became the first to study bacteria under the microscope. Despite the superficial resemblance to bacteria, biochemically and genetically, the archea are as different from bacteria as bacteria are from humans. Millions of years later, the ancestors of today's eukaryotes split off from the archaea. Many scientists now believe that the archaea and bacteria developed separately from a common ancestor nearly four billion years ago. Even older than the bacteria are the archeans (also called archaebacteria) tiny prokaryotic organisms that live only in extreme environments: boiling water, super-salty pools, sulfur-spewing volcanic vents, acidic water, and deep in the Antarctic ice. They are found practically everywhere on Earth and live in some of the most unusual and seemingly inhospitable places.Įvidence shows that bacteria were in existence as long as 3.5 billion years ago, making them one of the oldest living organisms on the Earth. They come in many shapes and sizes, from minute spheres, cylinders and spiral threads, to flagellated rods, and filamentous chains. They make it possible for ruminant animals (cows, sheep, goats) to digest plant cellulose and for some plants, (soybean, peas, alfalfa) to convert nitrogen to a more usable form.īacteria are prokaryotes, lacking well-defined nuclei and membrane-bound organelles, and with chromosomes composed of a single closed DNA circle. Bacteria give yogurt its tangy flavor and sourdough bread its sour taste. Although they are notorious for their role in causing human diseases, from tooth decay to the Black Plague, there are beneficial species that are essential to good health.įor example, one species that lives symbiotically in the large intestine manufactures vitamin K, an essential blood clotting factor. They are as unrelated to human beings as living things can be, but bacteria are essential to human life and life on planet Earth. Molecular Expressions Cell Biology: Bacteria Cell Structure ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |