binary fussion, or amitosis.
they separate their body into 2 parts.
2006-10-07 23:05:56
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answer #1
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answered by Papilio paris 5
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Bacteria (singular: bacterium) are a major group of living organisms. The term "bacteria" has variously applied to all prokaryotes or to a major group of them, otherwise called the eubacteria, depending on ideas about their relationships. Here, bacteria is used specifically to refer to the eubacteria. Another major group of bacteria (used in the broadest, non-taxonomic sense) are the Archaea. The study of bacteria is known as bacteriology, a subfield of microbiology.
Bacteria are the most abundant of all organisms. They are ubiquitous in soil, water, and as symbionts of other organisms. Many pathogens are bacteria. Most are minute, usually only 0.5-5.0 μm in their longest dimension, although giant bacteria like Thiomargarita namibiensis and Epulopiscium fishelsoni may grow past 0.5 mm in size. They generally have cell walls, like plant and fungal cells, but bacterial cell walls are normally made out of peptidoglycan instead of cellulose (as in plants) or chitin (as in fungi), and are not homologous with eukaryotic cell walls. Many move around using flagella, which are different in structure from the flagella of other groups.
All bacteria reproduce through asexual reproduction (one parent) binary fission, which results in cell division. Two identical clone daughter cells are produced. Some bacteria, while still reproducing asexually, form more complex reproductive structures that facilitate the dispersal of the newly-formed daughter cells. Examples include fruiting body formation by Myxococcus and arial hyphae formation by Streptomyces, or budding. Budding is resulted of a 'bud' of a cell growing from another cell, and then finally breaking away.
In the laboratory, bacteria are usually grown using two methods, solid and liquid. Solid growth media such as agar plates are used to isolate pure cultures of a bacterial strain. When quantitation of growth or large volumes of cells are required liquid growth media are generally used. Growth in liquid media, with stirring, most often occurs as an even cell suspension making the cultures easier to divide and transfer compared to solid media, although the isolation of individual cells from liquid media is extremely difficult. In both liquid and solid media there exist a finite amount of nutrients, which allows for the study of the bacterial cell cycle. These limitations can be avoided by the use of a chemostat, which maintains a bacterial culture under steady-state conditions by the continuous addition of nutrients and the removal of waste products and cells. Large chemostats are often used for industrial-scale microbial processes.
Most techniques commonly used to grow bacteria are designed to optimise the amount of cells produced, the amount of time needed to produce them, and the cost to produce them. In a bacterium's natural environment nutrients are limited, meaning that bacteria cannot continue to reproduce indefinitely. This constant limitation of nutrients has led the evolution of many different growth strategies in different types of organisms (see R/K selection theory). Some possess the ability to grow extremely rapidly when nutrients become available, such as the formation of algal (and cyanobacterial) blooms that often occur in lakes during the summer. Other organisms have devised more specialized strategies to make them more successful in a harsh environment, such as the production of antibiotics by Streptomyces; often at the expense of a slower growth rate. In a natural environment, many organisms live in communities (e.g. biofilms) which may allow for increased supply of nutrients and protection of environmental stresses. Often these relationships are essential for growth of a particular organism or group of organisms (syntrophy). These evolutionary tactics to overcome nutrient limitation must be accounted for in an industrial/laboratory bacterial growth experiment. For instance bacteria that tend to agglutinate may need more vigorous stirring to break apart any large bacterial masses. The main growth attribute that must be understood for controlled growth is that bacteria have defined growth phases.
A controlled bacterial growth will follow three distinct phases. Nearly all cultures start from taking a relatively old stock of bacteria and diluting them in to fresh media; these cells need to adapt to the nutrient rich environment. The first phase of growth is the lag phase, a period of slow growth most often attributed to the need for cells to adapt to fast growth. The lag phase has high biosynthesis rates; enzymes needed to metabolise a variety of substrates are produced. The second phase of growth is the logarithmic phase (log phase), also known as the exponential phase. The log phase is marked by rapid exponential growth. The rate at which cells grow during this phase is known as the growth rate (k). The time it takes the cells to double during the log phase is known as the generation time (g). During the log phase, nutrients are metabolised at maximum speed until one of the nutrients is depleted and starts limiting growth. The final phase of growth is the stationary phase. This phase of growth is caused by depleted nutrients. The cells begin to shut down their metabolic activity, as well as break-down their own non-essential proteins. The stationary phase is a transition from rapid growth to dormancy. Without positive signals from the environment transcription of many non-essential genes are no longer promoted to conserve ATP.
You could get more information from the link below...
2006-10-08 05:48:59
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answer #6
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answered by catzpaw 6
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