Реферат: Bacteria Reproduction Essay Research Paper Bacteria are
Bacteria Reproduction Essay, Research Paper
Bacteria are microscopic singular celled organisms grouped in the prokaryote kingdom. They have a seemingly simple internal structure but that is not so the internal structure of a bacterium is quite complicated. Bacterial growth is generally studied in cell cultures by ?visible count? estimation which shows an apparent growth curve. (Stephenson 50) The growth curve shows the stages of bacterial growth within a cell culture. (Thimann 623). Bacteria can survive in a number of different extreme environments from extreme heat to little water.
Bacterium have a internal structure that is more complicated than it seems at first. The first part of the bacterium is the plasma membrane which is a selectively permeable barrier that is the boundary of the cell. (Prescott 40) The next portion of a bacterium is the cytoplasmic matrix. The cytoplasmic matrix is the substance lying between the plasma membrane and the nucleoid. (Prescott 45) Although it is generally featureless in a microscopes it can be packed with ribosomes and is generally highly organized. (Prescott 45) The next one is the nucleiod of a bacterium.(Prescott 40) This is the area within a bacterium in which the genetic material of the cell is located. (Prescott 49) The nucleiod itself is not defined by a membrane but is an irregularly shaped region of the cell. (Prescott 50) The gas vacuole of a bacterium is used for buoyancy in aquatic environments. (Prescott 40) This is demonstrated by filling a bottle with Cyanobacteria stopping it with a stopper and then hitting the stopper with a hammer.(Prescott 45) The sudden pressure increase causes the gas vacuole to collapse so the bacteria sink to the bottom of the bottle.(Prescott 47) The inclusion bodies within a bacterial cell are storage for different substances such as carbon, phosphate and other substances. ( Prescott 40) The cell wall of Bacteria gives the bacteria shape and protects it from the outside environment. ( Prescott 40) The flagella of bacteria are tail like appendages of cells that are used for movement. (Prescott 40)
The method usually used for estimating the growth of bacteria is the? viable count? method. (Stephenson 50) When the total count of the bacteria is plotted against time it shows a growth curve. (Stephenson 50) Such curves are divided into eight differing phases.(Thimann 623) The first phase of the growth curve is an initial stationary phase in which no growth occurs. (Thimann 623) The second phase is one of an increasing rate of growth these first two phases constitute the lag phase. (Thimann 623) The reason for the lag phase is this when you first put bacteria in a culture they need time to get into a state of growth called the embryonic stage. (Thimann 625) This stage can be identified by observing the cells. The bacteria grow to a greater size than normal. (Thimann 625) The third phase is called the logarithmic growth stage.(Stephenson 50) During logarithmic growth stage the rate of increase remains constant and the cell size returns to normal. (Stephenson 50) The fourth phase is one of decreasing cell growth with many cells dying off. (Thimann 623) The fifth phase of cell growth is where the cells reach the maximum population of bacteria that the medium can support with growth and death balanced out. (Thimann 624) The sixth phase is one of increasing death rate. (Thimann 624) The seventh phase is the ?logarithmic? death phase which is the inverse of the logarithmic growth phase. (Thimann 624). The eighth and final phase of the growth curve is one of decreasing death rate. (Thimann 624) In this stage a small amount of bacteria can live almost indefinitely provided that the medium is still inhabitable. (Thimann 624) This curve shows the bacteria?s limitations dependent on your constants and variables within the growth curve experiment. The level of aeration the temperature and nutrient levels all are variables that lead to different results in this experiments.
Bacteria can grow in many harsh conditions. One type of classification for bacteria is based on the temperature at which a bacterium can survive. The thermopile bacteria are bacteria that can survive at temperatures of forty-two to one hundred degrees Celsius or more.(Edwards 2) These bacteria are generally found around hot geological sites such as volcanoes and geysers.(Edwards 2) Another class of bacteria are the Acidophiles. Acidophiles are Bacterium that can survive and reproduce within an extremely acidic environment.(Edwards 34) Their environments are highly acidic soils in mining and geothermal areas.(Edwards 34) Oligotrophs are bacteria that can survive on little organic matter such as carbon (Edwards 93) They are commonly found in ocean water. (Edwards 94) Osmophiles are bacteria that are able to survive in environments with little water.(Edwards 117) Halotolerant and halophilic bacteria are bacteria that can survive with little salt or lots of salt. (Edwards 147) These bacteria are commonly found in salt and soda lakes such as the Great Salt Lake in Utah, the Dead Sea and the soda lakes of the Great Rift Valley in Kenya.(Edwards 149) Metal tolerant bacteria are tolerant to heavy metals that are toxic to microbial life forms.(Edwards 178) All of these different types of bacteria show how they have evolved so that they can live almost every where. Conditions in which bacteria can not live are getting harder and harder to find.
Bacteria are thus are highly adaptable organisms that can live almost any where in the world. They have a seemingly simple but complex structure that is highly organized. Bacteria have different stages of reproduction that is shown in a growth curve that shows the limitations of bacterial reproduction. If bacterial reproduction was not limited the earth would be over run with bacteria.