Bacteria are microscopic singular celled organisms grouped in the prokaryotekingdom. They have a seemingly simple internal structure but that is not so theinternal structure of a bacterium is quite complicated .
Bacterial growth isgenerally studied in cell cultures by “visible count” estimation which showsan apparent growth curve. (Stephenson 50) The growth curve shows the stages ofbacterial growth within a cell culture. (Thimann 623). Bacteria can survive in anumber of different extreme environments from extreme heat to little water. Bacterium have a internal structure that is more complicated than it seems atfirst. The first part of the bacterium is the plasma membrane which is aselectively permeable barrier that is the boundary of the cell.
(Prescott 40)The next portion of a bacterium is the cytoplasmic matrix. The cytoplasmicmatrix is the substance lying between the plasma membrane and the nucleoid. (Prescott 45) Although it is generally featureless in a microscopes it can bepacked with ribosomes and is generally highly organized. (Prescott 45) The nextone is the nucleiod of a bacterium. (Prescott 40) This is the area within abacterium 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 shapedregion of the cell.
(Prescott 50) The gas vacuole of a bacterium is used forbuoyancy in aquatic environments. (Prescott 40) This is demonstrated by fillinga bottle with Cyanobacteria stopping it with a stopper and then hitting thestopper with a hammer. (Prescott 45) The sudden pressure increase causes the gasvacuole to collapse so the bacteria sink to the bottom of the bottle. (Prescott47) The inclusion bodies within a bacterial cell are storage for differentsubstances such as carbon, phosphate and other substances. ( Prescott 40) Thecell wall of Bacteria gives the bacteria shape and protects it from the outsideenvironment. ( Prescott 40) The flagella of bacteria are tail like appendages ofcells that are used for movement.
(Prescott 40) The method usually used forestimating the growth of bacteria is the ” viable count” method. (Stephenson50) When the total count of the bacteria is plotted against time it shows agrowth curve. (Stephenson 50) Such curves are divided into eight differingphases. (Thimann 623) The first phase of the growth curve is an initialstationary phase in which no growth occurs.
(Thimann 623) The second phase isone of an increasing rate of growth these first two phases constitute the lagphase. (Thimann 623) The reason for the lag phase is this when you first putbacteria in a culture they need time to get into a state of growth called theembryonic stage. (Thimann 625) This stage can be identified by observing thecells. The bacteria grow to a greater size than normal. (Thimann 625) The thirdphase is called the logarithmic growth stage.
(Stephenson 50) During logarithmicgrowth stage the rate of increase remains constant and the cell size returns tonormal. (Stephenson 50) The fourth phase is one of decreasing cell growth withmany cells dying off. (Thimann 623) The fifth phase of cell growth is where thecells reach the maximum population of bacteria that the medium can support withgrowth and death balanced out. (Thimann 624) The sixth phase is one ofincreasing 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 almostindefinitely provided that the medium is still inhabitable. (Thimann 624) Thiscurve shows the bacteria’s limitations dependent on your constants andvariables within the growth curve experiment.
The level of aeration thetemperature and nutrient levels all are variables that lead to different resultsin this experiments. Bacteria can grow in many harsh conditions. One type ofclassification for bacteria is based on the temperature at which a bacterium cansurvive. The thermopile bacteria are bacteria that can survive at temperaturesof forty-two to one hundred degrees Celsius or more. (Edwards 2) These bacteriaare generally found around hot geological sites such as volcanoes andgeysers.
(Edwards 2) Another class of bacteria are the Acidophiles. Acidophilesare Bacterium that can survive and reproduce within an extremely acidicenvironment. (Edwards 34) Their environments are highly acidic soils in miningand geothermal areas. (Edwards 34) Oligotrophs are bacteria that can survive onlittle organic matter such as carbon (Edwards 93) They are commonly found inocean water. (Edwards 94) Osmophiles are bacteria that are able to survive inenvironments with little water. (Edwards 117) Halotolerant and halophilicbacteria 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 asthe Great Salt Lake in Utah, the Dead Sea and the soda lakes of the Great RiftValley in Kenya. (Edwards 149) Metal tolerant bacteria are tolerant to heavymetals that are toxic to microbial life forms. (Edwards 178) All of thesedifferent types of bacteria show how they have evolved so that they can livealmost every where. Conditions in which bacteria can not live are getting harderand harder to find.
Bacteria are thus are highly adaptable organisms that canlive almost any where in the world. They have a seemingly simple but complexstructure that is highly organized. Bacteria have different stages ofreproduction that is shown in a growth curve that shows the limitations ofbacterial reproduction. If bacterial reproduction was not limited the earthwould be over run with bacteria.
