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.
