Bacteria
domain of unicellular prokaryotes that have cell walls a is Bacteria
Bacteria have a number of shapes, ranging containing peptidoglycan.
were among the first life to rods and spirals. Bacteria spheres from
. They habitats , and are present in most of its Earth forms to appear on
, and Earth's crust portions of deep , acidic hot springs , water, soil Inhabit
Bacteria also live environments. many other extreme
relationships with plants and parasitic and symbiotic in
many of the stages Bacteria are vital in recycling nutrients, with animals.
f fixation o dependent on these organisms, such as the nutrient cycles in
. putrefaction and atmosphere from the nitrogen
Origin and Early Evolution
of modern bacteria were unicellular microorganisms that The ancestors
to appear on Earth, about 4 billion years ago. first forms of life were the
oscopic, and bacteria For about 3 billion years, all organisms were micr
Gene sequences can be rchaea were the dominant forms of life. a and
, and these studies indicate phylogeny used to reconstruct the bacterial
erged first from the archaeal/eukaryotic lineage. that bacteria div
led a great evolutionary divergence which Bacteria were also involved in
to the formation of chloroplasts in algae and plants.
Size, Shape, and Movement
sizes. Bacterial cells are Bacteria display a wide diversity of shapes and
tenth the size of eukaryotic cells and are typically 0.5 - about one
in length. Most bacterial species are either spherical, micrometres 5.0
shaped, called - spiral or ; bacilli shaped, called - , or rod cocci called
. Prokaryotes can be distinguished by whether they move and spirilla
how they move. Some prokaryotes do not move at all. Others are
like - . Some glide slowly along a layer of slime flagella propelled by
material they secrete.
Nutrition and Metabolism
Like all organisms, bacteria need a supply of chemical energy, which they
such as sugars. Energy is released molecules store in the form of fuel
molecules during cellular respiration, fermentation, or both. from these
ria can obtain and release energy. There are diverse ways by which bacte
Some are able to change their method of energy capture or release
depending on the conditions of the environment.
Nutritional types in bacterial metabolism
Source of
energy
Source of carbon Examples
Phototrophs Sunlight
Organic compounds
(photoheterotrophs) or carbon
fixation (photoautotrophs)
Cyanobacteria, Green sulfur
bacteria, Chloroflexi, or Purple
bacteria
Lithotrophs
Inorganic
compounds
Organic compounds
(lithoheterotrophs) or carbon
fixation (lithoautotrophs)
Thermodesulfobacteria
or Nitrospirae
Organotrophs
Organic
compounds
Organic compounds
(chemoheterotrophs) or carbon
fixation (chemoautotrophs)
Bacillus, Clostridium
Growth and reproduction
, binary fission teria grow to a fixed size and then reproduce through Bac
Under optimal conditions, bacteria can . asexual reproduction a form of
two division cell In . grow and divide extremely rapidly
daughter cells are produced. clone identical
When growth conditions become unfavorable, many prokaryotic cells
a thick internal wall that encloses the DNA and a - endospore form an
ion of the cytoplasm. port
follows four phases. When a population of bacteria Bacterial growth
nutrient environment that allows growth, the cells - first enters a high
need to adapt to their new environment. The first phase of growth is
, a period of slow growth when the cells are adapting to lag phase the
nutrient environment and preparing for fast growth. The lag - the high
necessary for rapid growth phase has high biosynthesis rates, as proteins
also known , log phase The second phase of growth is the are produced.
. The log phase is marked by logarithmic or exponential phase as the
. The rate at which cells grow during this phase exponential growth rapid
, and the time it takes the cells to double is growth rate is known as the
. During log phase, nutrients are generation time known as the
metabolised at maximum speed until one of the nutrients is depleted
stationary and starts limiting growth. The third phase of growth is the
and is caused by depleted nutrients. The cells reduce their phase
essential cellular proteins. The - metabolic activity and consume non
transition from rapid growth to a stress response stationary phase is a
DNA state and there is increased expression of genes involved in
final phase is transport. The and antioxidant metabolism , repair
where the bacteria runs out of nutrients and dies. death phase the
Bacteria Human Uses of
Aside from their natural importance in the environment, Bacteria are
used in the production of a wide variety of foods and other commercial
products. For example, yogurt is produced by the bacterium
Lactobacillus. Some bacteria can even digest petroleum and remove
human made waste products and poison from water. Others are used to
synthesize drugs and chemicals through the techniques of genetic
engineering.
Bacteria can decompose materials, produce energy for
food chains, and fix nitrogen for plants. In conclusion, Bacteria are
essential in maintaining every aspect of the ecological balance of the
living world.
: References
These are the references and sources that helped us compose this
research project:
http://en.wikipedia.org/wiki/Bacteria#Growth_and_reproduction
Miller & Levine Biology
