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Bacteria and Archaea (pg.571) (Structural and Functional Adaption (Cell…
Bacteria and Archaea (pg.571)
Structural and Functional Adaption
Cell-Surface Structures
nearly all prokaryotic cells has a cell wall
which maintains the shape, protects the cell, and prevents it from bursting
archaeal cell wall
contains a variety of
polysaccharides and proteins but lacks peptidoglycan
bacterial cell wall
contains peptidoglycan
which is a polymer
composed of modified sugar cross-linked by short polypeptides
can be categorized with a technique
by the gram stain
developed by danish physician Hans Christian Gram
which is performed by
sample are first stained with crystal violet dye and iodine
then rinsed with alcohol
finally safranin is added
which enters the cell
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helps determine whether or not a patient has an infection
surrounded by a sticky layer of polysaccharides or proteins
this layer is called
capsules
can be dense and well-defined or slimy
which enables it to adhere to their substrate or to other individuals in a colony
some protects against dehydration
and shields against attacks by the host's immune system
endospores
are resistant cells when bacteria lacks water or essential nutrients
fimbriae
are hairlike appendages
used to stick to their substrate or to one another
Motaility
taxis
a directed movement towards or away from stimulus
can be enabled to move by
flagella
may be scattered over the entire surface of the cell
or concentrated on both ends
differs from eukaryotic cells by
one-tenth the width
not covered by an extension of plasma membrane
molecular composition
mechanism of propulsion
Evolutionary Origins of Bacterial Flagella
three main parts
motor, hook and filament
composed of 42 different kinds of proteins
Internal Organization and DNA
simpler than eukaryotes in internal structure and physical arrangement
has specialized membranes that performs metabolic functions
membranes are usually infolding of the plasma membrane
structure
has less DNA
circular chromosomes
lack a nucleus
may have plasmids
are smaller rings of independently replicating DNA molecules
Reproduction
binary fusion
a single prokaryotic cell divides into 2 cells
which then divides into 4, 8, 16 and so on
cannot constantly reproduce
because it'll exhaust its nutrient system
poison themselves with metabolic wastes
face competition with other microorganisms
or consumed by other organisms
Genetic Diversity in Prokaryotes
Rapid Reproduction and Mutation
does not reproduce sexually
new mutations
can increase genetic diversity quickly
in species with short generation times
and large populations
diversity can lead to
rapid evolution
causes bacteria to
survive and reproduce at higher rates than other individuals
Genetic Recombination
is the combining of DNA from two sources
which is done by three methods
transduction
phages carry prokaryotic genes from one host cell to another
results in accidents
that occurs in the phage replicative cycle
a virus that carries prokaryotic DNA
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conjugation
a process where
DNA is transferred between two prokaryotic cells
that are temporarily joined
DNA always transfers one way
one cell donates the DNA
and another receives it
transformation
the genotype and possibly phenotype
are altered by the uptake of foreign DNA from its surroundings
for example,
streptococcus pneumoniae
can be transformed into pneumonia-causing cells
if cells are exposed to DNA from a pathogenic strain
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discovered in lab cultures
cell-surface proteins that recognize DNA from
closely related species and transport it into the cell
once inside the cell,
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Diverse Nutritional and Metabolic Adaptions
phototrophs, heterotrophs, chemotrophs and autotrophs
are combined which results in
nitrogen metaboism
essential for the production of amino acids and nucleic acids
nitrogen fixation
conversion of atmospheric nitrogen to ammonia
the cells can incorporate "fixed" nitrogen
into amino acids and other organic molecules
has a large impact on other organisms
can increase nitrogen available to plants
leads to production of ammonia
oxygen in metabolism
obligate aerobes
must use oxygen for cellular respiration
and cannot grow without it
obligate anaerobes
are poisoned by oxygen
they either
live exclusively by fermenation
extract chemical energy by anaerobic respiration
which substances other than oxygen accept electrons
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metabolic ciiperation
cooperation between two prokaryotic cells
to use environmental resources
since a single cell cannot carry out both processes at the same time
anabaena
forms filamentous chains
can carry out phootosynthesis
heterocysts
can carry out only nitrogen fixation
surrounded by a thick cell wall
that resists entry of oxygen produced by neighboring photosynthetic cells
intercellular connections allow heterocyst to transport fixed nitrogen to neighboring cells and to receive carbohydrates
between two different prokaryotic cells
often occurs in surface-cooling colonies
known as biofilms
cells in biofilms
secrete signaling molecules that recruit nearby cells
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channels in biofilms
allow nutrients to reach cells in the interior and wastes to be expelled
Diverse Sets of Lineages
Bacteria
major groups
proteobacteria
alpha proteobacteria
beta proteibacteria
gamma proteobacteria
delta proteobacteria
epsilon bacteria
chalamydias
spirochetes
cyanobacteria
gram positive bacteria
Archaea
prokaryotic diversity
Crucial Roles in the Biosphere
Chemical Recycling
occurs when
the atoms that make up the organic molecules in all living things
that were at one time part of of inorganic substances
sooner or later,
those atoms return ti the nonliving environment
ecosystems
depend of the continual recycling
of chemical elements between the living and nonliving
components of the environment
prokaryotes play a role in this
decomposers
breaks down dead organisms
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conversions
of some molecules to forms
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can increase the availability of nutrients
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decrease availability of nutrients in plants
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Ecological Interactions
Prokaryotes Impacts on Humans
Mutualistic Bacteria
Pathogenic Bacteria
Prokaryotes in Research and Technology