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Chapter 27 Bacteria and Archaea (27.1 Structural and functional…
Chapter 27 Bacteria and Archaea
27.1 Structural and functional adaptations contribute to prokaryotic success
Cell-Surface Structures
peptidoglycan
polymer composed of modified sugars cross-linked by short polypeptides (allows for testing of gram stain)
gram stain
gram positive (crystal violet)
gram negative (saffranin)
basic structures
fimbriae
hairlike appendages that allow it to stick to substrate
fimbriae are shorter and more numerous than pili
pillus
appendage that pulls two cells together to transfer DNA
endospores
resistant cells developed when they lack water or nutrients
sticky outer layer of either polysaccharides or protein
capsule
dense and well-defined
slime layer
not very organized
Motility
taxis
a directed movement toward or away from a stimulus
Evolutionary Origins of Bacterial Flagella
exaptation
process in which structures originally adapted for one function take on new functions through descent with modification
flagella
structure that allows prokaryotes to move
Internal Organization and DNA
nucleoid
prokaryote chromosome located here, a region of cytoplasm not enclosed by a membrane
plasmids
smaller rings of independently replicating DNA molecules
Reproduction
binary fission
single prokaryotic cell divides into two
three factors for rapid population growth
reproduce by binary fission
short generation times
they are small
27.3 Diverse nutritional and metabolic adaptations have evolved in prokaryotes
Nitrogen Metabolism
nitrogen fixation
a process where atmospheric nitrogen (N2) is converted to ammonia (NH3)
Metabolic Cooperation
heterocysts
a few specialized cells that only do nitrogen fixation
bioofilms
a surface-coating colony where metabolic cooperation occurs between different prokaryotic species
The Role of Oxygen in Metabolism
3 types of prokaryotic metabolism
obligate anaerobes
can't use oxygen at all but can use anaerobic respiration
substances other than O2 such as nitrate or sulfate ions, accept electrons at the "downhill" end of electron transport chains
facultative anaerobes
can use oxygen if its present and do fermentation or anaerobic respiration in an anaerobic environment
obligate aerobes
must use oxygen for cellular respiration and can't grow without it
Table 27.1
Autotroph
Photoautotroph
carbon source: CO2 or related compounds
example: photosynthetic prokaryotes
energy source: light
Chemoautotroph
energy source: inorganic chemicals
carbon source: CO2 or related compounds
example: unique prokaryotes such as
Sulfolobus
Heterotroph
Photoheterotroph
energy source: light
carbon source: organic compounds
example: certain aquatic and salt-loving prokaryotes like
Rhodobacter, Chloroflexus
Chemoheterotroph
energy source: organic compounds
carbon source: organic compounds
examples: many prokaryotes, protists, fungi, animals and some plants
27.4 Prokaryotes have radiated into a diverse set of lineages
Archaea
extremophiles
extreme halophiles
live in very salty environments
extreme thermophiles
live in very hot places
methanogens
archaea that live in swamps/ marshes and produce methane as a waste product
Table 27.2
(Compare and Contrast Bacteria, Archaea and Eukarya
peptidoglycan in cell wall
Archaea: Absent
Eukarya: Absent
Bacteria: Present
response to the antibiotics streptomycin and chloramphenicol
Bacteria: growth usually inhibited
Archaea: growth not inhibited
Eukarya: growth not inhibited
membrane enclosed organelles
Bacteria: Absent
Archaea: Absent
Eukarya: Present
circular chromosome
Archaea: Present
Eukarya: Absent
Bacteria: Present
nuclear envelope
Archaea: Absent
Eukarya: Present
Bacteria: Absent
growth at temperatures > 100 degrees celsius
Bacteria: No
Archaea: some species (such as extremophiles)
Eukarya: No
27.6 Prokaryotes have both beneficial and harmful impacts on humans
Pathogenic Bacteria
exotoxins
proteins secreted by certain bacteria and other organisms
example: bacteria secretes an eotoxin, the exotoxin causes a disease like cholera even if the bacteria has already left
endotoxins
lipopolysaccharide components of the outer membrane of gram-negative bacteria
in contrast to an exotoxin, endotoxins can only be released when the bacteria dies
Prokaryotes in Research and Technology
CRISPR-Cas9 system
helps bacteria and archaea defend against viruses
bioremediation
the use of organisms to remove pollutants from soil, air or water
example: using bacteria to eat up the oil from an oil spill
Mutualistic Bacteria
gut mutualists/ bacteria in the intestines can help digest things our own intestine can't
27.2 Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes
Genetic Recombination
Transformation and Transduction
transformation
genotype and phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings
transduction
phages carry prokaryotic genes from one host cell to another
Conjugation and Plasmids
conjugation
DNA is transferred between two prokaryotic cells, usually the same species, and they are temporarily joined
The F Factor as a Plasmid
F plasmid
the F factor in its plasmid form
The F Factor in the Chromosome
chromosome genes can be transferred through conjugation if the donor cell's F factor is integrated in its chromosome
R Plasmids and Antibiotic Resistance
R plasmids
resistance genes carried by plasmids
basically, r plasmids help the genes resist antibiotics
F factor
a particular piece of DNA that allows it to form the sex pillus, and donate DNA through conjugation
genetic recombination
combining of DNA from two sources
Rapid Reproduction and Mutation
mutations
errors in DNA replication
because they have fast reproduction and short lives, its easier to get that one in a million chance of a mutation
27.5 Prokaryotes play crucial roles in the biosphere
Chemical Recycling
decomposers
live in the ground and break down dead organisms (chemoheterotrophic prokaryotes)
example: fungi
Ecological Interactions
mutualism
an ecological interaction in which both species benefit
commenalism
an ecological relationship in which one species benefits while the other isn't harmed or helped in any way
symbiosis
host
larger organism in a symbiotic relationship
symbiont
smaller organism in a symbiotic relationship
an ecological relationship in which two species (host and symbiont) live in close contact with each other
parasitism
:pathogen
a parasite that causes disease
example: the tick is a vector while the bacteria (and the disease it causes) is the pathogen
parasite
eats the cell contents, tissues or body fluids of its host
an ecological relationship in which a parasite harms but doesn't always kill its host
Compare and Contrast: Eukaryotic and Prokaryotic (Membrane Compartmentalization)
Eukaryotes
nucleoid
no membrane enclosing the DNA
thylakordmembrane and the respiratory membrane
used for photsynthesis and to make ATP
makes proteins
all three ways (DNA replication, transcription, and translation) done in the cytoplasm
Prokaryotes
organelles (chloroplast and mitochondria)
to do photosynthesis and make ATP
makes proteins
DNA replication and transcription done in the nucleous, translation done in the cytoplasm
nucleus
DNA enclosed by a membrane
