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Chapter 27: Bacteria and Archaea (Concept 27.2 (Conjugation & Plasmids…
Chapter 27: Bacteria and Archaea
Masters of Adaptation
Some organisms can live in harsh environments
Deinococcus radiodurans
- Survives radiation
Picrophilis oshimae
- Can grow in pH of .03
Halobacterium -
Thrives in salt
Compensates for water loss through osmosis
Other Prokaryotes
extreme hot or cold
most abundant
also well adapted to normal environments
Concept 27.1
Prokaryotes
Subjected to natural selection in different enviornments
unicellular & small
Variety of shapes
Well organized
1st organisms on Earth
achieve all life functions in a single cell
Cell Surface Structure
Prokaryotes cell wall
Maintains shape
Protects cell
Prevents it from bursting
Water loss can inhibit cell reproduction
Uses salt to preserve food
Prevents rapid multiplication
Eukaryotes cell wall
Plants & Fungi
Made of cellulose or chitin
Bacterial cell walls
Encloses bacterium
anchors other molecules
Contain Peptidoglycan
Archaeal cell walls
Contain variety of polysaccharides & proteins
Lack peptidoglycan
Gram Staining
Gram +
Simple walls
Thick layer of peptidoglycan
Gram -
More complex
Less peptidoglycan
Outter membrane of lipopolysaccharides
Valuable in medicine
Gram - Bacteria
Lipids are toxic
Fever/ Shock
Outter membrane protects from immune system & impedes entry of drugs
More resistant to antibiotics
Gram + Bacteria
Virulent strains
Resistant to 1 or more antibiotics
Outer layer of cell walls
Sticky layer
Capsule- well defined
Slime layer - not well organized
Protects from dehydration
Shields from attacks
Endospores
Thick coated
Multilayered structure
Developed by cells
survives harsh conditions
Fimbriae
Shorter, more numerous than pili
used to stick to mucus membrane
Hairlike
Motility
Taxis
Oriented movement
Chemotaxis
Negative- moves
away from
toxic substances
Positive - moves
Toward
nutrients/O2
Changes movement in reponse to chemicals
Flagella
Scattered over entire surface
or concentrated at 1 or both ends
Structure enabling movement
Bacterial Flagella
3 main parts
Motor
Hook
Filament
Originated as simple structures, modified over time
Prokaryotic cells differ from Eukaryotic cells
Prokaryotes are simpler
internal structure
Physical arrangements of DNA
Prokaryotes lack complex compartmentalization
Eukaryotes have membrane bound organelles
Some prokaryotes have specialized membranes
in foldings of plasma membrane
simple compartments
Perform metabolic functions
Reproduction
Prokaryotes can reproduce quickly in favorable environments
Can consist of trillions
Way more than Eukaryotes
Binary Fission- 1 cell divides into 2; those each divide 2 more x and so on
Potential for rapid population growth
Concept 27.2
Evolution can occur w/out genetic variation
Rapid reproduction & mutation
Prokaryotes do not reproduce sexually
Genetic variation
rapid growth
Mutation
new mutation is rare
Increases genetic diversity quickly
Individuals are genetically better equipped to survive
Prokaryotes are highly evolved & successfully respond to environmental challenges
Genetic Recombination
- DNA combined from 2 sources
Eukaryotes - Use Meiosis and Fertilization
Meiosis and fertilization do not occur in prokaryotes
3 Mechanisms that bring together DNA
Transduction
Conjugation
Transformation
Horizontal Gene Transfer
Transformation & Transduction
Transformation
Genotype of prokaryotic altered by uptake of foreign DNA
Recombinant
- chromosome containing DNA from 2 different cells
Many bacteria have cell surface proteins
Recognize DNA
Transport DNA into cell
Homologus DNA
- foreign DNA incorporated into genome
Transduction
Phages carry prokaryotic genes from 1 host cell to another
Results from accidents during phage replication cycle
A virus that carries prokaryotic DNA
May not be able to replicate
Lacks some or all of its genetic material
can attach to another prokaryotic cell (recipient)
Injects DNA from 1st cell (donor)
recombinant cell formed
Conjugation & Plasmids
DNA is transferred between 2 prokaryotic cells
In bacteria DNA transfer is always 1 way
1 cell donates DNA
1 cell receives DNA
Pilus of donated attaches to recipient
Pilus retracts pulling cells together
Mating bridge - Transfers DNA
F Factor
Donates DNA
Plasmid or segment of DNA
Forms DNA
F Factor in chromosomes
cell w/ F factor is donor
called Hfr (high frequency of recombination)
DNA from Hfr enters F- cell
Chromosomes align
Allows DNA exchange
Recipient becomes recombinant bacteria
F factor as a Plasmid
F+ Cells (contain F plasmid)
DNA Donors
F- Cells (lack F factor)
DNA Recipients
F+ cell converts F- to F+ if a copy of entire F plasmid is transferred
Recombinant cell if DNA transfers successfully
Plasmids and antibiotic resistance
Resistance to antibiotics evolved over time
R plasmids - Carry resistance genes
Antibiotics don't kill bacteria with resistance genes
Concept 27.3
Prokaryotes are categorized by how energy/carbon are obtained
Autotrophs
- Organisms that need only CO2 or related compounds for carbon source
Chemautotrophs
Energy from organic chemicals
Carbon source CO2 or related compound
Unique to certain prokaryotes
Photoautotroph
Gets energy from light
Carbon source CO2 or other related compound
Photosynthetic prokaryotes
Heterotrophs
- Require at least 1 organic nutrient
Photoheterotroph
Energy from light
Carbon source organic compounds
Unique to aquatic & salt loving prokaryotes
Chemoheterotrophs
Energy from organic compounds
Carbon source organic compounds
Many prokaryotes
O2 in metabolism
Prokaryotic metabolism varies with respect to O2
Obligate Aerobes require O2 for cellular respiration
Obligate Anaerobes are poisoned by O2 and live by fermintation
Facultative anaerobes can use O2 if present or use fermintation if not
Nitrogen Metabolism
Essential to produce Amino acids & nucleic acids in all organisms
Prokaryotes can metabolize nitrogen in a variety of ways
Some convert nitrogen to ammonia,
Nitrogen Fixation
Metabolic cooperation
Cooperation between prokaryotes allows them to use environmental resources
heterocysts exchange metabolic products
Biofilms - surface coating colonies
Concept 27.4
Prokaryotes date back 3.5 billion years
Prokaryotes inhabit every environment known
-
Overview of Prokaryotic Diversity
2 domains, Bacteria & Archaea
A few taxonomic groups are monophyletic
Advances in moleculer techniques add new branches to the tree of life
Horizontal gene transfer between prokaryotes obscures the root of the tree of life
Bacteria
Include the vast majority of prokaryotic species familiar to most people
Diverse nutritional types are represented among bacteria
Proteobacteria
5 subgroups of proteobacteria are recognized by molecular systematists
Some are anaerobic or aerobic
Gram negative bacteria
chemoautotrophs
heterotrophs
Photoautotrophs
Subgroup: Alpha Proteobacteria
Hypothesized that mitochondria evolved through endosymbiosis
Closely associated with eukaryotic hosts
Archaea
- Share certain traits with bacteria & others with eukaryotes
Extremophiles
live in extreme environments
Extreme halophiles- Salty
Extreme thermophiles - Very hot
Methanogens
- live in swamps & produce methane as waste
Strict anaerobes, poisoned by O2
Concept 27.5
If prokaryotes disappeared, life surviving on Earth would be dim
Chemical Recycling
Prokaryotes help in recycling chemical elements between living and nonliving componenet
Some function as decomposers
Prokaryotes can also decrease the availability of nutrients by using them in their own cells
Ecological Interactions
Symbiosis is an ecological relationship, 2 species live close together
Host
Symbiont
Prokaryotes form symbiotic relationships with larger organisms
Pathogens
- parasites that cause disease
Parasite
, harms but does not kill host
Commensalism
- 1 benefits, other is not affected
Mutualism
- Both n=benefit
Concept 27.6
Some prokaryotes are human pathogens, but some have interactions with humans
Mutualistic bacteria
Human Intestines have 500-1,000 species of bacteria
many are mutualists & break down food that is undigested by our intestines
Pathogenic Bacteria
Bacteria cause 1/2 of all human disease
Some bacterial disease are transmitted by other species
Endotoxins - secreted and cause disease
Endotoxins - release only when bacteria die and their cell walls break down
Horizontal gene transfer spread genes associated with virulence
Research & Technology
Experiments using prokaryotes have led to important advances in DNA technology
Bacteria can be used to make natural plastics
Bioremediation
- use of organisms to remove pollutants from environment
