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Chapter 19 & 27 - Coggle Diagram
Chapter 19 & 27
Chapter 27: Bacteria and Archae
27.1: Structural and functional adaptations contribute to prokaryotic success
Cell-Surface Structures
Prokaryotic cell walls contain peptidoglycan instead of chitin or cellulose
Gram stain is a technique which uses the presence of this polymer to categorize the bacteria
Gram-positive
Simple wall; more peptidoglycan
Gram-negative
Structurally complex; less peptidoglycan
More resistant to anitbiotics
Cell wall is surrounded by a sticky layer of polysaccharide or protein that allow for adherence
Capsule
Well- defined and dense
Slime layer
Not well organized
Endospores are resistant cells developed in the face of nutritional deficiencies
A copy of a cell's chromosome surrounded with a protective layer; can remain dormant for centuries in most conditions
Some stick to substrate and one-another with fimbriae
Short, abundant hair-like appendages
NOT pili
Appendages that pull two cells together to induce DNA transfer
Motility
Approximately 50% of prokaryotes capable of taxis
Intentional movement to or away from stimulus
Chemotaxis
Change in movement due to presence of chemicals
Negative
Away from toxic material
Positive
Toward nutrients/oxygen
Flagella are the most common structures responsible
Difference in prokaryotic and eukaryotic structure of flagella suggest independent emergence
Evolutionary Origins of Bacterial Flagella
Complex, three-part structure made from 42 separate proteins, although originated as simpler structures
27.2: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes
Rapid Reproduction and Mutation
Fast and large-scale reproduction leaves room for mutations to occur, encouraging genetic diversity that is not obtained through asexual reproduction
Ex. Escherichia coli
Genetic Recombination
Combining of DNA from two sources
Transformation
Genotype is altered by the introduction of foreign DNA from environment
Transduction
Phages carry prokaryotic cell genes to other prokaryotic cells
Conjugation
DNA is transferred via sex pilus between two prokaryotic cells that are temporarily joined
The ability to donate DNA in this way is dependent on the presence of a gene called the F-factor
Plasmids
F-factor in plasmid form is known as F plasmid; F+ cells contain this plasmid and function primarily to donate DNA to F- cells during conjugation
R-plasmids are resistance plasmids, or genes evolved with the purpose of resisting antibiotics
27.3: Diverse nutritional and metabolic adaptations have evolved in prokaryotes
Chemotrophs
Obtain energy from chemicals
Phototrophs
Obtain energy from light
Autotrophs
Only need CO2 or related compounds as carbon source
Heterotrophs
Require at least one organic nutrient to make other organic compounds
The Role of Oxygen in Metabolism
Obligate anaerobes
Will die with O2
Facultative anaerobes
Can use or cannot use O2
Obligate aerobes
Need O2
Nitrogen Metabolism
Some can convert N2 to NH3 - nitrogen fixation. Nitrogen is then used for organic molecules and amino acids
Metabolic Cooperation
If cells work as a unit, they can utilize and process environmental resources that would otherwise be unusable as individual cells
Biofilms are surface-coating colonies of these cell units
Heterocysts
Specialized cells that carry out nitrogen fixation
27.4: Prokaryotes have radiated into a diverse set of lineages
An Overview of Prokaryotic Diversity
Study of prokaryotic organisms reveal an astounding around of diversity of both the bacterial and archaeal kind
Archaea
Extremophiles
Prokaryotes functioning in extreme environments
Extreme halophiles
Prokaryotes functioning in highly saline environments
Extreme thermophiles
Prokaryotes functioning in extreme high temperature environments
Methanogens
Archaea that release methane as a by-product of how they obtain energy
Bacteria
Majority of prokaryotic species familiar to most people; represents every major mode of nutrition and metabolism
Proteobacteria, Chlamydias, Spirochetes, Cyanobacteria, Gram-Positive Bacteria
27.5: Prokaryotes play crucial roles in the biosphere
Chemical Recycling
Ecosystem depends on the cyclical, reusable nature of chemical elements between environmental components
Ex. decomposers break down the dead and release usable carbon
Ecological Interactions
Symbiosis
Two species live close contact; involves a larger host and a smaller symbiont
Mutualism
Both species involved in symbiosis benefit from the proximity
Commensalism
One species benefits and the other is unharmed in a symbiotic relationship
Parasitism
Ecological relationship in which a parasite feeds on its host
27.6: Prokaryotes have both beneficial and harmful impacts on humans
Mutualistic Bacteria
Ex. gut bacteria necessary for processing foods
Pathogenic bacteria
Ex. lung disease tuberculosis
Endotoxins
Lipopolysaccharide components of the outer membrane of gram-negative bacteria
Exotoxins
Proteins secreted by bacteria and other organisms
Antibiotic Resistance
Due to rapid reproduction capabilities and horizontal gene transfer, the evolution of antibiotic-resistant bacteria has surpassed the quantity and quality of current antibiotics
Prokaryotes in Research and Technology
Metabolic capabilities of prokaryotes allow for human wielding of fermentation (cheese, yogurt, etc.), new applications in biotechnology (PCR), reduced usage of petroleum, the CRISPR-Cas9 system, and bioredemiation
Bioremediation is the use of prokaryotic organisms to remove pollutants from the air, soil, and/or water
Chapter 19: Viruses
19.1: A virus consists of a nucleic acid surrounded by a protein coat
Structure of Viruses
Viral Genomes
May contain double-stranded DNA, single-stranded DNA, or single-stranded RNA
Typically organized as a single linear or circular molecule of nucleic acid; some contain more than one molecule of nucleic acid
Capsids and Envelopes
Capsids are the protein coat surrounding the genome
Consists of multiple protein subunits called capsomeres; kind of protein typically does not vary much
Most complex capsids are observed in bacteriophages
May be rod-shaped, polyhedral, or more complex
Viral envelopes surround the capsids of some viruses and are accessory structures made up of host cell phospholipids and membranous proteins
Extremely small infectious particles made up of one or more molecules of a nucleic acid enclosed in a protein coat or membranous envelope
19.2: Viruses replicate only in host cells
General Features of Viral Replicative Cycles
A virus may infect a host cell by injecting its DNA or via fusion with the membrane
Host range
The limited number of species a specific type of virus is permitted to infect
Viruses use the host cell's supply of protein-creating structures and mechanisms to replicate its own proteins
Typically, once a virus has satisfactorily replicated, they will all burst from the host cell at once, usually killing it
Replicative Cycles of Phages
The Lytic Cycle
Viruses that replicate solely via this cycle are known as virulent phages
Shorter duration than lysogenic cycle
The last stage of infection in which the host cell lyses and dies, releasing all replicated viral phages
Can demonstrate symptoms within hours of infection
The Lysogenic Cycle
Phage replicates inside host cell without causing it to lyse; coexists
Viruses that employ both cycles of regeneration are known as temperate phages
Longer duration than lytic cycle
Symptoms are only demonstrated when virus transitions to the lytic cycle; switchover is typically triggered environmentally
Once integrated into the bacterial DNA, viral DNA is referred to as a prophage
Bacterial Defenses Against Phages
Bacteria evolve to produce surface proteins not recognized as receptors by viral DNA
Restriction enzymes destroy foreign bacteria
CRISPR-Cas system
Replicative Cycles of Animal Viruses
Variation in viral infection are dependent on the nature of the viral DNA and the presence of an envelope
Viral Envelopes
Protruding glycoproteins from the envelope are used to bind to host cell and allow entry
Envelope is formed via the host cell's mechanisms and materials
Viral Genetic Material
Divided into six classes; (dsDNA, ssDNA, dsRNA, ssRNA, ssRNA template for mRNA synthesis, ssRNA template for DNA synthesis)
Class VI viruses are known as retroviruses; they have the most complicated replicative cycle and contain reverse transcriptase enzymes
Ex. HIV, the AIDS-causing virus
The viral DNA integrated into the host's genome, and which will remain there, is referred to as a provirus
19.3: Viruses and prions are formidable pathogens in animals and plants
Viral Diseases in Animals
Most symptomsm of viral infection originate from bodily response
Vaccines
A harmless portion of a pathogen introduced to the immune system in order to induce a defense response
Once present in the body, viral infections are mostly incurable by medical means; antibiotics target enzymes present in bacteria only
Emerging Viral Diseases
Viruses that become apparent suddenly
Ex. HIV, Ebola
Can be caused by mutation of existing viruses into new, quicker spreading emerging ones
Ex. RNA viruses due to lack of proofreading
Can be caused by the spread of a viral disease once isolated in a small community
Ex. HIV
Can be caused by the spreading of viral infections from other animals (75% of new human diseases)
Ex. HIV
Three types of Influenza virus
B
Infect only humans; have not caused an epidemic
C
Infect only humans; have not caused an epidemic
A
Infects a wide range of animals
Ex. H5N1 strain of avian virus
If animal is infected with multiple strains, any of which involve human-spread viruses, genomic RNA molecules can reassort, and additional viruses can potentially acquire ability to spread to humans
Viral Disease in Plants
Same basic structure and mode of replication as animal viruses
Spread by two major routes
Horizontal transmission
External source gets past plant's defensive epidermis and infects it
Vertical transmission
Plant inherits a viral infection from a parent
Viral infection spreads via enlargement of the plasmodesmata
Prions
Proteins that cause degenerative brain disease in animals
Ex. mad cow disease
Misfolded protein that's typically present in brain cells. Prions can somehow convert functional proteins into more prions once in contact - prion aggregation
Act very slowly; long incubation period
NOT destroyed by increased temperature