CH 27: Archaea and Bacteria Flashcards
What are prokaryotes?
a paraphyletic group consisting of bacteria and archaea
-Both lack a membrane bound nucleus
What was the Great Oxidation Event?
No Oxygen on earth until Cyanobacteria evolved ability to photosynthesize
-Oxygen is byproduct of photosynthesis and built up over millions of years
Why are prokaryotes so diverse?
- Short Generation times
- Live in almost all habitats
- Horizontal Gene Transfer
Which domain is Archaea more closely related to?
Eukarya
What gives Archaea its resilience, making them extremophiles?
Ether bonded lipids more resistant to heat
-Lipids have extra double/triple bonds that maintain shape and don’t denature under high temp/pH
What are extremophiles?
Organisms that can occupy habitats with extreme conditions
What are the types of extromphiles?
High Salt Content - halophiles
High Temperatures - Hyperthermophiles
What are the phyla that make up Domain Archaea?
1) Korachaeota
2) Nanoarchaeota
3) Thaumarchaeota
4) Crenarchaeota
5) Euryarchaeota
What kinds of living conditions do bacteria live in?
Mst favor moderate conditions
- some are extremophiles
- Some form symbiotic relationships with Eukaryotes
What are the Phyla we need to know for Domain Bacteria?
- Chlamydiae: Chlamydia
- Spirochaetes: Syphilis and Lyme disease
- Actinobacteria: Tuberculosis
- Cyanobacteria: O2 producers; blue-green algae; can cause toxic algal blooms
- Proteobacteria: Large group; metabolically diverse; E. coli, influenza
What are the characteristics of Phylum Cyanobacteria?
- Photosynthetic bacteria generates Oxygen
- Live in aquatic habitats, wetlands, arid soil surface
- Plant chloroplasts are derived from cyanobacteria
- Live as single cells, colonies or filaments
- Produce Organic Carbon and Fix Nitrogen
What Major Subgroup of Phylum Proteobacteria had a large impact on humans?
α-proteobacteria
•Ancestors of mitochondria, Rhizobium, Agrobacterium
What is horizontal gene transfer?
Movement of one or more genes from one species to another
•Contrasts with vertical gene transfer from parent to progeny
•Increases genetic diversity
What are the mechanisms of horizontal gene transfer?
Transformation, Transduction, and Conjugation
Explain the mechanism of horizontal gene transfer, transformation.
Transformation
•DNA fragment from donor cell released to environment & taken up by another bacterial cell
Explain the mechanism of horizontal gene transfer, transduction.
Transduction
•Virus infects donor cell & bacterial chromosome fragments
•Phage transfers fragment DNA to a recipient cell
Explain the mechanism of horizontal gene transfer, conjugation.
Conjugation
•Requires direct contact between bacteria cells
•One bacterium acts as a donor & transfers DNA to recipient cell
What are the important concepts of Bacteria and Archaea?
- Both evolved from common ancestor
- Eukaryotic nucleus and cytoplasm likely arose in ancient archaeal organism
- Mitochondria and plastids originated from proteobacteria and cyanobacteria by endosymbiosis
What are examples of more complex cell structures in bacteria?
Magnetosomes
- Magnetite Crystals
- Like compass that help bacteria find low O2 habitats
Gas Vesicle
-Adjust buoyancy
What are the major shapes of Bacteria?
1) Sphere - cocci
2) Rods - bacilli
3) Comma - vibrios
4) Spiral - spriochaetes
5) Single Cells, pairs, or Filaments
What is mucilage?
Also called glycocalyx
-Very sticky composed of polysaccharides and/or proteins
What are the functions of mucilage?
1) Evade host defenses
2) Hold colony together (biofilm)
3) Help aquatic bacteria float
4) Binds mineral nutrients
5) Defense against predators
6) Prevents UV damage
What are biofilms?
Biofilms: aggregates of microorganisms that secrete adhesive mucilage & glue themselves to surfaces
•Help remain in favorable areas for growth
What is quorum sensing?
given enough individuals, signaling molecules released by individuals cause collective behavior
•Moving to a common location
•Secreting mucilage
What are the major forms of bacterial cell walls?
Gram-positive or Gram-negative
-differ in peptidoglycan thickness, staining properties & response to antibiotics
What are the two methods of motility for bacteria?
Flagella and Pili
What are flagella used for in bacteria?
- Important for swimming
- Lack plasma membrane cover of proteins
- Lack internal cytoskeleton of microtubules
- Lack motor protein dynein
- Eukaryotic flagella: repeatedly bend & straighten
- Bacterial flagella: outboard motor
What are pili used for in bacteria?
- Twitch or glide across surfaces
- Threadlike structures on surface of cell
- If nutrients are low bacteria glide together & form tiny tree like colonies
- Important for reproduction
How do bacteria reproduce?
Binary fission –divide by splitting in two
- Circular DNA replicates within the cell
- DNA molecules migrate to opposite ends of cell
- Cell elongates
- Cell constricts at middle, pinches off
one cell can become millions in hours
How do bacteria survive harsh conditions?
By forming akinetes and endospores
What do all living cells require to build organic molecules?
Energy and a source of Carbon
How can you classify bacteria and archaea?
Can be classified by:
•Nutrition
•Response to oxygen
•Presence of specialized metabolic processes
What is a heterotroph and what are its types?
Heterotrophs: organisms that require at least one organic compound, and often more
Photoheterotroph: able to use light energy to make ATP but they must take in organic compounds from the environment
Chemoorganotroph: must obtain organic molecules for both energy and carbon source
What is an autotroph and what are its types?
Autotrophs: produce all or most of their own organic compounds
Photoautotroph: Uses light as energy source for synthesis of organic compounds from CO2or H2S
Chemoautotrophs: Use energy obtained from chemical modification of inorganic compounds to synthesize organic compounds
How are bacteria/archaea classified by oxygen response?
- Obligate aerobes –require oxygen
- Facultative aerobes –can use oxygen or not
- Obligate anaerobes –cannot tolerate oxygen
- Aerotolerantanaerobes –do not use oxygen but are not poisoned by it
How are bacteria/archaea classified by special metabolism?
Diazotrophs–conduct nitrogen fixation
•Enzyme nitrogenase converts inorganic nitrogen gas (N2) into ammonia (NH3)
•Autotrophs need ammonia to make N containing compounds
•Heterocysts–specialized cells for nitrogen fixation in cyanobacteria
What are the Ecological role of bacteria?
Carbon cycle
•Producers synthesize organic compounds used by other organisms as food
•Decomposers break down dead organisms to release minerals for reuse
- Methanogens make methane
- Methanotrophs consume methane
What are the symbiotic roles of bacteria?
- Symbiosis: An organism that lives in close association with one or more other organisms
- Parasitism: One partner benefits at the expense of the other
- Mutualism: Association is beneficial to both partners
What are the symbiotic roles of bacteria?
- Syntrophy–some bacteria live together and supply each other with essential nutrients
- Consortia–larger community of nutrient exchangers
What is a pathogen?
Pathogen–parasitic microbe causes disease symptoms
•Organisms that obtain organic compounds from living hosts (parasites)
