Flashcards in CH 27: Archaea and Bacteria Deck (40)
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?
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?
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?
1. Chlamydiae: Chlamydia
2. Spirochaetes: Syphilis and Lyme disease
3. Actinobacteria: Tuberculosis
4. Cyanobacteria: O2 producers; blue-green algae; can cause toxic algal blooms
5. 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?
•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.
•DNA fragment from donor cell released to environment & taken up by another bacterial cell
Explain the mechanism of horizontal gene transfer, transduction.
•Virus infects donor cell & bacterial chromosome fragments
•Phage transfers fragment DNA to a recipient cell
Explain the mechanism of horizontal gene transfer, 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?
-Like compass that help bacteria find low O2 habitats
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
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
1. Circular DNA replicates within the cell
2. DNA molecules migrate to opposite ends of cell
3. Cell elongates
4. Cell constricts at middle, pinches off
one cell can become millions in hours