Bacteria and Archaea Flashcards
What are prokaryotes?
– ancient organisms
– ubiquitous [occur/thrive almost everywhere including extreme habitats]
– successful [due to structural, functional and genetic adaptation]
– have simple internal organization [no nucleus, no membrane-bound organelles]
– Classified into two domains [based on structure, physiology and bio chemistry]
What are the three domains of the tree of life?
1.bacteria
2.archaea
3.eukaryotes
3, 500 million years ago oldest prokaryotic fossil
Why are prokaryotes much smaller than average eucaryotic protists, plant or animal cells?
Surface area: volume ratio
- limits size that functional cells can attain
- prokaryotic cell design reached its size limit
Prokaryotes are morphologically what? But metabolically what?
Prokaryotes are morphologically simple but metabolically diverse playing a key role in the cycling of matter on earth [global carbon cycle/global nitrogen cycle]
Internal cell structure of bacteria
– Cytoplasm
– internal membranes [specialized]
– genome organization [nucleoid region/plasmids]
– ribosomes
External cell structure of bacteria
– Plasma membrane – cell wall – flagella – capsule – Pili
What is peptidoglycan?
Cell walls contain peptidoglycan – polymer of modified sugars cross-link by short polypeptides [cell walls of Archaea lack peptidoglycan]
Gram positive structure
Cell wall (peptidoglycan layer) Plasma membrane
Gram negative structure
Lipopolysaccharide Cell wall (outer membrane then peptidoglycan layer) Plasma membrane
Lipopolysaccharides on walls of gram negative bacteria are often…
This means that outer membrane of gram negative bacteria are…
Toxic
Antibiotic resistant
Many antibiotics inhibit the synthesis of cross-links in peptidoglycan in inner membranes
What is bacteria?
– Unicellular
– have simple shapes (sphere [ coccus], rod [bacillus], helix [spirillus])
- are very small [have diameter in range of 1 to 10 µm]
How is bacterial cell diversity generated?
Bacteria have some additional unique processes that and genetic diversity – collectively referred to as horizontal gene transfer
List the 3 types of horizontal gene transfer
- Conjugation
- Transformation
- Transduction (viruses)
Why are bacterial genomes smaller than those of eukaryotes?
Bacterial genomes lack non-coding stretches of DNA compared to eukaryotes
diversity in prokaryotes due to mutations and vertical gene transfer from parent cells to daughter cells [mitosis]
Define Conjucation
And conjugation, DNA [usually a plasmid] from a donor cell is transferred through a pilus [strands of cytoplasm] into the recipient cell
Spreads novel jeans and bacterial population [example: antibiotic resistance]
plasmids used in genetic engineering techniques [GMO]
Direct contact (cell-cell)
Define Transformation
In transformation DNA released into the environment by dead cells and cell breakdown is taken up by a recipient cell
genes can be transferred from cell to cell without direct contact
Define transduction
In transduction DNA is transferred from a donor to a recipient cell by a virus
common in nature and as a technique in research labs [genetic engineering]
no direct contact (cell – virus – cell)
Metabolic roles of prokaryotes: list 4 biogeochemical cycles they are involved in
- carbon
- oxygen
- sulfur
- nitrogen
Role in carbon cycling linked to oxygen cycling
Evolution of oxygenic photosynthesis by Cyanobacteria - key to O2 accumulation in atmosphere
Major nutritional modes: Autotrophs Name nutritional mode Name energy source Name carbon source List types of organisms
Photoautotroph
Light
CO2
Photosynthetic prokaryotes (Cyanobacteria), plants, certain protists (algae)
Major nutritional modes: Autotrophs Name nutritional mode Name energy source Name carbon source List types of organisms
Chemoautotroph
Inorganic chemicals
CO2
Certain prokaryotes (ex. Sulfolobus)
Major nutritional modes: Heterotrophs Name nutritional mode Name energy source Name carbon source List types of organisms
Photoheterotroph
Light
Organic compounds
Certain prokaryotes
Major nutritional modes: Heterotrophs Name nutritional mode Name energy source Name carbon source List types of organisms
Chemoheterotroph
Organic compounds
Organic compounds
Many prokaryotes and Protista (fungi, animals and some plants)
What are microbial mats?
Surface layers have access to O2 and CO2 and light –use oxygenic photosynthesis and aerobic cellular respiration
Deeper layers do not have access to O2 – use anoxygenic photosynthesis and anaerobic respiration and fermentation
Explain how anoxygenic photosynthesis works
Anoxygenic photosynthesis = CO2 reduced to organic carbon
Absorbs sunlight using a different pigment – bacteriochlorophyll
Uses a single photo system and electron transport chain to produce ATP only
Electron donors are H2S, H2, ferrous iron (Fe2+) and arsenide (AsO3 3-)
Define anaerobic respiration and fermentation
Without O2, organic molecules are still oxidized to CO2 Oxidants used as electron acceptors instead of oxygen -ferric acid (Fe 3+) -hydrogen sullied (H2S) -sulfur (SO4 2-) -nitrogen (NO3 -) -manganese (Mn 4+) -arsenic (AsO4 3-)
Role of bacteria in sulfur cycle
SO4 taken up by plants
Reduced to forms (-SH molecules) that can be used to make amino acids (ex. Cysteine)
Animals get S from food
H2S is rapidly oxidized to sulfur in presence of O2
Toxic to eukaryotic organisms
Role of bacteria in nitrogen cycle
Nitrogen gas (N2) –> ammonia (NH3) –> Anammox
Anamoxx in Archaea: NH4+ + NO2- –> N2 + 2H2O
Ammonia –> nitrification (nitrite NO2-) –>nitrate (NO3-) –> denitrification
How are prokaryotes classified?
6 important groups
- proteobacteria
- Green bacteria
- cyanobacteria
- gram-positive bacteria
- spirochete
- chlsmydias
Prokaryotes is the what?
And bacteria is the what?
Prokaryotes is the domain
Bacteria is the classification
Have numerous evolutionary branches
Makes it difficult to define “species” when considering prokaryotes
What are the 2 subgroups of proteobacteria?
Gram-negative bacteria
Free-living gram-negative proteobacteria
Define gram-negative bacteria
- purple sulfur bacteria
- colour due to unique chlorophyll
- photoautotrophic or photoheterotrophic
Define free-living gram-negative proteobacteria
- chemoheterotroph
- intestinal bacteria (E.coli)
- some cause human disease
Name and define the subgroup of green bacteria
Gram-negative photosynthetic bacteria
- found in hot springs (photoautotrophic)
- marine and high salt environments (photoheterotrophic)
- distinctive chlorophyll compared to plants
- do not release oxygen as by-product of photosynthesis
Give the other name for and define cyanobacteria
Cyanobacteria=blue-green algae
- gram-negative aerobic photosynthetic prokaryotes
- responsible for oxygen-based life on earth (algae/plants)
- most morphologically diverse group of bacteria
- some species form colonies
- some species have specialized cell types
Define gram-positive bacteria
- primarily chemoheterotroph
- many pathogenic species (Bacillus anthracis, staphylococcus, streptococcus)
- some beneficial species (Lactobacillus–lactic acid fermentation–>pickles, yogurt)
Define spirochete
- gram-negative bacteria
- propelled by rotation of helically spiralled flagella
- enables movement in mud/sewage
- beneficial/harmless species
- found in human mouth
- in termite intestine that digest cellulose
- pathogenic species (syphilis)
Define Chlamydias
- gram-negative bacteria
- cell walls with membrane outside
- lack peptidoglycans
- intercellular parasites that cause disease in animals
What bacteria is tolerant to radiation and can break down radioactive waste?
Deinococcus radiodurans
What bacteria is tolerant to a high temperature, is used in PCR techniques to create copies of DNA, because DNA polymerase is so heat-stable?
Thermos aquaticus
Prokaryotes is the what?
Archaea is the what?
Prokaryotes is the domain
Archaea is the classification
What are some of the unique characteristics of archaea?
- some features like bacteria (prokaryotes, chromosomes, ribosomes
- some features like eukaryotes (histones, enzymes)
- some unique features (membranes, protein synthesis)
Bacteria: Nucleus and membrane bound organelles? DNA in circular form? Ribosome size? Photosynthesis with chlorophyll? Capable of nitrogen fixation? Capable of chemoautotrophy? Membrane lipids ester-linked?
NO YES 70s YES YES YES YES
Archaea: Nucleus and membrane bound organelles? DNA in circular form? Ribosome size? Photosynthesis with chlorophyll? Capable of nitrogen fixation? Membrane lipids ester-linked? Capable of chemoautotrophy?
NO YES 70S NO YES NO YES
Name and define the first group of euryarchaeota
Methanogens:
- methane generators
- low-oxygen environments
- obligate anaerobes in…anoxic sediments, large intestines of dogs/humans, hindguts of insects, rumen of livestock
Name and define the second group of euryarchaeotes
Halophiles:
- Highly saline environments
- aerobic chemoheterotroph
- obtain energy from sugars, alcohol, amino acids
- some use light as secondary energy source
Name and define the third group of euryarchaeotes
Extreme Thermophiles:
- heat loving
- hydrothermal vents, hotsprings
- tolerate temperatures of 70-95 degrees Celsius
Name and define the first group of crenarchaeota
Extreme thermophiles:
Higher optimal temperature range than euryarchaeota
Name and define the second group of crenarchaeota
Psychrophiles:
- cold loving
- temperatures between -10 to -20 degrees Celsius
- found in arctic and Antarctic oceans
Name and define the third group of crenarchaeota
Mesophiles:
-many plankton in cool marine waters
Define Korarchaeota
- recognized by samples of DNA sequences
- found in hydrothermal environments (never cultivated in lab)
- nothing is known about their physiology
Define Thaumarchaeota
- may be most abundant cells in ocean
- chemoautotrophs that use ammonia (Anammox reaction in nitrogen cycle)
Evolution of bacteria and archaea is a?
Intertwined network
What do prokaryote studies help us to understand?
- human mircobiome
- ecosystem process
- biotechnology
- bioprocessing
- biomimicry
