2 - Evolution And Diversity Flashcards
Surface origin hypothesis
‘Warm little pond’
- Primordial soup - evidence that organic molecules can form spontaneously)
- Unlikely due to hostile conditions on surface?
- High UV, meteor strikes, volcanic activity
Subsurface origin hypothesis
Hydrothermal vents at ocean floor
More stable conditions than surface (high UV, meteor strikes etc.)
Constant source of energy (reduced inorganic compounds)
Origins of cellular life
- key features
Cellular life arises around inorganic ions and other compounds (Oxygen, CO2 etc.)
- no organic starting material
Key features:
- Self replicating RNA (RNA world, ribozymes)
- Enzymatic proteins - from mutations in RNA ribozymes
- DNA - genetic code - as RNA is very unstable - DNA more stable, less chemically active
- Evolution of biochemical pathways (respiration etc.)
- Divergence of lipid biosynthesis
- Divergence of cell walls - increased chance of survival in more adverse conditions
- all features allow something like bacteria or archaea to exist
Ribozyme def
Something that can catalyse chemical reactions
- e.g. ribosomes - uses RNA in its processes
Landmarks in biological evolution
- early life dependent on H2 and CO2 - used to make acetate and methane
- bacteria making acetate
- archaea making methane
- energy and carbon metabolisms diversify
- phototrophy - using H2S as electron donor
- evolved into oxygenic photosystem using H2O
- this started oxygenation of atmosphere
- first eukaryotes will start to develop and use oxygen as final electron acceptor for respiration
Methanogenesis equation
(Production of methane)
CO2 + 4H2 —> CH4 + 2H2O
Anoxygenic photosysnthesis
H2S —> S0 + 2H
- reduction of hydrogen sulfide
Oxygenic photosysnthesis equation
- how can enzymes do this
2H2O —> O2 + 4H
- not much change needed for enzymes involved in anoxygenic photosynthesis with hydrogen sulfide, to use water
(Oxygen in same group as sulfur)
Phylogenetic method analysis of DNA - example
- Isolate DNA from cells
- PCR to amplify DNA
- DNA sequencing
- sequence analysis
- generate phylogenetic tree by comparing relationship between DNA sequences
Marker molecules used in diversity studies
- what traits do they need
- certain molecular sequences are useful in phylogenetic analysis
- must be universal
- contain variable and conserved regions
- must not be subject to horizontal gene transfer
- must be truly homologous
- Ribosomal RNA genes are a universal molecular marker as they are present in all forms of life
- Present in LUCA
- Other markers: ATPase subunits, EF-Tu, RecA
What molecule usually used in phylogenetic trees and analysis
Ribosomal RNA - used in most sequencing
Endosymbiosis theory
A eukaryotic organism captures a prokaryote and incorporates it into its structure
- e.g. mitochondria and chloroplasts for respiration and photosynthesis
- carbon fixation in chloroplasts
Evolution of eukaryotes theories
Endosymbiont theory:
- Mitochondria - incorporation of aerobic chemo-organotrophic bacteria into a host (bacterial?) cell
- Chloroplasts: incorporation of photographic Cyanobacteria info a eukaryotic cell
Hydrogen hypothesis:
- association of an archaeal host using H2 as energy source with an aerobic bacterium that produced hydrogen as a ‘waste’ product
Are humans more related to archaea that live in harsh conditions or prokaryotes - bacteria
Archaea - look at phylogenetic tree
Aquifex aeolicus bacteria info
(Maybe not needed)
- isolated from a hot spring
- hyperthermophilic (grows in up to 95C)
- chemolithoautotroph - oxidised H2 to water using O2 as electron acceptor
- Autotrophic - Carbon fixation
Deinococcus radiodurans info (not needed)
- very radiation resistant
- isolate from canned meat sterilised by gamma radiation
- very rapidly reassembles radiation damaged DNA
- could be used for bioremediation as remains viable in radiation contaminated slides
Types of virus that affect bacteria
Bacteriophages (phages for short)
What are xenophyophores?
amoeba-like single-celled organisms that live exclusively in deep oceans
What commonly are archaea?
Extremophiles - usually live in harsher, more adverse conditions
- Some do not, though
Viruses info and how they function
They dont carry out metabolic processes - they are not living or cells
- can have genomes consisting of double or single-stranded DNA and RNA
- lack cytoplasmic membrane, cyroplasm and ribosomes
- instead take over metabolic systems of infected cells and turn them into vessels to produce more viruses
- they infect cells from all 3 domains
What microorganisms affect
- act as agents on infectious disease
- uses in agriculture and human nutrition
- food - spoilage, uses in fermentation, alcoholic beverages, etc.
- uses in industry - brewing in fermenters, mass production of antibiotics, enzymes, insulin etc.
- general uses in biotechnology
Microorganisms in Industry
all via fermentation + more:
- alcohol production
- enzymes (insulin)
- antibiotic production
- production of sustainable, clean biofuels, e.g. methane
- bioremediation - clean up industrial pollution, e.g. oil spills
- waste water treatment
- biofilms
- biotechnology
Of Hydrogen Hypothesis and Endosymbiosis, which is more recognised
Hydrogen Hypothesis (HH)
Hydrogen Hypothesis (HH) Explanation
archaea and bacterium were physically touching
- as archaea used H2 produced by bacteria as a waste product
- this makes a syntrophic relationship
- they were so close, that the archaea egulfed the bacteria completely
- this made the proto-eukaryotic cell, with the bacterium eventually becoming the mitochondrion
- this makes HH a syntrophy hypothesis
Proteobacteria info and examples
- Subdivided in alpha, beta, gamma, delta and epsilon Proteobacteria
- Extremely metabolically diverse
Phototrophs, chemolithoautotrophs, heterotrophs
examples of importamt pathogens include: - cholera - vibrio cholerae
- the plague - yersinia pestis
- E. coli - food poisoning
- Salmonella - food poisoning
- Pseudomonas aeroginosa - cytsic fibrosis
Archaea info
Produce methane as a waster product
- are at bottom of food chain
- degrade the degradation products of other organisms, such as CO2, acetate, methylated compounds
- so release vast amounts of methane into atmosphere
Cyanobacteria and plastids info
- blue green algae
- plastids were originally Cyanobacteria
- morphological diverse
- ## widely distributed - found in most water sources
Firmicutes info
Low G+C gram positives
- mostly heterotrophs
- some form spores
- medically and industrially important - cause infections, useful in food processing etc.
Chlamydia info
- Obligate intracellular parasites
- distinct life cycle
- important human pathogens
- can infect the eye
- STD, can lead to infertility
Spirochaetes info
- Helically shaped
- motile - they spin to bore through mucus membrane
- gram negative
- flagellum inside their cell - apical filament drives motility
Actinobacteria info
- High GC gram positives
- varied morphology/metabolism
- heterotrophs
- Streptomycetes are major producers of antibiotics
- pathogens include:
- leprosy
- M. tuberculosis
- diptheria
Protebacteria info
Halophilic archaea info
- organisms that grow in a saturate salt solution (30%>)
- 20 times saltier than sea water
- salt lakes and ponds and salt crystals in subsurface
- strange shapes and colours
- Walsh square ‘bacterium’
