Microbial Origins of Life and Energy Conversions. Biol 251. Terms to Know for this Lecture. Science – Questioning Religion - Believing Fact – What most experts agree on… often becomes dogma (essentially the truth) Truth – What is… does anyone really know what truth is? Inherent bias….
Microbial Origins of Life and Energy Conversions
often becomes dogma (essentially the truth)
The “Big Bang” and Earth
Oldest sedimentary rocks, Greenland 3.8 bya
[CH4] [CO2] [H2O]
Atmosphere is warm
2.3 bya photosynthetic
3.5 bya anaerobic
lithotrophic and or
Atmosphere is cold
2.4 bya origin of
The primitive Earth was hot (>100°C), anaerobic with warm oceans
Simple organic molecules formed from atmospheric gases (CO2, NH3, H2S, CH4, HCN and CO) and dissolved in the oceans
Lightning, heat & UV light - energy
sugars, amino acids, nucleotides,
How do simple organic molecules form a protocell?
Laboratory experiments that attempt to address how cells developed
This experiment has been modified over the last 50 years and has yielded all 20 amino acids, nucleotides, lipids, sugars and ATP
4 parts to name
1. How they get energy (chemo- versus photo-)
2. Where they get electrons from? Organic versus
inorganic molecules (organo- versus litho- (rock eater)
3. Where do they get their carbon from? Auto- (CO2) versus hetero- (organic carbon source- e.g., glucose)
4. Add troph…
Banded domes of sedimentary rock similar to layered mats of heterotrophic bacteria & cyanobacteria
Stromatolites in western Australia
3.5 billion years old
microscopic resemblance to
The Origin of Prokaryotes
Divisions reminiscent of membranes or cell walls
The oldest eukaryotic fossils are 2.1 bya
How did organelles develop?
Node - LUCA
Last Universal Common Ancestor
Archaea or Bacteria?
Water temperatures >350°C
Tremendous diversity of
marine organisms surrounding
Minerals precipitate out of sea water
“Black Smoker” … smoke is
precipitate of metal sulfides from H2S
Global Energy Conversions –Microbes Rule the Earth!!
Microbes comprise nearly half of all biomass on Earth
All habitats that support plants and animals have abundant populations of microorganims.
Microorganisms also exist in habitats too extreme for plants and animals.
Prokaryotes are the most abundant form of life on Earth
Greatest amount of biomass and total numbers of species
Prokaryotes compose 90 % of the total combined weight of all organisms in the oceans
> 109 bacterial cells are present in 1.0 g of agricultural soil
Outnumber all eukaryotic cells by 10,000 : 1
are currently recognized
The main role of microorganisms in the biosphere is to act as catalysts of biogeochemical cycles.
Microorganisms catalyze reactions that cycle C, N, O, P and many other elements.
The Carbon Cycle
The Carbon Cycle
Free Living Nitrogen-Fixing Organisms
Symbiotic Nitrogen Fixing Organisms
Rhizobium & Bradyrhizobium
Symbiotic association with legume roots
N2 + 8H+ + 8e- + 16 ATP 2NH3 + H2 + 16 ADP + 16 Pi
Nitrification – ONLY in
Denitrification – ONLY in prokaryotes
NO3- NO2- N2O N2