BIO432 PROKARYOTIC DIVERSITY
Prof. Dr. Sevgi ERTUĞRUL KARATAY
INTRODUCTION
Many physical and geological changes have occurred in the world since its formation
New conditions and changes occurred in the world after microbial life was formed
Microbial activities (metabolism and physiology) caused many changes in today's biosphere.
The origin of the world
4.5 billion years ago compared to slow-degrading radioactive isotopes
New star (sun) caused nuclear fusion-heat and light energy
World not suitable for life .. (500 million years)
The water originated from volcanic gases and
comets in the planet, but in the form of steam due to the temperature.
A rock that could show the age of the world could not be identified (due to geological changes)
One of the oldest sediment rocks 3.86 billion years old have been found in southwest Greenland.
Mineral zircon crystals were found in old samples (ZrSiO4)
4.3 billion years ago it is believed that water concentrated in the form of the ocean
According to this, the world became suitable for life a few hundred million years after its formation.
Evidence of microbial life in the early World
Bacteria-like microfossils have been found in some old rocks (simple bacilli or cocci)
Microbial formations called “stromatolite” are very common in 3.5 billion years old rocks.
Stromatolite = fossilized filament prokaryote + stuck mineral material
Filamentous prokaryote = filamentous phototrophic bacteria, ancestors of example green sulfur-free
bacteria Chloroflexus
In summary, microfossils show:
1. There was a microbial life within 1 billion years or earlier after the World was formed.
2. And even microorganisms began to differentiate morphologically
Hypothesis of Formation of Life on Earth
The first cell, surrounded by membranes and self replicating, consists of a
primitive soup rich in organic and
inorganic compounds in a "warm little pond (Charles Darwin, On the origin of species).
This hypothesis is not possible. Because of sudden temperature change, meteor crash, radiation etc. makes the
formation hypothesis on earth impossible.
Formation hypothesis under the ground
Conditions are more favorable and stable in hydrothermal hot water sources
H2 and H2S permanent and abundant energy source
When very hot hydrothermal waters met ocean
waters containing cold and Fe, “montmorillonite”
clays containing Mg were formed. These are
structures with a jelly, absorbent surface, semi- permeable, closed and pores.
LUCA (Last Universal Common
Anchestor) started with this very
simple cell and evolved in two different directions (based on the
physicochemical properties in the niches where they were most
successful).
Then these two populations were
selected and today's cells were formed.
Some details differed as these two lineages evolved
