Microbial Evolution and Systematics (lec 11)

Origin of Life

• Prebiotic soup did not contain life forms, but it did contain organic compounds, water, and energy sources.
• The most likely origin of the first self-replicating systems is the RNA world hypothesis.
• Phosphorus is a component of certain essential cofactors and molecules.
• The primary function of RNA in early cellular life was to store and transmit genetic information.
• The major source of carbon for the earliest life on Earth was carbon dioxide.
• The event that led to the accumulation of O2 in the Earth's atmosphere was oxygenic photosynthesis.
• The criteria currently used to determine how closely related organisms are include comparative morphology, comparative embryology, and molecular biology.

Early Life on Earth

• Cellular life is believed to have evolved around 3.5-4.5 billion years ago.
• Early geological evidences of life include fossilized stromatolites, which are layered structures created by ancient bacteria.
• The subsurface origin hypothesis suggests that life originated deep in the Earth's crust.
• The main function of compartments in the origin of life was to provide a protected environment for chemical reactions.

Molecular Biology

• Molecular clocks are characterized by a constant rate of mutation over time.
• The best type of sequence to compare when using molecular clocks is a highly conserved sequence.
• 16S rRNA genes are characterized by a high degree of conservation and are often used in molecular clocks.
• A phylogenetic distance map from the 16S ribosomal RNA sequence shows the evolutionary relationships between organisms.
• Horizontal gene transfer is characterized by the transfer of genes between organisms other than by vertical inheritance.
• The purpose of multilocus sequence typing (MLST) in distinguishing between strains is to compare multiple genetic loci.

Genomics and Genome Evolution

• The core genome refers to the set of genes shared by all members of a species.
• The selective advantage of a reduced genome size is increased efficiency and reduced energy requirements.
• The endosymbiotic hypothesis suggests that mitochondria and chloroplasts originated from ancient bacteria.
• Mitochondria and chloroplasts have their own circular genomes.
• The function of chloroplasts is to carry out photosynthesis.
• The function of mitochondria is to generate energy for the cell through cellular respiration.
• Carl Woese revolutionized the organization system of domains from microbial organisms.

Symbiosis

• Mutualism is an example of symbiosis, in which both organisms benefit.
• Endosymbiosis is a type of symbiosis in which one organism lives inside another.
• Alpha-proteobacteria are believed to have undergone endosymbiosis to originate Eukaryotes.