Introdução Vida Microbiana...

Question 1

Microbial Life/ Diversity

Answer 1

• diversity in microbial cells is the product of almost 4 billion years of evolution
• Microorgs differ in size, shape, motility, physiology, pathogenicity…
• Microrgs have exploited every conceivable means of obtaining energy from the environment
• Microbes are found in almost every environment imaginable –> Extremophiles are Bacteria and Archaea that can grow in extremely harsh environments (Very hot/ cold; Very acidic/caustic; Very salty/ osmotically stressing; Very high pressure)

Question 2

Life on Earth through the ages

Answer 2

1. First cells appeared between 3.8 and 3.9 billion years ago
2. The atmosphere was anoxic until ~2 billion years ago
3. Metabolisms were exclusively anaerobic until evolution of oxygen- producing phototrophs
4. Life was exclusively microbial until ~1 billion years ago

5.Last universal common ancestor (LUCA): common ancestral cell from which all cells
descended –> Bacteria, Archaea & Eukarya

Question 3

Evolution, Phylogeny

Answer 3

Evolution
–> process of change over time that results in new varieties + species of organisms

Phylogeny

• -> Evolutionary relationships between orgs
• -> Relationships can be deduced by comparing genetic information in the different specimens: rRNA is excellent for determining phylogeny

__> Relationships visualized on a phylogenetic tree

Question 4

Why rRNA?

Answer 4

(1) universally distributed (2) functionally constant (3) highly conserved (slowly changing)
(4) adequate length to provide a deep view of evolutionary relationships

• -> Comparative rRNA sequencing has defined 3 distinct lineages of cells called domains:
• Bacteria (prokaryotic)
• Archaea (prokaryotic)
• Eukarya (eukaryotic)

Archaea and Bacteria are NOT closely related; Archaea are more closely related to Eukarya than Bacteria

Question 5

Horizontal gene transfer

Answer 5

transfer of genetic info between orgs vertical inheritance from parental organism(s).
May be extensive in nature. May cross phylogenetic domain boundaries

Transformation
Transduction
Conjugation

Question 6

Amplifying DNA

Answer 6

Polymerase chain reaction (PCR): method that produces multiple copies of DNA in vitro

–> PCR can amplify a target DNA fragment 1,000,000,000-fold from small amount of template

• -> UsesDNApolymerase
• -> Conceived by Kary Mullis (1988)
• -> performed in a thermocycler
• -> w/ Thermus aquaticus polimerase
• -> 3 steps: denaturation (1min, 94ºC) , annealing (45s, 54ºC, forward and reverse primers!), extension (2min, 72ºC, only dNTPs)
• -> takes only a few hours; exponential amplification

Applications of PCR:

• Phylogenetic studies
• Surveying dif groups of environmental orgs
• Amplifying small amounts of DNA
• Identifying a specific bacteria
• Looking for a specific gene
• Amplify DNA from mummified remains, fossilized plants and animals

Question 7

Prokaryotic Cells

Answer 7

• generally have a single, circular DNA molecule = chromosome
• DNA aggregates to form the nucleoid region
• may have small amounts of extrachromosomal DNA = plasmids –> confer special properties (e.g., antibiotic resistance)

Question 8

Properties of Cells

Answer 8

ALL CELLS:
metabolism (genetic & catalytic)
growth
evolution

SOME CELLS:
differentiation
communication
genetic exchange
motility