Download Slide 1

Chapter 27: The Prokaryotes
Objectives
1. Learn about the prokaryotic
adaptations that make them
successful, including the diverse
metabolic pathways.
2. Learn how rapid reproduction
promotes genetic diversity.
3. The important role of molecular
biology in the classification of
prokaryotic organisms.
4. Role of prokaryotic organisms.
5. The impacts of prokaryotic
organisms on humans.
Shapes and Size
1. Three basic
Shapes
2. Unicellular
3. Small
4. Some grow and
thrive in colonies
Cell Surface Structures
-All have cell wall (Protection and keep from bursting in hypotonic solution)
-All cell walled organisms have trouble reproducing in hypertonic solutions
(Salt can be used in preservation of food)
-Bacterial Cell walls are made up of peptidoglycan not cellulose or chitin (plants)
-Archaeal prokaryote walls don’t have either peptidoglycan or cellulose but other polysaccharides.
-Antibiotics work on the peptidoglycan of bacteria --- Eukaryotic cells don’t have peptidoglycan
Mostly Peptidoglycan
Two main categories of
bacteria
Much more complex
Motility or Movement
-Flagella are the most common means of movement
-Most movement is random
-Some bacteria have been found to exhibit taxis or movement in response to stimulus
ex. Movement towards other organisms of the same species forming colonies
Internal Structure
-Lack membrane bound organelles including nucleus
-Have extensions of plasma membrane that performs metabolic functions
-Chromosomes are located in a nucleoid region and have less nucleic acid then Eukaryotic Cells
Prokaryotic cells also may have a plasmid which is a ring of DNA with only a few genes.
Key Features of Prokaryotic Reproduction
1.
Small in size
2.
Binary Fission
3.
Short Generations
4.
Endospores may
develop to ensure
transfer of genetic
material
-Dormancy
-Hard Shell
-Dehydrated
-Stores nucleic
acid
5.
Can evolve quickly
6.
Population sizes can
be in the trillions
Reproduction promotes Genetic Diversity
1. Rapid Reproduction + Mutations = Much Diversity
E Coli Example
E coli reproduce by binary fission yielding offspring of identical genomes. Mutations occur one in 10 million
cell divisions. There are approximately 200 billion new E coli cells in the human intestine daily. The
total amount of mutations per day equal 9 million.
2. Genetic Recombination results from combining DNA from two
different sources.
R – plasmid strain
Antibiotic resistance
Transduction
-Use of viral
phage
-Part of
Bacterial DNA
is incorporated
into viral DNA
-New viral
DNA inserts
DNA into new
host
Conjugation – When two bacteria are linked by
a mating bridge – Donor cell extends Sex pilli.
***Note – Not all cells are donors (p. 563)
-Sex Pilli are formed by a fertility gene or F –
factor
- F – factors can be found either in the plasmid
(F+) or in the chromosomes (Hfr)
Bacteria use a variety of ways to gain energy and carbon
needed to make necessary organic molecules.
Role of Oxygen
1.
Obligate Aerobes –
need and use O2
2.
Obligate anaerobes –
are poisoned by O2
3.
Anaerobic Respiration
– use NO3-1 or SO4-2
instead of O2 as an
electron receptor
4.
Facultative Anaerobic
Respiration will use
O2 if present
Bacteria also cooperate
in colonies
-Some form biofilms
Archaea
-Methanogens – Anaerobes that
produce methane gas.
-Extremophiles – lovers of extreme
environments
-Thermophiles – heat loving
-Halophiles – salt loving
Eukarya
(p. 569)
-Gram +
-Gram –
-Cyanobacteria – only
photosynthesis process
that resembles plants.
Bacteria form ecological interactions like…
1.
Mutualism
2.
Commensalism – most bacteria on/in your body
3.
Parasitism/pathogens – disease causing
-Exotoxins – produced and excreted by bacteria
-Endotoxins – produced by breakdown of dead
bacteria’s cell walls
Bacteria are essential in
…
Bacteria are…..
1.
Decomposers
1.
Bioremediation
2.
Industry
3.
Genetic Engineering
4.
Making of synthetic
species