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

Much more complexMostly PeptidoglycanTwo main categories of

bacteria

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.

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)

R – plasmid strain

Antibiotic resistance

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 are…..

1. Decomposers

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 …

1. Bioremediation

2. Industry

3. Genetic Engineering

4. Making of synthetic species