Prokaryotes and Metabolic Diversity

Document Sample
Prokaryotes and Metabolic Diversity Powered By Docstoc
					Anthrax

Bacillus anthracis

Cutaneous anthrax

Microbial Diversity
Chapt. 27 – Prokaryotes and the Origins of Metabolic Diversity
& Chapt. 28 – The Origins of Eukaryotic Diversity

What are microbes?
Single-celled organisms and some non-cellular parasites

Kinds of microbes
Non-cellular, parasitic molecules
Viruses Viroids Prions

Prokaryotes
Domain Bacteria Domain Archaea

Eukaryotes
Several Kingdoms in Domain Eukarya

Nonliving parasitic molecules
Viruses Single or double stranded RNA or DNA with a protein coat Common cold, Ebola, HIV
HIV

Nonliving parasitic molecules
Viruses Single or double stranded RNA or DNA with a protein coat Common cold, Ebola, HIV Viroids Short, single strand of RNA w/o protein coat Primarily infect plants Prions Protein particles w/o genetic material Kuru, mad cow, chronic wasting disease

Kinds of microbes
Non-cellular, parasitic molecules
Viruses Viroids Prions

Prokaryotes
Domain Bacteria Domain Archaea

Eukaryotes
Several Kingdoms in Domain Eukarya

Carl Woese’s 3 Domains of Life

See Fig. 27.12

Based primarily on genetic sequence data; e.g., small subunit ribosomal RNA – present in all organisms

Carl Woese’s 3 Domains of Life
Prokaryotes Eukaryotes

NOTE: “Microbes” and “Prokaryotes” are not taxonomic categories
See Fig. 27.12

Carl Woese’s 3 Domains of Life
Prokaryotes Eukaryotes

NOTE: Eukarya & Archaea are more closely related than either is to Bacteria
See Fig. 27.12

Carl Woese’s 3 Domains of Life
Prokaryotes Eukaryotes

See Fig. 27.12

Even so, Archaea & Bacteria share more structural & functional properties than either does with Eukarya

Microbes are microscopic, but very diverse & extremely abundant
Bacteria on the tip of a pin

Relative sizes of microbes

Prokaryotes
Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles

Prokaryotes
Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles First organisms on Earth – at least 3 billion years ago

The oldest known fossils
Cyanobacteria > 3 billion years old

Prokaryotes
Domains Bacteria & Archaea Simple cells – with no nucleus or membrane-bound organelles First organisms on Earth – at least 3 billion years ago Distributed globally – including many extremophiles

Extreme Thermophiles
“Heat-loving” Archaea

Extreme Halophiles
“Salt-loving” Archaea

pink color due to halophiles

Australian Salt Lake

Methanogens
Methane-generating Archaea
Occur in oxygen-free habitats E.g., swamp mud, guts of ruminant animals

Ice Bacteria & Archaea

Cave Bacteria
Sometimes reaching acidity of pH 0.5

Prokaryotes
Domains Bacteria & Archaea Simple cells – with no nucleus or organelles First organisms on Earth – at least 3 billion years ago Distributed globally – including many extremophiles Nutrition – autotrophs & heterotrophs

Prokaryote Nutrition
All organisms require a source of energy & carbon

Autotrophs can obtain all their C from CO2

Prokaryote Nutrition
All organisms require a source of energy & carbon

Heterotrophs require at least one organic nutrient, e.g., glucose

Prokaryote Nutrition
All organisms require a source of energy & carbon

Phototrophs obtain their energy from the sun

Prokaryote Nutrition
All organisms require a source of energy & carbon

Chemotrophs obtain their energy from chemical compounds

Bacteria
Structure
Systematic / phylogenetic relationships among bacteria are based on genetic data, but structural properties are indispensable for identifying them

Bacteria
Structure
Cell wall – unique, peptidoglycan Peptidoglycan - structural polysaccharides (sugars) cross-linked by peptides (chains of amino acids)

Two biochemical groups of bacteria:
peptidoglycan
outer membrane

Two biochemical groups of bacteria:
peptidoglycan
outer membrane

will stain

will not stain

Gram positive bacteria

Gram negative bacteria

Gram stain
Distinguishes different cell wall types Gram positive Staphylococcus aureus Gram negative Escherichia coli

3 common bacterial shapes:
Cocci- spheres Bacilli- rods

Spirilli- spirals

Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer

E.g., slime layer allows bacteria to cling to tooth enamel or other substrates

Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer

Pili & Flagella

Pili (singular: pilus)
Protein filaments that attach bacteria to other cells & substrates

pili

Some prokaryotes have flagella
(singular: flagellum) Used for locomotion flagella

Base of a bacterial flagellum…
…the only known wheel in nature

50 nm

Fig. 27.6

What is “taxis”?
Motility allows some bacteria to move towards or away from stimuli Phototaxis Chemotaxis Magnetotaxis

Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer

Pili & Flagella Circular DNA molecule & plasmids

Bacteria
Reproduction
Asexual, through binary fission

Binary fission
Daughter cells are identical copies
Chromosome

Plasma membrane

(1)

(2)

(3)

(4)

(5)

(6)

Neither mitosis nor meiosis occurs in prokaryotes

Binary fission
E. coli

DNA

cell wall

Bacteria
Reproduction
Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes

Bacteria
Reproduction
Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Uptake of genetic material Transformation
from the environment

Bacteria
Reproduction
Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Transformation Transfer of genetic Transduction

material between prokaryotes by viruses

Bacteria
Reproduction
Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Transformation Transduction Direct transfer of genetic Conjugation
material from one prokaryote to another

Conjugation in E. coli
Sex pilus connects cells and draws them together Conjugation tube then forms

Sex pilus

Bacteria
Surviving harsh conditions
Endospore – forms inside a bacterium and then persists through inhospitable conditions

endospore

Bacteria – Impacts on other
organisms, including Human Society
Decomposition

Bacteria – Impacts on other
organisms, including Human Society
Decomposition
Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation

Bacteria – Impacts on other
organisms, including Human Society
Decomposition
Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation

Bacteria – Impacts on other
organisms, including Human Society
Decomposition
Louis Pasteur’s observations (1860s) on decomposition disproved spontaneous generation

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis
Especially common in the cyanobacteria

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis
Especially common in the cyanobacteria

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis N-fixation

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism
Rhizobium in the roots of a soybean plant

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism

Bacteria – Impacts on other
organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism

Bacteria are often agents of disease by producing toxins
causes tetanus by producing a toxin that interferes with nerve impulses and causes muscles to spasm

E.g., Clostridium tetani, the species that

Bacteria are often agents of disease by producing toxins
Robert Koch (late 1800s) was the first person to link diseases to specific species of bacteria
The “Germ Theory” revolutionized medicine in the early 20th century Koch’s Postulates guide the identification of disease agents:
1. Find the same pathogen in each victim 2. Isolate the pathogen & grow it in pure culture 3. Induce the disease in a healthy individual from culture 4. Isolate the same pathogen after disease occurs

Bacteria – Impacts on other
Organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism
What type of symbiont is Escherichia coli?
Normal strains provide K & B-complex vitamins

Bacteria – Impacts on other
Organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism
What type of symbiont is Escherichia coli?
Some infectious strains cause disease

Bacteria – Impacts on other
Organisms, including Human Society
Decomposition Photosynthesis N-fixation Symbiosis Mutualism, commensalism, parasitism Bioremediation
Oil spills, mine tailings, heavy metal dumps, etc.

Archaea
Structure
Several basic biochemical differences distinguish them from Bacteria E.g., No peptidoglycan in their cell walls

Archaea

Archaea
Many are extremophiles…

Archaea
Even so, archaea are not restricted to extreme habitats

Archaea account for 20-30% of marine microbial cells


				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:379
posted:4/18/2008
language:English
pages:70