Anthrax bacillus anthracis
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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.

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Anthrax Bacillus anthracis

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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

HIV

Viruses

Single or double stranded RNA or DNAwith a protein coat

Common cold, Ebola, HIV


Nonliving parasitic molecules

Viroids

Short, single strand of RNA w/o protein coat

Primarily infect plants

Viruses

Single or double stranded RNA or DNAwith a protein coat

Common cold, Ebola, HIV

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

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

See Fig. 27.12


Prokaryotes

Carl Woese’s 3 Domains of Life

Eukaryotes

NOTE: “Microbes” and “Prokaryotes” are not taxonomic categories

See Fig. 27.12


Prokaryotes

Carl Woese’s 3 Domains of Life

Eukaryotes

NOTE: Eukarya & Archaea are more closely related than either is to Bacteria

See Fig. 27.12


Prokaryotes

Carl Woese’s 3 Domains of Life

Eukaryotes

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

See Fig. 27.12


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 fossilsCyanobacteria > 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


MethanogensMethane-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

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

Structure


Bacteria

Cell wall – unique, peptidoglycan

Peptidoglycan - structural polysaccharides(sugars) cross-linked by peptides (chains of amino acids)

Structure


Two biochemical groups of bacteria:

outer

membrane

peptidoglycan


Two biochemical groups of bacteria:

outer

membrane

peptidoglycan

will stain

will not stain

Gram positive bacteria

Gram negative bacteria


Gram stainDistinguishes different cell wall types

Gram positiveStaphylococcus 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


flagella

Some prokaryotes have flagella(singular: flagellum)

Used for locomotion


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

Chromosome

Plasma membrane

Daughter cells are identical copies

(3)

(1)

(2)

(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

Transformation

Uptake of genetic material 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

Transduction

Transfer of genetic 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

Conjugation

Direct transfer of genetic 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

Louis Pasteur’s observations (1860s)

on decomposition disproved

spontaneous generation

Decomposition


Bacteria – Impacts on other organisms, including Human Society

Louis Pasteur’s observations (1860s)

on decomposition disproved

spontaneous generation

Decomposition


Bacteria – Impacts on other organisms, including Human Society

Louis Pasteur’s observations (1860s)

on decomposition disproved

spontaneous generation

Decomposition


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

Decomposition

Especially common in the cyanobacteria


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

Decomposition

Especially common in the cyanobacteria


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

N-fixation

Decomposition


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

N-fixation

Decomposition

Symbiosis

Mutualism

Rhizobium in the roots of a

soybean plant


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

N-fixation

Decomposition

Symbiosis

Mutualism, commensalism


Bacteria – Impacts on other organisms, including Human Society

Photosynthesis

N-fixation

Decomposition

Symbiosis

Mutualism, commensalism, parasitism


Bacteria are often agents of disease by producing toxins

E.g., Clostridium tetani, the species that causes tetanus by producing a toxin that interferes with nerve impulses and causes muscles to spasm


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

Photosynthesis

N-fixation

Decomposition

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

Photosynthesis

N-fixation

Decomposition

Symbiosis

Mutualism, commensalism, parasitism

What type of symbiont is Escherichia coli?

Some infectious strains cause disease


Bacteria – Impacts on other Organisms, including Human Society

Photosynthesis

N-fixation

Decomposition

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

No known pathogens!


Archaea

Many are extremophiles…


Archaea

Even so, archaea are not restricted to extreme habitats

Archaea account for 20-30% of marine microbial cells


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