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19. CLASSIFICATION: Bacteria


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Last update: 01.I.2003 (edited J)

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MAIN TOPICS OUTLINE

19.1 General Characteristics

19.2 Classification & Classification Criteria

19.21 Cell Wall Chemistry
19.22 Feeding Behavior
19.23 Cell shape

19.3 Archaebacteria

19.4 Eubacteria

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LECTURE OBJECTIVES

1. Distinguish between prokaryotes and eukaryotes.
2. Outline the characteristics of the bacteria.
3. Discuss some criteria used in classifying bacteria.
4. Know the major classification groups of bacteria.
5. Describe the principal shapes of true bacteria, give some examples of each, and list some beneficial and harmful effects, including some commercial uses of bacteria.
6. Give some examples of cyanobacteria.
7. Give some examples of archaea, and discuss some unique feeding and living requirements.
8. Define selected key terms.
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Key Terms:

def. Aerobic: Living or occurring only in the presence of free oxygen.
def. Anaerobic: Living or occurring only in the absence of free oxygen.
def. Antibiotic: Substance produced by certain microorganisms that can kill or inhibit bacteria.
def. Autotrophs
(ecology): Organisms capable of producing their own food from inorganic materials and using sunlight as energy source to do so (or another environmental energy source).
def. Bacillus (pl. Bacilli): Rod shaped bacteria

def. Binary fission: Asexual reproduction in bacteria and protista.
def. Cellulose: Material in eukaryotic cell walls (a polysaccharide).
def. Coccus (pl. Cocci): Spherical bacterium
def. Conjugation: "Sexual reproduction" in bacteria and protista, a mechanism by which a donor cell transfers genetic material to a recipient cell (usually another bacteria).
def. Eukaryotic cell: A cell that possesses a nucleus and other organelles.
def. Extremophiles: Organisms that prefer to live in extreme environmental conditions.
def. Halophile: A type of archaebacterium that lives in extremely saline habitats.
def. Heterotrophs
(ecology): organisms incapable of producing its own food, and therefore depend directly or indirectly on producers (autotrophs) to meet their food requirements.
def. Nitrogen cycle
(ecology): A biogeochemical cycle by which nitrogen circulates the air, soil, water, and organisms of the earth.
def. Nitrogen fixation
(ecology): Process by which a few bacteria in the soil convert gaseous nitrogen (N2) to ammonia, which can be used by living organisms.
def. Pathogen: An infectious agent that can invade organisms, multiply in them, and cause disease.
def. Peptidoglycan: Material in bacterial cell walls -- combination of protein (a polypeptide) and a carbohydrate (polysaccharide).
def. Photosynthetic: The ability to photosynthesize.
def. Plasmid: Accessory ring of bacterial DNA, often used in genetic engineering.
def. Prokaryotic cell: Cell lacking the organelles found in eukaryotic cells.
def. Spirillum (pl. Spirilla): Spiral or corkscrew shaped bacterium.
def. Thermophile: A type of archaebacterium of unusually hot aquatic habitats, as in hot springs or near hydrothermal vents.

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19.1 General Characteristics
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• Viruses are NOT bacteria

Viruses: -- Non-cellular particles
-- Structure:
1. Nucleic acid (DNA or RNA)
2. Protein capsid (capsule)
3. Lipid envelope (sometimes)

Diseases caused by viruses cannot be treated with antibiotics



• All bacteria are prokaryotic. That is why diseases caused by bacteria can be treated with antibiotics.

def. Prokaryotic cell: Cell lacking the organelles found in eukaryotic cells.
def. Eukaryotic cell: A cell that possesses a nucleus and other organelles.


1. single-celled (unicellular)
2. prokaryotic
-- no nucleus
-- circular DNA and a plasmids in the cytoplasm
4. has cell wall with peptidoglycan (few exceptions)
5. anaerobic and aerobic
6. heterotrophic or autotrophic (contain chlorophyll)
7. small


• Bacteria can reproduce both sexually and asexually

def. Binary fission: Asexual reproduction in bacteria and protista.
def. Plasmid: Accessory ring of bacterial DNA, often used in genetic engineering.
def. Conjugation: "Sexual reproduction" in bacteria and protista, a mechanism by which a donor cell transfers genetic material to a recipient cell (usually another bacteria).


• Some bacteria are the only organisms that can live permanently w/o oxygen

def. Aerobic: Living or occurring only in the presence of free oxygen.
def. Anaerobic: Living or occurring only in the absence of free oxygen.


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19.2. Classification & Classification Criteria
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• The evolutionary relationships of the bacteria have not been sorted out, so bacterial classification is therefore artificial.

Often it is based on cell wall characteristics (see 19.21), or on the method of obtaining energy (see 19.22) -- sunlight or feeding, or on cell shape (see 19.23). Recently bacteria, formerly in the kingdom Monera, have been divided into two domains, Archaea and Bacteria, using RNA differences (19.24).

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19.21 Cell wall
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def. Peptidoglycan: Material in bacterial cell walls -- combination of protein (a polypeptide) and a carbohydrate (polysaccharide).
def. Cellulose: Material in eukaryotic cell walls (a polysaccharide).
def. Antibiotic: Substance produced by certain microorganisms that can kill or inhibit bacteria.

1. cell walls w/o peptidoglycan (Archaebacteria)
2. cell wall with peptidoglycan or no cell wall (Eubacteria)


• GRAM STAINING identification technique

(problem: the way different bacteria stain does not have much to do with their evolutionary relationships)

a. thick cell wall -- gram positive bacteria (purple stain)
b. thin cell wall -- gram negative bacteria (red stain)
c. no cell wall (no stain)


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19.22 Feeding behavior (method of obtaining nutrients)
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def. Photosynthetic: The ability to photosynthesize.
def. Autotrophs
(ecology): Organisms capable of producing their own food from inorganic materials and using sunlight as energy source to do so (or another environmental energy source).
def. Heterotrophs
(ecology): organisms incapable of producing its own food, and therefore depend directly or indirectly on producers (autotrophs) to meet their food requirements.
def. Pathogen: An infectious agent that can invade organisms, multiply in them, and cause disease.
def. Nitrogen fixation
(ecology): Process by which a few bacteria in the soil convert gaseous nitrogen (N2) to ammonia, which can be used by living organisms.
def. Nitrogen cycle
(ecology): A biogeochemical cycle by which nitrogen circulates the air, soil, water, and organisms of the earth.
def. Extremophiles: Organisms that prefer to live in extreme environmental conditions.
def. Halophile: A type of archaebacterium that lives in extremely saline habitats.
def. Thermophile: A type of archaebacterium of unusually hot aquatic habitats, as in hot springs or near hydrothermal vents.


• Cyanobacteria (autotrophic)

-- responsible for first introducing oxygen into Earth's primitive atmosphere. Also nitrogen fixers.

• Nitrogen-fixing bacteria (heterotrophic)

-- Nitrogen is a necessary element in proteins. The atmosphere has a lot of nitrogen gas (N2). Nitrogen gas cannot be used by living organisms to produce necessary proteins. Nitrogen gas must first be converted to a usable form, ammonia (NH3). A few kinds of bacteria (e.g., Rhizobium in root-nodules on legumes, and cyanobacteria) can do this conversion -- this is called "Nitrogen Fixation". Plants use the ammonia to make amino acids, proteins, and nucleic acids. The nitrogen fixed by nitrogen fixing bacteria is therefore the primary source of nitrogen on Earth.

• Extremophiles (heterotrophic)

-- bacteria living in environments with extreme conditions (e.g. strongly anaerobic conditions, high salt concentrations or temperatures that normally would kill living organisms.)


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19.23 Cell shape (for True bacteria -- the Archaebacteria do not fit well into these shapes)
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def. Bacillus (pl. Bacilli): Rod shaped bacteria
def. Coccus (pl. Cocci): Spherical bacterium
def. Spirillum (pl. Spirilla): Spiral or corkscrew shaped bacterium.



• Rod shape (e.g., Bacillus bacteria)

-- Bacillus thuringiensis
(economic importance: produces insect toxin used in a natural insecticide)
-- Bacillus anthracis
(disease causing: originally obtained fr certain domestic livestock,
used for biological ware fare)
-- Lactobacillus bulgaricus
(economic importance: yogurt production)
-- Rhizobium leguminosarum
(economic importance: nitrogen fixing in soil -- symbiotic with legumes)
-- Salmonella enteritidis
(disease causing: salmonella food poisoning)
-- Escherichia coli
(normal intestinal body flora, disease causing:
if in the wrong place or out of balance)
-- Vibrio cholerae
(disease causing: cholera)
-- Clostridium botulinum
(disease causing: botulism food poisoning -- fatal, due to a toxin)
-- Mycobacterium tuberculosis
(disease causing: tuberculosis -- chronic respiratory infection)



• Spherical shape (e.g., Coccus bacteria)

-- Streptococcus thermophilus
(economic importance: yogurt production)
-- Staphylococcus aureus
(disease causing: “regular” food poisoning, toxic shock syndrome, wound infections)
-- Streptococcus pyogenes
(disease causing: strep throat, rheumatic fever, wound infections)
-- Neisseria gonorrhoeae
disease causing: gonorrhea -- sexually transmitted)
-- Chlamydia trachomatis
(disease causing: eye infection, genital infection -- the most common sexually transmitted bacterial infection)



• Spiral shape (Spirochetes, Spirillum)

-- Treponema pallidum
(disease causing: syphilis -- sexually transmitted)
-- Borrelia burgdorferi
(disease causing: lyme disease -- transmitted by ticks)



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19.3 Archaebacteria (Domain: Archaea)
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-- cell walls lack peptidoglycan, all heterotrophic, many are extremophiles


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• Methanogens (sewage and swamp bacteria)
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-- produce methane (swamp gas)

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• Halobacteria (salt tolerant bacteria)
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-- halophiles (loves salt)


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• Thermophilic Archaebacteria (hot springs bacteria)
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-- some are extreme thermophiles, e.g., Pyrodictium occultum. Lives around deep sea volcanic vents at temperatures around 105°C (Å217°F), and is anaerobic. (At sea level water boils at 100°C, but due to deep-sea pressure water boils above 105°C at these locations.)


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19.4 Eubacteria (Domain: Bacteria)
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-- cell walls have peptidoglycan (or lack cell wall -- rare), autotrophic or heterotrophic


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• Autotrophic eubacteria
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i. Phylum Cyanobacteria (Blue-green bacteria / blue-green algae)

contain chlorophyll ---> photosynthesize ---> release oxygen

Oscillatoria
Anabaena
Nostoc
Gleocapsa


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• Heterotrophic eubacteria ("True" bacteria)
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These are the bacteria listed earlier under the various shapes:

3 shapes

Coccus (spherical)
Bacillus (rod shaped)
Spirillum (spiral shaped)


Economic importance:

• Decomposers (soil producers)
• Food industry (cheese, yogurt)
• Intestinal bacteria (aid digestion, produce vitamin K)
• Nitrogen-fixing bacteria (symbiotic relationships -- roots of legumes and bacteria)
• Pathogens: disease-causing microbes (problem with resistance to antibiotics)


Copyright 2002, 2003, 2004, Jan A. Nilsson. Web page layout and design © and intellectual property Jan A. Nilsson. All rights reserved. Reproduction of the whole or any part of the contents without written permission is prohibited. Page created 10.XII.2002, last updated 16.II.2004, most likely during the wee hours of the morning on a G3 PowerBook owned by Jan A. Nilsson.

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