Notes on The Bacteria Eubacteria and Archaebacteria | BIOL 1110 | Papers Biology

biol1110_bacteria(eubacteria&archaebacteria) 6/23/04

BIOL 1110 REEDER

THE BACTERIA (EUBACTERIA AND ARCHAEBACTERIA)

I. Bacteria

A. General Characteristics

1 Believed to be the oldest life forms

a. Oldest fossils found to date: 3.8 billion years old resembling contemporary

photosynthetic blue-green bacteria (stromatolites)

2. Are the simplest and most abundant microorganisms

3. Inhabit every possible place where life can be found including in or on other organisms:

a. relatively few places in the world devoid of bacteria

b. tremendous biological success due to small size, reproductive ability, rapid rate of

mutation, ability to live almost anywhere, and form capsulated spores in a state of

suspended animation during unfavorable environmental conditions

4. Lack membrane-bound organelles and the genetic material is contained in a single circular

DNA molecule in the cytoplasm (nucleoid: haploid), not surrounded by a nuclear membrane:

PROCARYOTIC

a. Small amounts of genetic information may be present as smaller DNA molecules called

plasmids which replicate independently of the chromosome and often bears genes

involved in antibiotic resistance; subject of Recombinant DNA research; extra-

chromosomal DNA

5. Generally are smaller than eucaryotic cells, which may be attributed to the lack of cellular

organelles; [um (micron) = 0.001mm]

a. Procaryotes: 1 to 10um

b. Eucaryotes: few smaller than 7um

6. Very rapid growth and division, which often exceed a billion cells per milliliter of growth

medium

a. Because of rapid growth rates, genetic variability as a result of mutation is considerable

B. Taxonomy

1. Kingdom Eubacteria (holds principal forms)

a. Bacteria; formerly Kingdom Monera or Prokaryotae

b. Includes blue-green bacteria ("algae") or cyanobacteria

2. Kingdom Archaebacteria

a. Biochemically, are different from the other bacteria

1) Absence of peptidoglycan from their cell walls

2) Appear to be adapted to conditions characteristic of early earth (extreme

environments) particularly with extreme temperatures

b. Three major ecological subgroups:

1) Methanogens: anaerobic, deriving energy (ATP) from CO2 and H2 to CH4 (methane);

inhabit swamps, sediments and animal intestinal tracts

2) Halophiles: can live only in extremely salty environments (hypertonic); most are

aerobic heterotrophs; some are photosynthetic

3) Thermoacidophiles: normally grow in hot, acid environments as hot sulfur springs

near volcanic vents at the ocean floor or near waste piles of coal mines

C. Bacterial Form and Function

1. Characteristic cell shape that is maintained by a rigid cell wall in most forms

a. Common shapes

1) Coccus

(cocci, pl.): spherical

2) Bacillus (bacilli, pl.): rod-like or cylindrical; most bacterial species

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BIOL 1110 REEDER THE BACTERIA (EUBACTERIA AND ARCHAEBACTERIA)

I. Bacteria A. General Characteristics 1 Believed to be the oldest life forms a. Oldest fossils found to date: 3.8 billion years old resembling contemporary photosynthetic blue-green bacteria (stromatolites)

Are the simplest and most abundant microorganisms
Inhabit every possible place where life can be found including in or on other organisms: a. relatively few places in the world devoid of bacteria b. tremendous biological success due to small size, reproductive ability, rapid rate of mutation, ability to live almost anywhere, and form capsulated spores in a state of suspended animation during unfavorable environmental conditions
Lack membrane-bound organelles and the genetic material is contained in a single circular DNA molecule in the cytoplasm (nucleoid: haploid), not surrounded by a nuclear membrane: PROCARYOTIC a. Small amounts of genetic information may be present as smaller DNA molecules called plasmids which replicate independently of the chromosome and often bears genes involved in antibiotic resistance; subject of Recombinant DNA research; extra- chromosomal DNA
Generally are smaller than eucaryotic cells, which may be attributed to the lack of cellular organelles; [um (micron) = 0.001mm] a. Procaryotes: 1 to 10um b. Eucaryotes: few smaller than 7um
Very rapid growth and division, which often exceed a billion cells per milliliter of growth medium a. Because of rapid growth rates, genetic variability as a result of mutation is considerable B. Taxonomy
Kingdom Eubacteria (holds principal forms) a. Bacteria; formerly Kingdom Monera or Prokaryotae b. Includes blue-green bacteria ("algae") or cyanobacteria
Kingdom Archaebacteria a. Biochemically, are different from the other bacteria

Absence of peptidoglycan from their cell walls
Appear to be adapted to conditions characteristic of early earth (extreme environments) particularly with extreme temperatures b. Three major ecological subgroups:
Methanogens: anaerobic, deriving energy (ATP) from CO 2 and H 2 to CH 4 (methane); inhabit swamps, sediments and animal intestinal tracts
Halophiles: can live only in extremely salty environments (hypertonic); most are aerobic heterotrophs; some are photosynthetic
Thermoacidophiles: normally grow in hot, acid environments as hot sulfur springs near volcanic vents at the ocean floor or near waste piles of coal mines C. Bacterial Form and Function

Characteristic cell shape that is maintained by a rigid cell wall in most forms a. Common shapes

Coccus (cocci, pl.): spherical
Bacillus (bacilli, pl.): rod-like or cylindrical; most bacterial species

Spirillum (spirilla, pl.): helical or spiral; also called a spirochete b. Majority are unicellular with some cocci and rod forms linked together as a chain or in filaments (ribbon-like string of cells); colonial c. Cell wall not of cellulose but of other polysaccharides linked with polypeptides forming a tough molecular mesh: PEPTIDOGLYCAN
Primary function of the cell wall is to provide a strong, rigid structural component that can withstand the osmotic pressures caused by the high chemical concentrations of inorganic ions in the cell.
Without the cell wall, a bacterium under normal environmental conditions would take up water and burst (lysis in a hypotonic solution).

1. Most bacterial cell walls composed of peptidoglycan

The action of many antibiotics is directed at the point of synthesis of the bacterial cell wall resulting in its destruction: penicillin, ampicillin, amoxicillin

Cell membrane is very similar in structure to that of eucaryotes (procaryote lacks sterols).
Motile and nonmotile forms a. Some bacteria with flagellum: single or in bundles of flagella at one cell end, or flagella distributed over the entire surface; flagella is different in structure from the eucaryotic type. b. Blue-green bacteria lack flagella, but may exhibit a slow, gliding motion c. Axial filaments in spirochetes d. No forms with cilia
Other Surface Structures a. Capsules: externally secreted jellylike layer providing some protection against phagocytes for pathogenic forms although some nonpathogenic forms possess them; may serve as reserve food b. Fimbrae/Pili (pl.): external, filament-like appendages of some bacterial species functioning for adherence to a surface or other cells; involved in sexual conjugation of some forms; some pathogenic forms utilize them to resist phagocytosis although nonpathogenic forms may contain them as well
Symbiotic types: different species living together beneficial to at least one participant: normal flora of the body a. Commensalism: neither help nor harm the host; most symbionts are of this type; normal flora of humans b. Parasitic: live at the host's expense and may be pathogenic (disease causing) c. Mutualistic: benefits both organisms
Metabolism: tremendous variety in procaryotes

a. Most bacteria are heterotrophic; principally by utilizing external digestion followed by absorption, energy and nutrients are acquired from an external source
- 1. Majority are free-living saprobes (saprotrophic): nourishment from dead or dying organic matter (decomposition)
1. May utilize aerobic or anaerobic metabolic pathways a) Many species may switch back and forth when conditions change b) Organisms utilize either fermentation (strictly anaerobic) or respiration (aerobic or anaerobic) for their ATP synthesis c) Fermentation is the least efficient d) Aerobic: require oxygen for cell respiration; called aerobes (1) Facultative anaerobes: use oxygen if available, or metabolize anaerobically if necessary; majority of microorganisms: E.coli in your intestines

E. Eubacteria: includes true bacteria and cyanobacteria

Most are not pathogenic, but are harmless decomposers (plant material, milk, yogurt and dairy products) and are found commonly on and in animals: the human mouth, vagina, colon, and skin.
Pathogenic forms include diptheria, typhoid fever, tuberculosis, "strep throat", scarlet fever, pneumonia, wound, skin and ear infections, food poisoning, toxic shock syndrome, respiratory tract infections and meningitis.
Are further subdivided into Gram-negative and Gram-positive groups: medical significance and identification a. Gram stain is a differential stain (reveals chemical differences in bacterial structure) that results from cell wall differences between the two groups 1) Most bacteria are Gram-negative b. Gram-positive bacteria: retains the purple stain; are generally more susceptible to antimicrobial agents than are gram-negative types l) Structurally have a much thicker peptidoglycan layer in their cell wall than do Gram negative types 2) Have capacity for endospore formation: Bacillus, Clostridium a) Are resistant to heat, radiation, and toxic chemicals b) Proper sterilization with autoclaves in which the elevated pressure raises the boiling point of water to 121 o^ C is needed to kill the endospores 3) Many produce exotoxins: Clostridia (tetanus, gangrene, and botulism), diptheria, food poisoning and toxic shock (Staphylococcus) 4) Infectious Examples: Bacillus (anthrax), Clostridium, (food poisoning or botulism and agents of tetanus and gas gangrene); Corynebacterium (diptheria); Listeria (meningitis and food poisoning); Staphylococcus (infections such as pimples, boils, food poisoning, endocarditis, meningitis, pneumonia, toxic shock syndrome, urinary tract infection); Streptococcus (upper respiratory tracts infections, scarlet fever, rheumatic fever, rheumatoid arthritis). c. Gram-negative bacteria: take the red stain; most bacteria 1) More complex cell walls a) Wall comprised of a "second" membrane (lipopolysaccharide) external to their thinner peptidoglycan wall layer b) The lipopolysaccharide component is toxic to animals (endotoxin) and is responsible for high fevers that accompany Gram negative infections 2) Examples: Escherichia coli: (benign and beneficial role in healthy people, but when ingested with food causes traveler's diarrhea); Enterobacter (urinary tract infections); Salmonella (food poisoning); Treponema (syphilis); Vibrio (cholera); Neisseria (gonorrhea and meningitis)
Spirochetes a. Free-living forms in freshwater and marine habitats, commensal forms, and parasitic b. Syphilis and Lyme disease are caused by a pathogenic spirochete
Actinomycetes (mold-like bacteria) filamentous a. Credited with much of the decomposition of soil organics b. Several species known to produce antibiotics (streptomycin, erythromycin, chloramphenicol, tetracyclines).
Mycobacteria a. Presence of higher lipid content in cell envelope give them a waxy appearance and make them difficult to stain plus greater survival due to environmental resistance b. Pathogenic forms cause human tuberculosis and Hansen's disease (leprosy)

Rickettsias a. Are obligate intracellular parasites transmitted mostly by arthropod vectors such as fleas, lice, ticks and mites b. Diseases caused by the few species known to be pathogenic to humans are typhus and Rocky mountain spotted fever
Cyanobacteria: blue-green bacteria a. Found in ponds, lakes, swimming pools, moist soil, dead logs, tree bark, oceans, and hotsprings b. Some species form thick-walled spores that are resistant to adverse conditions and may remain dormant for years c. Many species fix nitrogen: ability to convert atmospheric nitrogen (N 2 ) into inorganic forms (ammonium, nitrates) which are then used by plants; enriches the soil, thereby, increasing crop yields; plants depend on this process for their ability to synthesize proteins d. Cell specialization (division of labor) evident 1) Vegetative cells = photosynthesis and metabolism; somatic cells; generally non- reproductive 2) Spore producing cells 3) Specialized cells for substrate attachment 4) Heterocysts: nitrogen fixation (Anabaena, Nostoc) e. Extensive reproduction ("bloom") during favorable conditions (plentiful nutrients, high temperature, increased sunlight) can ultimately result in water pollution (loss of aesthetic appearance, and unpleasant smells; some also produce toxins that can kill aquatic life: fish kills) f. Producers ecologically (significant to the energy and nutrient base of an ecosystem) F. Ecological Importance of Bacteria
Decomposition and cycling of carbon, nitrogen, phosphorus and sulfur in both terrestrial and aquatic ecosystems (saprobes); share significance with fungi.
Nitrogen cycle: a. Nitrogen fixation: symbiotic relationship in certain plants' roots growing as nodules on beans, peas, clover and other legumes; converts atmospheric nitrogen (N 2 ) to ammonia (NH 3 ); Rhizobium, Anabaena, and Nostoc b. Nitrification: bacteria oxidize NH 3 to NO 2 and then to NO 3 c. Ammonification: nitrogen excreted in organism waste or dead tissues is released as NH 3 d. Denitrification: certain bacteria convert nitrates back into atmospheric nitrogen (N 2 ). G. Beneficial to humans:
Mutualistic in man's intestinal tract: in exchange for food and shelter, bacteria synthesize vitamin K and some B vitamins
Typically out compete successfully against pathogenic forms that occasionally may occur; significance of the body's normal flora
Production of certain chemicals and food: acetic acid, buttermilk, yogurt, acidophilus milk, green olives, pickles, sauerkraut, alcohols,
Recombinant DNA research: genetics (E. coli)
Increasing agricultural yields by soil enrichment (Nitrogen fixation, nitrification, ammonification)
Filamentous algal type used to synthesize antibiotics; called actinomycetes bacteria.
Used in environmental accidents involving toxic waste: cleanup method involving decomposition as in oil spills (bioremediation)

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