Bacteria

  Concepts/Ideas/Notes:

1.  only monerans can convert nitrogen gas into forms of nitrogen plants can use

Definitions:

  1. Mycoplasma – smallest known cells.  They consist of a plasma membrane, DNA, RNA, ribosomes, soluble proteins, sugars, and lipids.  They lack a cell wall.
  2. Gram-Positive Bacteria – bacteria that retain purple dye (stains purple) when subjected to gram staining.  The cell wall ranges from 15 to 80 manometers thick and consists of a single marcromolecule of peptidoglycan, which is not present in eukaryotes.  Gram-positive bacteria are susceptible to anti-biotics.
  3. Gram-Negative Bacteria – bacteria that does not retain purple dye (stains pink) when subjected to gram staining.  The cell wall is about 10 manometers thick and has an additional outer layer of large molecules of lipopolysaccharides, which encases the peptidoglycan layer.
  4. Comensals – normal human microbial flora
  5. Bloom – rapid increase in the population of blue-green bacteria
  6. Saprophyte – heterotroph that feeds on dead or decaying organic matter
  7. Chemoautotrophs – use the energy of chemical reactions to synthesize food.
  8. Nitrogen Fixation – process by which gaseous nitrogen (N2 ) is converted into ammonia compounds (nitrates)
  9. Obligate Anaerobes – bacteria that live only in the absence of oxygen (tuberculosis)
  10. Facultative Anaerobes – bacteria that can survive and grow without oxygen but grow more vigorously in oxygen’s presence.  (E. coli)
  11. Binary Fission – asexual process whereby the DNA in the cell replicates, then the plasma membrane and cell wall grow inward, forming two daughter cells with identical genetic material.
  12. Pathogen – organism that causes a disease
  13. Antibiotics – chemicals that are capable of inhibiting the growth of some bacteria
  14. Toxin –poisonous substances that disrupts the metabolism of the infected organism

A.     Endotoxin – toxins found in the cell wall of gram-negative bacteria.  Endotoxins cause the same symptoms:  weakness, fever, and damage to the circulatory system.  Typhoid fever is an example of a endotoxin.

    1. Exotoxins – products of bacterial metabolism, they are secreted into the area surrounding the bacteria.  Exotoxins are the most potent poisons known.  Diphtheria and botulism are two examples of exotoxins.

Kingdom Monera

Archaebacteria – gram-positive bacteria that form colonies of branching, multicellular filaments

Schizophyta – largest monera phylum

  1. Class Eubacteria – contains largest number and many of the most common bacteria.  Most are free-living soil and water bacteria and live in less harsh habitats than archaebacteria.
  2. Class Actinomycota – gram-positive, rod-shaped organisms that form colonies of branching multicellular filaments
  3. Class Riclettsiae – mostly non-motile intracellular parasites that are gram-negative and can only reproduce in certain cells of a specific hosts.  Often insect carried.
  4. Class Spirochaeta – contain large spiral-shaped or curved bacteria that use flagella to move.  Cause syphilis (genus Treponema) and Lyme disease (genus Borrelia).
    1. Genus Leptospira (slender spirals) – thin, tightly coiled, hooked-end, water-borne bacteria.  It favors hosts’ livers, brains, kidneys causing fever and jaundice and is spread by swallowing or through open cuts.
    2. Genus Treponema (turning threads) – must pass from host to host. T.  pallidum causes pinta, a skin disease of children spread by casual contact, yaws, nonveneral syphilis (bejel), and syphilis!
    3. Genus Borrelia – less tightly and uniformly coiled and most live in ticks that transmit to mammals and birds.  Causes Lyme disease.

Phylum Cyanophyta

  1. Class Cyanophytes – blue-green bacteria that are photosynthetic and produce oxygen.  Often encased in a jelly-like substance and often clump together in colonies.  Can produce heterocystss, cells that convert nitrogen from the atmosphere into a form the organisms can use.

Phylum Prochlorophyta

  1. Class Prochlorophytes – photosynthetic bacteria that live symbiotically with the marine chordates known as turnicates.

Bacteria – smallest and structurally simplest organisms.

Characteristics of Bacteria:

  1. lack organized nucleus surrounded by a nuclear envelope
  2. do not have complex chromosomes
  3. have a single circular  molecule of double stranded DNA, which is found in an area of the cytoplasm called the nucleoid
  4. do not reproduce sexually but by fission
  5. ribosomes and granular inclusions included in cytoplasm.
  6. never truly multicellular
  7. lack organelles surrounded by membranes
  8. cell wall consists of matrix of disaccharides cross-linked by short chains of amino acids
  9. reproduce by fission

Bacteria Classification:

  1. Bacilli – straight, rod-shaped bacteria that may form chains
  2. Spirilla – long, helically coiled bacteria
  3. Cocci – spherical-shaped bacteria that may form chains

Genetic Recombination in Bacteria:

  1. Conjugation – transfer off a portion of DNA molecule from one cell to another through a bridge formed between two bacteria by the pili.  A portion of DNA passes across the bridge and lines up with the homologous piece of DNA in the recipient cell. The homologous portion of DNA is destroyed and the new DNA is substituted.
  2. Transduction – the carrying of fragments of DNA into a cell by a virus
  3. Transformation – the entering of DNA into a cell by a solution

Characteristics of Archaebacteria:

  1. lack of muramic acid in cell walls
  2. lipid composition of the plasma membranes
  3. specific base sequences of rRNA

Groups of Archaebacteria:

  1. Methanogens – anaerobic bacteria that produce methane as their major metabolic product.  Common in sewage-treatment plants, bogs, ocean depths, and in the digestive tract of ruminant mammals.  Most natural gas reserves was created by methanogens.
  2. Halophiles – bacteria that occur everywhere salt concentrations are high
  3. Thermophiles – heat loving, sulfur-metabolizing bacteria which live in temperatures ranging from 70 to 105 degrees C.
  4. Thermoplasma – single genus containing a single species.  Thermoplasma lack a cell wall and are found only in very acidic, self-heating (32o to 80o C) coal refuse piles.

Characteristics of Cynobacteria:

  1. in cynobacteria glycogen is the main storage product
  2. most cynobacteria have a mucilaginous sheath
  3. cynobacteria played the decisive role in the increase of oxygen in the early atmosphere
  4. often form filaments
  5. cynobacteria living in aquatic environments have gas vacuoles which allow them to regulate buoyancy.
  6. cynobacteria may occur as symbionts within the bodies of other organisms

Bacteria Structure:

  1. Plasmid – small circular stands of DNA in cytoplasm that can replicate independently
  2. Capsules – protective layers of polysaccharides around the cell wall
  3. Glycocalyx – net of polysaccharides that helps a bacteria to stick to the surface of objects.
  4. Pili (pilus) – a shorter and thinner type of flagella found in some bacteria that may function during the exchange of genetic material and may be important in the attachment of bacteria to surfaces.
  5. Endospores – thick-walls manufactured by bacteria that enclose the DNA, which enable bacteria to survive extended periods stress.

Wood Roots/Prefixes/Suffixes

Strepto – filament

Staphylo – cluster

Glyco – means sweet

Calyx – means cup

ILLUSTRATIONS of  BACTERIA

BACTERIA PICTURES