KINGDOM MONERA

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KINGDOM MONERA

• The Prokaryotes
• Archaebacteria and Eubacteria

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Characteristics of Bacteria

• Prokaryote means before a nucleus. They are
  single-celled organisms and the smallest,
  simplest organisms.
• This kingdom is subdivided into two kingdoms
• Archaebacteria- Found in anaerobic conditions
  with high salt concentrations, high temperatures
  and a low pH. These are believed to be the
  conditions on the primitive Earth. Earths early
  atmosphere didnt contain oxygen. (anaerobic)
  Scientists believe that all life kingdoms are
  descended from this group. Archabacterias phyla
  are based on their habitats.
• Anaerobic Methanogens- live in the gut of
  animals, swamps and marshes and produce all of
  the methane gas found in the Earths atmosphere.
  

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• Halophiles- salt-lovers found in salt lakes
  such as the Dead Sea.
• Thermophiles inhabit hot, acidic environments
  such as hot springs.
• ii. Eubacteria This group includes the
  traditional bacteria and is the largest and most
  successful of the two kingdoms.
• Eubacteria species have allowed scientists
  to separate them into six phyla.

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• Bacteria are the oldest and most abundant
  organisms living on the Earth. (i.e. 10mL of soil
  contains 1 bacteria.
• They are found in nearly every habitat studied,
  including habitats that no other organisms are
  able to withstand.
• Bacteria all share these five characteristics
• -All bacteria are single-celled
• -All bacteria are prokaryotes. Their DNA is not
  surrounded by a membrane.
• -Cell organelles in bacteria are not surrounded
  by membranes.
• -The DNA of bacteria is made of a single
  chromosome.
• -All bacteria reproduce asexually by binary
  fission.

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• Bacteria are the smallest organisms measuring
  from 1-10 micrometres.
• It contains a cell wall that provides support and
  protection for the contents of the cell.
• The cytoplasm contains ribosomes, responsible for
  the formation of proteins and DNA.
• The DNA forms a single chromosome and forms a
  ring rather than a strand.
• Some bacteria have a whip-like flagella that act
  like propellers moving the organism forward. Some
  are also covered by a slime capsule.
• Bacteria are classified by their shape, reaction
  to being stained, nutrition and respiration.

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Bacterial Cell Shape

• Bacteria can be classified by shape.
• -A spherical cell is called a coccus (pl. cocci)
• -A rod-shaped cell is called a bacillus (pl.
  bacilli)
• -A spiral-shaped cell is called a spirillum (pl.
  spirilla)

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• Cocci living as separate cells are called
  monococci, pairs are called diplococci, chains
  are called streptococci, and grapelike clusters
  are called staphlococci.
• Bacilli also exist as single cells, pairs
  (diplobacilli), or chains (streptobacilli).
• Spiral bacteria exist only as single cells.
• Staining bacteria results in two forms
  gram-positive (purple) vs. gram negative (pink).

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Nutrition

• Nutrition means obtaining energy and a source of
  carbon to produce the organic compounds needed
  for cellular metabolism.
• Most eubacteria are heterotrophs and obtain
  energy by breaking down organic molecules from
  their environment. Some are parasites, absorbing
  nutrients from living organisms. Others are
  saprobes, decomposing dead organic matter.
• Some eubacteria are autotrophs and produce their
  own organic compounds. (example- cyanobacteria
  (blue-green bacteria) are photoautotrophs using
  light for energy, but they lack true
  chloroplasts.

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Respiration

• Chemical reactions take place on the inner
  surface of the cell membrane so that gases can
  pass into and out of cells easily.
• All living things must carry out cellular
  respiration to receive energy. Bacteria differ
  in whether or not they require oxygen.
• If respiration requires oxygen, bacteria are
  termed aerobes. If oxygen is absolutely necessary
  for survival they are called obligate aerobes.
• Bacteria that carry out respiration without
  oxygen are called anaerobes. Presence of oxygen
  kills some bacteria and these are called obligate
  anaerobes. (example- Clostridium botulinum
  produces toxins that can cause an extreme form of
  food poisoning called botulism.)
• Another group of bacteria can survive with or
  without oxygen and they are called facultative
  anaerobes.

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Reproduction

• Bacteria reproduce asexually and divide by the
  process of binary fission. In binary fission, the
  parent cell divides into two offspring cells that
  are completely identical. There is no exchange
  of genetic material so the process is asexual.
  (example- E. coli produces between 10 and 100
  million bacteria in 12 hours.)

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• When conditions begin to fail, either through
  decrease of food or space, or cooler
  temperatures, some bacteria take part in a type
  of sexual reproduction called conjugation. In
  conjugation the two cells join briefly and one
  cell donates some DNA (called plasmid) to the
  other one. Sexual reproduction combines genetic
  information from two different individuals and
  increases variation.
• Ex. - Antibiotic resistance in the 1950s.

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• When growth conditions become extremely
  unfavourable, many gram positive bacteria form
  structures called endospores. Endospores are DNA
  and a small amount of cytoplasm enclosed in a
  tough cell wall. They are resistant to extremes
  in temperature, drying, and harsh chemicals.

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The pros and cons of Bacteria

• Bacteria convert atmospheric nitrogen into a
  useable form of nitrogen. (nitrogen-fixers)
• Bacteria play an important role in recycling by
  breaking down dead and decaying organic matter.
  Used to eliminate or neutralize toxic and
  hazardous waste and spills. Also used in sewage
  treatment to decompose the 5 billion kg of solid
  waste produced daily.
• Bacteria is used to produce dairy foods that help
  maintain a healthy balance of microorganisms in
  the digestive system.
• Only a small percentage of prokaryotes are
  pathogenic, or disease causing. These bacteria
  produce deadly toxins in the human body that
  cause disease symptoms. Endotoxins are seldom
  fatal and cause fever, vomiting and diarrhea. E.
  coli, Salmonella. Exotoxins are highly toxic, do
  not cause a fever and are often fatal. Tetanus
  and botulism.
• Example- Toxins released by the bacterium
  Streptococcus pneumoniae may result in symptoms
  of pneumonia.

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Review Questions

• 1. Why are bacteria classified in their own
  kingdom and not with plants, animals, protists,
  or fungi?
• 2. What features are shared by prokaryotes?
• 3. What feature(s) might cause cyanobacteria to
  be classified as plants by some taxonomists?
• 4. Describe three shapes that bacteria can have.
• 5. Why is endospore formation important to
  bacteria?
• 6. What method of reproduction is used in
  bacteria?
• 7. What is conjugation in monerans? Why is it
  important?
• 8. How is conjugation different from
  transformation?
• 9. A protective slime coat around some species of
  bacterium known as a ____ makes them more capable
  of causing disease.
• 10. Why are monerans considered more primitive
  than protists?
• 11. What is the difference between a saprobe and
  a parasite?
• 12. How do obligate aerobes differ from
  facultative aerobes?
• 13. _____ are organisms that die in the presence
  of oxygen.
• 14. Monerans belong to a group of organisms known
  as prokaryotes. Discuss the differences between
  eukaryotes and prokaryotes in terms of cell wall,
  nuclear membrane, and chromosomes.
• 15. Why does dried or salted food resist spoiling
  by bacteria?

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• 16. Give specific examples showing the importance
  of microbial sterility in
• a) your kitchen
• b) a microbiology lab
• 17. Describe the results if all bacteria died.
• 18. Endospores
• a) are produced by viruses b) are
  reproductive structures
• c) are very delicate and can easily be killed
  d) are resting structures
• 19. An obligate anaerobe would
• a) grow equally well with or without free oxygen
  
• b) grow well with free oxygen but better without
  it
• c) die without oxygen
• d) grow only in the absence of free oxygen
• 20. Why are archaebacteria considered the oldest
  organisms on Earth?