Introduction to Microbiology

 

 

Microorganisms are tiny unicellular organisms that can not be seen by the naked eye. They include:

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Bacteria

 

Bacteria are small prokaryotic (pro- before, karyon- nucleus) unicellular organisms that multiply by binary fission.

 Properties of bacteria:

  • Approximately 1 um in diameter.
  • Seen by light microscopy.
  • Have both of DNA and RNA.
  • Grow on artificial media.
  • Divide by binary fission.
  • Sensitive to anti-bacterial chemotherapy.

 

Differences between prokaryotes/eukaryotes

The prokaryotic cell, in contrast to the eukaryotic cell, has no nuclear membranes, mitochondria, endoplasmic reticulum, Golgi body, phagosomes and lysosomes. Prokaryotes generally possess only a single circular chromosome. Since there is no nuclear membrane, the chromosome is bound to a specific site on the cell membrane - the mesosome.  Prokaryotic ribosomes are 70S (S stands for Svedberg unit, a measure of size), whereas eukaryotic ribosomes are larger (80S). Prokaryotic ribosomal subunits are 30S and 50S (eukaryotic are larger). Bacterial membranes generally do not contain sterols (e.g. cholesterol).