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