Microorganisms include bacteria, fungi, protozoa, viruses, and helminths. There are two domains - bacteria and eukarya. Bacteria are unicellular while fungi, protozoa, and helminths can be unicellular or multicellular. Viruses are obligate intracellular parasites. Cells have DNA, cytoplasm, and organelles while viruses only have genetic material and cannot replicate on their own. Cells replicate through binary fission or mitosis but viruses replicate inside host cells by disassembling, producing copies of nucleic acids and proteins, and reassembling.

1. BACTERIOLOGY
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2. Basic Bacteriology
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3. Microorganism:
• Microbes are the microscopic organisms that
comprises of single cell, cell cluster or
multicellular or complex organisms.
• They include bacteria, fungi, protozoa, viruses
and helminths.
• Macroscopic organism like Thiomargarita
namibiensis.

4. Microbes that cause the infectious diseases:
These are bacteria, fungi, protozoa, viruses and helminths.
Two types of domains:
Bacteria Domain Eukarya Domain
Bacteria Fungi, protozoa and
helminths
Unicellular Fungi & Protozoa = Unicellular
and simple multicellular
Helminths = Complex
microorganisms

5. Viruses are the obligate intracellular parasites.
Features of Microbes:
Cellular and non cellular character is based on the three criteria;
1) Structure
2) Replication
3) Nucleic acid

6. Structure:
• Cells have a nucleus/nucleoid which contains DNA, is
surrounded by the cytoplasm where the proteins are synthesized
and energy is generated.
• Viruses have an inner core of genetic material i.e. DNA/RNA
• They have no cellular organelle, have no nucleus, no cytoplasm.
• They can not make energy and can not synthesize the protein.

7. Replication:
Cell replicate either by binary fission or by mitosis.
Prokaryotic cell replicate by binary fission e.g. bacteria and
Eukaryotic cells e.g. fungi, protozoa, helminths replicate by
mitosis.

8. Viruses replicates within the host cell.
Disassemble
Produce many copies of nucleic acid & proteins
Reassemble into multiple progeny virus

9. Nucleic acid:
Cell contains both DNA and RNA but viruses can not contains both