1. INTRODUCTION TO MICROBIOLOGY
@ Agents causing diseases in humans belong to the groups:
Bacteria,
fungi,
viruses,
chlamydia,
rickettsia
Parasites (protozoa and helminthes).

2. Biological Relationships of Pathogenic Micro-organisms:
Kingdom Pathogens Types of cells
Animal Helminthes Eukaryotic Plant None Eukaryotic Protist Protozoa Eukaryotic Protist Fungi Eukaryotic Prokaryote Bacteria Prokaryotic Viruses Non-cellular

3. @ Protozoa are unicellular
organisms
@ Fungi are simple multicellular
organisms.
@ Helminthes are complex
multicellular, metazoan
@ Viruses are not cells, but can
replicate inside cells.

4. Comparison of medically important organisms:
Property Viruses Bacteria Fungi Parasites
Cells No Yes Yes Yes
Diameter – 25
(µm) yeast trophozoite
DNA/RNA One Both Both Both
Nucleus None Prokar Eukar. Eukar.
Ribosomes Absent S S s
Mitochondria Absent Absent Present Present
Surface Capsid Rigid Rigid Membrane
Envelope Wall Wall
Motility None Some None Most
Replication No binary Binary Budding/ Mitosis
fission fission Mitosis

5. @ Eukaryotes have true nucleus surrounded by nuclear membrane, replicate by mitosis.
@ Prokaryotes have a nucleoid without a membrane or a mitotic apparatus.
@ Eukaryotes have: mitochondria, lysosomes, & prokaryotes : none

6. @ Eukaryotes have sterols
in cell membrane
@ Prokaryotes have none
(except Mycoplasma).
@ Protozoa locomote by
flagella, cilia, pseudopods,
@ Bacteria locomote by
flagella.

7. Comparison: Prokaryotes (bacteria) Eukaryotes (human)
Property Bacteria Human
DNA in a nuclear
Membrane No Yes
Mitotic division No Yes
DNA + histones No Yes
Chromosome number One More than one
Mitochondria
+ Lysosomes No Yes
Size of ribosomes S S
Peptidoglycan Yes No