Download INTRODUCTION TO MICROBIOLOGY

INTRODUCTION TO MICROBIOLOGY
LEARNING OBJECTIVES
• At the end of the session the student should be able to:
• Define Microbiology
• Briefly describe the different fields of microbiology and their role in Diagnosis
of infectious diseases.
• Differentiate between Eukaryote and Prokaryote cells and the importance of the
morphological difference in disease and dignosis of infections.
Micro-organisms and Microbiology
• Microbiology is the study of microorganisms; including bacteria,
parasites,fungi and viruses
• Microscopic, single cell, cluster, chains
carry out life processes independently as single cells
• Viruses- microscopic, non-cellular, RNA or DNA
Branches of study within microbiology
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Immunology
Public health microbiology & epidemiology
Food, dairy and aquatic microbiology
Biotechnology
Genetic engineering & recombinant DNA technology
History of Microbiology:
Antoj van Leeuwenhoek 1623-1723
1-Spontaneous generation
2-Germ theory of disease
AGENTS
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The agents of human infectious diseases belong to five major group
of organisms:
1) Bacteria (prokaryote kingdom)
2)The fungi (yeasts and molds)
(eukaryotes)
3) Protozoa (protists)
Helminths (worms) (animal kingdom)
Viruses (acellular)
EUKARYOTES and PROKARYOTES
• Cells have evolved into two fundamentally different types, eukaryotes
and prokaryotes. which can be distinguished on the basis of their
structure and the complexity of their organization.
• Fungi and the protozoa are eukaryotic where as bacteria are
prokaryotic
3 domains
• Eubacteria -true bacteria, peptidoglycan
• Archaea –odd bacteria that live in extreme environments, high salt,
heat, etc
• Eukarya- have a nucleus, & organelles
Naming micoorganisms
• Binomial (scientific) nomenclature
• Gives each microbe 2 names
– Genus - noun, always capitalized
– species - adjective, lowercase
• Both italicized or underlined
– Staphylococcus aureus (S. aureus)
– Bacillus subtilis
(B. subtilis)
– Escherichia coli
(E. coli)
Characteristics of microbes
PROKARYOTES
Components
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Cytoplasm
Ribosomes
Nuclear Zone
DNA
Plasmid
Cell Membrane
Mesosome
Cell Wall
Capsule (or slime layer)
Flagellum
• 1) The eukaryotic cell has a true nucleus with multiple chromosomes
surrounded by a nuclear membrane and uses a mitotic apparatus to
ensure equal allocation of the chromosomes to progeny cells.
• 2) The nucleoid of a prokaryotic cell consists of a single circular
molecule of loosely organised DNA lacking a nuclear membrane and
mitotic apparatus
• Prokaryotic cells like bacteria replicate by BINARY FISSION
• Eularyotic cells contain organelles such as mitochondia and lysosomes, and
larger (80S) ribosomes
• Whereas prokaryotic cells contain no organelles and smaller (70S) ribosomes
• Most prokaryotes have a rigid external cell wall that contains peptidoglycan a
polymer of aminoacids and sugars as its unique structural component.
• Eukaryotes do not contain peptidoglycan . They are bounded by a flexible cell
membrane
• The eukaryotic cell membrane contains sterol where as no prokaryotic
cell except the wall less Mycoplasma has sterol in its membrane
COMPARISION OF
PROKARYOTES
• Nucleus is absent.
• Nuclear membrane is absent.
• Dna is single,closely coiled loop
• Chromosome no. Is 1.
• Mambrane bound organelles absent
• Ribosome size 70s
• Dna not associated with histones.
• Cell wall contains peptidoglycan.
• Cell does not divide by mitosis.
EUKARYOTES.
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Nucleus is present
Nuclear membrane is present.
Dna is in arranged in multiple chromosomes
More than 1
Membrane bound organelles are present.
Ribisome size 80 s
DNA associated with histones.
Cell wall does not contain peptidoglycan.
Cell divides by mitosis
Hans Christian Gram 1843-1938
Gram (differential) stain – 1884
1. Fix organisms to slide with heat and stain with basic dye (crystal
violet ) - then rinse
2. Apply iodine solution to form dye-I2 complex - then rinse
3. Wash with ethyl alcohol or acetone
Gram-positive bacteria remain blue
4. Apply red counterstain (safranin)
Gram-negative bacteria stained red
Gram stain morphology
• Shape
– cocci (round)
– bacilli (rods)
– spiral or curved (e.g. spirochetes)
• Single or multiple cells
– clusters (e.g. staphylococci)
– chains (e.g. streptococci)
• Gram positive or negative
(NON-GRAM STAINING BACTERIA)
Viruses
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Acellular entities too small to be seen with a light miroscope
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Composed of nucleic acid and protein
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Bacteriophage: viruses that infect bacteria
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Viroids: nucleic acid without a protein coating
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Prions: Infectious proteinaeceous particles
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