Introduction to Microbiology

• Microbiology is the study of organisms too small to be seen clearly with the naked eye which is between 0.1-0.2mm in diameter
• These organisms are known as micro-organisms or microbes
• Micro-organisms include bacteria, viruses, fungi, algae and protozoa

Microbes in Health

• Humans have microbes as part of our normal microflora
• Microbial introduction and the establishment of microbiome is influenced by factors such as mode of delivery, diet
• The study of human microbiome diversity began with Antonie Van Leeuwenhoek

Divisions of Micro-organisms

• The main divisions of micro-organisms are into bacteria, viruses, fungi and protozoa
• It is important to distinguish between eukaryotes and prokaryotes
• Eukaryotes are large, complex, single or multi-cellular, and have a clearly defined nucleus along with membrane bound organelles
• Prokaryotes are small, simple and unicellular
• They have a nucleoid, not a nucleus, and lack internal membrane structure

Why Study Microbiology?

• Studying microbiology can improve or aid understanding of:
• Health
• Disease
• Prevention
• Manipulation of the host
• Infection
• Clinical appearance
• Host response
• Infection control
• Treatment/management/resistance
• Medical connection
• Local/global impact

How Micro-organisms Cause Disease

• The disease potential of micro-organisms relates to their products, antigenic nature, defences and the host

Products That Cause Disease

• Endotoxins, Exotoxins, Metabolites, Enzymes

Microbial Enzymes

• Microbial enzymes support invasiveness
• Enzymes are a form of catalyst used by bacteria to break down materials or synthesise their energy and building requirements
• Enzymes are capable of producing changes in other substances without changing themselves
• Invasiveness allows easy spread and provides protection and degrades the host response

Metabolites

• Products of metabolism, most relevant in dentistry e.g. Streptococcus mutans and production of organic acids to dissolve enamel and start caries

Environmental Factors for Microbial Growth

• Temperature
• pH
• Water, at least 80% of the microbial cell
• Light, prefer darkness
• Nutrition, require energy, nitrogen, carbon, water and sulphur
• Respiration