Introduction to Microbiology

Intended Learning Outcomes

• Students should be able to divide micro-organisms into bacteria, viruses, fungi, and protozoa, and distinguish between eukaryotes and prokaryotes.
• Students should be able to recognise the importance of microorganisms in health and disease.
• Students should be able to explain how micro-organisms cause disease.
• Students should be able to describe the conditions needed for microbial growth.
• Students should become familiar with terms associated with micro-organisms.

Microbiology

• It is the study of organisms too small to be seen with the naked eye (0.1-0.2mm diameter) and are called micro-organisms or microbes.
• Microbiology includes Bacteria, Viruses, Fungi, Algae and Protozoa.

Questions to consider before starting

• Microbes are part of normal microflora.
• Microbes are everywhere.
• There is most likely a 'normal microflora'.
• Human cells that make up the human body number 10^3.
• The number of microbes that inhabit the human body is 10^4.

Why study microbiology?

• For health, disease, and prevention understanding.
• To understand manipulation of the host, infection, and clinical appearance.
• To understand host response and infection control.
• Also for treatment/management/resistance understanding.
• For medical connection and local/global impact insights.

Eukaryotes and Prokaryotes

• These are the two main features of cells

Eukaryotes

• Large and complex
• Have clearly defined nucleus
• Contains membrane bound organelles
• Can be single or multi-cellular

Prokaryotes

• Small and simple
• Possesses a nucleoid rather than a nucleus
• Has no membrane
• Always unicellular

Micro-organisms

• Micro-organisms include: bacteria, fungi, viruses and protozoa/parasites

Micro-organisms in Health

• Microbes support us in maintaining health

Factors affecting the proportion of microbes

• Humans are born without a biome.
• Establishment of the microbiome begins at birth, the microbiome changes with age.
• Microbial introduction and establishment are influenced by factors like:
• Mode of delivery during birth.
• Diet.

How Micro-organisms cause disease

• Disease potential is related to:
• Products
• Antigenic nature
• Defences
• The host

Toxins

• Organisms produce toxins that cause disease
• Endotoxins
• Exotoxins

Microbial Enzymes

• Microbial enzymes support invasiveness
• Invasiveness
• allowing easy spread, protection, and degradation of host response.

Microbial Enzymes Definition

• These are a form of catalyst which bacteria use to break down materials or synthesise their energy and building requirements.
• Enzymes are capable of producing changes in other substances without undergoing change themselves.

Metabolites

• Products of metabolism.
• In dentistry, Streptococcus mutans and production of organic acids leads to dissolution of enamel and causes caries.

Gut interactions

• Gut-brain axis: Autism, Parkinson's, Depression and Multiple sclerosis
• Gut-airway axis: Asthma and allergy
• Gut-cardiovascular axis: Heart disease
• Small intestine: Celiac disease
• Colon: IBD, Colorectal cancer

Environmental Microbial Growth Considerations

• Environmental Microbial Growth Considerations include:
• Temperature
• pH
• Water
• Light
• Nutrition
• Respiration

Temperature and Bacteria Growth Rate

• Psychrophiles
• Mesophiles
• Thermophiles
• Hyperthermophiles

pH and Bacteria Growth Rate

• Acidophile
• Neutrophile
• Alkaliphile

Moisture for Microbial Cells

• 80% + of the microbial cell is water, and drying is tolerated differently by different species
• E.g. Staphylococci survive outside the host in a dry environment for days; Treponema pallidum dies in seconds.
• Bacteria may not grow in dehydrated food, but growth may recommence once water is added.

Light

• Parasitic micro-organisms grow and survive best in darkness. Ultra violet light is lethal and used in sterilisation.
• X-rays damage microbe DNA, can be used to sterilise medical supplies.

Nutrition For Microbial Growth

• Microbiology nutrition requirements: energy, nitrogen, carbon, water and sulphur source.
• Different enzyme systems are specific in breakdown of certain nutrient compounds (nutrient recycling).
• Microbial growth can be enhanced by enriching the growth medium with specific nutrients or retarded using growth inhibitors.

Respiration

• Respiration is covered in the bacteria lecture.

Explore the realm of microbiology, focusing on the classification of microorganisms such as bacteria, viruses, fungi, and protozoa. Understand the distinction between eukaryotes and prokaryotes and the importance of microorganisms in health and disease. Learn about the conditions that support microbial growth and become familiar with key microbiology terms.