Fundamentals of MicrobiologyFundamentals of Microbiology

““Introduction to the biology of bacterial and Introduction to the biology of bacterial and archaeal organisms” archaeal organisms”

Topics include microbial cell structure and Topics include microbial cell structure and function, methods of cultivation, genetics, function, methods of cultivation, genetics, phylogeny and taxonomy, and metabolic and phylogeny and taxonomy, and metabolic and genetic diversity.genetic diversity.” ”

Lecture 1Lecture 1

• 1.1 Microbiology1.1 Microbiology• 1.2 Microorganisms as Cells1.2 Microorganisms as Cells• 1.3 Microorganism and Their Natural 1.3 Microorganism and Their Natural

EnvironmentsEnvironments• 1.4 The Impact of Microorganisms on 1.4 The Impact of Microorganisms on

HumansHumans

What is Microbiology?What is Microbiology?

• The science of microorganisms (very small, The science of microorganisms (very small, unicellular organisms)unicellular organisms)

• The discipline is just over a century oldThe discipline is just over a century old• Has given rise to molecular biology and Has given rise to molecular biology and

biotechnologybiotechnology

Early Microbiology

• 3 historical discoveries– Invention of the microscope– Disproving spontaneous generation– Demonstrating microorganisms cause disease

Antoni van Leeuwenhoek

• Inventor of the first microscope (1684)

Spontaneous Generation

• Spontaneous generation:– Life can arise from non-living materials.

• Pasteur demonstrated that microorganisms in the air were responsible for food spoilage– Constructed a swan-necked flask

Germ Theory of Disease

• Proof that microorganisms caused disease• Robert Koch demonstrated that anthrax was

caused by Bacillus anthracis– Blood from a diseased animal caused disease in a

healthy animal

– Cultivated the disease causing agent outside the animal’s body, then introduced the agent into a healthy animal which subsequently developed the disease

Methods in Microbiology

• Three important techniques that allowed the advanced study of microbiology:

– Microscopy

– Sterilisation

– Pure culture

Electron Microscopy

• To visualise the internal structure - TEM• Electrons instead of light• Greater resolving power• Disadvantages:

– Expensive

– A high vacuum is required

– Very thin sections (<100 nm thick)

Figure 1.2a Bacterial cells viewed with light microscopeFigure 1.2a Bacterial cells viewed with light microscope

Figure 1.2b Bacterial cell viewed with electron microscopeFigure 1.2b Bacterial cell viewed with electron microscope

Root Nodule

Bacteroids within Root Nodule

Sterilisation and Pure Culture

• Culture: population of microorganisms grown under well defined conditions– Pure culture – one that contains one type of

microorganism– Mixed culture – more than one microorganism

• Need to isolate microorganism from mixed cultures

Sterilisation Techniques

• Sterilisation using heat– Dry heat: 160 ºC for 2 h

– Wet heat: Autoclave, 120 ºC

• Sterilisation using chemicals– Volatile, toxic (ethylene oxide)

– Sterilise plastics

• Filtration– Pore size approx. 0.22 µm

Pure Culture Technique

• Isolation pure cultures by plating (streak plate)

The Microbial World

• Microorganisms are everywhere: air, soil, water, plants, animals

• Microbial life is diverse– Bacteria have existed for 3x109 years

– Evolved to flourish in the most inhospitable environments

What are Microbes?What are Microbes?

Microbes show morphological diversity • Size - most are 1-5 microns, but range from 0.1 to

660 microns per cell. Viruses even smaller

prokaryotic cell

eukarotic cell

Why study Microbiology?Why study Microbiology?

• Microorganisms were the first life on earthMicroorganisms were the first life on earth• Microorganisms created the biosphere that allowed Microorganisms created the biosphere that allowed

multicellular organisms to evolvemulticellular organisms to evolve• Multicellular organisms evolved from Multicellular organisms evolved from

microorganismsmicroorganisms• >50% of the biomass on earth is comprised of >50% of the biomass on earth is comprised of

microorganismsmicroorganisms• Microorganisms will be on earth foreverMicroorganisms will be on earth forever

4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0

BYA

Formation of O2 atmosphere

Cyanobacterial microfossils(oxygenic photosynthesis)

Earth formed

First microorganisms?

algae,marine invertebrates insects

mammals

No free O2

Reducing environment

Why study Microbiology?Why study Microbiology?

• Our understanding of life has arisen largely Our understanding of life has arisen largely from studies of microorganisms from studies of microorganisms (biochemistry and genetics)(biochemistry and genetics)

• Studies of microorganisms continue to Studies of microorganisms continue to contribute to fundamental knowledge of life contribute to fundamental knowledge of life processesprocesses

• We still know very little about the We still know very little about the microorganisms that are present on Earthmicroorganisms that are present on Earth

Figure 1.4

Why study Microbiology?Why study Microbiology?

• HealthHealth• AgricultureAgriculture• FoodFood• EnvironmentEnvironment

Infectious diseases are no longer the leading cause of death in North America, due to the Infectious diseases are no longer the leading cause of death in North America, due to the development and use of antimicrobial agents, and improved sanitary practicesdevelopment and use of antimicrobial agents, and improved sanitary practices