MicrobiologyMicrobiology MicrobiologyMicrobiology

Zhu zhiyong

The college of Chemistry and Bioengeering

yichun University

1.1 What is a microbe? The word microbe (microorganism) is used to describe an organism that is so small that, normally, it cannot be seen without the use of a microscope. Viruses, bacteria, fungi, protozoa and some algae are all included in this category.

CHAPTER 1 The Microbial WorldCHAPTER 1 The Microbial World

1.2 The scope of microorganisms1.2 The scope of microorganisms

Microorganisms are usually divided into six suMicroorganisms are usually divided into six subgroups: bacterial, archaea, algae, fungi, protozoa anbgroups: bacterial, archaea, algae, fungi, protozoa and virus.d virus.

The nature of microorganisms makes them both The nature of microorganisms makes them both very difficult and easy to study. Easy, because they rvery difficult and easy to study. Easy, because they reproduce so rapidly and we can quickly grow large poeproduce so rapidly and we can quickly grow large populations in the laboratory. Difficult, because we can’t pulations in the laboratory. Difficult, because we can’t see them directly. see them directly.

1.3.1 The impact of microbes on earth

Microorganisms can be found nearly every-where from Microorganisms can be found nearly every-where from deep in the earth’s crust, to the polar ice caps and oceans, to deep in the earth’s crust, to the polar ice caps and oceans, to the bodies of plants and animals.the bodies of plants and animals.

1.3 The importance of microbiology1.3 The importance of microbiology

Microorganisms were the first life on earthMicroorganisms were the first life on earth. .

TheThe first bacterial appeared approximately 3.5 billion years ago first bacterial appeared approximately 3.5 billion years ago

Microbial involvement in energy and nutrient flowMicrobial involvement in energy and nutrient flow

Microbes are responsible fMicrobes are responsible for changing the atmosphere of or changing the atmosphere of the earth from one without oxythe earth from one without oxygen to one with oxygen. Photogen to one with oxygen. Photosynthetic microorganism accousynthetic microorganism account for more than 50% of the eant for more than 50% of the earth’s photosynthesis contributinrth’s photosynthesis contributing the majority of the oxygen to g the majority of the oxygen to the atmospherethe atmosphere

Microbes are responsible for the cycling of carbon, nitrogen Microbes are responsible for the cycling of carbon, nitrogen and phosphors (geochemical cycles), all essential components and phosphors (geochemical cycles), all essential components of living organisms. They are found in association with plants in of living organisms. They are found in association with plants in symbiotic relationships, maintain soil fertilitv and may also be ussymbiotic relationships, maintain soil fertilitv and may also be used to clean up the environment of toxic compounds. Some micred to clean up the environment of toxic compounds. Some microbes are devastating plant pathogens, which destroy important fobes are devastating plant pathogens, which destroy important food crops, but others may act as biological control agents againood crops, but others may act as biological control agents against these diseases.st these diseases.

1.3.2 Human use of microorganisms1.3.2 Human use of microorganisms

Infectious diseases and the human conditionInfectious diseases and the human condition

Nearly 2000 Nearly 2000 microbes are pamicrobes are pathogens that cathogens that cause infectious duse infectious deseases.eseases.

(the ten most common infectious (the ten most common infectious causes of death)causes of death)

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

The disease-causing ability of some microbes such as smallpox( 天花） , cholera （霍乱） and malaria, is well known. However, micro-organisms have also provided us with the means of their control in the form of antibiotics and other medically important drugs.

1.4 The characteristics of microorganism

1 ． Microscopic 2 ． independent units

3 ． less complex

4 ． rapid growth rates

5 ． opmipresent

1.5 The history of microbiology

The first person to accurately observe and describe microorganisms

Antony van Leeuwenhock (1632-1723)

Leeuwenkoek made his simple, single-lens microscope which could amplify the object being viewed 50 – 300 times. Between 1673 – 1723, he wrote a series of letters to the Royal Society of London describing the microbes he observed from the samples of rainwater, and humam mouth.

lens

Object being viewed

adjusting

screws

A drawing of one of the microscopes showing the lens a; mounting pin b; and focusing screws c and d.

A drawing of one of the microscopes showing the lens a; mounting pin b; and focusing screws c and d.

Leeuwenhoek’s drawings of bacteria from the human mouth.

Leeuwenhoek’s drawings of bacteria from the human mouth.

Final refutation of Final refutation of spontaneous generation spontaneous generation – birth of microbiology – birth of microbiology as a scienceas a scienceDiscovery of the Discovery of the existence of anaerobic existence of anaerobic life – fermentationlife – fermentationVaccinesVaccinesPasteurizationPasteurization

Pasteur’s contributions:

Louis Pasteur working in his laboratory

Louis Pasteur (1822 – 1895)Louis Pasteur (1822 – 1895)

1. Pasteur (1857) demonstrated that lactic acid fermentation is due to the activity of microorganisms.

2. Pasteur (1861) conflict over spontaneous generation – birth of microbiology as a science

3. Pasteur (1881) developed anthrax( 炭疽病 ) vaccine4. Pasteurization

Robert Kock in his laboratory

The recognition of microbial role in disease

Robert Koch (1843 – 1910)

1.1. The microorganisms must be present in every The microorganisms must be present in every case of the disease but absent from healthy case of the disease but absent from healthy organisms.organisms.

2.2. The suspected microorganisms must be The suspected microorganisms must be isolated and grown in a pure culture.isolated and grown in a pure culture.

3.3. The disease must result when the isolated The disease must result when the isolated microorganisms is inoculated into a healthy microorganisms is inoculated into a healthy host.host.

4.4. The same microorganisms must be isolated The same microorganisms must be isolated again from the diseased host again from the diseased host

Koch’s postulates

Sir Alexander Fleming discovered the antibiotic penicillin. He had the insight to recognize the significance of the inhibition of bacterial growth in the vicinity of a fungal contaminant when most other scientists probably would have simply discarded the contaminated plates.

Alexander Fleming (1881-1955)

1.6 Category The systemic taxa of mocroorganisms follow the systemic taxa built by Linnaeus ， including seven grades from top to bottom: Kingdom Phylum Class Order Family Genus Species

There are more than ten grades in the systemic taxa altogether, because each grade, if needed, could sub-divide some auxiliary units

Classification of microorganismsClassification of microorganisms

Five-kingdom of life Three-kingdom of lifeFive-kingdom of life Three-kingdom of life