Chapter 1 Main Themes of Microbi

Chapter 1 Main Themes of Microbiology

What is Microbiology ?

Microbiology is a study of microorganisms (microbes, germs) and their activities

What is a microorganism?
An organism too small to be seen without a microscope (Smaller than 0.5 mm) (Bacteria, Fungi, Protozoa, Algae, Viruses)

Branches of Microbiology

Medical Microbiology

Industrial Microbiology

Environmental Microbiology

Agricultural Microbiology

Microbiology is part of some other disciplines

• Biotechnology

• Food production (Dairy products (yoghurt, cheese), Sauerkraut, Pickles, Sausages, Bread, Beer, Wine, Etc.)

• Drug production (penicillin)

• Bioremediation – detoxification by use of microorganisms

• Genetic Engineering (Manipulation of genes of microbes in order to create new products)

The Impact of Microbes on Earth

• The first organisms on the planet Earth

– Ubiquitous – can be found everywhere

• Photosynthesis

– Oxygen production

• Primary production

– Synthesis of organic mater

• Decomposition

The Impact of Microorganisms on Human Health

• Microorganisms as disease agents

• Microorganisms live inside our bodies,

– normal microflora,

– pathogenic

• Our body resists the invasion of pathogenic microbes by

– skin,

– mucous membrane,

– stomach acid

– antimicrobial chemicals - interferons

• Introduction of antibiotics changed the rates for the leading causes of death

CELL TYPES

There are two basic cell types:

- Prokaryotic

Bacteria

Archea

- Eukaryotic

Fungi

Protozoa

Algae

(helimints, plants, animals)

Major difference - organization of nuclear structure

۞Viruses

CELLULAR ORGANIZATION IN MICROBES

Prokaryotic

• Cell envelope

• Nucleoid

Eukaryotic

• Cell envelope

• Organelles

• Nucleus

Viruses

• Do not have cellular structure

• One type of nucleic acid DNA or RNA

• Can reproduce only when inside a host cell - parasite

Microbial Dimensions

• Prokaryotic cells: 1-10 mm

• Eukaryotic cells: 10-100 mm

• Viruses : 10-100 nm

Lifestyle of Microbes

• Autotrophs

• Heterotrophs

• Parasites

Naming and Classifying Microorganisms

• Classification of organisms is called Taxonomy

• Based on the system introduced by Carl Linnaeus (1735)

Binomial system of nomenclature

Genus: Bacillus Species:Bacillus subtilis

• Bacterial taxonomy has relied on phenotypic analysis (Morphology, cell structures, storage products, Gr- staining, biochemical characteristics)

• Molecular taxonomy - Nucleic acid analysis

All organisms belong to three groups: The Three Domain System

– Bacteria

– Archaea

– Eukarya

History of Microbiology

Who Started Microbiology?

Antoni van Leeuwenhoek (1673-1723), a Dutch merchant

• The first person to see microbes as being ALIVE!

• Father of bacteriology.

What Leeuwenhoek Could See?

• Different shapes of bacteria

• Red blood cells, spermatozoa, plant and animal cells

• Magnification of his microscope was 32X

Robert Hooke’s Microscope Compared to Leeuwenhoek’s

• Robert Hook introduced the compound microscope (objective lens + ocular lens)

• Robert Hook (1665) reported that the smallest biological structural unites were “little boxes” - cells.

• CELL THEORY – all living things are composed of cells

Golden Age of Microbiology - 1830-1900

Scientists searched for answers to the following questions:

– Is spontaneous generation of microbial life possible?

– What causes fermentation?

– What causes disease?

– How can we prevent infection and disease?

Is Spontaneous Generation of Microbial Life Possible?

• Aristotle proposed spontaneous generation – living things can arise from non-living matter

• Toads and snakes could be born of moist soil

• Maggots (the larvae of flies) could arise from corpses

Finally!

• Arguments about spontaneous generation resolved by the French scientist Louis Pasteur – 1850’s

How he really did it?

• Pasteur’s S-shaped flask kept microbes out but let air in.

Pasteur’s discoveries

• Performed the most convincing experiments disproving the theory of spontaneous generation

• Role of yeast in alcohol fermentation

• Devised the process of pasteurization and basis of aseptic techniques

• Disease of vine - could be prevented by heating the wine for a short time to a temp.

55-60⁰C

• The first preventive treatment for rabies

What Causes Disease?

• Pasteur developed germ theory of disease, but had no proof…began working on Anthrax, but could not get a pure culture of the disease producing bacterium

1876 Robert Koch

German bacteriologist, studied causative agents of disease and PROVED the Germ Theory of Disease.

• Gave the first proof that bacteria cause disease (by isolating the anthrax bacillus in pure culture) - germ theory of disease

• Perfected the technique of isolating bacteria in pure culture - solid media -boiled potato

• Discovered Mycobacterium tuberculosis - the organism causing the tuberculosis. Tuberculin - substance used for diagnosis of tuberculosis.

• Introduced the staining procedure for M. tuberculosis (acid fast staining)

• First to stain bacterial smears

• Discovered the causative agent of cholera

• 1905 received the Nobel Prize for Medicine

Koch’s postulates - Identify criteria for proving that a specific type of a microorganism causes a specific disease:

1. The microorganism should be constantly present in a diseased animal

2. The microorganism must be cultivated in pure culture

3. When inoculated into a healthy animal, such microorganism should cause characteristic disease symptoms

4. The microorganism should be re-isolated from the experimental animal, and it should have the same characteristics as the original microorganism.

Joseph Lister

• Father of modern surgery

• Applied antiseptic (carbolic acid) treatment for prevention and care of wound infection

• Introduced the procedure of disinfection of operating rooms

Chemotherapy - treatment of disease by using chemical substances

• The first antibiotic was discovered by accident

• Alexander Fleming 1928 discovered penicillin

• Produced by mold: Penicillim chrysogenum

• Commercial production started in 1945 in the US

Problems with antibiotics

• Can be toxic to humans

• Spread of new varieties of resistant microorganisms

Development of techniques that facilitated further progress of microbiology

• Pure cultures (clone) is a culture consisting of only one type of microorganisms

• Use of Petri dishes

• Aseptic techniques

• Bacteria as distinct species

Developments of microbiology in the twentieth century

• Bacteriology

– Study of Bacteria. New species of bacteria are discovered regularly

• Mycology

– Study of fungi. Fungal infections rising

• Parasitology

– Study of protozoa and parasitic worms

• Immunology

- Study of immunity. Vaccines available for many diseases

• Virology

– 1892 Dimitri Iwanowski, reported on the presence of infectious agents much smaller than bacteria. He discovered the tobacco mosaic virus.

• Recombinant DNA technology

– Fragments of foreign DNA can be incorporated into bacterial genom

The Establishment of the Scientific Method

• Scientific method – based on an experimental system

• It includes:

– 1. Observation and description of a phenomenon

– 2. Formulation of an hypothesis to explain the phenomena

– 3. Performance of experimental tests (to confirm or disprove the hypothesis).

• If supported – Hypothesis becomes a theory