chapter 1 introduction & history of microbiology microbial world and you(1)
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Introduction & History
of Microbiology
The Microbial World and You
Microorganisms = Living things too small to be seen with the unaided eye
The Microbial World and You
Importance of microorganisms :
• for the maintenance of an ecological balance on Earth
• some microorganisms live in humans and other animals and are needed to maintain the host's health
• For the production of foods and chemicals
Some microorganisms cause disease = pathogenic
Naming and Classifying
Microorganisms (Taxonomy)
System of nomenclature by Carolus Linnaeus (1735):
• each living organism is assigned two names
genus and a specific epithet, both of which are underlined or italicized.
Naming and Classifying
Microorganisms (Taxonomy)
All organisms are classified on the basis of cellular structure into:
• Bacteria
• Archaea
• Eukarya
Protista
Fungi
Plantae
Animalia
Types of Microorganisms Bacteria
• unicellular organisms
• no nucleus and so are described as prokaryotic
• most have a peptidoglycan cell wall
• divide by binary fission
• may possess flagella
• can use a wide range of chemical substances for nutrition
• three major basic shapes of bacteria :
bacillus
coccus
spirillum
Types of Microorganisms
Peptidoglycan
• huge polymer that envelopes the entire cell
• sheath can often be isolated
• molecules consist of strings of sugar molecules linked together by chains of amino acids into a huge network
Types of Microorganisms Bacillus
Haemophilus influenzae on Sputum Culture Characteristic of Bacterial Pneumonia
Types of Microorganisms
Cocci
Types of Microorganisms
Types of Microorganisms
Spirillum
Types of Microorganisms
Archaea
• prokaryotic cells
• cell walls if present lack peptidoglycan
• Include:
methanogens
halophiles
extreme thermophiles
Types of Microorganisms
Some of the microbes in this picture are called methanogens (fancy name for methane makers). Methanogens live where there is no oxygen. Like other microbes that grow without oxygen, methanogens are called anaerobes.
The methane produced by this community is used for fuel, a flammable gas known as natural gas used to heat your home.
Types of Microorganisms
Some of the microbes in this picture are called methanogens (fancy name for methane makers). Methanogens live where there is no oxygen. Like other microbes that grow without oxygen, methanogens are called anaerobes.
The methane produced by this community is used for fuel, a flammable gas known as natural gas used to heat your home.
Types of Microorganisms
Halophiles
• salt-loving organisms that inhabit hypersaline environments
Types of Microorganisms
Halobacteria
Types of Microorganisms
In the foreground red-coloured prokaryotes grow where the water is hotter.
Types of Microorganisms
Temperature ranges of microorganisms: • Psychrophiles (cold-loving) can grow at 0oC, and some even
as low as -10oC; their upper limit is often about 25oC.
• Mesophiles grow in the moderate temperature range, from
about 20oC (or lower) to 45oC.
• Thermophiles are heat-loving, with an optimum growth
temperature of 50oC or more, a maximum of up to 70oC or more, and a minimum of about 20oC.
• Hyperthermophiles have an optimum above 75oC and thus can grow at the highest temperatures tolerated by any organism. An extreme example is the genus Pyrodictium, found on geothermally heated areas of the seabed. It has a temperature minimum of 82oC, optimum of 105o C and growth maximum of 110oC.
Types of Microorganisms
Fungi
• include mushroom, molds, and yeasts
• have eukaryotic cells (with a true nucleus)
• most fungi are multicellular
• obtain nutrients by absorbing organic material from their environment
Types of Microorganisms
Protista
• Protozoa
• Slime molds
• Algae
Types of Microorganisms
Protozoa
• unicellular eukaryotes
• obtain nourishment by absorption or ingestion through specialized structures
• move by pseudopodia, cilia, flagella
• can reproduce sexually or asexually
Types of Microorganisms
Slime molds are usually placed in the kingdom Fungi, although some authorities now place them in the kingdom Protoctista (Protista). Most fungi are composed of threadlike filaments of eukaryotic cells called hyphae, collectively referred to as a mycelium. Slime molds are composed of an acellular mass of naked protoplasm with no cell walls in its vegetative state. They are typically found in damp, shady areas with abundant organic matter, although they may move to bright areas to "fruit."
Types of Microorganisms
Algae
• photosynthetic eukaryotes
• sexual and asexual reproductive forms
• cellulose
• produce oxygen and carbohydrates
Types of Microorganisms
Plants
• cell walls
• chlorophyll
• autotrophic
• photosynthetic
Types of Microorganisms
• Multicellular Animals and Parasites
not microorganisms
some stages of their life cycle are microscopic
medical importance : helminths
include 2 major groups:
flatworms
round worms
Types of Microorganisms
Viruses • So small
• can be seen only with the aid of electron microscope
• very simple structure
• core made up of only DNA or only RNA
• core is surrounded by a protein coat
• sometimes an envelope may be present
• reproduce by using cellular machinery of other organisms
• parasites of other forms of life
A Brief History of Microbiology
The First Observations • Robert Hooke
observed plant material was composed of "little boxes“
introduced the term "cell" (1665)
• Hooke's observations laid the groundwork for development of the cell theory, the concept that all living things are composed of cells.
• Antoni van Leeuwenhoek used a simple microscope
was the first to observe microorganisms (1673)
A Brief History of Microbiology
The publication of Hooke’s Micrographia in 1665 marks one of the milestones in British science. This book contains numerous drawings of objects he viewed with the microscope: a bee sting, a razorblade, snow crystals, wood, cork and insects. He also created his own technique for the production of thin sections. In 1667 his studies on the composition of cork led him to suggest the use of the term ”cell”, paving the way to the utilization of the same word in today’s life sciences to describe the basic constituents of all living creatures.
Robert Hooke
A Brief History of Microbiology
The Debate over Spontaneous Generation • Until the mid-1880s, many believed in
spontaneous generation, the idea that living organisms could arise from nonliving matter.
• Francesco Redi demonstrated that maggots appear on decaying meat only when flies are able to lay eggs on the meat (1668).
• John Needham claimed that microorganisms
could arise spontaneously from heated nutrient broth (1745).
A Brief History of Microbiology The Debate over Spontaneous Generation
• Lazzaro Spallanzani repeated Needham's experiments
and suggested that Needham's results were due to microorganisms in the air entering his broth (1765).
• Rudolf Virchow introduced the concept of biogenesis: Living cells can arise only from preexisting cells (1858).
• Louis Pasteur demonstrated that microorganisms are in the air everywhere; offered proof of biogenesis (1861).
• Pasteur's discoveries led to the development of aseptic techniques used in laboratory and medical procedures to prevent contamination by microorganisms that are in the air.
Louis Pasteur
A Brief History of Microbiology
The Golden Age of Microbiology:
• Rapid advances in the science of microbiology were made between 1857 and 1914.
A Brief History of Microbiology
Fermentation and Pasteurization • Pasteur found that yeast ferments
sugars to alcohol and that bacteria can oxidize the alcohol to acetic acid.
• A heating process called pasteurization is used to kill bacteria in some alcoholic beverages and milk.
Louis Pasteur
A Brief History of Microbiology
The Germ Theory of Disease • Agostino Bassi (1835) & Pasteur (1865)
showed causal relationship between microorganisms and disease
• Joseph Lister introduced disinfectant to clean surgical dressings to control infections in humans (1860s)
• Robert Koch proved that microorganisms caused disease. Developed Koch's postulates (1876), a sequence of procedures to prove that a particular microorganism causes a particular disease.
Robert Koch
A page from Koch's lecture "The etiology of tuberculosis", delivered on 24 March 1882.
A Brief History of Microbiology
Vaccination
• In a vaccination, immunity (resistance to a particular disease) is conferred by inoculation with a vaccine.
• In 1798, Edward Jenner demonstrated that inoculation with cowpox material provides humans with immunity from smallpox.
• About 1880, Pasteur discovered that avirulent bacteria could be used as a vaccine for fowl cholera; he coined the word "vaccine".
• Modern vaccines are prepared from living avirulent microorganisms or killed pathogens, from isolated components of pathogens, or by recombinant DNA techniques.
Smallpox is the most deadly disease in our species’ history. Variola virus causes this disease and humans are the virus’ only natural host. It is transmitted person-to-person, most commonly through the air. Infected people exhale the virus from blisters in their mouth, and anyone who comes within 10 feet of a smallpox victim can inhale the aerosolized virus and catch the disease. There are no currently available anti-viral measures that doctors can use to treat smallpox. Antibiotics don’t work. Vaccination, however, protects a person from contracting this disease. More than 300 million people died from smallpox from 1900 to 1978, when the last case in the world occurred. The last case in the United States was in 1949. Doctors and public health officials eradicated the disease by mass vaccination
Variola virus causes small pox
The Birth of Modern Chemotherapy
Dreams of a "Magic Bullet"
Chemotherapy is the chemical treatment of a disease
• Two types of chemotherapeutic agents are:
synthetic / semi-synthetic drugs : chemically prepared in the laboratory
antibiotics: substances produced naturally by bacteria and fungi that inhibit the growth of other microorganisms
Paul Ehrlich introduced an arsenic-containing chemical called salvarsan to treat syphilis (1910). Coined terms "magic bullet" and "chemotherapy."
Paul Ehrlich
Salvarsan
The Birth of Modern Chemotherapy
Dreams of a "Magic Bullet"
Alexander Fleming • observed that the mold (fungus) Penicillium inhibited
the growth of a bacterial culture
• named the active ingredient "penicillin" (1928)
Penicillin has been used clinically as an antibiotic since the 1940s.
In 1939, Rene Dubos discovered two antibiotics produced by the bacterium Bacillus.
Researchers are tackling the problem of drug-resistant microbes.
Alexander Fleming
Modern Developments in
Microbiology
Bacteriology: bacteria
Virology: viruses
Mycology: fungi
Parasitology: parasitic protozoa (protozoology) and worms.
Modern Developments in
Microbiology Genomics: the study of all of an organism's
genes, to classify bacteria, fungi, and protozoa.
Immunology: study of AIDS, analysis of interferon action, and the development of new vaccines are among the current research interests in immunology.
Molecular biology and electron microscopy have provided tools for advancement of our knowledge of virology.
Recombinant DNA technology has helped advance all areas of microbiology.
Microbes and Human Welfare
Microorganisms • degrade dead plants and animals (saprophytes;
saprophytic)
• recycle chemical elements to be used by living plants and animals.
Bacteria • decompose organic matter in sewage
Bioremediation processes • use bacteria to clean up toxic wastes.
Biological controls • bacteria that cause diseases in insects
• Kill insect pests
• specific for the pest and do not harm the environment.
Microbes and Human Welfare
Biotechnology • Use of microbes to make products such as foods and
chemicals
Recombinant DNA • bacteria can produce substances such as proteins,
vaccines, and enzymes
Gene therapy • viruses are used to carry replacements for defective
or missing genes into human cells.
Genetic engineering • used in agriculture to protect plants from frost and
insects and to improve the shelf life of produce
Microbes and Human Disease normal microbiota or normal flora.
• Everyone has microorganisms in and on the body
pathogenicity; virulence • disease-producing properties of a species of
microbe and the host's resistance (immune response) are important factors in determining whether a person will contract a disease
infectious disease
• one in which pathogens invade a susceptible host
emerging infectious disease (EID)
• is a new or changing disease • shows an increase in incidence in the recent past or a
potential to increase in the near future