Microbiology Fundamentals

• Microorganisms, whether cellular or viral, have the ability to interact with human and nonhuman hosts in ways that can be beneficial, neutral, or detrimental.
• Microorganisms serve as essential models that offer insights into the fundamental knowledge of life processes.

Naming and Classifying Microorganisms

• Microscopic eukaryotes like fungi, protozoa, and algae share some processes with bacteria, but their cellular properties differ significantly.
• Carolus Linnaeus created a nomenclature system in 1735 where each living organism is assigned two names: a genus and a specific epithet, both of which are underlined or italicized.

Types of Microorganisms

• Bacteria: These are unicellular organisms lacking a nucleus (prokaryotic).
• Most bacteria possess a peptidoglycan cell wall, reproduce through binary fission, and may have flagella.
• Bacteria exhibit diverse nutritional strategies, utilizing a wide array of chemical substances.
• Archaea: These consist of prokaryotic cells without peptidoglycan in their cell walls.
• Archaea include methanogens, extreme halophiles, and extreme thermophiles.
• Fungi: These eukaryotic organisms (cells with a true nucleus) include mushrooms, molds, and yeasts, with most being multicellular.
• Fungi acquire nutrients through absorption of organic material.
• Protozoa: These unicellular eukaryotes obtain nourishment either by absorption or ingestion via specialized structures.
• Algae: These unicellular or multicellular eukaryotes obtain nourishment through photosynthesis.
• Algae generate oxygen and carbohydrates, which are utilized by other organisms.
• Viruses: These are noncellular, parasitic entities.
• Viruses consist of a nucleic acid core (DNA or RNA) enclosed by a protein coat, sometimes with an additional envelope.
• Helminths: These multicellular animal parasites include flatworms and roundworms.
• Microscopic stages in the life cycle of helminths can be identified through traditional microbiological procedures.

Classification of Microorganisms

• All organisms are classified into three domains: Bacteria, Archaea, and Eukarya.
• Eukarya includes protists, fungi, plants, and animals.

A Brief History of Microbiology

• Microbiology involves understanding between science and society.

The First Observations

• Robert Hooke's observations led to cell theory: all living things are composed of cells.
• Anton van Leeuwenhoek first observed microorganisms in 1673 using a simple microscope.

The Debate over Spontaneous Generation

• Until the mid-1800s, many believed living organisms could arise from nonliving matter (spontaneous generation).
• Francesco Redi demonstrated in 1668 that maggots only appeared on decaying meat when flies could lay eggs on it.
• John Needham claimed in 1745 that microorganisms could arise spontaneously from heated nutrient broth.
• Lazzaro Spallanzani repeated Needham's experiments in 1765 and suggested Needham's results were from microorganisms in the air entering the broth.
• Rudolf Virchow introduced the concept of biogenesis in 1858: living cells arise only from preexisting cells.
• Louis Pasteur proved in 1861 that microorganisms are everywhere in the air and offered proof of biogenesis.
• Pasteur's discoveries led to aseptic techniques, preventing contamination by microorganisms in laboratories and medical procedures.

The First Golden Age of Microbiology

• Microbiology rapidly advanced between 1857 and 1914.
• Pasteur found that yeast ferments sugars to alcohol, and bacteria oxidize alcohol to acetic acid.
• Pasteurization: a heating process used to kill bacteria in some alcoholic beverages and milk.
• Agostino Bassi (1835) and Pasteur (1865) found that microorganisms cause disease.
• Joseph Lister introduced using a disinfectant to clean surgical wounds in the 1860s to control infections in humans.
• Robert Koch proved microorganisms cause disease and developed Koch's postulates (1876) to prove a particular microorganism causes a particular disease.
• In 1798, Edward Jenner showed that inoculation with cowpox material gives humans immunity to smallpox.
• Around 1880, Pasteur discovered that avirulent bacteria could be used as a vaccine for fowl cholera and coined the word vaccine.
• Modern vaccines are prepared from living avirulent microorganisms, killed pathogens, isolated components of pathogens, and recombinant DNA techniques.

The Second Golden Age of Microbiology

• Began with the discovery of penicillin's effectiveness against infections.
• Chemotherapeutic agents: synthetic drugs (chemically prepared in the laboratory) and antibiotics (naturally produced substances from bacteria and fungi to inhibit the growth of other microorganisms).
• Paul Ehrlich introduced salvarsan, an arsenic-containing chemical, to treat syphilis in 1910.
• Alexander Fleming observed the Penicillium fungus inhibiting bacterial growth and named the active ingredient penicillin in 1928.
• Researchers now work on the problem of drug-resistant microbes.
• Bacteriology: the study of bacteria; mycology: the study of fungi; and parasitology: the study of parasitic protozoa and worms.
• Study of AIDS and the action of interferons are current research interests in immunology.
• New techniques in molecular biology and electron microscopy have helped advance virology.
• Recombinant DNA technology has helped advance all areas of microbiology.

The Third Golden Age of Microbiology

• Microbiologists use genomics, the study of all of an organism's genes, to study microbiomes in different environments.

Microbes and Human Welfare

• Cell genomes can be manipulated to alter cell function.
• Microbes are essential for life and the processes that support it (e.g., biogeochemical cycles and plant/animal microflora).
• Humans use and harness microorganisms and their products.
• Microorganisms degrade dead plants and animals and recycle chemical elements to be used by living plants and animals.
• Bacteria decompose organic matter in sewage.
• Bioremediation uses bacteria to clean up toxic wastes.
• Bacteria that cause diseases in insects are being used as biological controls of insect pests.
• Using microbes to make products like foods and chemicals is called biotechnology.
• Recombinant DNA allows bacteria to produce important substances like proteins, vaccines, and enzymes.
• In gene therapy, viruses carry replacements for defective or missing genes into human cells.
• Genetically modified bacteria protect plants from frost and insects and improve produce shelf life.

Microbes and Human Disease

• Disease-producing properties of a microbe and the host's resistance determine whether a person will contract a disease.
• Bacterial communities that form slimy layers on surfaces are called biofilms.
• An infectious disease occurs when pathogens invade a susceptible host.
• An emerging infectious disease (EID): a new or changing disease showing an increase in incidence in the recent past or a potential to increase in the near future.