1.1 Microbes in Our Lives

Microbes that live stably in and on the human body are called the human microbiome, or microbiota.
Many factors influence where and whether a microbe can indefinitely colonize the body as benign normal microbiota or be only a fleeting member of its community (known as transient microbiota).

1.2 Naming and Classifying Microorganisms

Bacteria (singular: bacterium) are relatively simple, single-celled (unicellular) organisms.
- Because their genetic material is not enclosed in a special nuclear membrane, bacterial cells are called prokaryotes.
Like bacteria, archaea consist of prokaryotic cells, but if they have cell walls, the walls lack peptidoglycan.
Fungi are eukaryotes, organisms whose cells have a distinct nucleus containing the cell’s genetic material (DNA), surrounded by a special envelope called the nuclear membrane.
Protozoa (singular: protozoan) are unicellular eukaryotic microbes.
Algae (singular: alga) are photosynthetic eukaryotes with a wide variety of shapes and both sexual and asexual reproductive forms.
Animal parasites are eukaryotes. The two major groups of parasitic worms are the flatworms and the roundworms, collectively called helminths.

1.3 A Brief History

Hooke’s discovery marked the beginning of the cell theory— the theory that all living things are composed of cells.
Until the second half of the nineteenth century, many scientists and philosophers believed that some forms of life could arise spontaneously from nonliving matter; they called this hypothetical process spontaneous generation.
In 1858 Rudolf Virchow challenged the case for spontaneous generation with the concept of biogenesis, hypothesizing that living cells arise only from preexisting living cells.
These discoveries form the basis of aseptic techniques, procedures that prevent contamination by unwanted microorganisms, which are now the standard practice in laboratories and many medical procedures.
Koch thus established Koch’s postulates, a sequence of experimental steps for directly relating a specific microbe to a specific disease
The protection from disease provided by vaccination (or by recovery from the disease itself) is called immunity.
Treatment of disease by using chemical substances is called chemotherapy.
Chemicals produced naturally by bacteria and fungi that act against other microorganisms are called antibiotics.
Chemotherapeutic agents prepared from chemicals in the laboratory are called synthetic drugs.
Bacteriology, the study of bacteria, began with van Leeuwenhoek’s first examination of tooth scrapings.
Mycology, the study of fungi, includes medical, agricultural, and ecological branches.
Parasitology is the study of protozoa and parasitic worms.
The study of viruses, virology, originated during the First Golden Age of Microbiology.
Microbial genetics studies the mechanisms by which microorganisms inherit traits, and molecular biology looks at how genetic information is carried in molecules of DNA.
Genomics is the study of all of an organism’s genes, scientists are able to classify bacteria and fungi according to their genetic relationships with other bacteria, fungi, and protozoa.
Recombinant DNA (rDNA) technology inserts recombinant DNA into bacteria (or other microbes) to make large quantities of a desired protein.

1.4 Microbes and Human Welfare

Microbial ecology, the study of the relationship between microorganisms and their environment, originated with the work of these scientists.
By using bacteria in these ways—a process known as bioremediation—toxins can be removed from underground wells, chemical spills, toxic waste sites, and oil spills, such as the massive oil spill from a British Petroleum offshore drilling rig in the Gulf of Mexico in 2010.
A very exciting and important outcome of recombinant DNA techniques is gene therapy—inserting a missing gene or replacing a defective one in human cells.

1.5 Microbes and Human Disease

This latter mode of behavior is called a biofilm, a complex aggregation of microbes.
An infectious disease is a disease in which pathogens invade a susceptible host, such as a human or an animal.
Since 2014, there have been 1800 confirmed human cases and 630 deaths caused by a new virus called Middle East respiratory syndrome coronavirus.
Because the first reported cases were linked to the Middle East, this latest emerging infectious disease is called Middle East respiratory syndrome.
H1N1 influenza (flu), also known as swine flu, is a type of influenza caused by a new virus called influenza H1N1.
Avian influenza A (H5N1), or bird flu, caught the attention of the public in 2003, when it killed millions of poultry and 24 people in southeast Asia.
In the 1980s, methicillin-resistant S. aureus, called MRSA, emerged and became endemic in many hospitals, leading to increasing use of vancomycin.
First detected in 1995, Ebola virus disease causes fever, hemorrhaging, and blood clotting in vessels.
Recorded cases of Marburg virus, another hemorrhagic fever virus, are rare.

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Chapter 1: The Microbial World and You

1.1 Microbes in Our Lives

Microbes that live stably in and on the human body are called the human microbiome, or microbiota.
Many factors influence where and whether a microbe can indefinitely colonize the body as benign normal microbiota or be only a fleeting member of its community (known as transient microbiota).

1.2 Naming and Classifying Microorganisms

Bacteria (singular: bacterium) are relatively simple, single-celled (unicellular) organisms.
- Because their genetic material is not enclosed in a special nuclear membrane, bacterial cells are called prokaryotes.
Like bacteria, archaea consist of prokaryotic cells, but if they have cell walls, the walls lack peptidoglycan.
Fungi are eukaryotes, organisms whose cells have a distinct nucleus containing the cell’s genetic material (DNA), surrounded by a special envelope called the nuclear membrane.
Protozoa (singular: protozoan) are unicellular eukaryotic microbes.
Algae (singular: alga) are photosynthetic eukaryotes with a wide variety of shapes and both sexual and asexual reproductive forms.
Animal parasites are eukaryotes. The two major groups of parasitic worms are the flatworms and the roundworms, collectively called helminths.

1.3 A Brief History

Hooke’s discovery marked the beginning of the cell theory— the theory that all living things are composed of cells.
Until the second half of the nineteenth century, many scientists and philosophers believed that some forms of life could arise spontaneously from nonliving matter; they called this hypothetical process spontaneous generation.
In 1858 Rudolf Virchow challenged the case for spontaneous generation with the concept of biogenesis, hypothesizing that living cells arise only from preexisting living cells.
These discoveries form the basis of aseptic techniques, procedures that prevent contamination by unwanted microorganisms, which are now the standard practice in laboratories and many medical procedures.
Koch thus established Koch’s postulates, a sequence of experimental steps for directly relating a specific microbe to a specific disease
The protection from disease provided by vaccination (or by recovery from the disease itself) is called immunity.
Treatment of disease by using chemical substances is called chemotherapy.
Chemicals produced naturally by bacteria and fungi that act against other microorganisms are called antibiotics.
Chemotherapeutic agents prepared from chemicals in the laboratory are called synthetic drugs.
Bacteriology, the study of bacteria, began with van Leeuwenhoek’s first examination of tooth scrapings.
Mycology, the study of fungi, includes medical, agricultural, and ecological branches.
Parasitology is the study of protozoa and parasitic worms.
The study of viruses, virology, originated during the First Golden Age of Microbiology.
Microbial genetics studies the mechanisms by which microorganisms inherit traits, and molecular biology looks at how genetic information is carried in molecules of DNA.
Genomics is the study of all of an organism’s genes, scientists are able to classify bacteria and fungi according to their genetic relationships with other bacteria, fungi, and protozoa.
Recombinant DNA (rDNA) technology inserts recombinant DNA into bacteria (or other microbes) to make large quantities of a desired protein.

1.4 Microbes and Human Welfare

Microbial ecology, the study of the relationship between microorganisms and their environment, originated with the work of these scientists.
By using bacteria in these ways—a process known as bioremediation—toxins can be removed from underground wells, chemical spills, toxic waste sites, and oil spills, such as the massive oil spill from a British Petroleum offshore drilling rig in the Gulf of Mexico in 2010.
A very exciting and important outcome of recombinant DNA techniques is gene therapy—inserting a missing gene or replacing a defective one in human cells.

1.5 Microbes and Human Disease

This latter mode of behavior is called a biofilm, a complex aggregation of microbes.
An infectious disease is a disease in which pathogens invade a susceptible host, such as a human or an animal.
Since 2014, there have been 1800 confirmed human cases and 630 deaths caused by a new virus called Middle East respiratory syndrome coronavirus.
Because the first reported cases were linked to the Middle East, this latest emerging infectious disease is called Middle East respiratory syndrome.
H1N1 influenza (flu), also known as swine flu, is a type of influenza caused by a new virus called influenza H1N1.
Avian influenza A (H5N1), or bird flu, caught the attention of the public in 2003, when it killed millions of poultry and 24 people in southeast Asia.
In the 1980s, methicillin-resistant S. aureus, called MRSA, emerged and became endemic in many hospitals, leading to increasing use of vancomycin.
First detected in 1995, Ebola virus disease causes fever, hemorrhaging, and blood clotting in vessels.
Recorded cases of Marburg virus, another hemorrhagic fever virus, are rare.