Chapter 1

An Invisible World

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Summary

Microorganisms (or microbes ) are living organisms that are generally too small to be seen without a microscope Throughout history, humans have used microbes to make fermented foods such as beer, bread, cheese, and wine Long before the invention of the microscope, some people theorized that infection and disease were spread by living things that were too small to be seen. They also correctly intuited certain principles regarding the spread of disease and immunity

Chapter 2

How We See the Invisible World

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Summary

A lens is a medium with a curved surface that refracts and focuses light to produce an image Light waves interacting with materials may be reflected , absorbed , or transmitted , depending on the properties of the material Light waves can interact with each other ( interference ) or be distorted by interactions with small objects or openings ( diffraction ) Refraction occurs when light waves change speed and direction as they pass from one medium to another.

Key terms

lens

a medium with a curved surface that refracts and focuses light to produce an image

Chapter 3

The Cell

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Summary

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks Experimentation by Francesco Redi in the 17th century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation

Chapter 4

Prokaryotic Diversity

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Summary

The totality of forms of prokaryotes (particularly bacteria) living on the human body is called the human microbiome, which varies between regions of the body and individuals, and changes over time The totality of forms of prokaryotes (particularly bacteria) living in a certain region of the human body (e.g., mouth, throat, gut, eye, vagina) is called the microbiota of this region Prokaryotes are unicellular microorganisms whose cells have no nucleus Prokaryotes can be found everywhere on our planet, even in the most extreme environments

Key terms

human body

called the human microbiome, which varies between regions of the body and individuals, and changes over time

Chapter 5

The Eukaryotes of Microbiology

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Summary

Helminth parasites are included within the study of microbiology because they are often identified by looking for microscopic eggs and larvae Protists are a diverse, polyphyletic group of eukaryotic organisms Protists may be unicellular or multicellular. They vary in how they get their nutrition, morphology, method of locomotion, and mode of reproduction

Key terms

study of microbiology because they

often identified by looking for microscopic eggs and larvae

Chapter 6

Acellular Pathogens

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Summary

Viruses are generally ultramicroscopic, typically from 20 nm to 900 nm in length. Virions are acellular and consist of a nucleic acid, DNA or RNA, but not both, surrounded by a protein capsid . There may also be a phospholipid membrane surrounding the capsid Viruses are obligate intracellular parasites

Chapter 7

Microbial Biochemistry

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Summary

The most abundant elements in cells are hydrogen, carbon, oxygen, nitrogen, phosphorus, and sulfur Each carbon atom can bind to another one producing a carbon skeleton that can be straight, branched, or ring shaped The same numbers and types of atoms may bond together in different ways to yield different molecules called isomers . Isomers may differ in the bonding sequence of their atoms ( structural isomers ) or in the spatial arrangement of atoms whose bonding sequences are the same ( stereoisomers ), and their physical and chemical properties…

Key terms

most abundant elements in cells

hydrogen, carbon, oxygen, nitrogen, phosphorus, and sulfur

Chapter 8

Microbial Metabolism

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Summary

Metabolism includes chemical reactions that break down complex molecules ( catabolism ) and those that build complex molecules ( anabolism ) Organisms may be classified according to their source of carbon. Autotrophs convert inorganic carbon dioxide into organic carbon; heterotrophs use fixed organic carbon compounds Organisms may also be classified according to their energy source.

Chapter 9

Microbial Growth

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Summary

Most bacterial cells divide by binary fission . Generation time in bacterial growth is defined as the doubling time of the population Cells in a closed system follow a pattern of growth with four phases: lag , logarithmic (exponential) , stationary , and death Cells can be counted by direct viable cell count .

Chapter 10

Biochemistry of the Genome

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Summary

DNA was discovered and characterized long before its role in heredity was understood. Microbiologists played significant roles in demonstrating that DNA is the hereditary information found within cells In the 1850s and 1860s, Gregor Mendel experimented with true-breeding garden peas to demonstrate the heritability of specific observable traits In 1869, Friedrich Miescher isolated and purified a compound rich in phosphorus from the nuclei of white blood cells; he named the compound nuclein.

Chapter 11

Mechanisms of Microbial Genetics

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Summary

The genotype of a cell is the full collection of genes a cell contains. The phenotype is a cell’s observable characteristics resulting from the proteins it is producing at a given time under specific environmental conditions The DNA replication process is semiconservative , which results in two DNA molecules, each having one parental strand of DNA and one newly synthesized strand DNA serves two important cellular functions: It is the genetic material passed from parent to offspring and it serves as the information to direct and regulate the construction of the proteins necessary for the cell to…

Key terms

phenotype

a cell’s observable characteristics resulting from the proteins it is producing at a given time under specific environmental conditions

DNA replication process

semiconservative , which results in two DNA molecules, each having one parental strand of DNA and one newly synthesized strand

genotype of a cell

the full collection of genes a cell contains

Chapter 12

Modern Applications of Microbial Genetics

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Summary

Biotechology is the science of utilizing living systems to benefit humankind. In recent years, the ability to directly alter an organism’s genome through genetic engineering has been made possible due to advances in recombinant DNA technology, which allows researchers to create recombinant DNA… Molecular cloning involves methods used to construct recombinant DNA and facilitate their replication in host organisms. These methods include the use of restriction enzymes (to cut both foreign DNA and plasmid vectors) , ligation (to paste fragments of DNA together), and the introduction of recombinant DNA into a host organism (often…

Chapter 13

Control of Microbial Growth

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Summary

Inanimate items that may harbor microbes and aid in their transmission are called fomites . The level of cleanliness required for a fomite depends both on the item’s use and the infectious agent with which the item may be contaminated The CDC and the NIH have established four biological safety levels (BSLs) for laboratories performing research on infectious agents. Each level is designed to protect laboratory personnel and the community.

Chapter 14

Antimicrobial Drugs

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Summary

The use of narrow-spectrum antimicrobial drugs is preferred in many cases to avoid superinfection and the development of antimicrobial resistance The dosage and route of administration are important considerations when selecting an antimicrobial to treat and infection. Antimicrobial drugs produced by purposeful fermentation and/or contained in plants have been used as traditional medicines in many cultures for millennia The purposeful and systematic search for a chemical “magic bullet” that specifically target infectious microbes was initiated by Paul Ehrlich in the early 20th century

Key terms

use of narrow-spectrum antimicrobial drugs

preferred in many cases to avoid superinfection and the development of antimicrobial resistance

dosage and route of administration

important considerations when selecting an antimicrobial to treat and infection

Chapter 15

Microbial Mechanisms of Pathogenicity

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Summary

An acute disease is short in duration, whereas a chronic disease lasts for months or years. Some infections cause disease , which is any deviation from the normal function or structure of the host Signs of a disease are objective and are measured. Symptoms of a disease are subjective and are reported by the patient

Key terms

disease

objective and are measured

acute disease

short in duration, whereas a chronic disease lasts for months or years

Chapter 16

Disease and Epidemiology

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Summary

Incidence is the number of new cases (morbidity or mortality), usually expressed as a proportion, during a specified time period; prevalence is the total number affected in the population, again usually expressed as a… Epidemiology is the science underlying public health Morbidity means being in a state of illness, whereas mortality refers to death; both morbidity rates and mortality rates are of interest to epidemiologists Sporadic diseases only occur rarely and largely without a geographic focus.

Key terms

specified time period; prevalence

the total number affected in the population, again usually expressed as a…

Chapter 17

Innate Nonspecific Host Defenses

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Summary

Nonspecific innate immunity provides a first line of defense against infection by nonspecifically blocking entry of microbes and targeting them for destruction or removal from the body The physical defenses of innate immunity include physical barriers, mechanical actions that remove microbes and debris, and the microbiome, which competes with and inhibits the growth of pathogens The skin, mucous membranes, and endothelia throughout the body serve as physical barriers that prevent microbes from reaching potential sites of infection. Tight cell junctions in these tissues prevent microbes from passing through

Chapter 18

Adaptive Specific Host Defenses

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Summary

The five classes of antibody are IgM , IgG , IgA , IgE , and IgD , each differing in size, arrangement, location within the body, and function. Adaptive immunity is an acquired defense against foreign pathogens that is characterized by specificity and memory. The first exposure to an antigen stimulates a primary response , and subsequent exposures stimulate a faster and strong secondary response Adaptive immunity is a dual system involving humoral immunity (antibodies produced by B cells) and cellular immunity (T cells directed against intracellular pathogens)

Key terms

five classes of antibody

IgM , IgG , IgA , IgE , and IgD , each differing in size, arrangement, location within the body, and function

Chapter 19

Diseases of the Immune System

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Summary

An allergy is an adaptive immune response, sometimes life-threatening, to an allergen Type I hypersensitivity requires sensitization of mast cells with IgE, involving an initial IgE antibody response and IgE attachment to mast cells. On second exposure to an allergen, cross-linking of IgE molecules on mast cells triggers degranulation and release of preformed and newly formed chemical mediators of inflammation. Type I hypersensitivity may be localized and relatively minor (hives and hay fever) or system-wide and dangerous (systemic anaphylaxis )

Key terms

allergy

an adaptive immune response, sometimes life-threatening, to an allergen

Chapter 20

Laboratory Analysis of the Immune Response

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Summary

Antibodies bind with high specificity to antigens used to challenge the immune system, but they may also show cross-reactivity by binding to other antigens that share chemical properties with the original antigen Injection of an antigen into an animal will result in a polyclonal antibody response in which different antibodies are produced that react with the various epitopes on the antigen Polyclonal antisera are useful for some types of laboratory assays, but other assays require more specificity. Diagnostic tests that use polyclonal antisera are typically only used for screening because of the possibility of false-positive and false-negative results

Chapter 21

Skin and Eye Infections

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Summary

Human skin consists of two main layers, the epidermis and dermis , which are situated on top of the hypodermis , a layer of connective tissue The skin is an effective physical barrier against microbial invasion The skin’s relatively dry environment and normal microbiota discourage colonization by transient microbes The skin’s normal microbiota varies from one region of the body to another

Key terms

skin

an effective physical barrier against microbial invasion

conjunctiva of the eye

a frequent site for microbial infection, but deeper eye infections are less common; multiple types of conjunctivitis exist

Chapter 22

Respiratory System Infections

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Summary

Air enters the upper respiratory tract through the nasal cavity and mouth, which both lead to the pharynx . The upper respiratory tract is colonized by an extensive and diverse normal microbiota, many of which are potential pathogens. The respiratory tract is divided into upper and lower regions at the epiglottis The lower respiratory tract extends from the larynx into the trachea before branching into the bronchi , which divide further to form the bronchioles , which terminate in alveoli , where gas exchange occurs

Key terms

upper respiratory tract

colonized by an extensive and diverse normal microbiota, many of which are potential pathogens

infected tissues; these conditions

given names ending in -itis , such as rhinitis , sinusitis , otitis , pharyngitis , and bronchitis

respiratory tract

divided into upper and lower regions at the epiglottis

Chapter 23

Urogenital System Infections

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Summary

The urinary system includes the kidneys, ureters , urinary bladder , and urethra ; the bladder and urethra are the most common sites of infection The urinary system is responsible for filtering the blood, excreting wastes, and helping to regulate electrolyte and water balance The most commons sites of infection in the female reproductive system are the vulva, vagina , cervix, and fallopian tubes Pyelonephritis is a serious kidney infection that is often caused by bacteria that travel from infections elsewhere in the urinary tract and may cause systemic complications

Key terms

urinary system

responsible for filtering the blood, excreting wastes, and helping to regulate electrolyte and water balance

female reproductive system

the vulva, vagina , cervix, and fallopian tubes

bladder and urethra

the most common sites of infection

Chapter 24

Digestive System Infections

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Summary

The digestive tract, consisting of the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine, has a normal microbiota that is important for health The constant movement of materials through the gastrointestinal canal, the protective layer of mucus, the normal microbiota, and the harsh chemical environment in the stomach and small intestine help to prevent… Infections or microbial toxins in the oral cavity can cause tooth decay , periodontal disease , and various types of ulcers Infections and intoxications of the gastrointestinal tract can cause general symptoms such as nausea, vomiting, diarrhea, and fever.

Chapter 25

Circulatory and Lymphatic System Infections

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Summary

The circulatory system moves blood throughout the body and has no normal microbiota The lymphatic system moves fluids from the interstitial spaces of tissues toward the circulatory system and filters the lymph. The circulatory and lymphatic systems are home to many components of the host immune defenses Infections of the circulatory system may occur after a break in the skin barrier or they may enter the bloodstream at the site of a localized infection.

Key terms

circulatory and lymphatic systems

home to many components of the host immune defenses

circulatory system

almost universally serious

Chapter 26

Nervous System Infections

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Summary

Tissues of the PNS and CNS are formed of cells called glial cells and neurons The nervous system consists of two subsystems: the central nervous system and peripheral nervous system The skull and three meninges (the dura mater , arachnoid mater , and pia mater ) protect the brain Since the blood-brain barrier excludes most microbes, there is no normal microbiota in the CNS

Key terms

PNS and CNS

formed of cells called glial cells and neurons