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TitleBacteria and Viruses [elem txt] - K. Rogers (Britannica Educ., 2011) SWW
TagsMedical
LanguageEnglish
File Size24.7 MB
Total Pages238
Table of Contents
                            TITLE
COPYRIGHT
CONTENTS
INTRODUCTION
CHAPTER 1 BACTERIAL MORPHOLOGY AND REPRODUCTION
	BACTERIA AS PROKARYOTES
	DIVERSITY OF STRUCTURE OF BACTERIA
	MORPHOLOGICAL FEATURES OF BACTERIA
		THE GRAM STAIN
		THE CELL ENVELOPE
		CAPSULES AND SLIME LAYERS
		FLAGELLA, FIMBRIAE, AND PILI
		CYTOPLASM
		BIOTYPES OF BACTERIA
	BACTERIAL REPRODUCTION
		REPRODUCTIVE PROCESSES
		EXCHANGE OF GENETIC INFORMATION
CHAPTER 2 GROWTH, ECOLOGY, AND EVOLUTION OF BACTERIA
	BIOSYNTHESIS, NUTRITION, AND GROWTH OF BACTERIA
		GROWTH OF BACTERIAL POPULATIONS
		FACTORS AFFECTING BACTERIAL GROWTH
		BACTERIAL METABOLISM
		BIOSYNTHETIC PATHWAYS OF BACTERIA
	BIOFILMS
	DISTRIBUTION IN NATURE
	THE IMPORTANCE OF BACTERIA TO HUMANS
		BACTERIA IN FOOD
		BACTERIA IN INDUSTRY
		BACTERIA IN MEDICINE
	EVOLUTION OF BACTERIA
CHAPTER 3 TYPES OF BACTERIA
	APPROACHES TO BACTERIAL CLASSIFICATION
		CLASSIFICATION BY GENETIC DIVERGENCE
		CLASSIFICATION BY MORPHOLOGY, BIOCHEMISTRY, AND OTHER FEATURES
	MAJOR TYPES OF BACTERIA
		GRAM-NEGATIVE BACTERIA
		GRAM-POSITIVE BACTERIA
	ARCHAEA
		HABITATS OF THE ARCHAEA
		CHARACTERISTICS OF THE ARCHAEA
	EXTREMOPHILES
CHAPTER 4 VIRUS MORPHOLOGY AND EVOLUTION
	DEFINITION OF A VIRUS
	HOST RANGE AND DISTRIBUTION
	SIZE AND SHAPE
		THE NUCLEIC ACID
		THE PROTEIN CAPSID
		THE LIPOPROTEIN ENVELOPE
	EVOLUTIONARY ORIGINS
	EVOLUTION OF NEW VIRUS STRAINS
CHAPTER 5 CYCLES AND PATTERNS OF VIRAL INFECTION
	THE CYCLE OF INFECTION
	VIRAL DNA INTEGRATION
		LYSOGENY
		MALIGNANT TRANSFORMATION
	ROLE OF VIRUSES IN DISEASE
		INFECTIOUS PATTERNS
		LATENCY
		CHRONIC AND SLOWLY PROGRESSIVE DISEASES
		VIRUSES AND VACCINES
		CONTROLLING VIRAL INFECTION
CHAPTER 6 TYPES OF VIRUSES
	DISTINGUISHING TAXONOMIC FEATURES
	MAJOR GROUPS OF DNA VIRUSES
		ADENOVIRUS
		ASFARVIRUS
		HEPADNAVIRUS
		HERPESVIRUS
		IRIDOVIRUS
		PAPILLOMAVIRUS
		PARVOVIRUS
		POLYOMAVIRUS
		POXVIRUS
	MAJOR GROUPS OF RNA VIRUSES
		ARENAVIRUS
		BUNYAVIRUS
		CALICIVIRUS
		CORONAVIRUS
		FLAVIVIRUS
		FILOVIRUS
		MYXOVIRUS
		ORTHOMYXOVIRUS
		PARAMYXOVIRUS
		PICORNAVIRUS
		REOVIRUS
		RETROVIRUS
		RHABDOVIRUS
	CONCLUSION
GLOSSARY
BIBLIOGRAPHY
INDEX
                        
Document Text Contents
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7 Bacteria and Viruses 7

98

including rainbow trout and Pacific salmon. In these spe-
cies, Y. ruckeri causes enteric redmouth disease, which is
characterized by hemorrhaging of the subcutaneous tis-
sues under the fins and around the eyes and mouth.

Gram-Positive Bacteria

Gram-positive bacteria are distinguished from Gram-
negative organisms by the thick peptidoglycan layer in
their cell walls. Dye that enters the cells during Gram
staining is retained after treatment with a solvent, which
is unable to penetrate through the cell wall to remove
the stain. As a result, Gram-positive bacteria are purple
in colour when viewed under the microscope following
staining. Examples of important groups of Gram-positive
organisms include Lactobacillus, Staphylococcus, and
Streptococcus.

Actinomycetes

Actinomycetes are Gram-positive, generally anaerobic
bacteria noted for a filamentous and branching growth
pattern that results, in most forms, in an extensive colony,
or mycelium. The mycelium in some species may break
apart to form rod- or coccoid-shaped forms. Many gen-
era also form spores. The sporangia, or spore cases, may
be found on aerial hyphae, on the colony surface, or free
within the environment. Motility, when present, is con-
ferred by flagella. Many species of actinomycetes occur in
soil and are harmless to animals and higher plants, while
some are important pathogens, and many others are ben-
eficial sources of antibiotics.

Many authorities recognize eight different groups of
actinomycetes, though these groups are themselves het-
erogeneous and will require further study to classify fully.
Of the specific types of actinomycetes, Nocardia asteroides

Page 120

99

causes tissue infections in humans, and Dermatophilus
congolensis causes dermatophilosis, a severe dermatitis of
cattle, sheep, horses, and occasionally humans. Several
species of Streptomyces cause the disease actinomycosis in
humans and cattle. Many of the actinomycetes are sources
of antibiotics such as streptomycin.

Bacillus

Bacillus is a genus of rod-shaped, Gram-positive, aerobic
or (under some conditions) anaerobic bacteria widely
found in soil and water. The term bacillus has been applied
in a general sense to all cylindrical or rodlike bacteria. The
largest species are about 2 μm across by 7 μm long and fre-
quently occur in chains.

In 1877 German botanist Ferdinand Cohn described
two different forms of hay bacillus (now known as Bacillus
subtilis): one that could be killed upon exposure to heat
and one that was resistant to heat. He called the heat-
resistant forms “spores” (endospores) and discovered
that these dormant forms could be converted to a vegeta-
tive, or actively growing, state. Today it is known that all
Bacillus species can form dormant spores under adverse
environmental conditions. These endospores may remain
viable for long periods of time. Endospores are resistant
to heat, chemicals, and sunlight and are widely distributed
in nature, primarily in soil, from which they invade dust
particles.

Some types of Bacillus bacteria are harmful to humans,
plants, or other organisms. For example, B. cereus some-
times causes spoilage in canned foods and food poisoning
of short duration. B. subtilis is a common contaminant of
laboratory cultures (it plagued Louis Pasteur in many of
his experiments) and is often found on human skin. Most
strains of Bacillus are not pathogenic for humans but may,
as soil organisms, infect humans incidentally. A notable

7 Types of Bacteria 7

Page 237

7 Bacteria and Viruses 7

216

new strains of, 133–135
role in disease, 154–167
size and shape of, 123–128

W
warts, 145, 167, 176, 177, 178
West Nile virus, 185, 186
whooping cough, 9, 64
Woese, Carl, 5, 7, 108
World Health Organization

(WHO), 163

X
Xanthomonas, 91

Y
yellow fever, 159, 185

Z
zidovudine, 151, 166
Zoogloea, 18

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