Download - 28.1 The Microbial World Chapter 28
1
Chapter 28Microbiology
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
28.1 The Microbial World
• Antonie van Leeuwenhoek (1632–1723)
improved microscope in 1600s
– Described “animacules”
– Believed in spontaneous generation
• Louis Pasteur used microbes to discredit the
theory of spontaneous generation in 1659
Pasteur’s Experiments
FIRST EXPERIMENT
flasks outside building
opened briefly
89% show growth
32% show growth
flasks inside building
opened briefly
boiling to
sterilize
broth
boiling to
sterilize
broth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pasteur’s Experiments
SECOND EXPERIMENT
boiling to
sterilize
broth
flask is open to air
air here is pure
air enter shere
bacteria collect here
100% have no growth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
28.1 The Microbial World
• Microbiology– Study of bacteria, archaea, protists, fungi, viruses,
viroids and prions
• Many microbes provide important benefits– Normal microflora on our bodies
– Ecosystems• Decomposers (bacteria and fungi)
• Photosynthesis
– Industry• Food processing
• Medicine
• Biotechnology
28.2 Bacteria and Archaea
• Domain Bacteria and Domain Archaea
– Molecular and cellular differences separate
the two
• Both are prokaryotes
– Do not have nuclei or the membrane-bound
cytoplasmic organelles found in eukaryotic
cells
28.2 Bacteria and Archaea
• Biology of Bacteria
– Most between 0.2-10!m in size
– 3 basic shapes
• Rod (bacillus, pl., bacilli); spherical (coccus, pl.,
cocci); and spiral-shaped or helical
– All have a plasma membrane
– Most have a cell wall
28.2 Bacteria and Archaea
28.2 Bacteria and Archaea
• Biology of Bacteria
– Most bacteria have a single circular
chromosome
• Many also have plasmids
– Accessory rings of DNA
– Ribosomes
– Motile bacteria have flagella
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
fimbriae flagellumnucleoidchromosome
(DNA)
storage
granule
capsule ribosomes cell wall plasma
membrane
28.2 Bacteria and Archaea
• Bacterial Reproduction
– Reproduce asexually
– Binary fission
• Bacterial cell replicates its genome and divides in
half
• Each daughter cell is a clone – exact copy
– In harsh conditions, some bacteria can form a
resistant endospore
Binary FissionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cytoplasm
b.
a.
chromosome
cell wall
nucleoid
0.5 !m
b: © CNRI/SPL/Photo Researchers, Inc.
28.2 Bacteria and Archaea
• Bacterial Reproduction
– No sexual reproduction
– 3 mechanisms of genetic recombination
• Conjugation: donor cell passes DNA to a recipient
cell by way of a sex pilus
• Transformation: bacterium takes up DNA fromenvironment released by dead bacteria
• Transduction: viruses carry bacterial DNA fromcell to cell
28.2 Bacteria and Archaea
• Bacterial Metabolism
– Most are heterotrophic
• Require an outside source of organic compounds
– Some are chemoautotrophs
• Reduce carbon dioxide to an organic compound
using energy from chemicals such as ammonia,
hydrogen gas or hydrogen sulfide
– Some are photosynthetic
• Cyanobacteria - have chlorophyll
28.2 Bacteria and Archaea
• Bacterial Diseases in Humans
– Most bacteria do not cause diseases!
28.2 Bacteria and Archaea
• Bacterial Diseases in Humans
– Streptococcus Infections
• Cause more disease than any other bacteria
• Streptococcus pneumoniae: pneumonia, meningitis, and
middle ear infections
• Streptococcus mutans: contributes to tooth decay
• Streptococcus pyogenes: causes the most diseases of any
strep
– Pharyngitis: commonly called strep throat
– Impetigo in infants: mild skin disease
– Scarlet fever: strain produces red rash
– Rheumatic fever: from endotoxins
– Necrotizing fasciitis: “flesh-eating” bacteria
28.2 Bacteria and Archaea
• Bacterial Diseases in Humans
– Staphylococcus aureus and MRSA
• About 20% of people are carriers on their skin
without symptoms
• Disease usually limited to skin infections
• A strain resistant to methicilin is called MRSA
– Killing young, otherwise healthy individuals
– Often posses genes coding for toxins not found in other
S. aureus strains
28.2 Bacteria and Archaea
• Bacterial Diseases
– Tuberculosis (TB)
• Leading cause of death
worldwide due to
infectious disease
• 1/3 of the world’s
population is infected
• Caused by
Mycobacterium
tuberculosis
• Active lesions in lung
cause tubercles from
immune response
– Become calcified
© Leonard V. Crowley, An Introduction to Human Disease: Pathology and Pathophysiology
Correlations 5/e, page 383 right and page 385 left; 2001: Jones and Bartlett Publishers,
Sudbury, MA. Reprinted with permission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. b. 1 mm
tubercle
28.2 Bacteria and Archaea
• Bacterial Diseases in Humans– Food Poisoning
• Bacteria cause food poisoning by two methods
– Produce a toxin while growing in food
» Causes vomiting and diarrhea, usually self-limiting
» Clostridium botulinum – produces one of themost toxic substances on Earth
– Cause an infection while growing in theintestines
• Salmonella
28.2 Bacteria and Archaea
• Bacterial Diseases in Humans
– Drug Control of Bacterial Diseases
• Antibiotics inhibit bacteria by interfering with
unique metabolic pathways
– Not effective against viruses
• Problems related to antibiotic therapy
– Potentially fatal allergic reactions
– Killing off of normal flora
– Bacterial resistance
28.2 Bacteria and Archaea
• Biology of Archaea
– Archaea are more closely related to Eukarya than
bacteria
– Many inhabit extreme environments
• Extreme thermoacidophiles: live in habitats with high
temperature and low pH
• Methanogens: live in anaerobic environments
• Halophiles: live in salty habitats
28.2 Bacteria and Archaea
• Archaeal Structure
– 0.1-15 !m in size
– DNA genome is a single, closed circular molecule
– Plasma membrane of archaea differs markedly from
those of bacteria and eukaryotes
• Single lipid layer branched side chains
– Chemical characteristics make them acid and heat
tolerant
– Reproduce asexually by binary fission
28.3 Protists
• Protists are eukaryotes
– Contain a nucleus and membranous
organelles
• Generally microscopic and unicellular
• Best definition is they are not a plant,
animal, or fungus
• Fungi, plants, and animals all trace their
ancestry to a protist
28.3 Protists
• Biology of Protists
– Can be unicellular, colonial, or multicellular
– Structurally diverse
– May have cell wall or shell
– May have organelles not found in other eukaryotes
– Most carry out asexual reproduction
• Under unfavorable conditions sexual reproduction may be an
option
• May form spores
• May have complicated life cycles
28.3 Protists
• Diversity of Protists
– Traditionally classified by their source of
energy and nutrients
• Algae are photosynthetic
• Protozoans are heterotrophic by ingestion
• Water molds and slime molds heterotrophic by
absorption
– Newer genetic sequence information has
resulted in controversy
• Use 6 groups according to major shared
characteristics
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Alg
ae
Pro
tozo
a
Unicellular
eukaryotic
ancestor
Fu
ng
uslike
pro
tists
Photosynthetic protists
Flagellates
Ciliates
Amoeboids
Sporozoans
Water molds
and slime molds
28.3 Protists
• Photosynthetic Protists (Algae)
– Size ranges from unicellular types about the size of
bacteria to multicellular forms 100 feet long (“seaweeds”)
– Green Algae
• Closely related to plants as they have some similar
characteristics
– Cell walls contain cellulose
– Have chlorophyll a and b
– Store food as starch
– Diatoms
• Most numerous unicellular algae in the oceans
• Variety of elaborate shells made of silica
– Dinoflagellates
• Best known for causing red tide
– Produces potent toxin that accumulates in shellfish
28.3 Protists
• Protozoa
– Flagellates
– Ciliates
– Amoeboids
– Sporozoans
• Trypanosoma brucei
– Cause of African sleeping
sickness is transmitted by the
tsetse fly
– Attacks the patient’s blood,
causing inflammation that
decreases oxygen flow to the
brain
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
b.
flagellum
undulating membrane
trypanosome
red blood cell
a: © Eye of Science/Photo Researchers, Inc.
28.3 Protists
• Sporozoans
– Malaria
• Most widespread and dangerous sporozoan
disease
• Caused by one of several Plasmodium species
• Spread by mosquitoes
– Other sporozoan diseases
• Toxoplasmosis caused by Toxoplasma
• Gastroenteritis caused by Cryptosporidium
28.3 Protists
• Water Molds– Saprophytic - live off dead matter
– Asexual and sexual reproduction
• Slime Molds– Plasmodial (acellular) slime molds
• Exist as plasmodium - diploid, multinucleated, cytoplasmicmass enveloped by a slime sheath
– Cellular slime molds• Exist as individual amoeboid cells
28.4 Fungi
• Fungi are eukaryotes
• General Characteristics
– Strict heterotrophs
– Release enzymes into environment - digestion
is outside of body
– Most are saprophytic
• Along with bacteria, fungi are important as
decomposers
28.4 Fungi
• Biology of Fungi
– Body of fungus is a mass of individual
filaments called hyphae
– Mass of filaments called a mycelium
– Fungal Cell Structure
• Cell walls contain chitin instead of cellulose
• Energy reserve is glycogen like in animal cells
• Fungi are nonmotile
• Move toward food source by growing toward it
28.4 Fungi
• Fungal Disease of Humans (mycoses)– Athlete’s foot
– Ringworm – not a worm
– Black mold (Stachybotrys chartarum)• Sick building syndrome
– Candidiasis (Candida albicans)• Infections of the vagina or mouth occur when normal flora
disturbed by antibiotics or in immunocompromised patients
28.4 Fungi• Diversity of Fungi
– Traditionally classified based on their mode of
sexual reproductionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
common ancestor
common
ancestor
Club fungi
Sac fungi
AM fungi
Zygospore fungi
Chytrids
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
fertilization
zygospore
meiosisSexual
Asexual
sporangium
mycelium
+ strain
– strain
© Runk/Schoenberger/Grant Heilman Photography
Rhizopus stolonifer
“black bread mold”
28.4 Fungi
• Sac Fungi (phylum Ascomycota)
– Cup fungi, morels, and truffles
– Most fungal pathogens – powdery mildew,
chestnut blight, Dutch elm disease
– Penicillium
• Original source of antibiotic penicillin
• Used to make blue cheese
– Yeasts – unicellular sac fungi
• Saccharomyces cerevisiae – brewer’s yeast
28.4 Fungi
• Club Fungi
– Characteristic sexual reproductive structure is
called a basidium
• Contained within a basidiocarp
– Edible part of a mushroom is the basidiocarp
– Amanitas phalloides, also known as the death
cap, causes 90% of fatalities related to
mushroom poisoning
Sexual Reproduction in Club FungiCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
basidiocarp
fusion meiosis
a. Sexual reproduction
spores
nuclei in
basidium
gill of
mushroom
+!
• Club Fungi
– Smuts and rusts parasitize cereal crops, such as
corn, wheat, oats, and rye
28.4 Fungi
• Lichens - Symbiotic Relationships of Fungi and
Photosynthesizers
• Associations between fungi and cyanobacteria or
green algae
• Can colonize poor soil, rocky surfaces
• Fungi portion offers protection and delivers water
• Photosynthesis gives the fungus nutrients
28.4 Fungi
• Symbiotic Relationships of Fungi
– Mycorrhizal Fungi
• Mutualistic relationships with plant roots
– Helps plants to grow more successfully in poor soils
– Plant provides organic nutrients to the fungus
– Fungus brings water and minerals to the plant
– Found on most plant roots
28.5 Viruses, Viroids, and Prions
• Biology of Viruses
– Viral Structure
• Smaller than bacteria
– 0.03-0.2!m
• Two main components to all viruses
– Capsid (outer portion comprised of proteins)
– Nucleic acid core (DNA or RNA)
– Infect almost every type of organism on earth
– Viruses are specific to a particular host
28.5 Viruses, Viroids, and Prions
• Viral Diseases in Humans– The Common Cold and Influenza
• Colds are caused mainly by rhinoviruses
– Runny nose, mild fever (possible), fatigue
– Lasts around a week
• Flu is caused by influenza viruses
– High fever, chills, body aches, severe fatigue
– Can be fatal
– May last several weeks
• Antigens on cold and flu viruses can change
28.5 Viruses, Viroids, and Prions
• Viral Diseases in Humans
– Measles
• Very contagious human disease
• Spread by respiratory route
• 7-12 day incubation period before flu-like
symptoms and rash appear
• 10-15% fatality rate in less-developed countries
• MMR vaccine protects against measles (and
mumps and rubella)
28.5 Viruses, Viroids, and Prions
• Viral Diseases in Humans
– Herpesviruses
• Remain latent much of the time
• Four types of herpesviruses that cause disease in
humans
– Herpes simplex type 1: cold sores and fever
blisters
– Herpes simplex type 2: genital herpes
– Varicella-zoster: chickenpox and shingles
– Epstein-Barr virus: infectious mononucleosis
28.5 Viruses, Viroids, and Prions
• Viral Diseases in Humans
– Antiviral Drugs
• Because viruses use the machinery of host cells
for viral replication, it is difficult to develop drugs
that affect viral replication without harming host
cells
• Antibiotics are not effective against viruses
• Some antiviral drugs interfere with viral replication
• Other antiviral drugs may affect virus attachment
• Many times, no drugs are available for viral
infections
28.5 Viruses, Viroids, and Prions
• Viroids and Prions - Acellular Pathogens– Viroids are naked RNA molecules which do not code
for proteins• Infect plant cells and cause disease
– Prions are proteinaceous infectious particles• Normal protein change their shape, this causes other normal
proteins to change their shape
• Causes degenerative diseases of the nervous system
• Prions are passed through ingestion of infected tissues
• Scrapie in sheep
• Mad cow disease in cattle
• Creutzfeld-Jakob disease in humans
• Kuru: human to human transmission throughcannibalism