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Bacteria
Chapter 19-1
Microscopic organisms
• Viruses = not living, but studied as micro• Bacteria = divided into 2 kingdoms; most
are helpful, harmful tracked by CDC &
WHO
• Protists = most diverse;
show fungal, plant or
animal characteristics
• Fungus = decomposers;
most are helpful, some
are disease-causing
Prokaryote characteristics
Single-cell organisms
Anucleated (no nucleus)
Small (1-5 m)
Lacks organelles
Variety of shapes
Variety of growth patterns
Two kingdoms:
Eubacteria and
Archaebacteria
Bacterial characteristics:
• Prokaryotic (no nuclear membrane)
– Ribosomes only
– Pili = for attachment
– Capsule = outermost layer for extra protection
•
•
•
•
Unicellular (some colonial)
Varied metabolism & nutritional types
Often flagellated
May contain endospores…
to survive harsh conditions
• Binary fission to reproduce
Archaebacteria
• Extremophiles:
organisms that prefer
extreme environments
• Ex: salt marshes, deep
sea ocean vents,
swamps, etc.
aerobic halophil
Archaebacteria
• Lack the peptidoglycan
of Eubacteria
• Have different
membrane lipids
• DNA sequences
are more like
those of eukaryotes
Chemosynthetic bacteria
in deep sea vents
Photosynthetic Cyanobacteria
in fresh-water ponds or streams
Eubacteria cell structure
Peptidoglycan
Cell Cell
Ribosome
wall membrane
Flagella
DNA Pili
See page 465
Practice
Bacterial shapes
•
•
•
•
Bacillus = rod-shaped (ex: Lactobacillus)
Coccus = sphere (ex: Streptococcus)
Spirillum = coiled (ex: Spirochete)
Strepto(chains)
• Staphylo(clusters)
(like grapes)
• Diplo- (pairs)
Bacterial morphology
Coccus
Bacillus
Spirillum
Blue = causes
Lyme
disease
Black = causes
syphilis
A Bacilli with and without flagella
B Streptococci
C Staphylococci
D Diplococci
E Spirochete
F Club rod
G Filamentous
H Streptobacilli
Movement
• Depending upon how
the cells is flagellated,
movements such as
gliding or tumbling
may occur.
flagellated E. coli
Gram stain
• a technique that determines the differences
in the composition of bacterial cell walls
(thick or thin) which helps to determine
which antibiotics to use.
Gram-positive bacteria
thick peptidoglycan cell
walls.
Gram-negative bacteria
thinner cell walls with a
outer lipid layer.
Gram negative
Gram positive
How bacteria obtain nutrition
• Heterotrophs:
consume carbon
matter to make ATP
– Chemoheterotroph:
consumes only
– Photoheterotroph:
consumes and
photosynthesizes
Gram-negative,
facultative anaerobic
How bacteria obtain nutrition
• Autotrophs:
produces carbon
matter to make ATP
• Photoautotroph:
produces with light
energy
(photosynthesis)
• Chemoautotroph:
produces carbon
matter without light
source
Chemoautotroph: Purple
sulfur bacteria
Nutritional diversity
(Recap)
• Autotrophs: (producers)
– Photosynthetic = Cyanobacteria
– Chemosynthetic = bacteria in deep ocean
vents use sulfur instead of light for energy
• Heterotrophs: (consumers)
– Saprobes = decomposers feed on dead
organic matter (nitrogen-fixing bacteria)
– Parasitic = feed on living host (pathogenic)
Oxygen requirements
• Obligate aerobe: requires constant oxygen
supply in environment
• Facultative aerobes: prefers oxygen, but not
necessary
• Facultative anaerobe: can survive with or without
oxygen
• Obligate anaerobe: requires constant lack of
oxygen in environment
Binary fission
• asexual method
of reproduction
• parent cell splits
into two daughter
cells
• Daughter cells are
identical to parent
cell
Binary fission
• Cell Replication
• (cloning) for
prokaryotic cell
• Much simpler than
mitosis (like
cytokinesis without
the 4 other stages)
Conjugation
• Genetic material
exchange
• Increases genetic
variation within
bacterial
population
Spore formation
• In unfavorable growth conditions, structures
(endospores) form to protect the bacterium.
• Thick wall encloses the DNA and a small amount
of cytoplasm.
• The rest of the cell dies off.
• The spore can survive in tough conditions for
years.
• Ex: Bacillus anthracis (anthrax) causes black necrotic
lesions, sudden massive chest oedema followed by cardiovascular
shock then death
Endospore formation
Methods of Microbe Transmission
1) Direct
Contact:
2) Air:
3) Fomites:
(inanimate
objects)
Early microbiologists
• Louis Pasteur
• Concluded that
microorganisms
cannot spontaneously
generate
• Showed world how
heat kills
microorganisms
(pasteurization)
Microorganisms & You
• Food for heterotrophs
typically are carbonbased macromolecules:
• Carbohydrates, lipids, &
proteins
• Bacteria & fungus are
responsible for food
spoilage because many
are saprobes
Helpful bacteria
• Decomposers
• Nitrogen fixers:
Rhizobium
• Symbiosis with
humans in large
intestines
• Food production
Rhizobium
Food & Microorganisms:
Making cheese
• Bacteria placed in an
anaerobic environment,
and the milk breaks down
to form cheese
• Milk (sugar source) + little
oxygen → lactic acid +
protein solids + curds
“Little Miss Muffet, sat on
her tuffet, eating her…
cottage cheese”
Yogurt:
• Yogurt is produced by a mixed culture of 2 types
of bacteria. Imbedded in particles of the protein
casein, you will see chains of cocci or diplococci
(Streptococcus thermophilus) and big rod-shaped
bacilli (either Lactobacillus acidophilus or L.
bulgaricus).
Buttermilk:
• Buttermilk is the fermentation of milk by a culture
of lactctic-acid producing Streptococcus lactis plus
Leuconostoc citrovorum which converts lactic acid
to aldehydes and ketones which gives buttermilk
its flavor and aroma.
Making cured meats
• Some bacteria are able to ferment meat
products
• The final products are sausages, bologna,
salami, country cured hams, etc
Making pickled vegetables
• Sauerkraut is a product of lactic acid
fermentation of Lactobacillus genus
bacteria.
• Bacteria ferments the cabbage, but salt
is added to prevent other bacteria from
spoiling the product.
Some cured food
products
• Cured animal
products:
• Beef
• Corned beef
• Bresaola
• Tapa
• Pork
• Ham
• Prosciutto
• Jambon de Bayonne
• Jamón serrano
• Jinhua ham
• Coppa
• Lomo
• Capicola
• Lardon
Bacon and Pancetta
Elenski but
Sausage
Salami
Pepperoni
Chorizo
Linguiça
Fish
Anchovy
Salt cod
Lox (salmon)
Pickled herring
Cured vegetable products:
Tofu
Sauerkraut
Kimchi
Pickled cucumbers
Olive (fruit)
Nitrogen cycle includes nitrogen
fixation
How else are bacteria helpful?
• Nitrogen-fixation
• decomposing bacteria convert
atmospheric N2 for use by autotrophs
• Symbiotic bacteria allow a host to live a
different lifestyle than would normally be
possible
• Cyanobacteria (& unicellular algae)
produce most of the world’s oxygen
by photosynthesis
Microorganisms & your health
Antibiotics that kill pathogenic
microorganisms are made
from microorganisms