Download Bacteria - Fort Bend ISD

BACTERIA
Structure of a Bacterium
Peptidoglycan
Cell
wall
Flagellum
Cell
membrane
DNA
Ribosome
Pili
Structure of a Bacterium
Capsule: some have a sticky gelatinous
capsule around the cell wall (these
bacteria are more likely to cause
disease)
 Cell wall: gives the cell shape;
composed of a peptidoglycan (sugarprotein complex)
 Plasma membrane: surrounds the cell
and regulates what enters and leaves

Structure of a Bacterium
Pilus: hairlike structures emerging from
the cell surface; helps bacteria stick to a
surface or exchange DNA between
bacterial cells
 Flagellum: long, whiplike structure that
enables movement

Structure of a Bacterium
Chromosome: single DNA molecule
arranged as a circular chromosome; not
enclosed in a nucleus
 Plasmid: small circular chromosome
piece containing a few genes

Classifying Bacteria

Bacteria are classified according to:
Shape
 Arrangement
 Gram stain

Classifying Bacteria

Shape
Spherical - Cocci
 Rod - Bacilli
 Corkscrew - Spirillae

Classifying Bacteria

Arrangement
Singular
 Pairs – Diplo
 Chains – Strepto
 Clusters – Stapylo

Classifying Bacteria

Gram stain
Staining method involving two dyes
 The dye absorbed by the bacteria depends
on properties of the cell wall
 Bacteria are either Gram positive or Gram
negative
 Positive stain bluish-purple
 Negative stain reddish-pink

Prokaryote Cell Wall Structure
Gram-positive bacteria
Gram-Positive bacteria
peptide side
chains
cell wall
peptidoglycan
plasma membrane
That’s
important for
your doctor
to know!
protein
peptidoglycan = polysaccharides + amino acid chains
lipopolysaccharides = lipids + polysaccharides
Gram-negative bacteria
cell wall
outer membrane of
lipopolysaccharides
outer
membrane
peptidoglycan
plasma
membrane
Metabolism
Obligate aerobes – must have oxygen
to survive
 Obligate anaerobes – cannot live if
oxygen is present
 Facultative anaerobes- can live either
with or without oxygen

Classification

Eukaryote
3 Domain system

Prokaryote
reflects a greater
understanding of
evolution & molecular
evidence

Bacteria: Eubacteria

Archae: Archaebacteria

Eukaryotes:

Protists

Plants

Fungi

Animals
Archaebacteria
&
Bacteria
Classification of Bacteria

All bacteria are prokaryotes
Very simple organisms
 All are unicellular
 In general, they are smaller than
eukaryotes
 Circular DNA which is not enclosed in a
nucleus
 Lack membrane-bound organelles

Classification of Bacteria
Archaebacteria
 Eubacteria

Heterotrophic eubacteria
 Autotrophic eubacteria
 Chemosynthetic eubacteria

Archaebacteria



a.k.a. Extremophiles
Live in oxygen-free environments
Obtain energy from sun or inorganic
molecules
Archaebacteria: Thiobacilli


Heat- and acid-loving bacteria
Live in sulfur springs
Archaebacteria: Thiobacilli



Consume sulfur
Combine it with oxygen to produce
energy
Produce sulfur dioxide as by-product
Archaebacteria: Thiobacilli

Sulfur dioxide can combine with water
to form sulfuric acid
Archaebacteria: Halobacteria


Salt-loving bacteria
Live in saturated salt water like the
Great Salt Lake
Archaebacteria: Halobacteria


Produce purple pigments
Use purple pigment to carry out
photosynthesis the way plants use
chlorophyll
Archaebacteria: Alkalophytes


Live in aquatic environments with high
pH
Forms the food basis upon which
thousands of large organisms are
dependent
Lake Nakuru
Archaebacteria: Methane
Bacteria


Cannot live in the presence of oxygen
Live in stomachs of cows and sewage
treatment ponds
Archaebacteria: Methane
Bacteria

Obtain energy from CO2 and hydrogen
gas
Archaebacteria: Deep Subsurface
Bacteria

Live in rocks beneath Earth’s surface
(as deep as 3,000 feet)
Archaebacteria: Deep Subsurface
Bacteria

Obtain energy from H+ produced from
reaction between minerals in rock and
groundwater seeping in
Classification of Bacteria
Archaebacteria
 Eubacteria

Heterotrophic eubacteria
 Autotrophic eubacteria
 Chemosynthetic eubacteria

Heterotrophic Eubacteria

Obtain food from other living organisms


parasites
Obtain food from dead organisms or
organic waste

Recycle nutrients in decomposing organic
material
Classification of Bacteria
Archaebacteria
 Eubacteria

Heterotrophic eubacteria
 Autotrophic eubacteria
 Chemosynthetic eubacteria

Autotrophic Eubacteria
Obtain energy from light
 Perform photosynthesis

Autotrophic Eubacteria

Cyanobacteria
Most contain blue-green pigment (but some
are red or yellow)
 Form chains: not unicellular

Classification of Bacteria
Archaebacteria
 Eubacteria

Heterotrophic eubacteria
 Autotrophic eubacteria
 Chemosynthetic eubacteria

Chemosynthetic Eubacteria
Obtain energy from breakdown of
inorganic substances (S and N
compounds)
 Key for agriculture:


Convert atmospheric N to a form plants can
use
Reproduction in Bacteria
Can reproduce rapidly (every 20
minutes)
 Luckily, most run out of nutrients and
water before the colony gets very large
 Most reproduce by binary fission

Bacterium copies its chromosome
 Old chromosome and copy attach to the
plasma membrane at opposite ends
 Cell grows and becomes larger

Reproduction in Bacteria

Most reproduce by binary fission
Growth causes two chromosomes to
separate
 Partition forms and separates the cell into
two
 Each new cell has one copy of the original
chromosome
 Creates two cells genetically identical to one
another

Genetic Exchange in Bacteria

Conjugation
Sexual form of bacterial reproduction
 One bacterium passes all or part of its
chromosome to another cell
 Transfer occurs across pili
 Creates two bacteria genetically different
from one another
 They then reproduce by binary fission

Genetic Exchange in Bacteria

Transduction: Transfer of genes from
one bacterium to another by a
bacteriophage.

Ex. Toxin gene in Corynebacterium
diphtheriae
Genetic Exchange in Bacteria

Transformation: Taking in DNA from
the outside environment.

Ex. Rough Streptococcus pneumoniae
transformed into smooth S. pneumoniae.
Bacterial species in biofilm communities.
Survival
If conditions become less than ideal
some bacteria can form endospores
 Tough outer covering resistant to:

Drying out
 Temperature extremes (boiling water)
 Harsh chemicals

Survival

Closturidium botulinum
Produces a deadly toxin
 Endospores can withstand boiling
temperatures
 Canned foods must be pressure cooked to
kill the endospores


Six week old infant with botulism, which is evident as a
marked loss of muscle tone, especially in the region of
the head and neck.
Survival

Closturidium tetani
Obligate anaerobe that produces a deadly
neurotoxin
 Endospores are found on nearly every
surface on the planet
 When endospores get into a moist,
oxygen-free environment (such as inside a
puncture wound) they germinate
 Reason for getting a tetanus shot

Tetanus
Survival

Bacillus anthracis
Aka. Anthrax
 Endospores live in soil
 When inhaled they germinate

Decomposers
Break down dead organisms and
recycle the nutrients that make them
 Without decomposition we would run
out of the molecules necessary for life

Nitrogen-fixation
Plants and animals need nitrogen to
make protein
 The atmosphere is mostly nitrogen but
plants and animals can’t use it

Nitrogen-fixation
Nitrogen-fixing bacteria convert
nitrogen in the atmosphere into
nitrogen plants can take up with their
roots
 Animals get their nitrogen by eating
plants

Biotechnology
Production of foods like butter, cheese,
and yogurt
 Cleaning up oil spills
 Synthesizing drugs and chemicals

Digestion
Much of what we eat would pass through
our bodies without being digested if we
didn’t have bacteria in our digestive
tracts
 They break down plant matter and
synthesize vitamins for us

Bacterial Diseases

Bacteria cause illness one of two ways:
Breaking down host cells or tissues for food
 Normal metabolic processes generate
toxins

Bacterial Diseases

Most food-borne illnesses are caused by
bacteria:
E. coli comes from infected, undercooked
beef
 Salmonella comes from infected,
undercooked poultry (meat and eggs)
 Botulinum causes botulism – a deadly form
of food poisoning

Controlling Bacteria

Antibiotics are drugs that kill bacteria
(NOT VIRUSES)
Controlling Bacteria
Most bacteria like warm, moist, dark
conditions
 Exposing them to other conditions kills
them or slows reproduction

Controlling Bacteria

Examples:
Cooking foods makes it too hot for most
bacteria to survive
 Refrigerating or freezing foods makes it too
cold for them to reproduce
 Drying foods makes it impossible for
bacteria to reproduce
 Pickling causes bacterial cells to burst
