Bacteria
Structure
• One celled organisms that occur alone or in chains or
groups
• Three basic shapes
– Spheres, called cocci
– Rods, called bacilli
– Spirals, called spirilla
• Cell contains cytoplasm surrounded by cell membrane
and cell wall
• Ribosomes in cytoplasm, too
Structure Continued
• Classified as prokaryotic because they don’t
contain a membrane bound nucleus or other
organelles
• Genetic material is found in its one circular
chromosome in cytoplasm
– Some have smaller circular piece of DNA called a
plasmid
Special Features
• Some bacteria have:
– Thick, gelatin like capsule
around cell wall for
protection and to help stick
to surfaces
– Hair-like projections- help
stick to surfaces
– Slime layer- enables
bacteria to stick to
surrounding surfaces and
reduce water loss
– Flagella- whip-like tails that
help bacteria move
Reproduction
• Fission- process that produces two new cells
with identical genetic material to each other
and that of the original cell
• Some bacteria exchange genetic material by
lining up next to each other and exchanging
DNA through a small tube
Obtaining Food and Energy
Producers
• Some bacteria contain
chlorophyll or other
pigments to make own food
using energy from Sun
• Others use energy from
chemical reactions
Consumers
• Some break down dead
organisms to obtain energy
• Others live as parasites of
living organisms and absorb
nutrients from their host
Aerobic Vs. Anaerobic
Aerobe
• Break down food and obtain
energy through respiration
• Most bacteria (and us!)
Anaerobe
• Organism adapted to live
without oxygen
– Anaerobic bacteria live in
intestinal track of humans
– Some bacteria cannot survive
when exposed to oxygen
Kingdoms
• Bacteria classified into two kingdoms
– Eubacteria Scientists study many characteristics
to classify eubacteria into smaller groups
– Archaebacteria contain bacteria found in
extreme conditions, such as hot springs
Cyanobacteria
• A eubacteria producer that makes own food using carbon
dioxide, water, and energy from sun. produce oxygen as a
waste. Live in colonies are an important food source for some
organisms in lakes, ponds, and oceans. Oxygen produced by
them is used by other aquatic organisms. However, can cause
blooms that are harmful to organisms
Consumer Eubacteria
• Classified into two categories based on results of
Gram’s stain
– Bacteria treated with chemical called stain.
• Gram positive bacteria stain purple because they have
thicker cell walls
• Gram negative bacteria stain pink because they have
thinner cell walls
– Composition of cell wall can determine how effective certain
medicines will be against the bacteria
• One group does not have cell walls, allowing
them to change shape. One type of these causes
pneumonia
Archaebacteria
• One group lives in salty environments like
Dead Sea
• Others love hot or acidic environments, living
near ocean vents or hot springs
Methane producers
• Some archaebacteria use carbon dioxide for
energy and release methane gas as a waste.
– They are used in sewage treatment by breaking
down the waste material that has been filtered
out
Beneficial Bacteria
• Some bacteria produce chemicals called
antibiotics that limit the growth of other
bacteria
• Consumer bacteria called saprophytes uses
dead organisms as food and energy sources
– By helping to recycle nutrients, the nutrients
become available to other organisms
Nitrogen fixing bacteria
• Plants and animals need nitrogen to make
proteins and nucleic acids
– Plants need nitrogen from the soil or air
• Nitrogen-fixing bacteria change nitrogen from
the air into forms that plants and animals can
use
– Some plants, like peanuts, have nodules that
contain these bacteria
Bioremediation
• Using organisms to help clean up
environmental pollutants
• One type uses bacteria to break down wastes
and pollutants into simpler harmless
compounds
– Oil spill cleanup by bioremediation likely to
increase in future
Bacteria and Food
• Bacteria used to make
yogurt, cheese, and
buttermilk
• Other foods made using
bacteria are sauerkraut,
vinegar, pickles, olives,
soy sauce
Other Uses of Bacteria
• Medicines, enzymes,
cleansers, adhesives
• Methane gas produced
by bacteria used as fuel
for heating, cooking,
and industry, as well as
breaking down plant
and animal material
Harmful Bacteria
• Not all bacteria is good!
• Pathogen- any organism that causes disease
– Bacteria causes strep throat, whooping cough,
anthrax, botulism, and more
Bacteria and Toxins
• Some bacteria produce poisonous substances
known as toxins
– Ex: botulism a type of food poisoning that can
cause paralysis or death
• When growing conditions unfavorable, bacteria
can produce thick-walled structures called
endospores, which can exist hundreds of years
before resuming growth
– Commercially canned food undergo process that uses
steam at high pressure to kill bacteria and endospores
Pasteurization
• Unless it’s been sterilized, all food contains
bacteria
• Pasteurization process of heating food to a
temperature that kills most harmful bacteria
but causes little change to taste of food
– ex: milk, some fruit juice, yogurt all pasteurized
Treating Bacterial Diseases
• Bacterial diseases usually
treated with antibiotics.
– Penicillin, an antibiotic,
prevents bacteria from
making cell walls
• Vaccines made from
damaged particles taken
from bacteria cell walls or
dead bacteria. When
vaccine injected, white
blood cells recognize
bacteria so that if it enters
body again, white blood
cells will attack it