Ch. 7
Viruses, Bacteria, Protists, and Fungi
Section 2: Bacteria
 The Bacterial Cell
 A Dutch merchant named Anton van Leeuwenhoek found
bacteria in the late 1600s
 Cell Structure
 Bacteria are prokaryotes. The genetic material in their cells is not
contained in a nucleus
 A bacterial cell lacks a nucleus and also lacks many other structures, such
as mitochondria and Golgi bodies, that are found in the cells of
eukaryotes
 Flagellum: a long, whip-like structure that helps a cell to move.
Section 2: Bacteria
 The Bacterial Cell
 Cell Sizes
 Bacteria very greatly in size
 The largest is as big as a period at the end of a sentence
 The smallest is about a micrometer which is on millionth of a meter
 Cell Shapes
 Three basic shapes: spherical, rod-like, or spiral
 The chemical makeup of the cell wall determines the shape of a bacterial
cell
Section 2: Bacteria
 Obtaining Food and Energy
 Bacteria must have a source of food and a way of breaking down
the food to release its energy.
 Obtaining Food
 Some bacteria are autotrophs (make their own food)
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Some capture the sun’s energy
Some use the chemical substances in their environment
 Respiration
 Some bacteria need oxygen to break down their food
 Some bacteria don’t need oxygen, in-fact, those bacteria die if there is
oxygen in their surroundings
Section 2: Bacteria
 Reproduction
 Asexual Reproduction
 Bacteria reproduce by a process called binary fission, in which one cell
divides to form two identical cells
 Asexual reproduction: is a reproductive process that involves only one
parent and produces offspring that are identical to the parent
 During binary fission, a cell first duplicates its genetic material and then
divides into two separate cells
Section 2: Bacteria
 Reproduction
 Sexual Reproduction
 Sexual reproduction: two parents combine their genetic material to
produce a new organism, which differs from both parents
 Conjugation: one bacterium transfers some genetic material to another
bacterium through a threadlike bridge
 Conjugation results in bacteria with new combinations of genetic
material, then divide by binary fission, the new combinations pass to the
offspring
Section 2: Bacteria
 Reproduction
 Endospore Formation
 Endospore: is a small, rounded, thick-walled, resting cell that forms
inside a bacterial cell
 It contains the cells genetic material and some its cytoplasm
 Endospores can resist freezing, heating, and drying, they can survive for
many years
Section 2: Bacteria
 The Role of Bacteria in Nature: bacteria are involved in
oxygen and food production, environmental recycling and
cleanup, and in health maintenance and medicine production
 Oxygen Production
 As autotrophic bacteria use the sun’s energy to produce food, they also
release oxygen into the air
 Scientists believe that autotrophic bacteria were responsible for first
adding oxygen to Earth’s atmosphere
Section 2: Bacteria
 The Role of Bacteria in Nature
 Food Production
 Helpful bacteria include the making of cheese, sauerkraut, or pickles
 Harmful bacteria causes food to spoil when they break down the food’s
chemicals
 Pasteurization: the food is heated to a temperature that is high enough to
kill most harmful bacteria without changing the taste of the food
Section 2: Bacteria
 The Role of Bacteria in Nature
 Environmental Recycling
 Decomposers: organisms that break down large chemicals in dead
organisms into small chemicals; called “natures recyclers”
 They return basic chemicals to the environment for other living things to
reuse
 Nitrogen-fixing bacteria help bacteria convert nitrogen gas from the air
into nitrogen products that plants need to grow
Section 2: Bacteria
 The Role of Bacteria in Nature
 Environmental Cleanup
 Some bacteria help to clean up Earth’s land and water
 Some prefer the oil, they convert the poisonous chemicals in oil into
harmless substances
 Scientists put these bacteria to work cleaning up oil spills
Section 2: Bacteria
 The Role of Bacteria In Nature
 Health and Medicine
 Some bacteria help you digest food but other compete for space with
disease causing organisms, preventing the harmful bacteria from attaching
to your intestines and making you sick
 The first medicine-producing bacteria were made in the 1970s
 By manipulating the bacteria's genetic material, scientists engineered
bacteria to produce human insulin
Section 2: Bacteria
 Closing Activity
 List ways that bacteria are involved in oxygen and food
production, in environmental cleanup, and in health
maintenance and medicine production.