Chapter 18

Bacteria

Section 19-1

Concept Map

are classified into the kingdoms of

live in harsh environments such as

include a variety of lifestyles such as

Bacteria

Eubacteria Archaebacteria

Infecting large

organismsThick mud

Living in soil

Animal digestive

tractsSalty lakes

Hot springs

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Bacteria are part of two kingdoms: Archaebacteria Eubacteria

Eubacteria The larger of the two kingdoms prokaryotes Cell walls contain peptidoglycan

Archaebacteria

Prokaryotes, although the DNA are more like those of eukaryotes than eubacteria

Cell walls lack peptidoglycanMembrane lipids are different

than those of eubacteriaMany scientists think that

archaebacteria may be the ancestors of eukaryotes

Archaebacteria (cont.)

Many archaebacteria live in harsh environments Methanogens – produce methane

gas Extreme halophiles – salt-loving

archaebacteria Thermoacidophiles – live in extremely

acidic environments that have extremely high temperatures, like hot springs

Identifying Prokaryotes

Shape Bacilli – rod-shaped Cocci- spherical Spirilla – spiral and corkscrew shaped

Identifying Prokaryotes (cont.)

Cell wallsTwo different types of cell walls

in eubacteria The Gram stain is used to tell them apartGram-positive – stain purple

Gram-negative – stain red/pink

Identifying Prokaryotes (cont.)

Movement flagella- whip-like structures used for

movement Other prokaryotes lash, snake, or spiral

forward Some other prokaryotes glide slowly

along slime they produce Many prokaryotes do not move at all

Obtaining Energy

Autotrophs – produce their own food Photoautotrophs – use light for the

energy source Example: cyanobacteria

Chemoautotrophs – obtain energy from inorganic molecules (such as ammonia)

Heterotrophs – obtain energy by the food it consumes

Photoheterotrophs – obtain energy from light and also from inorganic molecules

Releasing Energy

Cellular respiration – requires oxygenCalled obligate aerobes

Fermentation – does not require oxygenCalled obligate anaerobes

Some bacteria can survive with or without oxygenCalled facultative anaerobes

Growth and Reproduction

Replicates DNA and simply divides in half (asexual reproduction) Binary fission

Some bacteria can transfer genetic material from one cell to another Conjugation

When growth conditions become unfavorable, some bacteria form endospores to protect their genetic material

Bacteria in Nature

Decomposers – bacteria act as “recyclers Nitrogen fixation

Convert nitrogen from N2 into a form that plants can use

Bacteria and Disease – disease causing bacteria are called pathogens Bacteria cause disease in one of two ways

Damage tissues by breaking them down for food

Release toxins (poisons) that harm the body Antibiotics can be used to kill bacteria

Tooth decay

Lyme disease

Tetanus

Tuberculosis

Salmonella food poisoning

Pneumonia

Cholera

Streptococcus mutans

Borrelia burgdorferi

Clostridium tetani

Mycobacterium tuberculosis

Salmonella enteritidis

Streptococcus pneumoniae

Vibrio cholerae

Regular dental hygiene

Protection from tick bites

Current tetanus vaccination

Vaccination

Proper food-handling practices

Maintaining good health

Clean water supplies

Disease Pathogen Prevention

Section 19-2

Common Diseases Caused by Bacteria

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