Chapter 18.2: Archaebacteria and Eubacteria

AE/P/FPA

Brief Comparison

Archaebacteria Both Eubacteria

-Cell wall has no peptidoglycan-has a unique DNA

-Prokaryotic-Unicellular-autotrophic and heterotrophic

-cell wall has peptidoglycan-heterotrophic photosynthetic (cyanobacteria)-heterotrophic chemosynthetic (nitrogen-fixing bacteria)

Bacteria Structure

• Same as most prokaryotic cells and it has a cell wall

• Cell wall is important because it prevents bacterial cell from bursting– Most cells naturally take on water by osmosis; live

in a hypotonic solution

Bacteria Identification

• “Gram-Staining”– Reflects a difference in cell walls (they also will

react to different antibiotics)• Gram positive = turns purple when stained• Gram negative = turns pink when stained

Bacteria Identification

• Shape– 1. spheres = “cocci”– 2. rods = “bacilli”– 3. spirals = “spirilla”

• Good example of all 3 shapes can be seen in Fig 18.12 of our textbook

Bacteria Identification

• Arrangement– 1. Diplo = paired arrangement– 2. Staphylo = “grape” like arrangement– 3. Strepto = “chains of cells” arrangement

Bacteria Reproduction

• Asexual reproduction– “binary fission”

• Sexual reproduction– “ conjugation” with the use of a PILUS (“pili” =

plural form)

• Fig 18.13 and 18.14

Bacteria Reproduction:Binary Fission vs. Conjugation

Other terms to be familiar with

• Obligate Anaerobes– One of the first bacteria to evolve– Killed by oxygen– Release energy using fermentation

• Obligate Aerobes– Require oxygen for respiration– Release energy using cellular respiration

Bacteria Survival Mechanism

• Endospore– A tiny structure that contains a bacteriums DNA

and a small amount of its cytoplasm, encased by a tough outer covering the resists temperature extremes and harsh chemicals

– Protects the DNA during “hard times”– Botulism can be caused by an endospore of B.

botulinum germinates

Bacteria Survival Mechanisms

• Toxin– Poison produced by a bacterium

The Importance of Bacteria

• Nitrogen fixation– Taking nitrogen from atmosphere and putting it

into a form plants can use

• Recycling of nutrients (decomposers)• Foods and medicines• Bacteria cause Disease– Now due to development of better antibiotics, the

average human life expectancy has increased to 75 years old

TODAYS ASSIGNMENT

• Homework over the weekend:– 18.2 Reinforcement and Study Guide– My suggestion is that you complete it here while

you have 30 minutes left in class.