19–1 Bacteria

19–1 BacteriaThe smallest and most common microorganisms are prokaryotes—unicellular organisms that lack a nucleus.

Prokaryotes divided into two kingdoms: Eubacteria Archaebacteria.

Classifying Prokaryotes

Eubacteria

Most bacteria are in this group Most are heterotrophs Live in water, land and in other organisms

Eubacteria

Cell wall protects the cell and determines its shape. Cell wall contain peptidoglycan. Some have a second cell membrane.

PiliFlagellum DNA

Live in a variety of environments, including: Fresh and salt water On land In the human body

Eubacteria

Cell walls lack peptidoglycan. DNA sequences of genes are more like those of eukaryotes than those of eubacteria. Have different types of ribosomes.

Archaebacteria 

Found in harsh environments Do not require oxygen Can live in extremely salty environments as well as extremely hot environments Undersea volcanic vents Acidic hot springs Thick mud and animal digestive tracts

Archaebacteria 

Methanogens, archaebacteria that live in oxygen free and extreme environments. Swamps, animal digestive tracts.

Archaebacteria

Some live in salty environments, Halophiles. In hot springs with boiling temps.

Archaebacteria

Archaebacteria

By characteristics such as: shape chemical nature of their cell walls the way they move the way they obtain energy

Identifying Prokaryotes

Shapes  Rod-shaped prokaryotes are called bacilli. ba·cil·lus

Bacilli

Identifying Prokaryotes

Spherical prokaryotes are called cocci.

Cocci

Identifying Prokaryotes

Spiral and corkscrew-shaped prokaryotes are called spirilla. spirillum

Spirilla

Identifying Prokaryotes

Cell Walls Two different types of cell walls are found in eubacteria. A method called gram staining tells them apart.

Identifying Prokaryotes

Gram-positive have thick cell walls with large amounts of peptidoglycan. Stains purple Single lipid layer Can be treated effectively with antibiotics

Identifying Prokaryotes

Gram negative Thin layer of peptidoglycan in cell wall. Thick layer of lipids in cell wall. Stain pink or reddish Harder to treat with antibiotics.

Identifying Prokaryotes

Metabolic Diversity

Autotrophs Photoautotrophs –perform photosynthesis; use light energy to make carbon compounds.

Chemoautotrophs -perform chemosynthesis; Uses chemical energy to make carbon compounds.

Metabolic Diversity

Heterotrophs Chemoheterotrophs-use organic molecules for both energy and a carbon source Photoheterotrophs-use sunlight for energy, but take in organic compounds as a carbon source

Metabolic Diversity

Releasing Energy  Bacteria need a constant supply of energy, which is released by the processes of cellular respiration or fermentation or both.

Metabolic Diversity

Organisms that require supply of oxygen in order to live are called. obligate aerobes.

Metabolic Diversity

Bacteria that live without oxygen because they may be killed by it are called obligate anaerobes.

Metabolic Diversity

Bacteria that can survive with or without oxygen are known as facultative anaerobes.

Metabolic Diversity

Growth and Reproduction

Binary Fission  Type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells.

Conjugation  During conjugation, a hollow bridge forms between two bacterial cells, and genes move from one cell to the other.

Growth and Reproduction

Growth and Reproduction

Spore Formation  An endospore forms when a bacterium produces a thick internal wall that encloses its DNA and some of its cytoplasm.

Growth and Reproduction

Spore Formation  Can remain dormant for months or years Allow bacteria to survive harsh conditions

Decomposers Bacteria break down dead organic material and recycle nutrients in the environment

Nitrogen Fixers Convert nitrogen gas into a form plants can use.

Importance of Bacteria

Human Uses of Bacteria We depend on bacteria for many things, including: foods and beverages removal of waste and poisons from water mining minerals from the ground synthesis of drugs and chemicals via genetic engineering production of vitamins in human intestines

Importance of Bacteria

19.1 Vocab

19.1 Vocab

Name____________________________ Class __________________ Date __________

Prokaryote StructureA prokaryote is a unicellular organism that lacks a nucleus. Mostprokaryotes have a cell wall, a cell membrane, and cytoplasm. Thebacterium below is one example of a prokaryote.Follow the prompts to locate structures in a typical bacterium.

• Color the cell membrane yellow.• Color the cell wall blue.• Color the flagella red.• Color the pili orange.• Color the DNA green.

Use the diagram to answer the questions. Circle the correct answer.

1. What does the bacterium use to move?

pili flagellum

2. What is the bacterium’s genetic material called?

cell membrane DNA

© Pearson Education, Inc., publishing as Pearson Prentice Hall.177

Name____________________________ Class __________________ Date __________

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Chapter 19 Bacteria and Viruses

Section 19–1 Bacteria (pages 471–477)

This section describes two groups of prokaryotes and explains how theydiffer. It also explains what factors are used to identify prokaryotes.

Introduction (page 471)

1. What are prokaryotes? They are single-celled organisms that lack a nucleus.

2. Is the following sentence true or false? Prokaryotes are much smaller than most eukaryotic cells.

Classifying Prokaryotes (pages 471–472)

3. What are the two different groups of prokaryotes?a. b.

4. Which is the larger of the two kingdoms of prokaryotes? Eubacteria

5. Where do eubacteria live? They live almost everywhere—including in water, on land, and on

and within the human body .

6. What protects a prokaryotic cell from injury? The cell wall protects it.

7. Circle the letter of what is within the cell wall of a prokaryote.a. another cell wall c. archaebacteriab. cell membrane d. pili

8. What is peptidoglycan? It is a carbohydrate in the cell walls of eubacteria.

9. Some eubacteria have a second outside the cell membrane.10. Circle the letter of each sentence that is true about archaebacteria.

a. Their membrane lipids are different from those of eubacteria.b. They lack a cell wall.c. They lack peptidoglycan.d. They look very similar to eubacteria.

11. What is significant about the DNA sequences of key archaebacterial genes?They are more like those of eukaryotes than those of eubacteria.

12. How are archaebacteria related to eukaryotes? Scientists reason that archaebacteria may

be the ancestors of eukaryotes.

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ArchaebacteriaEubacteria

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