Abstract

The structure of the procaryotic cell is introduced. The organization of a representative cell is presented in diagram form. The means of motility is described, along with the cell wall, cell membrane, nucleoid region, ribosomes, mesosomes, and other internal and external structures. Important differences between the Gram positive cell wall and the Gram negative cell wall are noted, and the differences in their responses to the Gram stain procedure will be revisited in the laboratory. Differences in cell shapes (coccus, bacillus, and spirillum) are noted, along with the types of arrangements commonly exhibited by the different classification groups of bacteria. Some unusual forms are noted, some of medical importance, others simply because they are different.

Learning Objectives

• renew awareness of the key internal and external structures of a representative bacterial cell
• note the main shapes commonly demonstrated by bacteria
• note the most common arrangements of groups of bacterial cells
• relate the Importance of differences in the cell walls of bacteria to their classification and their medical importance

• list a few representatives of bacteria having unusual cell wall composition, or none at all

Lecture / Study Outline

1. Bacterial cell morphology
1. external features
2. internal features
3. Representative bacterial cell
1. Appendages
2. motility
3. attachment
4. exchange of genetic material

D. Basic cell wall composition

1. Gram positive bacteria
2. Gram negative bacteria
3. practical / medical considerations
4. bacteria with exceptional cell walls

E. The cell membrane (plasma membrane)

1. multipurpose
2. roles in metabolism (performs functions of certain organelles in their absence)
3. mesosomes (and binary fission)

F. Protoplasm and its contents

1. ribosomes
2. chromatin body ("bacterial chromosome")
3. nucleoid region
4. plasmids
5. granules
6. endospores

1. resistant "survival forms"
2. medical importance
3. practical significance

II. Bacterial Shapes and arrangements

A. shapes

1. coccus
2. bacillus
3. spirillum
4. spirochetes
5. vibrio
6. pleomorphism

B. arrangements

1. single
2. pairs

a. diplococcus

3. regular clusters

1. tetrads
2. sarcina

1. irregular clusters
2. chains
3. other

III. Bacterial Identification and classification

    A. criteria

1. microscopic morphology (cell shape / arrangement)
2. macroscopic morphology
3. biochemical profile
4. chemical analysis
5. serological typing
6. DNA / RNA composition

                                        a. genetic and molecular analysis

                                        b. nucleic acid sequencing

IV. Survey of bacterial groups with unusual characteristics

    A. medically significant bacteria

        1. Rickettsias

        2. Chlamydias

B. free-living, non-pathogenic bacteria

        1. photosynthetic bacteria

            a. Cyanobacteria (formerly blue-green algae)

            b. green and purple, gliding, fruiting bacteria

            c. Mensicutes or Archaebacteria

Key Words / Terms

Define / describe each of the following as they relate to microbiology.

spirochete    plasmid    pleomorphic     diplo-

bacteria    pilus (-i)   ribosome   staphylo-

archaea    fimbria (-ae) inclusioon   strepto-

Flagellum    bacterial conjugation endospore      sarcina

monotrichous lysis    sporangium    palisades

lophotrichus periplasmic coccus Gracilicutes

amphitrichous mesosome bacillus Firmicutes

peritrichous chromatin        vibrio         Tenericutes

chemotaxis nucleoid        spirillum Mendosicutes

Study Helps

        nucleoid region           cytoplasm plasma membrane      mesosome

        cell wall                     fimbria(-e) pilus(-i)                       flagellum(-a)

        ribosomes                 capsule (slime Layer)                 chromatin body (= bacterial chromosome)

3. Describe the functions of each of the following cell components:

ribosomes        plasma membrane         fimbriae         pilus(-i)

chromatin body        cell wall                flagelum(-a) capsule

4. Draw and label diagrams comparing the structure and composition of a Gram negative bacterial cell wall to that of a Gram positive cell wall.

5. Explain the basis for the Gram stain reaction.

6. Diagram and label the following:

    a. the three basic shapes commonly found among bacteria

    b. four basic arrangements common among groups of bacterial cells

    c. name a kind of bacteria (Genus species) representing each of the groups listed above.

7. List six different general criteria commonly used to identify and/or classify bacteria.

8. Describe how each of he following organisms is unusual as compared to "ordinary" bacteria:

    a. Rickettsia

    b. Chlamydia

    c. Mycoplasma

    d. Cyanobacteria

Talaro Chapter 4.

Concept Questions numbers: 1a-c; 3a-c; 4a-c, 6a-f; 7a-b; 8a-b; 12a-f

Critical Thinking Questions numbers: 1; 4

Carefully review the following: