Biological Foundations 112, Lecture 21

Bacteria and Cyanobacteria

Chapter 25, pages 498-504
Chapter 25, pages 509-517
Basic Botany-1 0:00-4:22
Five Kindgoms-2 0:00-17:00

I.   Characteristics of Kingdom Monera

      A.   Cells very small

             1.   About 1/1000 (0.001) the volume of the smallest eukaryotic cells

             2.   About 1/10 (0.1) the length of the smallest eukaryotic cell

      B.   Morphology

             1.   Most unicellular

             2.   Some colonies contain specialized cells

             3.   Some filaments contain specialized cells

      C.   Anatomy

             1.   Contains ribosomes

             2.   Lacks membrane-bound organelles typical of eukaryotes

                   a.   Thus none of the following:

                         (1)  Mitochondria

                         (2)  Endoplasmic reticulum

                         (3)  Golgi complex

                         (4)  Lysosomes

                   b.   Genetic material

                         (1)  Single circular DNA molecule loose in cytoplasm

                         (2)  No nuclear membrane

                         (3)  DNA replicates before cell division by simply splitting which avoids the      
                               complexity of mitosis

             3.   Most have a cell wall surrounding the cell membrane which differs in composition    
                   and structure from eukaryotes

             4.   Some have flagella but flagella differ in composition and structure from eukaryotes

                   a.   Eukaryote flagella - two central hollow microtubules surrounded by 9 pairs of
                                                           similar microtubules

                   b.   Prokaryote flagella - solid structure made of long filaments of protein

             5.   No prokaryotes have cells

II.  Archaebacteria

      A.   Bacteria appear similar under the microscope but differ biochemically

      B.   Characteristics of archaebacteria

             1.   No peptidoglycan in the cell wall

             2.   Inhabit extreme environments

      C.   Three groups

             1.   Extreme halophiles

                   a.   Occur only in extremely salty environments

                   b.   Found in salt brines used to cure fish (red patches on fish)

                   c.   Osmotic potential of cell usually within range of most bacteria

                   d.   Some are photosynthetic, using the purple pigment bacteriorhodopopsin

             2.   Methanogens

                   a.   Anaerobes

                   b.   Produce methane from carbon dioxide and hydrogen

                   c.   Inhabit sewage and swamps and are common in digestive tracts

                   d.   Most common of the archaebacteria

             3.   Thermacidophiles

                    a.   Grow in hot, acidic environments

                    b.   Common in hot sulfur springs

III. Cyanobacteria (Cyanophyta)

      A.   Occurrence

             1.   Ponds, lakes, swimming pools

             2.   Moist soils, dead logs, and the bark of trees

             3.   Oceans

             4.   Some in hot springs and on snow

      B.   Morphological  forms

             1.   Few are unicellular

             2.   All are microscopic

             3.   Most are large globular colonies or long filaments held together by extracellular        

             4.   Some cells that are in a colony show specializations for division of labor

                   a.   Fixing of nitrogen

                   b.   Reproduction

                   c.   Attachment of colony to substrate

      C.   Most are photosynthetic autotrophs

             1.  Chlorophyll a - green pigment found in eukaryotes also

             2.  Carotenoids - orange pigment also found in eukaryotes

             3.   Phycocyanin - blue pigment found only in cyanobacteria and red algae

             4.   Phycoerythrin - red pigment found only in cyanobacteria and red algae

             5.   None of these pigments are in plastids.  The pigments are dispersed along                
                   membranes in the periphery of the cell or stacked in the cytoplasm.

      D.   Reproduction

             1.   Only asexually by fission

                   a.   The circular chromosome replicates to two chromosomes

                   b.   Cell pinches in two with each new cell getting a chromosome

             2.   Colonies or filaments may fragment

             3.   Fragments are called hormogonia

             4.   Endospores

                   a.   Thick-walled cells

                   b.   Highly resistant to adverse conditions

                   c.   Can remain dormant for many years and still be viable

                   d.   Form when the colony/filament/individual cell begins to experience adverse        

      E.   Structure

            1.   Photosynthetic lamellae

                  a.   Internal membranes within the cell near the margins of the cell

                  b.   Other prokaryotes do not contain lamellae

                  c.   Contain chlorophyll and enzymes needed for photosynthesis

            2.   Cell wall

                  a.   No cellulose in cell wall

                  b.   Polysaccharides, that are not cellulose, are linked with polypeptides to form the  
                        microfibrils of the cell wall

                  c.  May secrete a thin gelatinous sheath or a thick matrix around the cell wall

                       (1)  Often contains pigments

                       (2)  Often contains toxins that prevent other organisms from feeding on them

            3.   Color of various species

                  a.   About half of the species are blue-green in color, the rest are different colors

                  b.   The various colors of the cyanobacteria are due to the different relative amounts  
                        of each of the pigments are included

                  c.   Various colors of the different species:  brown,  black, purple, yellow, blue,        
                        green, and red

                  d.   Red Sea - gets its name form a cyanobacterium that produces a red algal bloom
                                          there occasionally

            4.   Locomotion

                  a.   None contain flagella or organs of mobility

                  b.   Some are able to sway back and forth slowly

                  c.   Some have a slow gliding motion

      F.   Significance of Cyanobacteria

            1.   Producer of oxygen and organic material

            2.   Fix nitrogen

                  a.   Produce nitrates and ammonia

                  b.   Because of cyanobacteria in rice paddies in Southeast Asia, rice is grown for      
                        many years on the same land without nitrogen fertilizer

                  c.   Added to soil to increase crop yield in some areas

            3.   Spirulina is used directly as human food

            4.   Symbiotic relationships with other organisms

                  a.   Protists, fungi and some plants

                  b.   With fungi they form some kinds of lichens

                  c.   Endosymbosis

                        (1)  Within the cells of other organisms

                        (2)  Usually the cyanobacterium lacks a cell wall and functions like a chloroplast  
                               within the host cell

                               (a)  Prochloron - lives in the cloaca of a tunicate

                               (b)  Possesses both chlorophyll a and b

            5.   Tolerates extreme environmental conditions

                  a.  Tolerates extreme:

                       (1)  Salinity

                       (2)  Temperature

                       (3)  pH

                 b.   Can thrive in polluted lakes and ponds

                 c.   Often become the dominant species in polluted lakes and ponds

                 d.   These cyanobacteria are usually inedible for fish

                 e.   Cyanobacteria produce blooms in the water

                       (1)  Many individuals of algae will die because of overcrowding and shading

                       (2)  Their decomposition by heterotrophic bacteria consumes large amounts of    
                              oxygen from the water

                       (3)  Fish die from lack of oxygen

                       (4)  During the day, the cyanobacteria produce enough oxygen for both the fish    
                             and the cyanobacteria, however at night when the fish and algae must            
                             breathe oxygen, there isn't enough because no photosynthesis is                    
                             occurring and the fish die

                 f.   Produce toxic metabolic products that will also kill fish and other animals

IV. Eubacteria

      A.   Introduction

             1.   Most bacteria belong to this group (classic bacteria)

             2.   Almost universally present

             3.   What happens when there is adverse conditions for bacteria?

                   a.   Most can form naturally dehydrated endospores

                   b.   Remain viable for years

                   c.   Ice and rock from glaciers in antarctica contain viable bacteria that have been    
                         dormant for 10,000 years

      B.   Structure

             1.   Morphology

                   a.   Most are single-celled

                   b.   Some species are colonies

                   c.   Some are filaments

                   d.   Cell membrane present with electron transport system attached to the cell

                   e.   Cell Wall

                         (1)  Contains peptidoglycan

                         (2)  Peptidoglycan is found only in prokaryotes and is one of the major
                                components of  the bacterial cell wall

                         (3)  Peptidoglycan is two types of sugar linked with a short peptide

                         (4)  The short peptide is two amino acid molecules long

                         (5)  The cell wall keeps the cell membrane from bursting when the cell is in a      

                         (6)  The bacterial cell can live without a cell wall but to do so it must be in an    
                                isotonic solution 

                         (7)  Most bacterial cells cannot live in a hypertonic solution

             2.   Staining Properties

                   (a)  Gram-positive bacteria

                          (1)  Absorb and retain crystal violet stain

                          (2)  Cell walls are very thick and consist primarily of peptidoglycan

                          (3)  Examples:  Streptococcus and Staphylococcus

                   (b)  Gram-negative bacteria

                          (1)  Do not absorb and retain crystal violet stain

                          (2)  Cell wall is composed of three layers:  

                                 (a)  Inner cell membrane

                                 (b)  Thin peptidoglycan layer

                                  (c)  Thick outer layer of lipoprotein and lipopolysaccharide

                          (3)  Examples:  Escherichia coli and Salmonella

             3.   Significance of gram-positive and gram-negative bacteria

                   a.    Cell strength

                          (1)  Gram-positive

                                 (a)  Thick peptidoglycan layer makes cell wall less likely to break under    

                                 (b)  More susceptible to attack by lysozymes (present in human tears)

                          (2)  Gram-negative

                                 (a)  Breaks easier under stress

                                 (b)  Semipermeable outer membrane protects from lysozyme penetration

                   b.    Penicillin is effective against gram-positive bacteria because it interferes with    
                          peptidoglycan synthesis, resulting in a fragile cell

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