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PowerPoint® Lecture Presentations prepared by Bradley W. Christian, McLennan Community College

C H A P T E R

© 2016 Pearson Education, Inc.

The Prokaryotes: Domains Bacteria and Archaea

11


Table 11.1 Classification of Selected Prokaryotes*


Proteobacteria

•  From the mythological Greek god Proteus, who could assume many shapes

•  Gram-negative •  Chemoheterotrophic •  Largest taxonomic group of bacteria •  Five classes

alpha, beta, gamma, delta, epsilon


The Alphaproteobacteria

•  Rickettsia •  Obligate intracellular parasites •  Cause spotted fevers

•  R. prowazekii: epidemic typhus (lice) •  R. typhi: endemic murine typhus •  R. rickettsii: Rocky Mountain spotted fever

•  Transmitted by insect and tick bites

•  Ehrlichia •  Transmitted by ticks •  Cause ehrlichiosis


Slime layer Scattered

rickettsias Chicken embryo cell Nucleus

Masses of rickettsias in nucleus

Rickettsias grow only within a host cell, such as the chicken embryo cell shown here. Note the scattered rickettsias within the cell and the compact masses of rickettsias in the cell nucleus.

A rickettsial cell that has just been released from a host cell

Figure 11.1 Rickettsias.


The Betaproteobacteria

•  Neisseria •  N. gonorrhoeae: cause of gonorrhoea •  N. meningitidis: cause of meningococcal meningitis

•  Bordetella •  Non-motile rods •  B. pertussis: causes whooping cough


Host-cell membrane

Bacteria

Figure 11.6 The gram-negative coccus Neisseria gonorrhoeae.


The Gammaproteobacteria

•  Pseudomonadales •  Pseudomonas

•  Opportunistic pathogens; nosocomial infections •  Metabolically diverse •  Polar flagella; common in soil •  P. aeruginosa: wound and urinary tract infections

•  10% of all nosocomial infections •  Can grow in refrigerators, resistant to many antibiotics

•  Legionellales •  Legionella

•  Found in streams, warm-water pipes, and cooling towers •  Causes legionellosis (Legionaire’s Disease)


Figure 11.7 Pseudomonas.



•  Vibrionales •  Found in aquatic habitats

•  V. cholerae causes cholera (rice water – stool) •  V. parahaemolyticus causes gastroenteritis


Figure 11.8 Vibrio cholerae.



•  Enterobacteriales •  Commonly called enterics — inhabit the intestinal tract;

ferment carbohydrates •  Facultative anaerobes •  Peritrichous flagella



•  Enterobacteriales (cont'd) •  Proteus (vulgaris) (mirabilis)

•  Swarming motility; colonies form concentric rings •  Yersinia (the Black Death)

•  Y. pestis causes plague •  Transmitted via fleas


Flagella

Proteus mirabilis with peritrichous flagella

A swarming colony of Proteus mirabilis, showing concentric rings of growth

Figure 11.9 Proteus mirabilis.



•  Enterobacteriales (cont'd) •  Escherichia

•  E. coli: indicator of fecal contamination; causes foodborne disease and urinary tract infections

•  Salmonella •  2400 serovars •  Common form of foodborne illness •  Salmonella typhi causes typhoid fever



•  Enterobacteriales (cont'd) •  Shigella

•  Causes bacillary dysentery •  Klebsiella

•  K. pneumoniae causes pneumonia •  Serratia

•  Produces red pigment •  Common cause of nosocomial infections



•  Enterobacteriales (cont'd) •  Enterobacter

•  E. cloacae and E. aerogenes cause urinary tract infections and nosocomial infections


The Deltaproteobacteria

•  Bdellovibrio •  Attacks other gram-negative bacteria


Figure 11.10 Bdellovibrio bacteriovorus.


The Epsilonproteobacteria

•  Helical or curved; microaerophilic •  Campylobacter

•  One polar flagellum •  C. jejuni causes foodborne intestinal disease

•  Helicobacter •  Multiple flagella •  H. pylori - Cause peptic ulcers and stomach cancer


Flagella

Figure 11.12 Helicobacter pylori.


The Nonproteobacteria Gram-Negative Bacteria Cyanobacteria (The Oxygenic Photosynthetic Bacteria) Green sulfur: phylum Chlorobi Green nonsulfur: phylum Chloroflexi


Figure 11.13 Cyanobacteria.

Heterocysts

Glycocalyx

Filamentous cyanobacterium showing heterocysts, in which nitrogen-fixing activity is located

A unicellular, nonfilamentous cyanobacterium, Gloeocapsa. Groups of these cells, which divide by binary fission, are held together by the surrounding glycocalyx.


Figure 11.14 Purple sulfur bacteria.


Chlamydiae

•  No peptidoglycan in the cell wall; grow intracellularly

•  Chlamydia and Chlamydophila •  Form an elementary body that is infective •  Chlamydia trachomatis causes trachoma and urethritis •  Chlamydophila psittaci causes respiratory psittacosis


The elementary bodies are released from the host cell.

The reticulate bodies begin to convert back to elementary bodies.

Elementary body The bacterium's infectious form, the elementary body, attaches to a host cell.

Nucleus

Host cell

Vacuole forming

Vacuole

Reticulate body

The elementary body reorganizes to form a reticulate body.

The reticulate body divides successively, producing multiple reticulate bodies.

The host cell phagocytizes the elementary body, housing it in a vacuole.

Life cycle of the chlamydias, which takes about 48 hours to complete

Figure 11.15a Chlamydias.


Micrograph of Chlamydophila psittaci in the cytoplasm of a host cell. The elementary bodies are the infectious stage; they are dense, dark, and relatively small. Reticulate bodies, the form in which chlamydias reproduce within the host cell, are larger with a speckled appearance. Intermediate bodies, a stage between the two, have a dark center.

Elementary body

Reticulate body

Intermediate body

Figure 11.15b Chlamydias.


Spirochaetes

•  Coiled and move via axial filaments •  Treponema

•  T. pallidum causes syphilis

•  Borrelia •  Causes relapsing fever and Lyme disease


Axial filaments

Sheath

This cross section of a spirochete shows numerous axial filaments between the dark cell and the outer sheath.

Axial filament anchored at one end to cell body Sheath Body of cell

Axial filament The end of an axial filament (endoflagellum) is attached to the cell and extends through most of the length of the cell. Another axial filament is attached to the opposite end of the cell. These axial filaments do not extend away from the cell but remain between the body of the cell and the external sheath. Their contractions and relaxations cause the helical cell to rotate in a corkscrew fashion.

Figure 11.18 Spirochetes.


The Gram-Positive Bacteria

•  Firmicutes (low G + C ratios) •  Actinobacteria (high G + C ratios)


Firmicutes (Low G + C Gram-Positive Bacteria)

•  Clostridiales •  Clostridium

•  Endospore-producing •  Obligate anaerobes •  Includes disease-causing C. tetani, C. botulinum, C.

perfringens, and C. difficile •  Epulopiscium

•  Can be seen with the unaided eye •  Daughter cells form within the parent cell; no binary

fission


Endospore

Figure 11.19 Clostridium difficile.


Epulopiscium

Paramecium

Figure 11.20 A giant prokaryote, Epulopiscium fishelsoni.



•  Bacillales •  Bacillus

•  Endospore-producing rods •  B. anthracis causes anthrax •  B. cereus causes food poisoning

•  Staphylococcus •  Grapelike clusters •  S. aureus causes wound infections, is often antibiotic

resistant, and produces an enterotoxin


Figure 11.22 Staphylococcus aureus.


Firmicutes (Low G + C Gram-Positive Bacteria) •  Lactobacillales (cont'd)

•  Streptococcus •  Spherical in chains •  Produce enzymes that destroy tissue •  Beta-hemolytic streptococci hemolyze blood agar;

includes S. pyogenes •  Non-beta-hemolytic streptococci include S. pneumoniae

and S. mutans, which causes dental caries


Figure 11.23 Streptococcus.



•  Lactobacillales (cont'd) •  Enterococcus

•  Found in intestinal tract; hospital contaminants •  E. faecalis and E. faecium infect surgical wounds and the

urinary tract •  Listeria

•  L. monocytogenes contaminates food


Actinobacteria (High G + C Gram-Positive Bacteria) •  High G + C •  Gram-positive


Actinobacteria (High G + C Gram-Positive Bacteria)

•  Mycobacterium •  Outermost layer of mycolic acids that is waxy and water-

resistant •  Often slow-growing •  M. tuberculosis causes tuberculosis •  M. leprae causes leprosy

•  Corynebacterium •  C. diphtheriae causes diphtheria

•  Propionibacterium •  Forms propionic acid •  P. acnes causes acne


Actinobacteria (High G + C Gram-Positive Bacteria)

•  Streptomyces •  Isolated from soil; produce most antibiotics


Diversity Within the Archaea

•  Distinct taxonomic grouping; lack peptidoglycan •  Extremophiles

•  Halophiles •  Require salt concentration >25%

•  Thermophiles •  Require growth temperature >80 C

•  Methanogens •  Anaerobic and produce methane

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