The Prokaryotes: Domains Bacteria and Archaea 11 The Prokaryotes: Domains Bacteria and Archaea

Table 11.1 Classification of Selected Prokaryotes*

Gram-Negative Bacteria Learning Objectives 11-1 Differentiate the alphaproteobacteria described in this chapter by drawing a dichotomous key. 11-2 Differentiate the betaproteobacteria described in this chapter by drawing a dichotomous key. 11-3 Differentiate the gammaproteobacteria described in this chapter by drawing a dichotomous key. 11-4 Differentiate the deltaproteobacteria described in this chapter by drawing a dichotomous key. 11-5 Differentiate the epsilonproteobacteria described in this chapter by drawing a dichotomous key.

Proteobacteria From the mythological Greek god Proteus, who could assume many shapes Gram-negative Chemoheterotrophic Largest taxonomic group of bacteria Five classes

The Alphaproteobacteria Most are capable of growing with very low levels of nutrients Many have stalks or buds known as prosthecae

The Alphaproteobacteria Pelagibacter One of the most abundant microorganisms in oceans Extremely small Advantage in low-nutrient environments Important role in Earth's carbon cycle

The Alphaproteobacteria Azospirillum Grows in soil, using nutrients excreted by plants Forms associations with roots Fixes nitrogen Acetobacter and Gluconobacter Convert ethanol into acetic acid

The Alphaproteobacteria Rickettsia Obligate intracellular parasites Cause spotted fevers R. prowazekii: epidemic typhus R. typhi: endemic murine typhus R. rickettsii: Rocky Mountain spotted fever Transmitted by insect and tick bites Ehrlichia Transmitted by ticks Cause ehrlichiosis

scattered rickettsias within the cell and the compact masses of Figure 11.1 Rickettsias. Slime layer Scattered rickettsias Chicken embryo cell 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. Masses of rickettsias in nucleus A rickettsial cell that has just been released from a host cell

The Alphaproteobacteria Caulobacter and Hyphomicrobium Found in low-nutrient aquatic environments Form stalks and prosthecae Reproduce via budding rather than binary fission

Figure 11.2 Caulobacter.

Hypha Holes in filter Bud Bud Figure 11.3 Hyphomicrobium, a type of budding bacterium. Hypha Holes in filter Bud Bud

The Alphaproteobacteria Rhizobium and Bradyrhizobium Fix nitrogen in the roots of leguminous plants Known by the common name of rhizobia Agrobacterium Plant pathogen; causes crown gall Inserts a plasmid into plant cells, inducing a tumor

Figure 9.19 Crown gall disease on a rose plant.

The Alphaproteobacteria Bartonella Human pathogen B. henselae: cat-scratch disease Brucella Obligate parasite of mammals; survives phagocytosis Causes brucellosis

The Alphaproteobacteria Nitrobacter and Nitrosomonas Chemoautotrophic; use inorganic chemicals as energy source; CO2 as carbon source Nitrosomonas: NH4+ → NO2– Nitrobacter: NO2– → NO3–

The Alphaproteobacteria Wolbachia Endosymbiont of insects Affects reproduction of insects

Applications of Microbiology 11.1a

Unfertilized female infected Infected female offspring Applications of Microbiology 11.1b Males Females Neither infected Uninfected offspring Male infected No offspring Female infected Infected offspring Both infected Infected offspring Wolbachia Unfertilized female infected Infected female offspring

Check Your Understanding  Make a dichotomous key to distinguish the alphaproteobacteria described in this chapter. (Hint: See page 292 for a completed example. 11-1

The Betaproteobacteria Acidithiobacillus Chemoautotrophic; oxidize sulfur to sulfates: H2S → SO42– Spirillum Found in freshwater Move via flagella Sphaerotilus Found in freshwater and sewage Form sheaths to aid in protection and nutrient gathering

Figure 11.4 Spirillum volutans.

Figure 11.5 Sphaerotilus natans. Bacterial cells Sheath

The Betaproteobacteria Burkholderia B. cepacia: degrades more than 100 organic molecules B. pseudomallei: causes meliodosis Bordetella Non-motile rods B. pertussis: causes whooping cough

The Betaproteobacteria Neisseria N. gonorrhoeae: cause of gonorrhoea N. meningitidis: cause of meningococcal meningitis Zoogloea Important in the activity of the activated sludge system

Bacteria Host-cell membrane Figure 11.6 The gram-negative coccus Neisseria gonorrhoeae. Bacteria Host-cell membrane

Check Your Understanding  Make a dichotomous key to distinguish the betaproteobacteria described in this chapter. 11-2

The Gammaproteobacteria Thiotrichales Beggiatoa Grows in aquatic sediments Chemoautotrophic; oxidize H2S to S0 for energy Francisella F. tularensis: causes tularemia

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

Figure 11.7 Pseudomonas.

The Gammaproteobacteria Pseudomonadales (cont'd) Azotobacter and Azomonas Nitrogen-fixing Moraxella M. lacunata: causes conjunctivitis Acinetobacter A. baumanii: respiratory pathogen; resistant to antibiotics

The Gammaproteobacteria Legionellales Legionella Found in streams, warm-water pipes, and cooling towers Causes legionellosis Coxiella C. burnetii: causes Q fever; transmitted via aerosols or milk

Figure 24.13b Coxiella burnetii, the cause of Q fever.

The Gammaproteobacteria Vibrionales Found in aquatic habitats V. cholerae causes cholera V. parahaemolyticus causes gastroenteritis

Figure 11.8 Vibrio cholerae.

The Gammaproteobacteria Enterobacteriales Commonly called enterics — inhabit the intestinal tract; ferment carbohydrates Facultative anaerobes Peritrichous flagella

The Gammaproteobacteria 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

The Gammaproteobacteria Enterobacteriales (cont'd) Shigella Causes bacillary dysentery Klebsiella K. pneumoniae causes pneumonia Serratia Produces red pigment Common cause of nosocomial infections

The Gammaproteobacteria Enterobacteriales (cont'd) Proteus Swarming motility; colonies form concentric rings Yersinia Y. pestis causes plague Transmitted via fleas Erwinia Plant pathogens

Proteus mirabilis with peritrichous flagella Figure 11.9 Proteus mirabilis. Flagella Proteus mirabilis with peritrichous flagella A swarming colony of Proteus mirabilis, showing concentric rings of growth

The Gammaproteobacteria Enterobacteriales (cont'd) Enterobacter E. cloacae and E. aerogenes cause urinary tract infections and nosocomial infections Cronobacter Discovered in 2007 C. sakazakii causes meningitis; found in a variety of environments and foods

The Gammaproteobacteria Pasteurellales Pasteurella Pathogen of domestic animals P. multocida is transmitted to humans via animal bites Haemophilus Require X factor (heme) and V factor (NAD+, NADP+) in media H. influenzae causes meningitis, earaches, and epiglottitis

Check Your Understanding  Make a dichotomous key to distinguish the orders of gammaproteobacteria described in this chapter. 11-3

The Deltaproteobacteria Bdellovibrio Attacks other gram-negative bacteria Desulfovibrionales Use S0 or SO42– instead of O2 as final electron acceptors Desulfovibrio is found in anaerobic sediments and intestinal tracts

Figure 11.10 Bdellovibrio bacteriovorus.

The Deltaproteobacteria Myxococcales Myxo = mucus Move by gliding and leave a slime trail Cells aggregate and form a fruiting body containing myxospores

Myxobacteria fruiting body Figure 11.11 Myxococcales. Myxobacteria fruiting body Myxospores Myxospores are resistant resting cells released from sporangioles upon favorable conditions. Myxospores Sporangiole Germination Myxospores germinate and form gram-negative vegetative cells, which divide to reproduce. Mounds of myxobacteria differentiate into a mature fruiting body, which produces myxospores packed within sporangioles. Vegetative growth cycle Vegetative myxobacteria are motile by gliding, forming visible slime trails. Mounding Aggregations of cells heap up into a mound, an early fruiting body. Aggregation Under favorable conditions, the vegetative cells swarm to central locations, forming an aggregation.

Check Your Understanding  Make a dichotomous key to distinguish the deltaproteobacteria described in this chapter. 11-4

The Epsilonproteobacteria Helical or curved; microaerophilic Campylobacter One polar flagellum C. jejuni causes foodborne intestinal disease Helicobacter Multiple flagella Cause peptic ulcers and stomach cancer

Figure 11.12 Helicobacter pylori. Flagella

Check Your Understanding  Make a dichotomous key to distinguish the epsilonproteobacteria described in this chapter. 11-5

The Nonproteobacteria Gram-Negative Bacteria Learning Objective 11-6 Differentiate planctomycetes, chlamydias, Bacteroidetes, Cytophaga, and Fusobacteria by drawing a dichotomous key. 11-7 Compare and contrast purple and green photosynthetic bacteria with the cyanobacteria. 11-8 Describe the features of spirochetes and Deinococcus.

Cyanobacteria (The Oxygenic Photosynthetic Bacteria) Carry out oxygenic photosynthesis Many contain heterocysts that can fix nitrogen Gas vesicles that provide buoyancy Unicellular or filamentous

Filamentous cyanobacterium showing heterocysts, in which 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.

The Phyla Chlorobi and Chloroflexi (The Anoxygenic Photosynthetic Bacteria) Carry out anoxygenic photosynthesis Green sulfur: phylum Chlorobi Green nonsulfur: phylum Chloroflexi Purple sulfur and purple nonsulfur photosynthetic bacteria are proteobacteria

Figure 11.14 Purple sulfur bacteria.

Table 11.2 Selected Characteristics of Photosynthesizing 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

Figure 11.15a Chlamydias. The elementary bodies Elementary body are released from the host cell. Elementary body The bacterium's infectious form, the elementary body, attaches to a host cell. Nucleus The reticulate bodies begin to convert back to elementary bodies. The host cell phagocytizes the elementary body, housing it in a vacuole. Host cell Vacuole forming Vacuole Reticulate body The reticulate body divides successively, producing multiple reticulate bodies. The elementary body reorganizes to form a reticulate body. Life cycle of the chlamydias, which takes about 48 hours to complete

Figure 11.15b 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

Planctomycetes Gemmata obscuriglobus has a membrane around DNA resembling a eukaryotic nucleus

Figure 11.16 Gemmata obscuriglobus. Nucleoid Nuclear envelope

The Nonproteobacteria Gram-Negative Bacteria Bacteroidetes Anaerobic Bacteroides are found in the mouth and large intestine Cytophaga degrade cellulose in soil Fusobacteria Are found in the mouth; cause dental abscesses

Figure 11.17 Fusobacterium.

Spirochaetes Coiled and move via axial filaments Treponema Borrelia T. pallidum causes syphilis Borrelia Causes relapsing fever and Lyme disease Leptospira Excreted in animal urine

This cross section of a spirochete Figure 11.18 Spirochetes. 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 Body of cell Sheath 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.

Deinococci Deinococcus radiodurans Thermus aquaticus More resistant to radiation than endospores Thermus aquaticus Found in a hot spring in Yellowstone National Park Source of Taq polymerase

Check Your Understanding  Which gram-negative group has a life cycle that includes different stages? 11-6  Both the purple and green photosynthetic bacteria and the photosynthetic cyanobacteria use plantlike CO2 fixation to make carbohydrates. In what way does the photosynthesis carried out by these two groups differ from plant photosynthesis? 11-7  The axial filament distinguishes what genera of bacteria? 11-8

The Gram-Positive Bacteria Learning Objective 11-9 Differentiate the genera of firmicutes described in this chapter by drawing a dichotomous key. 11-10 Differentiate the actinobacteria described in this chapter by drawing a dichotomous key.

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

Figure 11.19 Clostridium difficile. Endospore

Epulopiscium Paramecium Figure 11.20 A giant prokaryote, Epulopiscium fishelsoni. Epulopiscium Paramecium

Firmicutes (Low G + C Gram-Positive Bacteria) Bacillales Bacillus Endospore-producing rods B. anthracis causes anthrax B. thuringiensis is an insect pathogen B. cereus causes food poisoning Staphylococcus Grapelike clusters S. aureus causes wound infections, is often antibiotic resistant, and produces an enterotoxin

Bacillus thuringiensis. The diamond-shaped Figure 11.21 Bacillus. Endospore Collapsed B. thuringiensis Toxic crystal Bacillus thuringiensis. The diamond-shaped crystals shown next to the endospore are toxic to insects that ingest them. This electron micrograph was made using the technique of shadow casting.

Figure 11.22 Staphylococcus aureus.

Firmicutes (Low G + C Gram-Positive Bacteria) Lactobacillales Aerotolerant anaerobes; produce lactic acid from simple carbohydrates Lactobacillus colonize the body and are used commercially in food production

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.

Firmicutes (Low G + C Gram-Positive Bacteria) 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

Firmicutes (Low G + C Gram-Positive Bacteria) Mycoplasmatales Lack a cell wall; pleomorphic M. pneumoniae causes mild pneumonia

Figure 11.24 Mycoplasma pneumoniae.

Check Your Understanding  To which genus is Enterococcus more closely related: Staphylococcus or Lactobacillus? 11-9

Actinobacteria (High G + C Gram-Positive Bacteria)

Actinobacteria (High G + C Gram-Positive Bacteria) Often pleomorphic; branching filaments Often common inhabitants of soil Mycobacterium Outermost layer of mycolic acids that is waxy and water-resistant Often slow-growing M. tuberculosis causes tuberculosis M. leprae causes leprosy

Actinobacteria (High G + C Gram-Positive Bacteria) Corynebacterium C. diphtheriae causes diphtheria Propionibacterium Forms propionic acid P. acnes causes acne Gardnerella G. vaginalis causes vaginitis Frankia Forms N-fixing nodules on tree roots

Actinobacteria (High G + C Gram-Positive Bacteria) Streptomyces Isolated from soil; produce most antibiotics Actinomyces Form filaments in the mouth and throat; destroy tissue Nocardia Form fragmenting filaments; acid-fast N. asteroides causes pulmonary infections

Drawing of a typical streptomycete showing filamentous, branching Figure 11.25 Streptomyces. Conidiospores in coils Filament Drawing of a typical streptomycete showing filamentous, branching growth with asexual reproductive conidiospores at the filament tips Filament Conidiospores in coils Coils of conidiospores supported by filaments of the streptomycete

Figure 11.26 Actinomyces.

Check Your Understanding  What group of bacteria makes most of the commercially important antibiotics? 11-10

Diversity Within the Archaea Learning Objective 11-11 Name a habitat for each group of archaea.

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

Figure 11.27 Archaea.

Check Your Understanding  What kind of archaea would populate solar evaporating ponds? 11-11

Microbial Diversity Learning Objective 11-12 List two factors that contribute to the limits of our knowledge of microbial diversity.

Microbial Diversity Bacteria size range Thiomargarita (diameter of 750 µm) Carsonella ruddii (182 genes) PCR indicates up to 10,000 bacterial species per gram of soil Many bacteria have not been identified Have not been cultured Are a part of complex food chains requiring the products of other bacteria

Figure 11.28 Thiomargarita namibiensis.

Check Your Understanding  How can you detect the presence of a bacterium that cannot be cultured? 11-12