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Table 11. 1 Classification of Selected Prokaryotes* © 2016 Pearson Education, Inc.

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. © 2016 Pearson Education, Inc.

Proteobacteria • From the mythological Greek god Proteus, who could assume many shapes • Gram-negative • Chemoheterotrophic • Largest taxonomic group of bacteria • Five classes © 2016 Pearson Education, Inc.

The Alphaproteobacteria • Most are capable of growing with very low levels of nutrients

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Figure 11. 1 Rickettsias. Slime layer Scattered rickettsias Chicken embryo cell Nucleus Masses of rickettsias in nucleus A rickettsial cell that has just been released from a host cell © 2016 Pearson Education, Inc. 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.

The Alphaproteobacteria • Caulobacter and Hyphomicrobium • Found in low-nutrient aquatic environments • Form stalks and prosthecae • Reproduce via budding rather than binary fission © 2016 Pearson Education, Inc.

Figure 11. 2 Caulobacter. © 2016 Pearson Education, Inc.

Figure 11. 3 Hyphomicrobium, a type of budding bacterium. Hypha Holes in filter 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 © 2016 Pearson Education, Inc.

Figure 9. 19 Crown gall disease on a rose plant. Crown gall © 2016

The Alphaproteobacteria • Bartonella • Human pathogen • B. henselae: cat-scratch disease • Brucella • Obligate parasite of mammals; survives phagocytosis • Causes brucellosis © 2016 Pearson Education, Inc.

The Alphaproteobacteria • Nitrobacter and Nitrosomonas • Chemoautotrophic; use inorganic chemicals as energy source; CO 2 as carbon source • Nitrosomonas: NH 4+ → NO 2– • Nitrobacter: NO 2– → NO 3– © 2016 Pearson Education, Inc.

The Alphaproteobacteria • Wolbachia • Endosymbiont of insects • Affects reproduction of insects ©

Applications of Microbiology 11. 1 a © 2016 Pearson Education, Inc.

Applications of Microbiology 11. 1 b 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 © 2016 Pearson Education, Inc.

Check Your Understanding Make a dichotomous key to distinguish the alphaproteobacteria described in this

The Betaproteobacteria • Acidithiobacillus • Chemoautotrophic; oxidize sulfur to sulfates: H 2 S → SO 42– • Spirillum • Found in freshwater • Move via flagella • Sphaerotilus • Found in freshwater and sewage • Form sheaths to aid in protection and nutrient gathering © 2016 Pearson Education, Inc.

Figure 11. 4 Spirillum volutans. © 2016 Pearson Education, Inc.

Figure 11. 5 Sphaerotilus natans. Bacterial cells Sheath © 2016 Pearson Education, Inc.

The Betaproteobacteria • Burkholderia • B. cepacia: degrades more than 100 organic molecules • B. pseudomallei: causes meliodosis • Bordetella • Non-motile rods • B. pertussis: causes whooping cough © 2016 Pearson Education, Inc.

The Betaproteobacteria • Neisseria • N. gonorrhoeae: cause of gonorrhoea • N. meningitidis: cause of meningococcal meningitis • Zoogloea • Important in the activity of the activated sludge system © 2016 Pearson Education, Inc.

Figure 11. 6 The gram-negative coccus Neisseria gonorrhoeae. Bacteria Host-cell membrane © 2016 Pearson

Check Your Understanding Make a dichotomous key to distinguish the betaproteobacteria described in this

The Gammaproteobacteria • Thiotrichales • Beggiatoa • Grows in aquatic sediments • Chemoautotrophic; oxidize H 2 S to S 0 for energy • Francisella • F. tularensis: causes tularemia © 2016 Pearson Education, Inc.

The Gammaproteobacteria • Pseudomonadales • Pseudomonas • • Opportunistic pathogens; nosocomial infections Metabolically diverse Polar flagella; common in soil P. aeruginosa: wound and urinary tract infections © 2016 Pearson Education, Inc.

Figure 11. 7 Pseudomonas. © 2016 Pearson Education, Inc.

The Gammaproteobacteria • Pseudomonadales (cont'd) • Azotobacter and Azomonas • Nitrogen-fixing • Moraxella • M. lacunata: causes conjunctivitis • Acinetobacter • A. baumanii: respiratory pathogen; resistant to antibiotics © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Figure 24. 13 b Coxiella burnetii, the cause of Q fever. © 2016 Pearson

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

Figure 11. 8 Vibrio cholerae. © 2016 Pearson Education, Inc.

The Gammaproteobacteria • Enterobacteriales • Commonly called enterics — inhabit the intestinal tract; ferment carbohydrates • Facultative anaerobes • Peritrichous flagella © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

The Gammaproteobacteria • Enterobacteriales (cont'd) • Shigella • Causes bacillary dysentery • Klebsiella • K. pneumoniae causes pneumonia • Serratia • Produces red pigment • Common cause of nosocomial infections © 2016 Pearson Education, Inc.

The Gammaproteobacteria • Enterobacteriales (cont'd) • Proteus • Swarming motility; colonies form concentric rings • Yersinia • Y. pestis causes plague • Transmitted via fleas • Erwinia • Plant pathogens © 2016 Pearson Education, Inc.

Figure 11. 9 Proteus mirabilis. Flagella Proteus mirabilis with peritrichous flagella © 2016 Pearson

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Check Your Understanding Make a dichotomous key to distinguish the orders of gammaproteobacteria described

The Deltaproteobacteria • Bdellovibrio • Attacks other gram-negative bacteria • Desulfovibrionales • Use S 0 or SO 42– instead of O 2 as final electron acceptors • Desulfovibrio is found in anaerobic sediments and intestinal tracts © 2016 Pearson Education, Inc.

Figure 11. 10 Bdellovibrio bacteriovorus. © 2016 Pearson Education, Inc.

The Deltaproteobacteria • Myxococcales • Myxo = mucus • Move by gliding and leave

Figure 11. 11 Myxococcales. Myxobacteria fruiting body Myxospores are resistant resting cells released from sporangioles upon favorable conditions. Sporangiole Mounds of myxobacteria differentiate into a mature fruiting body, which produces myxospores packed within sporangioles. Mounding Aggregations of cells heap up into a mound, an early fruiting body. Myxospores Germination Myxospores germinate and form gram-negative vegetative cells, which divide to reproduce. Vegetative growth cycle Vegetative myxobacteria are motile by gliding, forming visible slime trails. Aggregation Under favorable conditions, the vegetative cells swarm to central locations, forming an aggregation. © 2016 Pearson Education, Inc.

Check Your Understanding Make a dichotomous key to distinguish the deltaproteobacteria described in this

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 © 2016 Pearson Education, Inc.

Figure 11. 12 Helicobacter pylori. Flagella © 2016 Pearson Education, Inc.

Check Your Understanding Make a dichotomous key to distinguish the epsilonproteobacteria described in this

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. © 2016 Pearson Education, Inc.

Cyanobacteria (The Oxygenic Photosynthetic Bacteria) • Carry out oxygenic photosynthesis • Many contain heterocysts that can fix nitrogen • Gas vesicles that provide buoyancy • Unicellular or filamentous © 2016 Pearson Education, Inc.

Figure 11. 13 Cyanobacteria. Heterocysts Glycocalyx Filamentous cyanobacterium showing heterocysts, in which nitrogen-fixing activity is located © 2016 Pearson Education, Inc. 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 © 2016 Pearson Education, Inc.

Figure 11. 14 Purple sulfur bacteria. © 2016 Pearson Education, Inc.

Table 11. 2 Selected Characteristics of Photosynthesizing Bacteria © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Figure 11. 15 a Chlamydias. Elementary body The elementary bodies are released from the host cell. The bacterium's infectious form, the elementary body, attaches to a host cell. Nucleus The reticulate bodies begin to convert back to elementary bodies. Host cell The host cell phagocytizes the elementary body, housing it in a vacuole. Vacuole forming Vacuole Reticulate body The reticulate body divides successively, producing multiple reticulate bodies. Life cycle of the chlamydias, which takes about 48 hours to complete © 2016 Pearson Education, Inc. The elementary body reorganizes to form a reticulate body.

Figure 11. 15 b Chlamydias. Elementary body Reticulate body Intermediate body © 2016 Pearson Education, Inc. 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.

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

Figure 11. 16 Gemmata obscuriglobus. Nucleoid Nuclear envelope © 2016 Pearson Education, Inc.

The Nonproteobacteria Gram-Negative Bacteria • Bacteroidetes • Anaerobic • Bacteroides are found in the mouth and large intestine • Cytophaga degrade cellulose in soil • Fusobacteria • Anaerobic • Are found in the mouth; cause dental abscesses © 2016 Pearson Education, Inc.

Figure 11. 17 Fusobacterium. © 2016 Pearson Education, Inc.

Spirochaetes • Coiled and move via axial filaments • Treponema • T. pallidum causes syphilis • Borrelia • Causes relapsing fever and Lyme disease • Leptospira • Excreted in animal urine © 2016 Pearson Education, Inc.

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 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. © 2016 Pearson Education, Inc.

Deinococci • Deinococcus radiodurans • More resistant to radiation than endospores • Thermus aquaticus • Found in a hot spring in Yellowstone National Park • Source of Taq polymerase © 2016 Pearson Education, Inc.

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 CO 2 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 © 2016 Pearson Education, Inc.

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. © 2016 Pearson Education, Inc.

The Gram-Positive Bacteria • Firmicutes (low G + C ratios) • Actinobacteria (high G

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 © 2016 Pearson Education, Inc.

Figure 11. 19 Clostridium difficile. Endospore © 2016 Pearson Education, Inc.

Figure 11. 20 A giant prokaryote, Epulopiscium fishelsoni. Epulopiscium Paramecium © 2016 Pearson Education,

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 © 2016 Pearson Education, Inc.

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. © 2016 Pearson Education, Inc.

Figure 11. 22 Staphylococcus aureus. © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Figure 11. 23 Streptococcus. © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Firmicutes (Low G + C Gram-Positive Bacteria) • Mycoplasmatales • Lack a cell wall;

Figure 11. 24 Mycoplasma pneumoniae. © 2016 Pearson Education, Inc.

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

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

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 waterresistant • Often slow-growing • M. tuberculosis causes tuberculosis • M. leprae causes leprosy © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

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 © 2016 Pearson Education, Inc.

Figure 11. 26 Actinomyces. © 2016 Pearson Education, Inc.

Check Your Understanding What group of bacteria makes most of the commercially important antibiotics?

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

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 © 2016 Pearson Education, Inc.

Figure 11. 27 Archaea. © 2016 Pearson Education, Inc.

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

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 © 2016 Pearson Education, Inc.