Lecture 16 Proteobacteria

Question 1

Who are the Proteobacteria?

Answer 1

All proteobacteria are gram-negative, with an outer membrane composed mainly of lipopolysaccharides. Many move about using flagella, but some are nonmotile or rely on bacterial gliding.

Question 2

List the characteristics of the puple nonsulf bacteria.

Answer 2

• Mainly all are alpha-proteobacteria
• Morphologically diverse
  
  • Most motile by polar flagella
• In absence of light, most grow aerobically as chemoorganoheterotrophs
  
  • May carry out fermentations and grow anaerobically
• Found in mud and water of lakes and ponds with abundant organic matter and low sulfide levels; some marine species.

Question 3

Describe the metabolism of purple nonsulfur bacteria.

Answer 3

• They are metabolically flexible
  
  • Normally grow anaerobically as anoxygenic photoorganoheterotrophs
    
    • Possess bacteriochlorophylls a or b in photosystems located in membranes that are continuous with plasma membrane
    • Some can use low levels of H2S as electron source

Question 4

Decribe the characteristics of Rickettsia and Coxiella.

[Proteobacteria]

Answer 4

• Rod-shaped, coccoid, or pleomorphic
  
  • Typical gram negative cell walls
  • No flagella
  • Very small
• Parasitic or mutualistic
  
  • Parasitic species grow in vertebrate erythrocytes, macrophages, and vascular endothelial cells
    
    • Also live in blood-sucking arthropods, which serve as vectors or primary hosts

Question 5

Talk about the parasitic lifestyles of Rickettsia and Coxiella.

Answer 5

Rickettsia

Enters host by phagocytosis -> escapes phagosome -> reproduces in cytoplasm -> host cell bursts

Coxiella

Enters host by phagocytosis -> remains in phagosome -> reproduces in phagolysosome -> host cell bursts

Question 6

What are some of the important diseases caused by pathogens belonging to Rickettsia and Coxiella?

Answer 6

• Typhus fever
• Rocky Mountain Spotted Fever
• Q Fever
• Many are important pathogens in dogs, horses, sheep, and cattle

Question 7

Decsribe the characteristics of Caulobacteraceae and Hyphomicrobiaceae.

[Proteobacteria]

Answer 7

• Have at least one of three distinguishing features:
  
  • Prostheca: extension of cell, including plasma membrane, that is narrower than mature cell
  • Stalk: nonliving appendage produced by cell and extending from it
  • Reproduction by budding: progeny cell is a bud that first appears as a small protusion on parent cell and enlarges to form mature cell

Question 8

What are nitrifying bacteria?

Answer 8

• Gram-negative bacteria that DO NOT produce endospores.
• Aerobic metabolism
• Undergoes nitrification.
  
  • Converson of ammonia to nitrate
• Fate of nitrates
  
  • Easily used by plants
  • Lost from soil through leaching or denitrification

Question 9

Describe everyone’s favorite STI pathogenic genus, the Neisseria.

Answer 9

• Nonmotile, gram-negative cocci
  
  • Most often occur in pairs with adjacent sides flattened
  • May have capsules or fimbriae
• Aerobic chemooragnotrophs
  
  • Oxidase positive and usually catalase positive
• Inhabitants of mucous membranes of mammals
  
  • Some human pathogens cause gonorrhea and meningitis

Question 10

What’s so important abou the genus Burkholderia in the agricultural world?

Answer 10

• Degrades >100 organic molecules
  
  • Very active in recycling organic material
• Plant pathogen
• Can cause disease in hospital patients
  
  • Particular problem for cystic fibrosis patients

Question 11

What are the functions of sheaths in some bacteria?

Answer 11

• Attachment to surfaces
• Obtaining nutrients from slowly running water
• Protection against predators

Question 12

Describe some characteristics of the purple sulfur bacteria.

[Proteobacteria]

Answer 12

• Strict anaerobes
• Usually photoautolithotrophs
  
  • Use H2S as electron donor
    
    • Deposit sulfur granules internally
    • Often eventually oxidize sulfur to sulfate
  • May also use hydrogen as electron donor
• Grow in sulfur-rich habitats

Question 13

What’s so special about Order Pseudomonas?

[Proteobacteria]

Answer 13

• Chemoheterotrophs with respiratory metabolism
  
  • Usually use oxygen as electron acceptor
  • Some times use nitrate as electron acceptor
  • Have functonal TCA cycle
  • Mose hexoses are degraded by Entner-Doudoroff pathway

Question 14

What are the practical importances of Pseudomonads?

Answer 14

• Metabolically versatile
  
  • Degrade wide variety of organic molecules
  • Mineralization: microbial breakdown of organic materials to inorganic substrates
• Important experimental subjects
• Some are major animal and plant pathogens
• Some cause spoilage of refrigerated food because they can grow at 4*C

Question 15

Which proteobacteria causes cholera?

Answer 15

Vibrio cholerae. They become pathogenic after sensing a change in pH.

Question 16

What’s so special about the Order Enterobacteriales?

Answer 16

• Facultative anaerobes
• Chemoorganiottrophs that degrade sugars by glyolytic pathway
  
  • Can cleave pyruvate to yield formic acid (formic acid fermentation)
• Most important for microbiologists. These are the guys that live mostly in your gut.

Question 17

Ahhh the Escherichia coli. It is the media’s favorite bacteria to blame for illness. List these guys’ characteristics.

Answer 17

• Probably the best studied bacterium
• Inhabitant of intestinal tracts of many animals
• Used as indicator organisms for testing water for fecal contamination
• Some strains are pathogenic
  
  • Gastroenteritis
  • Urinary tract infections

Question 18

What are some important pathogenic enteric bacteria?

Answer 18

• Salmonella - typhoid fever and gastroenteritis
• Shigella - bacillary dysentery
• Klebsiella - pneumonia
• Yersinia - plague
• Erwinia - blights, wilts, etc., or crop plants

These guys typically have lots of “protection” in extracellular space (i.e. OMVs), making it hard for the immune system to combat them.

Question 19

What are some of the important pathogens from the Order Pasteurellales?

[Proteobacteria]

Answer 19

• Pasteurella multilocida - fowl cholera
• Pasteurella haemolytica - pneumonia in cattle, sheep and goats
• Haemophilus influenzae - variety of diseases, including meningitis in children

Question 20

What’s so important about the Order Myxococcales?

Answer 20

• They are aerobic chemoorganotrophs with respiratory metabolism.
• Most are micropredators or scavengers that lyse bacteria and yeasts by secretion of digestive enzymes.
  
  • Most use amino acids as major source of C, N, and energy

Question 21

What are myxospores?

Answer 21

• Spores formed by Myxobacteria
• Frequently enclosed in walled structures called sporangioles (sporangia)
• Dormant and desiccation-resistant
  
  • May survive up to 10 years

Question 22

What is septicemia? What is enteritis?

Answer 22

Septicemia: pathogens or their toxins in blood

Enteritis: inflammation of intestinal tract

Question 23

The Genus Helicobacter belongs to the smallest class of proteobacteria, Class Epsilonproteobacteria. What is this genus’s importance in the medical world?

Answer 23

• At least 14 species isolated from stomachs and upper intestines of humans, dogs, cats, and other mammals.
• Helicobacter pylori is known to cause gastritis and peptic ulcer disease.
• Produces large quantitise of ureases.
  
  • Urea hydrolysis appears to be associated with virulence!!