Prokaryotes

• The Prokaryotes


  • Bacteria
  • Archaea
• The prokaryotes are divided into domains

  
• Proteobacteria


  • Largest group of bacteria with more than 500 genera and 2,000 species
  • All are gram-negative; some are motile
  • Most are facultative anaerobes
  • Named after mythical Greek God Proteus
  • Divided into 5 classes: alpha, beta, gamma, delta, and epsilon

  
• Alphaproteobacteria


  • Known for living in low-nutrient environments
  • Have unusual morphology including buds or stalks
  • Stalks used to adhere to a surface are called prosthecae

  
• Caulobacter are stalked bacteria found in lakes (class 1)
• Pelagibacter ubique


  • Accounts for 25% of all prokaryotes in the oceans and 0.5% of all prokaryotes in the world
  • Assists with carbon cycles and serve as carbon sinks

  
• Alphaproteobacteria in agriculture


  • Some are good for plants and crops, allowing nitrogen fixation at the roots and helping plants grow faster and stronger
  • Agrobacterium can insert a DNA plasmid into a plant's cells, inducing tumor formation and causing Crown Gall disease
• Alphaproteobacteria as human pathogens

  • Obligate intracellular parasites that cannot make their own ATP
  • The genus Rickettsia can only reproduce within mammalian cells and are generally transmitted via insect bites such as lice, ticks, and mites
• Alphaproteobacterial diseases


  • Typhus
  • Rocky Mountain spotted fever
• Petechia rash


  Rash typically seen on the wrists, ankles, palms, soles, and forearms

  
• Ticks are often vectors of diseases
• Diseases transmitted by ticks

  • Lyme Disease
  • Alpha-gal allergy (allergy to red meat)
• Cat scratch fever


  Caused by Bartonella henselae, results in low-grade fever and enlarged tender lymph nodes for 1-3 weeks after exposure, with a pustule at the site of infection
• Betaproteobacteria


  • Need a lot of nutrients to survive
  • Include several major human pathogens that use us as a nutrient source
• Betaproteobacteria are often found in sewage and decomposition sites

  
• Betaproteobacterial pathogens


  • Neisseria gonorrhoeae
  • Neisseria meningitidis

  
• Neisseria


  Fastidious, gram-negative cocci that live in mucosal membranes of mammals, usually grown on chocolate agar, and appear as diplococci resembling two coffee beans
• Bordetella pertussis


  Gram-negative, non-motile, aerobic bacillus that causes whooping cough by producing toxins that paralyze the cilia in the respiratory tract, resulting in severe cough and mucous buildup
• Gammaproteobacteria


  • Largest subgroup of Proteobacteria and the most diverse group
  • Many are human and plant pathogens as well as normal gut flora
  • Genera are separated by metabolic pathways, growth requirements, appearance, and motility

  
• Pseudomonadales


  • Include Pseudomonas, Moraxella, and Acinetobacter
  • Motile, gram-negative rods with polar flagella
  • Most are considered opportunistic pathogens
  • Many species have evolved to grow inside antiseptics
  • Often produce water-soluble pigments
• Moraxella


  Causative agent of pink eye (chronic conjunctivitis)
• Pseudomonas


  • Often associated with burn patient infections and lung infections
  • Can cause UTIs, ear infections, and build biofilms making them hard to treat
  • Generally found in the environment and water sources
  • Often produce water-soluble pigments
• Legionella


  • Found in streams, warm-water pipes, and cooling towers
  • L. pneumophilia causes Legionnaires' disease, named after 1976 outbreak in Philadelphia
• Vibrio


  • Found in coastal, fresh water
  • Vibrio parahaemolyticus causes gastroenteritis
  • Vibrio cholerae causes cholera
• Vibrio cholerae


  • Facultative anaerobe
  • Gram-negative, curved rods
• Vibrio cholerae can cause death from dehydration
• Pasteurellales


  • Pasteurella can cause pneumonia and septicemia
  • Transmitted by inhalation of droplets, ingestion of contaminated food/water, animal bites/scratches/licks
  • Animal bites will show signs of cellulitis within 24 hours
• Enterobacteriales (Enterobacteriaceae)


  • Enterobacter
  • Erwinia
  • Escherichia
  • Klebsiella
  • Shigella
  • Yersinia
  • Proteus
  • Serratia
  • Salmonella

  
• Enterobacteriales inhabit the intestinal tracts of humans and other animals, have peritrichous flagella, and are facultative anaerobes
• Salmonella enterica


  • Has hundreds of serotypes often named by place of origin
  • Causes salmonellosis
• Enterobacteriales (Enterobacteriaceae)


  • Inhabit the intestinal tracts of humans and other animals
  • Have peritrichous flagella
  • Are facultative anaerobes
• Gram-negative, facultative anaerobes in Enterobacteriales


  • Enterobacter
  • Erwinia
  • Escherichia
  • Klebsiella
  • Shigella
  • Yersinia
  • Proteus
  • Serratia
  • Salmonella
• Salmonella enterica


  • Hundreds of serotypes
  • Often named by place of origin
• Salmonellosis


  Usually associated with food and eggs
• Salmonella typhi


  Causes typhoid and typhoid fever
• Mary Mallon (Typhoid Mary)


  • 1869-1938
  • Carrier of typhoid but asymptomatic
• Escherichia and Enterobacter


  • Opportunistic pathogens
  • Commonly associated with UTIs
• Serratia marcescens


  Often associated with nosocomial infections
• Shigella


  Causes bacillary dysentery or shigellosis
• Proteus


  Swarming colonies that can cause UTIs