PROKARYOTES

• Proteobacteria


  • Largest taxonomic group of bacteria
  • Most of the Gram-negative chemoheterotrophic bacteria included
  • Named after Proteus, Greek god of the sea, who is capable of assuming many different shapes
• Classes of Proteobacteria


  • Alphaproteobacteria
  • Betaproteobacteria
  • Gammaproteobacteria
  • Deltaproteobacteria
  • Epsilonproteobacteria
• Alphaproteobacteria


  • Most of the proteobacteria capable of growth at very low levels of nutrients
  • Some agriculturally important bacteria capable of inducing nitrogen fixation in symbiosis with plants
  • Pelagibacter (Pelagibacter ubique) - One of the most abundant microorganisms on Earth, found in the ocean environment
  • Rickettsia - Gram-negative bacilli or coccobacilli, transmitted to humans by bites of insects or ticks, obligate intracellular parasite of phagocytes
  • Ehrlichia - Gram-negative rickettsia-like bacteria, obligate intracellular parasite of white blood cells, transmitted by ticks
  • Bartonella - Gram-negative bacilli known to cause human disease such as the cat scratch disease, transmitted by fleas & ticks to cats
  • Brucella - Small non-motile coccobacilli, transmitted from infected animals or unpasteurized animal products
• Betaproteobacteria


  • Group of bacteria that often use nutrient substances that diffuse away from areas of anaerobic decomposition of organic matter
  • Burkholderia - Aerobic gram-negative motile flagellated bacilli, can degrade over 100 organic molecules, can grow on respiratory secretions in the lung, can grow in disinfectant
  • Bordetella - Non-motile aerobic, gram negative bacillus, causes pertussis (whooping cough)
  • Neisseria - Aerobic, gram-negative diplococci that usually inhibit the mucous membranes of mammals, causes gonorrhea and meningococcal meningitis
• Gammaproteobacteria


  • Largest subgroup of proteobacteria
  • Francisella - Small pleomorphic bacteria, causes tularemia (rabbit fever, rodent fever)
  • Pseudomonas - Aerobic gram-negative bacilli with polar flagella, Pseudomonas aeruginosa can infect the urinary tract, burns, wounds, and can cause blood infections, abscesses, and meningitis
  • Legionella - Thin non-capsulated poorly-staining gram-negative bacteria, difficult to grow on usual culture media, common in steam and warm-water supply lines and air-conditioning system, causes Legionnaire's Disease
  • Vibrio - Facultatively anaerobic gram-negative curved rods found mostly in seawater habitats, causes cholera
  • Enterics (Enterobacteriales) - Gram-negative bacilli, facultatively anaerobic, & active fermenters of glucose & other carbohydrate, inhabit the intestinal tracts of humans & animals, includes E.coli, Salmonella, Shigella, Klebsiella, Serratia, Proteus, Yersinia, Haemophilus
• Deltaproteobacteria


  • Includes bacterial species that act as predators of other bacteria, includes important contributors in the sulfur cycle
• Epsilonproteobacteria


  • Slender gram negative rods that are helical/curved
  • Campylobacter - Microaerophilic vibrios, include species that cause fetal abortions in animals and foodborne intestinal disease
  • Helicobacter - Microaerophilic vibrios with multiple flagella, Helicobacter pylori is the most common cause of peptic ulcers in humans and can cause stomach cancer
• Gram positive bacteria


  Bacteria with thick peptidoglycan cell wall that stains blue/violet on gram staining technique
• Groups of gram positive bacteria

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


  • Group of gram positive bacteria that have less than 50% of G+C ratio
  • Endospore forming bacteria
  • Clostridium - Genus of obligate anaerobic bacilli that contain endospore that distends the cell, includes C. tetani (tetanus) and C. botulinum (botulism)
  • Bacillus - Genus of endospore forming aerobic bacteria
• Uni


  Causes foodborne intestinal disease (jejunum) and ingestion of raw chicken
• Helicobacter


  Microaerophilic vibrios with multiple flagella
• Helicobacter pylori (H. pylori)

  Polymorphic bacteria - Most common cause of peptic ulcers in humans and can cause stomach cancer if ulcers are not treated
• Bacteria with thick peptidoglycan cell wall that stains blue/violet on gram staining technique
• Groups of gram positive bacteria based on G+C ratio

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


  • Group of gram positive bacteria that have less than 50% of G+C ratio
  • Endospore forming bacteria
• Clostridium


  Genus of obligate anaerobic bacilli that contain endospore that distends the cell
• Clostridium


  • C. tetani (tetanus) - thrive in soil & rusty metals; cause fatal disease
  • C. botulinum (botulism) - contaminant of canned food, wounds & infant umbilicus; cause fatal neurological disease
• Bacillus


  Gram positive rods that produce endospores, common in the soil
• Bacillus


  • B. anthracis (anthrax, biological warfare) - a deadly disease causing skin changes such as itchy bumps or sores/ulcers with a black
  • B. thuringiensis (BT crops) - pest control
  • B. cereus (food poisoning, reheated fried rice) - Fried rice syndrome: food spoilage/poisoning in reheated food
• Staphylococcus


  • Gram positive cocci occurring as grape-like clusters and mostly facultative anaerobes
  • Grow well under conditions of high osmotic pressure & low moisture
• Staphylococcus aureus


  • Named for their golden yellow-pigmented colonies which possibly confer protection from sunlight
  • Toxins produced cause disease by increasing its ability to invade or damage the body
  • Causes various diseases such as: Surgical wound infection, food poisoning, toxic shock syndrome
• Lactobacillus


  • Microaerotolerant lactic acid-producing bacilli capable of fermentation of carbohydrates
  • In humans, found inside the vagina, oral cavity & intestinal tract
  • Used commercially in the production of yoghurt, sauerkraut, pickles & buttermilk
• Streptococcus


  Complex group of gram positive cocci in chains responsible for more illnesses & causing greater variety of diseases than any group
• Types of Streptococci based on blood agar growth

  • β-Hemolytic streptococci
  • Non-β-Hemolytic streptococci
• β-Hemolytic streptococci


  • Streptococcus pyogenes: causes scarlet fever, impetigo, erysipela, strep throat, and rheumatic fever
  • Streptococcus agalactiae: important cause of sepsis/infection in the newborn
• Non-β-Hemolytic streptococci


  • Streptococcus pneumonia: important cause of pneumococcal pneumonia
  • Streptococcus viridans: causes endocarditis and valvular heart disease
• Listeria


  • Includes the pathogenic Listeria monocytogenes which can contaminate dairy products and can survive within phagocytes
  • L. cytomonogenes can cause stillbirths among infected pregnant women
• Mycoplasma


  • Highly pleomorphic bacteria that lack a cell wall & can produce filaments that resemble fungi
  • Very small bacterial cells, about 5% the size of a typical bacillus, that could pass through filters
  • Most genetically-related to gram positive species like Streptococcus & Bacillus
  • Do not have cell walls, but rather contain sterols in their cell membrane (similar to eukaryotes)
  • Can be grown on media containing sterols and form small colonies with "fried egg appearance"
• Mycoplasma pneumonia


  • Cause of a mild form of atypical pneumonia (walking pneumonia)
  • Not as detectable as typical pneumonia, but if untreated can cause serious complications
• Actinobacteria (high G+C ratio bacteria)

  Highly pleomorphic bacteria
• Mycobacterium


  • Aerobic, non-endospore forming bacilli, that occasionally form filamentous growths (Myco- or fungus like)
  • Acid-fast bacteria that contains a waxy outer layer of mycolic acid in their cell wall
  • Makes the bacteria resistant to drying methods or many antibiotics
  • Not stainable with Gram staining
• Mycobacterium


  • M. tuberculosis (tuberculosis) - Chronic lung disease causing lung destruction or fibrosis, cachexia, chronic cough & bloody phlegm
  • M. leprae (leprosy) - Chronic disease affecting nerves and skin that may present with leonine fascies & loss of sensation
• Corynebacterium


  Extremely pleomorphic bacteria
• Proprionibacterium


  • Gram positive fermenting bacteria capable of producing proprionic acid
  • Proprionibacterium acnes: Commonly found in the skin and primary bacterial cause of acne
• Actinomycetes (mold-like filamentous bacteria)


  • Refers to mold-like filamentous bacteria that have radiate or star-like growth appearance because of their often branching filaments
  • Filamentous bacteria are very common inhabitants in soil, where they bridge water-free gaps between soil particles to move & give an "earthy" aroma
• Cyanobacteria


  Photosynthetic (oxygenic) bacteria with a distinct blue-green pigmentation
• Chlamydiae


  • Atypical bacteria that do not have peptidoglycan in their cell wall
  • Intracellular gram-negative coccoid bacteria having a unique life cycle
  • Similar to rickettsiae who are intracellular
  • Transmitted by person-to-person contact and body fluids
• Chlamydia


  Gram-negative coccoid bacteria
• Fusobacterium


  • Long and slender, gram-negative rods with pointed rather than blunt ends
  • In humans, they are found most often in the gingival crevice of the gums and may be responsible for some dental abscesses