Ch. 4

Gram-negative Bacteria

  • Spirochetes: helical shape, flexible, thin, difficult to stain, endoflagella, move in corkscrew pattern

    1. Treponema pallidum

      • Syphilis

    2. Borrelia burgdorferi

      • Lyme disease                

    3. Borrelia recurrens

      • relapsing fever

  • Alphaproteobacteria, oligotrophs: capable of living in low nutrient environments, obligate intracellular parasites, can’t make ATP

    1. Chlamydia trachomatis

      • cocci shaped bacteria

      • transmitted to humans by interpersonal contact or by airborne respiratory routes

      • form a reticulate and elementary bodies in infected cells

      • causes blindness in humans and nongonococcal urethritis (most common STD in US)

    2. Rickettsia rickettsii

      • rod shaped bacteria

      • highly pleomorphic

      • transmitted to humans by insects and ticks

      • rocky mountain spotted fever

  • Betaproteobacteria, eutrophs: require large amounts of organic nutrients, often live between aerobic and anaerobic areas

    1. Genus Neisseria: diplococci, require moisture and high CO2 levels to grow, frequently found on mucous membranes, only grow well and around body temperature

      1. Neisseria gonorrhea

        • gonorrhea

      2. Neisseria meningiditis

        • bacterial meningitis

    2. Bordatella pertussis

      • aerobic, fastidious

      • whooping cough

  • Gammaproteobacteria

    1. Pseudomona aeruginosa

      • rods with polar flagella

      • many secrete pigments in media

      • urinary tract infections (UTIs), septicemia, abscesses, burns, pulmonary infections in cystic fibrosis patients, meningitis

    2. Legionella pneumophila

      • rods that live in natural waters, frequently found in air conditioning systems, humidifiers, showers, spas, fountains

      • Legionnaires’ disease (pneumonia) and Pontiac fever

  • Gammaproteobacteria, family Enterobacteriaceae: inhabit intestinal tracts of animals, motile bacteria with peritrichous flagella or nonmotile, many have fimbriae for attachment to mucous membranes and sex pili for exchange of DNA

    1. Escherichia coli

      • common inhabitant of human intestinal tract, most trains are not pathogenic, but others can cause UTIs, traveler’s diarrhea and food borne disease

    2. Genus Salmonella: almost all members are potential pathogens, common inhabitant of animal GI tract, can contaminate food

      1. Salmonella typhi

        • typhoid fever, severe illness

      2. Salmonella enteritidis

        • causes salmonellosis, the second most common bacterial food-borne disease

    3. Genus Shigella: second most common cause of travelers’ diarrhea

      1. Shigella sonnei

        • most common species in US

      2. Shigella flexneri

        • most common species in US

      3. Shigella dysenteriae

        • can be deadly, rare in the US

    4. Klebsiella pneumoniae

      • cause respiratory and UTIs

      • antibiotic resistant strains cause pneumonia and nosocomial infections

    5. Yersinia pestis

      • causes bubonic plague

      • transmitted by fleas, respiratory droplet, and contact with animals

  • Gammaproteobacteria, Family Vibrionaceae, Genus Vibrio: slightly curved rods, inhabit seawater, flagellated, motile, may produce toxin that causes hypersecretion of water and electrolytes in stool

    1. Vibrio cholerae

      • cholera, disease characterized by profuse, explosive, and wattery diarrhea, fatal in up to 50% of untreated cases

    2. Vibrio parahemolyticus

      • Gastroenteritis associated with consumption of shellfish

  • Gammaproteobacteria, Family Pasterellaceae: found in aquatic habitats, straight or slightly curved rods

    1. Hemophilus influenzae

      • important pathogens that inhabit mucous membranes of upper respiratory tracts, mouth, vagina, and intestinal tract, require blood in culture

      • cause meningitis, ear infections, bronchitis, arthritis, and pneumonia in children

    2. Gardnerella vaginalis

      • causes common forms of bacterial vaginitis

  • Gammaproteobacteria, Family Moraxellaceae: plump rods, nonmotile

    1. Acinetobacter baumannii

      • infections of bone, lung, blood, surgical wounds, skin, eyes, urinary tract and CSF

      • early reports in Iraq war veterns

      • growing cause of nosocomial infections

      • ICU and surgery patients on ventilators, catheters, and/or dialysis are at high risk

      • multiple drug resistance

  • Deltaproteobacteria, Genus Desulfovibrio: reduce sulfur, can be used for removal of toxic and radioactive waste

    1. Desulfovibrio orale

      • causes periodontal disease

  • Epsilonproteobacteria: smallest group of proteobacteria, microaerophilic bacteria

    1. Campylobacter jejuni

      • most common cause of bacterial food-borne intestinal disease in US, associated with undercooked chicken

    2. Campylobacter fetus

      • causes abortions in domestic animals

    3. Helicobacter pylori

      • causes most gastric ulcers and stomach cancer in humans

Gram-positive bacteria

  1. Staphyloccocus aureus (MRSA)

    • grow well under high osmotic pressure and low moisture

    • very common infections, almost always found on skin and in nasal mucous membranes

    • yellow pigmented colonies

    • produce several toxins

    • cause pimples, sties, skin abscesses, toxic shock syndrome, food poisoning, and nosocomial infections

    • antibiotic resistant S. aureus is a growing problem

    • vancomycin is last line of defense against antibiotic resistant strains

  • Genus Streptococcus: most are pathogens that cause a wide range of important human and animal diseases, some are beneficial probiotics, tend to appear in chains or pairs, do not use oxygen, most are aerotolerant, classified based on their effect on red blood cells

    1. Streptococcus pneumoniae

      • Causes bacterial pneumonia, ear infections, meningitis, and sinus infections

    2. Streptococcus pyogenes

      • causes strep throat, scarlet fever, rheumatic fever, impetigo, skin infections, erysipelas, childbirth fever, glomerulonephritis, and flesh-eating infections

  • Non-sporing gram-positive rods

    • Genus Lactobacillus: produce lactic acid which inhibits the growth of other bacteria, beneficial bacteria that live in human vagina, intestinal tract, and mouth, commonly used at probiotics

      1. Lactobacillus bulgaricus

      2. Lactobacillus acidophilus

      3. Lactobacillus rhamnosus GG

        • used commercially to make yogurt, pickles, sauerkraut, and buttermilk

    • Listeria monocytogenes

      • contaminates dairy products

      • survives in phagocytic cells and grows in refrigerators

      • infection of pregnant women can cause stillbirth or severe damage to fetus

  • Endospore forming: aerobic to strictly anaerobic, motile and nonmotile, survive harsh environmental conditions

    1. Bacillus anthracis

      • rod shaped bacteria

      • causes anthrax a disease of cattle, large nonmotile facultative anaerobe

    2. Bacillus thuringiensis

      • rod shaped bacteria

      • kills insects, used by gardeners

    3. Clostridium tetani

      • rod shaped bacteria, obligate anaerobes

      • causes tetanus

    4. Clostridium botilinum

      • rod shaped bacteria, obligate anaerobes

      • causes botulism, source of botox

    5. Clostridium perfringens

      • rod shaped bacteria, obligate anaerobes

      • causes gas gangrene and foodborne diarrhea

    6. Clostridium dificile

      • causes diarrhea, especially after antibiotics

  • Irregular non-sporing gram-positive rods

    1. Corynebacterium diphtheriae   

      • club shaped rods

      • pleomorphic

      • palisade arrangement of rods

      • may be anaerobic or aerobic

      • cause diphtheria

    2. Propionibacterium acne

      • causes acne

  • Mycobacteria: aerobic, non-spore forming rods, stain gram-positive but cell wall structure is more similar to gram-negative bacteria, waxy cell wall with mycolic acids, acid-fast, drug resistant, resistant to drying, and pathogenic due to waxy cell wall, grow very slowly, tend to cause chronic infections

    1. Mycobacterium tuberculosis

      • causes tuberculosis

    2. Mycobacterium leprae

      • causes leprosy

  • Nocardioforms, Genus Nocardia: gram-positive, filamentous, aerobic, many acid fast, common in soil, form filaments which fragment into short rods to reproduce

    1. Nocardia asteroides

      • pulmonary infections similar to tuberculosis, mycetoma, abscesses

Wall-less Bacteria/Mycoplasma: don’t form cell walls, highly pleomorphic, most aerobes or facultative anaerobes, resistant to many antibiotics, can form filaments that resemble fungi, produce very small colonies, smallest free-living cells, can pass through bacterial filters

  1. Mycoplasma pneumoniae

    • most important human pathogen

    • walking pneumonia

Archaea, Class Halobacteria: require high concentration of of sodium chloride in their aquatic environment, use the protein bacteriorhodopsin to perform photosynthesis which gives them and the water they inhabit a purple color

  1. Halobacterium salinarum

    • may be the oldest bacterium on earth, found in fossils over 250 million years old

Deeply Branching Bacteria: bacteria very close to the base of the phylogenetic tree of life

  1. Deinococcus radiodurans

    • considered a polyextremophile

    • can survive extreme heat, acidity, vacuum, drought, and radiation