unti 3 chapter 4 pt 2

Deinococcus radiodurans

  • Discovered in 1956 from irradiated meat; survives radiation doses a thousand times greater than lethal for humans.

  • Resistant to UV radiation, gamma rays, cold, dehydration, vacuum of space, acid, etc.

  • Listed in the Guinness Book of World Records as the world's toughest bacteria.

  • Habitat: soil, feces, meat, sewage, room dust; not a pathogen.

  • Pink pigment aids in radiation resistance.

  • Name origin: Deinococcus means "strange berry" and radiodurans means "radiation resistant".

Chlamydia trachomatis

  • Pathogen causing sexually transmitted infections (STIs).

  • Leads to cervicitis in women, urethritis and proctitis in men.

  • Untreated can result in pelvic inflammatory disease, infertility, ectopic pregnancies, chronic pelvic pain, etc.

  • Most common STI in the U.S.; also spreads to newborns during birth, leading to conjunctivitis or pneumonia.

  • Obligate intracellular parasite; cannot grow on standard bacteriological media.

  • Can cause trachoma, a leading cause of blindness in underdeveloped countries.

  • Elementary bodies (infectious) transform into reticulate bodies (active and replicative) within the host cell.

Chlorobium

  • Non-human pathogen; thermophilic green sulfur bacteria.

  • Isolated from hot springs in New Zealand; lives in hydrogen sulfide-rich warm environments.

  • Conducts anoxygenic photosynthesis, producing elemental sulfur as a waste product.

Spirochetes Overview

  • Corkscrew-shaped organisms; often examined using darkfield microscopy to avoid staining damage.

  • Diverse oxygen requirements: some aerobic, some anaerobic, others facultative anaerobes.

Treponema pallidum

  • Spirochete that causes syphilis.

  • Obligate intracellular parasite; requires host cells to function.

Borrelia burgdorferi

  • Causative agent of Lyme disease; transmitted by deer ticks.

  • Named after Lyme, Connecticut, where it was first identified.

  • Can present with a bullseye rash, but not all patients exhibit this symptom.

Mycoplasmas

  • Lack a cell wall, smallest free-living bacteria (~1/4 size of E. coli).

  • Example: Mycoplasma pneumoniae causes atypical pneumonia (walking pneumonia); generally less severe, may not require hospitalization.

  • Colonies appear small and fry-egg-like under a microscope, often requiring specialized media for growth.

Mycobacteria

  • Acid-fast bacteria with waxy cell walls due to mycolic acid; slow-growing.

Mycobacterium tuberculosis

  • Causes tuberculosis (TB); antibiotic resistant and may require long treatment regimens.

  • Tested via PPD skin test to determine exposure or infection.

Mycobacterium leprae (Hansen's Disease)

  • Causes leprosy; obligate intracellular parasite.

  • Grows only in specific hosts (armadillos, foot pads of mice). 95% of humans are innately resistant.

Gram Positive Cocci

Staphylococcus aureus (Staph aureus)

  • Common skin resident; can cause skin infections, food poisoning, toxic shock syndrome (TSS).

  • Drug-resistant strains: MRSA (methicillin-resistant) and VRSA (vancomycin-resistant).

Streptococcus pyogenes (Group A Strep)

  • Causes strep throat, necrotizing fasciitis, rheumatic fever, endocarditis.

  • Known for producing toxins, which can lead to severe complications like TSS.

Streptococcus agalactiae (Group B Strep)

  • Colonizes vaginal tract; pathogen during childbirth; can cause neonatal meningitis.

Streptococcus mutans

  • Found in the mouth, leading to tooth decay and gum disease.

Gram Positive Rods (Endospore Formers)

Bacillus anthracis

  • Causes anthrax (cutaneous, gastrointestinal, pulmonary forms).

  • Endospore-forming; pulmonary form is most deadly.

Clostridium botulinum

  • Causes botulism, flaccid paralysis; produces potent neurotoxin.

  • Types: foodborne, wound, infant botulism (honey caution for infants).

Clostridium tetani

  • Causes tetanus; produces a potent neurotoxin causing spastic paralysis.

  • Vaccination available (DTaP vaccine).

Clostridioides difficile (C. Diff)

  • Found in the gastrointestinal tract; can proliferate post-antibiotic use, causing infections.

  • Produces toxins leading to toxin-mediated illness.

Gram Positive Rods (Non-Endospore Formers)

Lactobacillus acidophilus

  • Probiotic; aids digestion; used in yogurt production.

Listeria monocytogenes

  • Causes foodborne illness; especially harmful to pregnant women, elderly, and young.

  • Can grow at refrigeration temperatures.

Cutibacterium acnes

  • Normal skin resident; overgrowth causes acne.

Archaeans

  • Distinct from bacteria; lack peptidoglycan in cell walls and can thrive in extreme environments.

Methanogens

  • Example: Methanobacterium; anaerobic, produces methane gas, important in biogas production.

Halophiles

  • Example: Halobacterium; thrives in high salt concentrations (Dead Sea, Great Salt Lake).

Hyperthermophiles

  • Example: Sulfolobus; live in extremely hot, acidic environments (volcanic springs).

Key Takeaways

  • Study these distinct bacteria and archaea, focusing on their characteristics, pathogenic effects, and ecological significance. Use flashcards for memorization and review key concepts discussed.