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.