Prokaryotes, Bacteria, & Archaea

Domain Archaea

• Prokaryotes

• Some have CW (No PDG)

• Live in extreme environments

• NOT known to cause disease in humans

Methanogens

Produce methane as a waste product from respiration

Extreme Halophiles

Live in extreme salty environments

Extreme Thermophiles

Live in hot sulfurous water

Alphaproteobacteria

• G-

• Capable of growth with very low levels of nutrients

• Capable of nitrogen fixation in symbiosis with plants & plant & human pathogens

Alphaproteobacteria (Genera)

• Rickettsia

• Bartonella

Rickettsia

• G-

• Rod shaped or coccobacilli

• Transmitted → humans by insects & tick bites

• Enter host cell by inducing phagocytosis, enter cytoplasm of the cell & begin reproducing binary fission

• Responsible for spotted fever group

• Damage permeability of blood capillaries → characteristic SPOTTED RASH

R. prowazekii

• R = rickettsia

• Transmitted by lice

• Causes typhus

R. typhi

• R = rickettsia

• Transmitted by rat flees

• Causes murine typhus

R. rickettsii

• Transmitted by ticks

• Causes Rocky Mountain spotted fever

B. henselae

• B = bartonella

• G-

• Bacillus that causes cat scratch disease

• Parinaud oculoglandular syndrome

• Typical intraocular presentations include neuroretinitis with optic nerve edema, macular star formation & discrete white retinal or choroidal lesions

Betaproteobacteria

• Overlap with alphaproteobacterial

• Use nutrient substances that diffuse away areas of anaerobic decomposition of organic matter such as: hydrogen gas, ammonia, & methane

Betaproteobacteria (Genera)

• Bordetella

• Neisseria

Bordetella

• G- rod

• Nonmotile

• Aerobic

B. Pertussis

• B = Bordetella

• Causes whooping cough

Neisseria

• Aerobic

• G- cocci

• Live in mucous membranes of mammals

• N. gonorrhoeae

N. meningitidis

• N = Neisseria

• Causes meningococcal meningitis

Gammaproteobacteria

• G-

• Largest subgroup of proteobacteria

Gammaproteobacteria (Genera)

• Pseudomas

• Moraxella

• Actinetobacter

• Legionella

• Enterobacteriales

Pseudomonas

• Aerobic G- rods

• Motile by polar flagella (singular or tufts)

• Can be resistant to antibiotics

P. aeruginosa

• P = pseudomonas

• Can infect urinary tracts, burns & wounds, & cause blood infections, abscesses & meningitis

Moraxella

Strictly aerobic coccobacilli

M. lacunata

• M = Moraxella

• Causes conjunctivitis

Acinetobacter

• Aerobic

• Typically forms in pairs

A. baumanii

• A = Acinetobacter

• Common in healthcare settings

• Becoming more resistant to antibiotics

• Primarily respiratory pathogen

• High mortality rates due to resistance

Legionella

• Common in streams, warm-water supply lines in hospitals, & water in AC systems

• Hard to eradicate

Enterobacteriales

• AKA Enterics

• Facultative anaerobes

• G-

• If motile: peritrichously flagellated

• Inhabit animal intestine

• Have fimbriae that help them attach to surfaces

• Produce bacteriocins that cause the lysis of other bacteria

Enterobacteriales (Types)

• Escherichia

• Salmonella

• Shigella

• Klebsiella

• Serratia

• Enterobacter

Nonproteobacteria G-

• Cyanobacteria

• Chlamydia

• Spirochetes

Cyanobacteria

• Carry out oxygen in photosynthesis

• Capable of fixing Nitrogen

• Types:

  • Unicellular forms that divide by binary fission

  • Colonial forms that divide by multiple fission

  • Filamentous forms that reproduce by fragmentation of the filaments

Chlamydia

• G- coccoid

• Most distinguished by their unique developmental cycle

• Elementary body: infective agent

• Transmitted by interpersonal contact

• Related to Chlamydophila genus that causes airborne respiratory disease

C. trachomatis

• C = chlamydia

• Trachoma

• Causes blindness, nongonococcal urethritis (STI), & lymphogranuloma venereum (STI)

Life Cycle of Chlamydia

1. Bacterium’s infectious form, elementary body, attaches to a host cell

2. Host cell phagocytizes the elementary body, housing it in a vacuole

3. Elementary body recognizes to form a reticulate body

4. Reticulate body divides successively, producing multiple reticulate bodies

5. Reticulate bodies begin to convert back → elementary bodies

6. Elementary bodies are released from the host cell

• 48 hours (short)

Spirochetes

• Develop axial filaments

• Help in motility

• Can move 100 times its body length in a second

• Can be found in human oral cavity

Spirochetes (Genera)

• Treponema

• Borrelia

T. pallidum

• T = trepnonema

• Causes syphilis

• Includes many important pathogenic bacteria

B. burgdorferi

• B = Borellia

• Causes Lyme disease

• Most often in Northeast, mid-Atlantic, upper Midwest areas of US

• Carried by ticks

• Causes:

  • Fever, rash, facial paralysis, irregular heartbeat, & arthritis

Gram-Positive

• Firmicutes (Low G+C G+)

• Actinobacteria (High G+C G+)

Firmicutes

• Low G+C G+

• Endospore forming

Firmicutes (Genera)

• Clostridium

• Bacillus

• Staphylococcus

• Enterococcus

• Streptococcus

• Listeria

• Mycoplasmas

Clostridium

• Obligate anaerobes

• Rod shaped G+

• Usually contain endospores

• C. tetani, botulinum, difficile

Bacillus

• G+ Rods

• Produce endospores

• Common in soil

• Few are pathogenic to humans

• Several used to produce antibiotics

B. anthracis

• B = bacillus

• Nonmotile facultative anaerobes

• Cause of anthrax in cattle, sheep, humans

Staphylococcus

• Grapelike clusters G+

• S. aureus = yellow pigmented colonies

• Facultative anaerobes

• Grow well under high osmotic P and low moisture

• Carried in our noses & on skin

• Can infection surgical wounds

• Can be resistant against penicillin

• Produce toxins responsible for toxic shock syndrome

• Produce enterotoxins — one of most common causes of food poisoning

S. epidermidis

• S = staphylococcus

• Part of normal flora but can cause infections

Enterococcus

• Well-adapted to areas of the body that are rich in nutrients, but low in oxygen like the GI & oral cavity

• G+

• Can be found in human stool

• HIGH resistance to antibiotics

• Known for many surgical wounds & urinary tract infections

• Enter bloodstream through invasive procedures (indwelling catheters)

Streptococcus

• G+

• Spherical chains

• Causative of a greater variety of diseases more than other groups of bacteria

• Produce extracellular substances that destroy phagocytic cells & produce enzymes that digest host’s connective tissue

• Bacterial enzymes digest the fibrin of blood clots → infections spread

L. monocytogenes

• L = listeria

• Contaminate foods especially in dairy products

• Survives within phagocytic cells & is capable of growth at refrigeration T

• Can cause stillbirth or serious damage to fetus of pregnant women

M. pneumoniae

• M = mycoplasma

• Cause of mild pneumonia

Mycoplasma

• Polymorphic

• Lack of CW

• Can produce filaments that resemble fungi

• Mykes = fungus, plasma = formed

• Very small 0.1-0.25 microns; cell volume 5% of typical bacillus

• Smallest self-replicating organism capable of free-living existence

• Related to G+ bacteria like Bacillus & Streptococcus but have lost genetic material over time = degenerative evolution

• Special: CM contain STEROLS unlike other prokaryotes

Actinobacteria

• HIGH G+C G+

• Actino = ray

  • Radiate or starlike form of growth by often branching filaments

• Morphology = filamentous fungi

  • Allows for higher S:V ratio & enhances absorbing nutrients

• Filaments have a diameter much smaller than eukaryotic molds

• Some carry asexual spores used for reproduction

Actinobacteria (Genera)

• Mycobacterium

• Corynebacterium

• Actinomyces

Mycobacterium

• Aerobic, non-endospore forming rods

• Myco (fungus-like) b/c of occasional exhibition of filamentous growth

• Acid-fast stain, drug resistance, pathogenicity all related to their distinctive CW containing mycolic acid forming waxy, water-resistant layer

• CW causes resistance to stresses like drying & antimicrobial to enter cell, but also slows down entrance of nutrients thus slow growth rate of bacteria

• Two distinct groups:

  • Slow-growing = more pathogenic

  • Rapid growers = mostly infectious to wounds but are more nonpathogenic soil & water microbes

M. tuberculosis & leprae

• M = mycobacterium

• Tuberculosis — causes TB

• Leprae — causes leprosy

Corynebacterium

• Corynebacterium = club-shaped

• Pleomorphic: follow specific path of change

C. diptheriae

• C = corynebacterium

• Causes diphtheria

Actinomyces

• Facultative anaerobes

• Live in mouth & throat of humans & animals

• Occasionally form filaments that can fragment

Actinomyces israelii

• Causes Actinomycosis

• Tissue: destroying disease affecting the head, neck, or lungs

• Can cause multiple eye conditions including caniculitis