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Gram Positive Bacteria
• Grouped based on C + G ratio (nitrogen bases cytosine and guanine)
• Divided into 2 Phyla– Firmicutes (low C + G ) – Actinobacteria (High C + G)
• Low G + C ratio • Includes endospore forming and wall-less bacteria
Firmicutes
• Phylum: Firmicute
• 3 Classes:– Clostridia – Bacilli– Mollicutes (mycoplasmas)
Clostridia• Clostridiales
• Clostridium– Obligate anaerobes– Endospores
• C. tenani – tetanus• C. botulinum - botulism
• Epulopiscium– Very large bacteria– Huge genome– Endosymbiont in
surgeonfish– Reproduces by releasing
cells through slit
• Thiomargarita– gamma Proteobacteria – Anaerobic chemolithotroph
that oxidizes sulfur and reduces nitrates
– Even larger than Epulopiscium
– Large vacuole to increase surface area to volume ratio
Single Thiomargarita cell
Fruit Fly
• Bacillales – Includes both rods and cocci – Includes medically/ commercially
important genera
• Bacillus– Endospore-producing rods– Aerobe or facultative anaerobe– B. anthracis- anthrax – B. thuringiensis – insecticide– B. cereus - food borne illness
Bacilli
• Staphylococcus - grapelike clusters of cocci
– facultative anaerobes – Yellow pigmented colonies– common inhabitant of skin and the nasal cavity – grows in foods with high osmotic pressure – S. epidermidis and S. aureus
– S. aureus highly virulent – surgical wound infections– toxic shock syndrome toxin – enterotoxin - induces vomiting– exfolatin toxin – scalded skin syndrome– Folliculitis– Impetigo– MRSA and VRSA
• Lactobacillales
– Commercially important
– Aerotolerant or facultative anaerobes
• Lactobacillus– Aerotolerant; Lactic acid fermenting rod
– common in vagina, intestinal tract, and oral cavity
– used in production of pickles, buttermilk, and yogurt
• Streptococcus– chains of cocci– Aerotolerant; Lactic acid fermenter – Pathogenic strains produce multiple
extra-cellular enzymes and toxins– Responsible for more illnesses and a
greater variety of diseases than any other group of bacteria
• Beta-hemolytic streptococci – S. pyogenes
• Impetigo, strep throat, scarlet fever, necrotizing fascitis
• Alpha-hemolytic streptococci– S. pneumoniae
• Pneumonia, ear infections, sinusitis, meningitis
– S. mutans • Dental carries
• Listeria
– Facultative anaerobe– L. monocytogenes– Contaminates dairy
products– Psychrotroph– Survives inside phagocytes – May be responsible for
stillbirths and birth defects
Mollicutes (mycoplasmas)
• Mycoplasmatales
– Wall-less, highly pleomorphic
– Very small (0.1 - 0.24 µm)
– May produce filaments
– Degenerative evolution
• Mycoplasma – M. pneumoniae– walking pneumonia
• Spiroplasma– Corkscrew morphology– plant pathogen and parasite
of plant feeding insects
• High G + C
Actinobacteria
• Mycobacterium – acid fast; aerobic rods;
filamentous growth– non-endospore former;
mycolic acid – M. tuberculosis – tuberculosis– M. leprae - leprosy
• Corynebacterium– Club shaped, metachromatic
granules– C. diphtheriae –diphtheria
• Propionibacterium • propionic acid fermenter
– Important in swiss cheese production
– P. acnes commonly found on human skin; primary cause of bacterial acne
• Gardnerella• gram variable; highly plemorphic
– G. vaginalis – bacterial vaginitis
• Actinomycetes– Common soil inhabitants– Branching filaments – Asexual spores – Frankia, Streptomyces, Actinomyces
• Streptomyces– most antibiotics are produced by Streptomyces
species– about 500 known species– asexual spores (conidospores)– Produce gaseous geosmin
• Actinomyces – facultative anaerobes
– mouth and throat of animals – A. israelii - actinomycosis (tissue-destroying
disease affecting the head, neck, or lungs)
• Frankia – nitrogen fixing bacteria– Forms root nodules with alder trees
• Highly diverse morphology and physiology• Frequently inhabit extreme environments• Three primary groups are halophiles, thermophiles
and methanogens
Domain Archaea
• Currently classified into 3 Phyla– Crenarchaeota– Euryarchaeota– Korarchaeota
Euryarchaeota• Gram+ to gram variable halophiles, methanogens
and a few thermophiles – Halobacteriales
• Obligate halophiles– Bacteriorhodopsin based light capturing system
• Methanobacteriales– Methanogens
• Convert CO2, H2 and organic acids into methane
– Largest known group of archaea
– Gram +; Obligate anaerobes
Crenarchaeota– Gram-; most thermophiles– Sulfolobales
• acidophilic thermophilic sulfur metabolizers
– Desulfurococcales• Hyperthermophiles
• Korarchaeota– No members have ever been observed– Known only from environmental rRNA
samples