Bacterial classification

Genus	Important species	Gram staining	Shape	Capsulation	Bonding tendency	Motility	Respiration	Growth medium	Intra/Extracellular
Bordetella	Bordetella pertussis	Gram-negative	Small coccobacilli	Encapsulated	singly or in pairs		aerobic	Regan-Lowe agar	extracellular
Borrelia	Borrelia burgdorferi	Gram-negative, but stains poorly			Long, slender, flexible, spiral- or corkscrew-shaped rods	highly motile		(difficult to culture)	extracellular
Brucella	Brucella abortus Brucella canis Brucella melitensis Brucella suis	Gram-negative	Small coccobacilli	Unencapsulated	singly or in pairs		aerobic	Blood agar	intracellular
Campylobacter	Campylobacter jejuni	Gram-negative	Curved, spiral, or S-shaped with single, polar flagellum			characteristic darting motion	microaerophilic	Blood agar inhibiting other fecal flora	extracellular
Chlamydia and Chlamydophila	Chlamydia pneumoniae Chlamydia trachomatis Chlamydophila psittaci	(not Gram-stained)	Small, round, ovoid			motile	Facultative or strictly aerobic		Obligate intracellular
Clostridium	Clostridium botulinum Clostridium difficile Clostridium perfringens Clostridium tetani	Gram-positive	Large, blunt-ended rods			mostly motile	Obligate anaerobic	Anaerobic blood agar	extracellular
Corynebacterium	Corynebacterium diphtheriae	Gram-positive (unevenly)	Small, slender, pleomorphic rods	unencapsulated	clumps looking like Chinese characters or a picket fence	nonmotile	Mostly facultative anaerobic	Aerobically on Tinsdale agar	extracellular
Enterococcus	Enterococcus faecalis Enterococcus faecium	Gram-positive	Round to ovoid		pairs or chains		Facultative Anaerobic	6.5% NaCl, bile-esculin agar	extracellular
Escherichia	Escherichia coli	Gram-negative	Short rods				Facultative anaerobic	MacConkey agar	extracellular
Francisella	Francisella tularensis	Gram-negative	Small, pleomorphic coccobacillus				strictly aerobic	(rarely cultured)	Facultative intracellular
Haemophilus	Haemophilus influenzae	Gram-negative	Ranging from small coccobacillus to long, slender filaments					Chocolate agar with hemin and NAD⁺	extracellular
Helicobacter	Helicobacter pylori	Gram-negative	Curved or spiral rods pultiple polar flagella			rapid, corkscrew motility		Medium containing antibiotics against other fecal flora	extracellular
Legionella	Legionella pneumophila	Gram-negative, but stains poorly	Slender rod in nature, cocobacillary in laboratory. monotrichious flagella	unencapsulated		motile		Specialized medium	facultative intracellular
Leptospira	Leptospira interrogans	Gram-negative, but stains poorly	Long, very slender, flexible, spiral- or corkscrew-shaped rods			highly motile		Specialized medium	extracellular
Listeria	Listeria monocytogenes	Gram-positive, darkly	Slender, short rods		diplobacilli or short chains	Distinct tumbling motility in liquid medium		enriched medium	intracellular
Mycobacterium	Mycobacterium leprae Mycobacterium tuberculosis Mycobacterium ulcerans	(none)	Long, slender rods			nonmotile	aerobic	M. tuberculosis: Lowenstein-Jensen agar M. leprae: (none)	extracellular
Mycoplasma	Mycoplasma pneumoniae	(none)	Plastic, pleomorphic		singly or in pairs			(rarely cultured)	extracellular
Neisseria	Neisseria gonorrhoeae Neisseria meningitidis	Gram-negative	Kidney bean-shaped		diplococci		aerobic	Thayer-Martin agar	Gonococcus: facultative intracellular N. meningitidis: extracellular
Pseudomonas	Pseudomonas aeruginosa	Gram-negative	rods	encapsulated		motile	Obligate aerobic	MacConkey agar	extracellular
Rickettsia	Rickettsia rickettsii	Gram-negative, but stains poorly	Small, rod-like coccobacillary					(rarely cultured)	Obligate intracellular
Salmonella	Salmonella typhi Salmonella typhimurium	Gram-negative					Facultative anaerobic	MacConkey agar	Facultative intracellular
Shigella	Shigella sonnei	Gram-negative	rods				Facultative anaerobic	Hektoen agar	extracellular
Staphylococcus	Staphylococcus aureus Staphylococcus epidermidis Staphylococcus saprophyticus	Gram-positive, darkly	Round cocci		in bunches like grapes		Facultative anaerobic	enriched medium (broth and/or blood)	extracellular
Streptococcus	Streptococcus agalactiae Streptococcus pneumoniae Streptococcus pyogenes	Gram-positive	ovoid to spherical		pairs or chains	nonmotile	Facultative anaerobic	blood agar	extracellular
Treponema	Treponema pallidum	Gram-negative, but stains poorly	Long, slender, flexible, spiral- or corkscrew-shaped rods			highly motile		none	extracellular
Vibrio	Vibrio cholerae	Gram-negative	Short, curved, rod-shaped with single polar flagellum			rapidly motile	Facultative anaerobic	blood- or MacConkey agar. Stimulated by NaCl	extracellular
Yersinia	Yersinia pestis	Gram-negative, stains bipolarly	Small rods	encapsulated		nonmotile	Facultative Anaerobe	MacConkey or CIN agar	extracellular

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