Gram-Negative

Klebsiella oxytoca

STRUCTURE AND PHYSIOLOGY K. oxytoca is a Gram-negative, rod-shaped, facultatively anaerobic bacterium with a bi-membrane structure. Unlike its relative K. pneumoniae, K. oxytoca is indole-positive (ability to convert tryptophan into indole) and can perform lactose fermentation for metabolism. It is a naturally occurring bacterium in soil, and some strains can...

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Bordetella bronchiseptica

STRUCTURE AND PHYSIOLOGY B. bronchiseptica is a Gram-negative, aerobic, non-endospore forming coccobacillus. This bacterium is motile and oxidase and catalase positive.  TRANSMISSION AND DISEASE The pili of B. bronchiseptica attach to the ciliated epithelium of the respiratory tract. Although a primary pathogen for a wide range of animals, B. bronchiseptica, has been...

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Vibrio cholerae

STRUCTURE AND PHYSIOLOGY Vibrio cholerae is a Gram-negative, comma-shaped, highly motile, facultative anaerobic bacterium that has the ability to survive with or without oxygen. Humans are the only natural host for V. cholerae, but the bacterium can also live freely in fresh or salt water. TRANSMISSION AND DISEASE Cholera is a highly...

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Vibrio fischeri

STRUCTURE AND PHYSIOLOGY Vibrio fischeri is a Gram-negative, motile, rod-shaped bacterium that possesses the ability to produce light (bioluminescence) at high cell densities. The marine bacterium can live both as a free organism or as a symbiont for various marine fish and squids, particularly the Hawaiian bobtail squid. TRANSMISSION AND DISEASE Although...

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Shigella sonnei

STRUCTURE AND PHYSIOLOGY Shigella sonnei is a Gram-negative, rod-shaped, nonmotile, non-spore-forming bacterium and has historically been responsible for causing dysentery. S. sonnei is highly clonal (genetically identical cells), and a selective group of lineages is found worldwide. TRANSMISSION AND DISEASE S. sonnei causes the disease shigellosis, an intestinal infection that is spread...

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Proteus mirabilis

STRUCTURE AND PHYSIOLOGY Proteus mirabilis is a Gram-negative, rod-shaped, motile bacterium that produces high levels of urease, a protein that hydrolyzes urea to ammonia. P. mirabilis can be detected in the lab by its unique characteristic to swarm when grown on agar plates. Additionally, this bacterium gives off a strong...

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Porphyromonas gingivalis

STRUCTURE AND PHYSIOLOGY Porphyromonas gingivalis is a Gram-negative, rod-shaped, non-motile bacterium found in the human oral cavity. It is able to bind to host cells as well as with other bacteria to form a biofilm. TRANSMISSION AND DISEASE P. gingivalis secretes various potential virulence factors such as proteins that cause damage to...

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Haemophilus influenzae

STRUCTURE AND PHYSIOLOGY Haemophilus influenzae is a Gram-negative, coccobacillary (intermediate shape between cocci and bacilli), facultative anaerobic pathogenic bacterium. H. influenzae is capnophilic, meaning it thrives in environments with high levels of carbon dioxide. TRANSMISSION AND DISEASE While H. influenzae was believed to cause of influenza until 1933, this species of bacteria...

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Campylobacter jejuni

STRUCTURE AND PHYSIOLOGY Campylobacter comes from the Greek word meaning “curved rod”. Campylobacter jejuni is a helical-shaped, non-spore-forming, Gram-negative, nonfermenting motile bacteria with a single flagellum at one or both sides. C. jejuni is microaerophilic and can survive on low amounts of oxygen. When it is exposed to atmospheric oxygen,...

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Bacteroides fragilis

STRUCTURE AND PHYSIOLOGY Bacteroides fragilis is a Gram-negative, rod-shaped, non-motile bacterium found in the human colon. B. fragilis is an aerotolerant anaerobic bacteria, which allows it to survive in environments with low levels of oxygen. Maintaining a generally beneficial relationship with the host when retained in the gut, B. fragilis...

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Salmonella typhii

STRUCTURE AND PHYSIOLOGY A subspecies of S. enterica, Salmonella typhii is motile, Gram-negative, rod-shaped bacteria. The flagella present on this microorganism allow it to evade the host immune system, increasing its virulence. TRANSMISSION AND DISEASE The causative agent of typhoid fever, S. typhii is rare in developed countries, though still prevalent in...

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Klebsiella aerogenes

STRUCTURE AND PHYSIOLOGY K. aerogenesis a gram-negative, rod-shaped, motile bacterium common to the gastrointestinal tract of humans. It is generally not pathogenic in healthy individuals. K. aerogenes was originally classified as Enterobacter aerogenes until its recent reclassification. TRANSMISSION AND DISEASE These bacteria can cause illness, such as sepsis, in hospital settings or...

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Pseudomonas fluorescens

STRUCTURE AND PHYSIOLOGY P. fluorescens is a gram-negative, rod-shaped bacterium that is found in soil, plants, and water. This microorganism is commonly found in the rhizosphere of plants where it produces antibiotics against other soil-borne plant pathogens as well as promotes overall plant growth and health. TRANSMISSION AND DISEASE P. fluorescens does...

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Pseudomonas aeruginosa

STRUCTURE AND PHYSIOLOGY P. aeruginosais a gram-negative, rod-shaped, strict anaerobe that is ubiquitous in the environment as it is found in humans, animals, and plants as well as soil and water. It is capable of surviving in low oxygen environments provided the right conditions and is known to form persistent...

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Pluralibacter gergoviae

STRUCTURE AND PHYSIOLOGY P. gergoviaeis a gram-negative, rod-shaped, facultative anaerobe that can be found in some plants, insects, and spring water. TRANSMISSION AND DISEASE It is considered an uncommon human pathogen associated with nosocomial infections in immunocompromised individuals. Risk factors include long hospital stays, use of steroids or antimicrobial agents, foreign devices,...

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Pasteurella multocida

STRUCTURE AND PHYSIOLOGY Pasteurella multocida is a Gram-negative, coccobacillus, aerobic bacterium. It is oxidase and catalase positive. TRANSMISSION AND DISEASE Pasteurella multocida is the most common cause of soft tissue infections following a bite or scratch from a domestic pet. The bacteria enter the wound at the time of injury and can...

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Elizabethkingia meningosepticca

STRUCTURE AND PHYSIOLOGY Elizabethkingia meningosepticca is a Gram-negative slightly curved rod-shaped bacterium. This organism produces large, smooth colonies on blood and chocolate agars within 24 hours. The microorganism is found worldwide in soil, river water, and reservoirs. TRANSMISSION AND DISEASE E.meningosepticca can cause meningitis in newborns and immune-compromised individuals. However, outbreaks are...

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Rhizobium radiobacter

STRUCTURE AND PHYSIOLOGY Rhizobium radiobacter is an aerobic, gram-negative, bacilli found in soil worldwide. Colonies are typically circular, convex, semi-translucent, and raised on yeast-mannitol-mineral salts agar. TRANSMISSION AND DISEASE Rhizobium radiobacter is a plant pathogen that rarely affects humans who are not immunocompromised. In plants, Rhizobium radiobacter can cause Crown Gall Disease...

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Fusobacterium necrophorum

STRUCTURE AND PHYSIOLOGY: Fusobacterium necrophorum is a rod-shaped, gram-negative bacteria commonly found in the gastrointestinal tract of humans and other animals. TRANSMISSION AND DISEASE Fusobacterium necrophorum is transmitted via mucous membrane contact and contact with infected body fluids. Fusobacterium necrophorum can cause sore throat, peritonsillar abscesses, meningitis, thrombosis, and infection of the...

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Pseudomonas putida

STRUCTURE AND PHYSIOLOGY Pseudomonas putida is a rod-shaped, aerobic bacteria with multiple flagella typically found in the soil and moist environments. TRANSMISSION AND DISEASE Pseudomonas putida is an occasional cause of catheter-related bacteremia as well as urinary tract infections, neonatal sepsis and war wounds but is generally considered non-pathogenic in non-immunocompromised individuals. UNIQUE...

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Klebsiella pneumoniae

Klebsiella pneumoniae

Structure and Physiology Klebsiella pneumoniae is a Gram-negative, rod-shaped, facultative anaerobic bacterium. It is encapsulated and undergoes lactose fermentation for metabolic purposes when conditions allow. This nonmotile bacterium is found in humans within the normal flora of the mouth, skin, and intestines. It is a naturally occurring bacterium in the soil...

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Legionella pneumophila

Legionella pneumophila

Structure and Physiology This bacteria is a Gram-negative, flagellated aerobe that is nonencapsulated and pleomorphic. L. pneumophila is a facultative, intracellular parasite, meaning that while able to survive and replicate outside of a host, the natural resevoir of this microorganism is inside of free-living, ubiquitous ameoba, where it uses the host...

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Acinetobacter baumannii

Acinetobacter baumannii

Structure and Phisiology This bacteria is a Gram-negative, rod-shaped aerobe. A. baumannii can be responsible for infections such as pneumonia and septicemia in immunodeficient patients. The natural reservoir of this organism remains to be determined. These are among a class of bacteria that are "naturally transformable" - meaning that the...

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Enterobacter aerogenes

Enterobacter aerogenes

Structure and Physiology This bacteria is Gram-negative, rod-shaped, and radially surrounded by flagellum. It can be found in dairy products, soil, and the gastrointestinal tract of animals. E. aerogenes is closely related to a wide range of other common microorganisms including Escherichia, Klebsiella, Shigella, and Serratia.    Transmission and Disease This bacteria can be involved in...

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Enterobacter cloacae

Enterobacter cloacae

Structure and Physiology This bacteria is a Gram-negative, rod shaped, facultative anaerobe commonly found in the gastrointestinal tract of humans. It is not usually a primary pathogen although it is sometimes associated with urinary and respiratory tract infection. Transmission and Disease Enterobacter cloacae can be acquired through the skin, urinary tract, or gastrointestinal...

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Salmonella enterica

Salmonella enterica

Structure and Physiology Salmonella enterica is a Gram-negative, rod-shaped, facultative anaerobic bacterium that is common to all parts of the world. S. enterica contains flagella that are used for locomotion and a sensory organelle to measure the chemical nature and temperature of the extracellular space. A characteristic of this bacterium...

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Escherichia coli

Escherichia coli

Structure and PhysiologyEscherichia coli is a Gram-negative, rod-shaped, facultative anaerobic bacterium that is commonly found in the gastrointestinal tract of warm-blooded animals. Although most serotypes of this organism are harmless inhabitants of the intestinal flora, there are pathogenic strains of E. coli that produce toxins which cause illness in...

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Burkholderia cepacia

Burkholderia cepacia

Structure and Physiology This bacteria is Gram-negative, rod shaped, and capable of growth in a variety of environments including soil, water, animals, and plants. B. cepacia is closely related to Pseudomonas spp. and exhibits several similar morphological characteristics. Transmission and Disease Typically identified as a plant and human pathogen, it is known...

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N. gonorrhoeae

Neiserria gonorrhoeae

Structure and Physiology This bacteria is a Gram-negative diplococci. Transmission and Disease Neisseria gonorrhoeae is the causative agent of the sexually transmitted infection gonorrhea. This bacteria is capable of transformation and conjugation to spread genes and mutations. This makes it difficult for the immune system to recognize and an area of interest...

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Bordetella pertussis

Bordetella pertussis

Structure and Physiology This bacterium is a Gram-negative, non-motile, coccobacillus aerobe. Transmission and Disease B. pertussis is the organism responsible for whooping cough and is transmitted via airborne droplets contaminated with the organism, such as those produced by the act of coughing itself.  Once adhered to the surface of the thoat, B. pertussis releases a...

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S. marcescens

Serratia marcescens

Structure and Physiology This bacteria is a Gram-negative, rod-shaped, facultative anaerobe that has been classified as an opportunistic pathogen for immunocompromised individuals. This bacteria can be commonly found in damp environments like bathrooms, where it manifests as a pink-orange film due to a reddish-orange pigment called prodigiosin. Transmission and Disease S. marcescens can...

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