This is a gram-negative rod common in activated sludge and fresh water ditches. It is not considered clinically significant.
These gram-negative rods occur naturally in soil, water, and sewage.
These gram-negative rods are parasitic or commensal in humans, many mammals, and birds.
These slender gram-positive rods occur mainly in the oral cavity and on mucous membranes of warm-blooded vertebrates. They commonly cause infections in association with other bacteria.
These gram-negative rods occur in fresh water and sewage. Some species are pathogenic to frogs, fish, and humans (e.g. A. hydrophila for humans, which can cause gastrointestinal (GI) infections).
These gram-negative rods occur in water, soil and the intestinal tracts of vertebrates. They occasionally cause opportunistic infections in humans.
This gram-negative rod usually occurs in stagnant freshwater environments.
These gram-positive rods are widely distributed in the environment, principally in soils.
These gram-positive rods are found in soil and dairy products, but are probably widely distributed in the environment.
Bacillus is a gram-positive rod that is found in a wide range of habitats. A few species are pathogenic to animals and humans (e.g. B. anthracis, and B.cereus, B. thuringiensis, which can cause GI infections.
This is a zoonotic pathogen indigenous to dogs and cats.
These gram-positive rods are found in the mouth and intestinal tract of warm-blooded vertebrates, in insects, and in sewage. They are usually considered nonpathogenic.
These gram-positive rods are widely distributed in dairy products and are found on human skin.
Brevundimonas (Originally named Pseudomonas)
These environmental organisms are found in water, soil, and on plants, including fruits and vegetables. They are rarely associated with human infection.
These gram-negative rods occur in the nasal flora of humans. They can be pathogenic to humans.
These gram-positive rods are widely distributed in soils and decaying vegetable matter.
This gram-negative bacterium was first classified as Cellulomonas. It was originally isolated from the hindgut contents of the Australian termite Mastotermes darwiniensis (Froggatt). It has also been isolated from humus soils
These gram-negative rods are soil and water organisms. One species occasionally causes infections in mammals, including humans.
These gram-negative rods are not normally found in the environment but in warm-blooded animals, where they may be occasionally pathogenic.
These gram-positive rods are obligate parasites of flowering plants, in which they are pathogenic.
This is a gram-negative rod commonly found in the environment. It constitutes a significant proportion of many terrestrial and aquatic environmental microbial communities
These gram-positive rods are primarily obligate parasites of mucous membranes or skin of mammals, but occasionally they are found in other sources. Some species are pathogenic for mammals (e.g. C. diphtheriae, which can cause diphtheria, and C. jeikeium, which can cause urinary tract infections)
These gram-positive rods occur on plants, in soil, and in oil brine. One species is a plant pathogen.
This gram-positive coccus is probably widely distributed in the environment
These gram-negative rods are widely distributed in nature, occurring in fresh water, soil, sewage, plants, vegetables, and animal and human feces. Several species are opportunistic pathogens.
This gram-positive coccus occurs widely in the environment, particularly in the feces of vertebrates. Sometimes this organism can cause infections (e.g. E.faecalis and E. faecium, which can cause urinary tract infections and septicaemia).
Members of this genus (gram-negative rods) are a diverse group of organisms that primarily colonize plants, and have rarely been isolated from humans. Some of them are important pathogens of potato and other crops.
This is a gram-positive rod found in the environment, which is not considered clinically significant.
This gram-negative rod is found in the general environment, and in warm-blooded animals, where it may be occasionally pathogenic.
These gram-negative rods are widely distributed in soil and water. They are also found in raw meat, milk and other food, in the hospital environment, and in human clinical material.
These gram-positive or gram-variable rods are isolated from soil and some sputa.
This is a gram-negative rod found in the environment, specifically in activated sludge and lake snow.
This is a gram-negative rod, occurring in soil and water, common in temperate climates. It occasionally causes food spoilage.
These gram-negative rods occur in human feces and clinical specimens, soil, water, grain, fruits, and vegetables. Some species are opportunistic pathogens.
These gram-negative rods occur in food, soil, sewage, and human clinical specimens. They are infrequently opportunistic pathogens.
These gram-positive rods are widely distributed in the environment, and are common in animal feces and meat products.
This fastidious gram-negative rod is isolated from surface water, mud, and thermally polluted lakes and streams. There is no known soil or animal source. It is pathogenic for humans, causing pneumonia (Legionnaires’ disease) or a mild, febrile disease (Pontiac fever).
This gram-positive rod is widely distributed in the environment. Some species are pathogenic for humans and animals (e.g. L. monocytogenes).
These are mostly isolated from water and leaf surface microflora, and are facultative methylotrophs, that is capable of growing on one-carbon compounds such as formate, formaldehyde, and methanol as the sole source of carbon and energy, as well as on a wide range of multicarbon substrates.
This gram-positive rod is found in dairy products, sewage, and insects.
These gram-positive cocci occur primarily on mammalian skin and in soil, but are commonly isolated from food products and the air.
This gram-negative rod is parasitic on the mucous membranes of humans and other warm-blooded animals.
These gram negative rods were originally included with Sphingomonas (see Sphingomonas).
These gram-negative rods are isolated from plant surfaces, seeds, soil, and water, as well as from animals and human clinical specimens. They are opportunistic human pathogens.
These gram-negative rods are isolated from human clinical specimens and from penguins.
This gram-negative rod is widely distributed in nature. Some species are pathogenic for humans, animals, or plants (e.g. P. aeruginosa).
This gram-negative rod is associated with fish, processed meat and poultry products. Some strains have been isolated from pathological specimens from humans and animals.
These gram-negative rods occur in freshwater. They are occasionally isolated from human clinical specimens, but are not considered clinically significant.
Some of these species are phytopathogens of terrestial plants. Their main habitats are their respective plant hosts.
These organisms are aerobic, Gram positive actinomycetes. These widely-occurring organisms are of considerable environmental and biotechnological importance due to their broad metabolic diversity and array of unique enzymatic capabilities, plus their capacity to degrade hydro-carbons. They are able to survive for a long time in soil. They are the most efficient in oil degradation and, relatively speaking, the most abundant in soils and marine environments.
This is the common name given to a group of small, rod-shaped, gram negative bacteria, which are able to produce nodules on the roots, or on some cases the stems, of leguminous plants.
These gram-negative rods occur in human clinical specimens, soil, water, plant surfaces, and other environmental sites, digestive tracts of rodents, and insects. Some species are opportunistic pathogens.
This is a gram-negative rod found in soil, on plants, foodstuffs, and in water sources.
These gram negative rods were originally included with Sphingomonas (see Sphingomonas).
This is a relatively new genus derived from Pseudomonas paucimobilis. These organisms are widely distributed, including having been found in water. Only Sphingomonas paucimobilis is considered clinically significant, and has been isolated from a variety of clinical specimens.
This gram-positive coccus is mainly associated with the skin and mucous membranes of warm-blooded vertebrates, but they are often isolated from food products, dust and water. Some species are opportunistic pathogens of humans and animals, or produce extracellular toxins.
These gram-positive rods are isolated from soil, human sputum, and parts of bed bugs. Some strains can be pathogenic.
This gram-negative rod is not known in the general environment. It is apparently a parasite, saprophyte, or commensal of the internal surfaces of humans or other warm-blooded animals.
These gram-negative rods occur in a broad spectrum of habitats, including humans, animals, soil, water, dairy products, and other foods. Some species are pathogenic for humans and animals; others are opportunistic pathogens, yet others are nonpathogenic.
Most of these gram-negative rods are plant pathogens, or occur in association with plants. X.maltophilia is the only exception, being an opportunistic pathogen of humans.
Bergey’s Manual of Determinative Bacteriology, Ninth Edition
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GLOSSARY OF TERMS
Commensal – organisms existing in or on an animal or human without causing disease.
Extracellular – produced, then excreted outside the organism.
Gram-positive – bacteria that stain purple (positive) with the gram stain.
Gram-negative – bacteria that do not stain purple (pink – negative) with the gram stain.
Habitat – where an organism is found.
Indigenous – where normally found
Opportunistic – an organism that will only cause disease in a patient with a poor or somehow weakened immune system.
Pathogens – organisms that cause disease.
Saprophyte – an organism that normally grows on dead material.
Toxins – compounds produced by an organism that are poisonous to other organisms
Zoonotic – organism normally found in or on animals.
Bacteria are naturally present in the environment and on and in humans and animals. They have many good uses:
- They line the gut, where they aid digestion.
- They remove debris on the skin.
- They are important in many foodstuffs, such as cheeses and yogurts.
- They aid in the maturation of meat.
- They remove trash in the environment.
A "normal" environmental system will have an assortment of different bacterial types, none of which will be particularly predominant. In areas where there are high numbers of humans, there may be higher levels of gram-positive cocci, such as Staphylococcus and Micrococcus, in the environment. Unlike molds, higher numbers of bacteria in the air inside can be normal.
High levels of one type of bacteria, especially gram-negative rods, notably those in the Enterobacteriaceae, are considered significant:
- Enterobacteriaceae are indicative of sewage contamination, and therefore of pathogenic organisms. Pathogenic bacteria themselves are rarely recovered, as they are rapidly outgrown by environmental bacteria, hence the development of the sewage screen to detect potential gastrointestinal pathogens.
- When one organism has removed the natural competition, it implies more than just simple co-existence of several different types, but suggests a more aggressive role by the dominant organism.