Bacterial Glossary

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.

Methylobacterium

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.

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.

See Pseudomonas.

See Klebsiella.

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.

See Pseudomonas

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.

REFERENCES

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.