Bacteria and Related Topics

A cluster of Escherichia coli bacteria magnified 10,000 times

Microorganism

Organism of microscopic size, which may exist in its single-celled form or as a colony of cells.

Antonie van Leeuwenhoek was the first to study microscopic organisms.

Lazzaro Spallanzani showed that boiling a broth stopped it from decaying.

Vardhmana Mahavira postulated the existence of microscopic creatures in the sixth century BC.

Louis Pasteur showed that Spallanzani's findings held even if air could enter through a filter that kept particles out.

Robert Koch showed that microorganisms caused disease.

Staphylococcus aureus bacteria magnified about 10,000x

Euglena mutabilis, a photosynthetic flagellate

A tetrad of Deinococcus radiodurans, a radioresistant extremophile bacterium

The photosynthetic cyanobacterium Hyella caespitosa (round shapes) with fungal hyphae (translucent threads) in the lichen Pyrenocollema halodytes

Wastewater treatment plants rely largely on microorganisms to oxidise organic matter.

The eukaryotic parasite Plasmodium falciparum (spiky blue shapes), a causative agent of malaria, in human blood

Two of the three domains Archaea and Bacteria, only contain microorganisms.

An agar plate streaked with microorganisms

Bacteriology

Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.

Louis Pasteur in his laboratory, painting by A. Edelfeldt in 1885

Bacteriology is the branch and specialty of biology that studies the morphology, ecology, genetics and biochemistry of bacteria as well as many other aspects related to them.

Neisseria gonorrhoeae (small red dots) in pus from a man with a urethral discharge (Gram stain)

Pathogenic bacteria

An abscess caused by opportunistic S. aureus bacteria.

Pathogenic bacteria are bacteria that can cause disease.

A rotten apple after it fell from a tree

Decomposition

Process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts.

Decomposing fallen nurse log in a forest

Pig carcass in the different stages of decomposition: Fresh > Bloat > Active decay > Advanced decay > Dry remains

A decaying peach over a period of six days. Each frame is approximately 12 hours apart, as the fruit shrivels and becomes covered with mold.

Decomposition begins at the moment of death, caused by two factors: 1.) autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes, and 2.) putrefaction, the breakdown of tissues by bacteria.

Probiotic

Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut flora.

Élie Metchnikoff first suggested the possibility of colonizing the gut with beneficial bacteria in the early 20th century.

Probiotics are considered generally safe to consume, but may cause bacteria-host interactions and unwanted side effects in rare cases.

Extremophile

Organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temperature, radiation, salinity, or pH level.

Microscopic image from the hypersaline Lake Tyrrell (salinity> 20% w/v), in which the eukaryotic chlorophyte, Dunaliella salina, can be tentatively identified. Dunaliella salina is grown commercially for the carotenoid, β-carotene, which is widely used as a natural food colorant as well as a precursor to vitamin A. Alongside is the haloarchaeon, Haloquadratum walsbyi, which has flat square-shaped cells with gas vesicles that allow flotation to the surface, most likely to acquire oxygen.

Some bacteria were found living in the cold and dark in a lake buried a half-mile deep under the ice in Antarctica, and in the Marianas Trench, the deepest place in Earth's oceans.

Electron micrograph of Treponema pallidum

Syphilis

Typical presentation of secondary syphilis with a rash on the palms of the hands

Reddish papules and nodules over much of the body due to secondary syphilis

Model of a head of a person with tertiary (gummatous) syphilis, Musée de l'Homme, Paris

Histopathology of Treponema pallidum spirochetes using a modified Steiner silver stain

This poster acknowledges the social stigma of syphilis, while urging those who possibly have the disease to be tested (circa 1936).

Micrograph of secondary syphilis skin lesions. (A/B) H&E stain of SS lesions. (C/D) IHC staining reveals abundant spirochetes embedded within a mixed cellular inflammatory infiltrate (shown in the red box) in the papillary dermis. The blue arrow points to a tissue histiocyte and the read arrows to two dermal lymphocytes.

Portrait of Mr. J. Kay, affected with what is now believed to have been congenital syphilis c. 1820

Jarisch–Herxheimer reaction in a person with syphilis and human immunodeficiency virus

Syphilis deaths per million persons in 2012

Portrait of Gerard de Lairesse by Rembrandt van Rijn, circa 1665–67, oil on canvas. De Lairesse, himself a painter and art theorist, had congenital syphilis that deformed his face and eventually blinded him.

An early medical illustration of people with syphilis, Vienna, 1498

A Work Projects Administration poster about syphilis c. 1940

Preparation and Use of Guayaco for Treating Syphilis, after Stradanus, 1590

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum subspecies pallidum.

Nitrogen fixation

Chemical process by which molecular nitrogen, with a strong triple covalent bond, in the air is converted into ammonia or related nitrogenous compounds, typically in soil or aquatic systems but also in industry.