''Geobacillus stearothermophilus'' (previously ''Bacillus stearothermophilus'') is a rod-shaped,

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and a member of the phylum

Bacillota The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. The renaming of phyla such as Firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the ear ...

. The bacterium is a

thermophile A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the ea ...

and is widely distributed in soil, hot springs, ocean sediment, and is a cause of spoilage in food products. It will grow within a temperature range of 30 to 75 °C. Some strains are capable of oxidizing carbon monoxide aerobically. It is commonly used as a challenge organism for sterilization validation studies and periodic check of sterilization cycles. The biological indicator contains

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

s of the organism on filter paper inside a vial. After sterilizing, the cap is closed, an ampule of growth medium inside of the vial is crushed and the whole vial is incubated. A color and/or

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can c ...

change indicates the results of the sterilization process; no change indicates that the sterilization conditions were achieved, otherwise the growth of the spores indicates that the sterilization process has not been met. Recently a fluorescent-tagged strain, Rapid Readout(tm), is being used for verifying sterilization, since the visible blue fluorescence appears in about one-tenth the time needed for pH-indicator color change, and an inexpensive light sensor can detect the growing colonies. Biological indicators are used in conjunction with

chemical indicator A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence ...

s and

process indicator A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

s to validate sterilization processes. It was first described in 1920 as ''Bacillus stearothermophilus'', but, together with '' Bacillus thermoglucosidasius'', it was reclassified as a member of the genus ''Geobacillus'' in 2001.

Applications in molecular biology

DNA Polymerase

Recently, a

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create ...

derived from these bacteria, ''Bst'' polymerase, has become important in molecular biology applications. ''Bst'' polymerase has a

helicase Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating ...

-like activity, making it able to unwind DNA strands. Its optimum functional temperature is between 60 and 65 °C and it is denatured at temperatures above 70 °C. These features make it useful in loop-mediated isothermal amplification (LAMP). LAMP is similar to the polymerase chain reaction (PCR) but does not require the high temperature (96 °C) step required to denature DNA.

Reverse transcriptase

In 2013, a

thermostable In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperature. ...

group II intron Group II introns are a large class of self-catalytic ribozymes and mobile genetic elements found within the genes of all three domains of life. Ribozyme activity (e.g., self- splicing) can occur under high-salt conditions '' in vitro''. Howeve ...

reverse transcriptase (TGIRT), GsI-IIC-MRF, from ''G. stearothermophilus'' was found to retain activity up to 70 °C and to exhibit high

processivity In molecular biology and biochemistry, processivity is an enzyme's ability to catalyze "consecutive reactions without releasing its substrate". For example, processivity is the average number of nucleotides added by a polymerase enzyme, such as ...

and a low error rate. These properties make this enzyme useful for reverse transcribing long and/or highly structured

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohyd ...

molecules. A method for determining RNA secondary structure, DMS-MaPseq, uses this enzyme because it converts normal RNA to DNA accurately but introduces mutations at unpaired bases that have been

methylated In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

dimethyl sulfate Dimethyl sulfate (DMS) is a chemical compound with formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as ( CH3)2 SO4 or Me2SO4, where CH3 or Me is methyl. Me2SO4 is mainly used as a methylating agent ...

, and the mutations can be identified via

sequencing In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succi ...

References

External links

Type strain of ''Geobacillus stearothermophilus'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
Bacillaceae {{Bacilli-stub