''Priestia'' is a genus of mostly

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 bacte ...

( ''Priestia flexa'' stains Gram-variable and ''Priestia koreensis'' stains

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

) rod-shaped bacteria in the family ''

Bacillaceae The Bacillaceae are a family of gram-positive, heterotrophic, rod-shaped bacteria that may produce endospores. Motile members of this family are characterized by peritrichous flagella. Some Bacillaceae are aerobic, while others are facultative ...

'' from the order ''

Bacillales The Bacillales are an order of Gram-positive bacteria, placed within the Bacillota. Representative genera include ''Bacillus'', ''Listeria'' and ''Staphylococcus''. See also * List of bacteria genera * List of bacterial orders This article li ...

.'' The type species of this genus is ''Priestia megaterium.'' Members of ''Priestia'' are previously species belonging to ''

Bacillus ''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacilli ...

'', a genus that has been recognized as displaying extensive

polyphyly A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

within its members due to the vague criteria used to assign species to this clade. Multiple studies have been conducted using comparative phylogenetic analyses as a means to clarify the evolutionary relationships between ''Bacillus'' species, resulting in the transfer of species into numerous novel genera such as ''

Alkalihalobacillus ''Alkalihalobacillus'' is a genus of gram-positive or gram-variable rod-shaped bacteria in the family ''Bacillaceae'' from the order ''Bacillales''. The type species of this genus is '' Alkalihalobacillus alcalophilus.'' This genus comprises s ...

'', ''

Brevibacillus ''Brevibacillus'' is a genus of Gram-positive bacteria in the family Paenibacillaceae The Paenibacillaceae are a family of Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain tes ...

Solibacillus ''Solibacillus'' is a genus of Gram positive, rod shaped, spore-forming bacteria. The first member of ''Solibacillus'' was first isolated in 1999, and was originally called ''Bacillus silvestris''. However, further studies on ''B. silvestris'' ...

'', ''

Alicyclobacillus ''Alicyclobacillus'' is a genus of Gram-variable, rod-shaped, spore-forming bacteria. The bacteria are able to grow in acidic conditions, while the spores are able to survive typical pasteurization procedures. Overview ''Alicyclobacilli'' are s ...

,'' ''

Virgibacillus ''Virgibacillus'' is a genus of Gram-positive, rod-shaped (bacillus) bacteria and a member of the phylum Bacillota. ''Virgibacillus'' species can be obligate aerobes (oxygen reliant), or facultative anaerobes and catalase enzyme positive. Under s ...

'' and ''

Evansella ''Evansella'' is a genus of Gram-positive rod-shaped bacteria in the family ''Bacillaceae'' within the order ''Bacillales''. The type species for this genus is ''Evansella cellulosilytica.'' Members of ''Evansella'' was transferred from the genu ...

''. In addition, the genus ''Bacillus'' has been restricted to only include species closely related to ''

Bacillus subtilis ''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus ''Bacillu ...

'' and ''

Bacillus cereus ''Bacillus cereus'' is a Gram-positive rod-shaped bacterium commonly found in soil, food, and marine sponges. The specific name, ''cereus'', meaning "waxy" in Latin, refers to the appearance of colonies grown on blood agar. Some strains are ha ...

.'' The name ''Priestia'' was named after the British microbiologist Professor Fergus G. Priest (Heriot-Watt University, Edinbugth; 1948–2019) for his many contributions to the systematics and uses of the members of the genus ''Bacillus''.

Biochemical Characteristics and Molecular Signatures

Members of this genus are

aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cellu ...

and found in diverse locations such as soil, faeces, upper atmosphere, inner tissues of cotton plants, sea sediment and the rhizosphere of willow roots. All members can produce endospores and most are motile. ''Priestia'' can grow in temperatures ranging from 5°C to 48°C but the optimal growth temperature is in the range of 28-37°C, so it can be qualified as a

mesophile A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37°C. The term is mainly applied to microorganisms. Organi ...

and psychrotrophic organism. ''Priestia aryabhattai'' is industrially important as it is resistant to arsenic and UV radiation allowing for an affordable alternative to conventional, expensive, metal remediation technologies. Two

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

(CSIs) have been identified through genomic analysis as exclusive for this genus in the proteins oligoribonuclease NrnB or cAMP/cGMP phosphodiesterase and DHH superfamily protein, and can be used to reliably differentiate this genus from other ''Bacillaceae'' genera and bacteria in molecular terms.

Taxonomy

''Priestia'', as of May 2021, contains a total of 10 species with validly published names. This genus was identified as a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

clade and phylogenetically unrelated to other ''Bacillus'' species in studies examining the taxonomic relationships within ''Bacillus''. This branching pattern is also observed in the

Genome Taxonomy Database The Genome Taxonomy Database (GTDB) is an online database that maintains information on a proposed nomenclature of prokaryotes, following a phylogenomic approach based on a set of conserved single-copy proteins. In addition to breaking up parap ...

(GTDB). Two non-validly published species, "Bacillus pseudoflexus" and "Bacillus zanthoxyli", are also found to group with other members of ''Priestia'' in phylogenetic trees as well as share the same molecular markers in the form of

(CSIs). However, their transfer was not officially proposed due to the lack of culture strain information. Further revision of this genus is required as additional genomes and novel species are discovered and assigned.

References

{{reflist Bacillaceae Bacteria genera