''Mesobacillus'' is a genus of

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 bact ...

or gram-variable, 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 o ...

'' within the order ''

Bacillales The Bacillales are an order of Gram-positive bacteria, placed within the Bacillota. Representative genera include ''Bacillus'', ''Listeria'' and ''Staphylococcus ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staph ...

''. The type species for this genus is ''Mesobacillus jeotgali.'' Members of ''Mesobacillus'' was transferred from the genus ''

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 ''Bacill ...

''. ''Bacillus'' is a large, phylogenetically complicated genus, with unclear interspecies evolutionary relationships due to the vague criteria used to assign species into the genus. The efforts of multiple phylogenetic and comparative genomics analyses studies have transferred many ''Bacillus'' species into novel genera such as ''

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 Enzyme ...

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'' ...

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 ...

'' and '' Ectobacillus''. The genus itself has also been emended and 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 ''Bacillus ...

'' 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 har ...

''. The name ''Mesobacillus'' is derived from its taxonomic position in phylogenetic trees. The prefix "meso-" comes from the Greek adjective ''mesos'', and translates to "middle". Bacillus comes from the Latin noun ''bacillus'', referring to both 'a small staff or rod' and ''Bacillus'', the bacterial genus. Put together, the name ''Mesobacillus'' refers to a genus in between other ''Bacillus''.

Biochemical Characteristics and Molecular Signatures

Members of the genus ''Mesobacillus'' are either

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 cel ...

facultatively anaerobic A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus' ...

. They mostly demonstrate endospore formation under adverse environmental or nutritional conditions. Species can be found in a variety of environments, ranging from soil, human gut, groundwater, wastewater systems, hypersalinic lakes and thermal aquifers. Cells can be either motile or non-motile. Some specific species are high salt tolerant and even require high salt concentration for growth (ie. ''Mesobacillus persicus''). ''Mesobacillus'' can survive in temperatures ranging from 10°C to 45°C, but optimal growth occurs in the range of 25-37°C. Genome sequence analyses have identified three

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) uniquely found in members of ''Mesobacillus'' in the proteins PhoH family protein,

TrkA Tropomyosin receptor kinase A (TrkA), also known as high affinity nerve growth factor receptor, neurotrophic tyrosine kinase receptor type 1, or TRK1-transforming tyrosine kinase protein is a protein that in humans is encoded by the ''NTRK1'' gen ...

family

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

uptake protein and a hypothetical protein. These molecular markers provide a reliable means to distinguish ''Mesobacillus'' species from other ''Bacillaceae'' genera and bacteria.

Taxonomy

As of May 2021, there are a total of 14 species with validly published names in the genus ''Mesobacillus''. In phylogenetic trees constructed based on concatenated sequences from various datasets of conserved proteins and 16S rRNA sequences, members of this genus group together and forms a monophyletic branch. This grouping is also reflected n 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 paraph ...

(GTDB). The non-validly published species "Bacillus mediterraneensis" has been found to branch with other members of ''Mesobacillus'' as well as share molecular markers unique to the clade. However, transfer of these species into ''Mesobacillus'' was not proposed due to the lack of strain culture information. This indicates the requirement for additional analyses of this clade as more genomic and strain information become available.

References

Bacillaceae Bacteria genera {{Improve categories, date=May 2021