Neobacillus Explained

Neobacillus is a genus of rod-shaped bacteria that show Gram-positive or Gram-variable staining.[1] This genus belongs under the family Bacillaceae within the order Bacillales.[2] The type species of Neobacillus is Neobacillus niacini.

Members of this genus were previously part of the genus Bacillus. It has long been recognized that the genus Bacillus comprises a wide range of phylogenetically unrelated bacteria, demonstrated through multiple phylogenetic studies and comparative genome studies.[3] [4] Bacillus species were assigned based on vague criteria such as the ability to form endospores in the presence of oxygen, a criterion that many diverse, unrelated bacteria share.[5] [6] The result is a big genus comprising over 300 species with distinct biochemical characteristics that are not uniquely shared by all members, leaving no way to reliably distinguish Bacillus species from other bacteria. Subsequently, many studies have used phylogenetic analyses as a means to clarify the evolutionary relationships between Bacillus species, resulting in the establishment of many novel genera such as Virgibacillus, Solibacillus, Brevibacillus, and Ectobacillus.[7] [8] [9] [10] Additionally, Bacillus has been restricted to included only species closely related to Bacillus subtilis and Bacillus cereus.

The name Neobacillus is pieced together using the prefix "neo-" (from the Greek adjective, translating to new) and the suffix "-bacillus" (from the Latin noun, referring to a small staff or rod and Bacillus, the bacterial genus). Together, the name translates to "new Bacillus".

Biochemical Characteristics and Molecular Signatures

Members of Neobacillus can be either aerobic or facultatively anaerobic. Motility is variable, some species are motile while others are non-motile. All studied species are observed to form endospores under adverse environmental or nutritional conditions. Neobacillus can be found in a variety of environments, including soil, human origin (gut and skin) and plant roots. Neobacillus can grow in temperatures up to 50-55°C, but optimal growth occurs in the range of 25-37°C.

11 conserved signature indels (CSIs) have been identified through genomic analysis as exclusive for Neobacillus in proteins such as 50S ribosomal protein L24, flagellar M-ring protein FliF, 50S ribosomal protein L11 methyltransferase, imidazole glycerol phosphate synthase subunit HisH, ATP phosphoribosyltransferase regulatory subunit, LTA synthase family protein, type I DNA topoisomerase, nicotinate phosphoribosyltransferase, bifunctional hydroxymethylpyrimidine kinase/phospho- methylpyrimidine kinase, single-stranded-DNA-specific exonuclease RecJ and 1-deoxy-d-xylulose-5-phosphate synthase. These CSIs provide reliable methods to differentiate Neobacillus from other Bacillaceae genera and bacteria in molecular terms.

Taxonomy

As of May 2021, there are a total of 17 species with validly published names in the genus Neobacillus.[11] Members of this genus group together and forms a monophyletic branch in phylogenetic trees created from concatenated sequences from various datasets of conserved proteins as well as 16S rRNA gene sequences. The Genome Taxonomy Database (GTDB) also shows members of Neobacillus grouping together.[12]

Additional phylogenetic studies have identified a number of non-validly published species ("Bacillus ferrooxidans", "Bacillus rubiinfantis", "Bacillus marasmi" and "Bacillus salipaludis") that are considered to be members of this genus based on taxonomic placement in phylogenetic trees as well as shared molecular markers (specifically conserved signature indels) with other members of Neobacillus.[13] However, transfer was not proposed due to the lack of strain culture information. As additional culture information and genome sequences become available in the future, it would be necessary to revisit the taxonomic classifications proposed for this genus to update and validate the results, as done in 2022 for Bacillus dielmonensis.

Notes and References

  1. Patel. Sudip. Gupta. Radhey S.. 2020-01-01. A phylogenomic and comparative genomic framework for resolving the polyphyly of the genus Bacillus: Proposal for six new genera of Bacillus species, Peribacillus gen. nov., Cytobacillus gen. nov., Mesobacillus gen. nov., Neobacillus gen. nov., Metabacillus gen. nov. and Alkalihalobacillus gen. nov.. International Journal of Systematic and Evolutionary Microbiology. en. 70. 1. 406–438. 10.1099/ijsem.0.003775. 31617837. 1466-5026. free.
  2. Book: 2005. Brenner. Don J.. Krieg. Noel R.. Staley. James T.. Garrity. George M.. Boone. David R.. De Vos. Paul. Goodfellow. Michael. Rainey. Fred A.. Schleifer. Karl-Heinz. Bergey's Manual® of Systematic Bacteriology. 10.1007/0-387-28022-7. 978-0-387-24144-9.
  3. Logan. N.A.. 2011-12-20. Bacillus and relatives in foodborne illness. Journal of Applied Microbiology. 112. 3. 417–429. 10.1111/j.1365-2672.2011.05204.x. 1364-5072. 22121830. free.
  4. La Duc. Myron T. Satomi. Masataka. Agata. Norio. Venkateswaran. Kasthuri. March 2004. gyrB as a phylogenetic discriminator for members of the Bacillus anthracis–cereus–thuringiensis group. Journal of Microbiological Methods. 56. 3. 383–394. 10.1016/j.mimet.2003.11.004. 0167-7012. 14967230.
  5. Ash. Carol. Farrow. J.A.E.. Wallbanks. Sally. Collins. M.D.. 2008-06-28. Phylogenetic heterogeneity of the genus Bacillus revealed by comparative analysis of small-subunit-ribosomal RNA sequences. Letters in Applied Microbiology. 13. 4. 202–206. 10.1111/j.1472-765x.1991.tb00608.x. 82988953. 0266-8254.
  6. Logan. N. A.. Berge. O.. Bishop. A. H.. Busse. H.-J.. De Vos. P.. Fritze. D.. Heyndrickx. M.. Kampfer. P.. Rabinovitch. L.. Salkinoja-Salonen. M. S.. Seldin. L.. 2009-06-30. Proposed minimal standards for describing new taxa of aerobic, endospore-forming bacteria. International Journal of Systematic and Evolutionary Microbiology. 59. 8. 2114–2121. 10.1099/ijs.0.013649-0. 19567583. 1466-5026. free.
  7. Heyndrickx. M.. Lebbe. L.. Kersters. K.. Hoste. B.. De Wachter. R.. De Vos. P.. Forsyth. G.. Logan. N. A.. 1999-07-01. Proposal of Virgibacillus proomii sp. nov. and emended description of Virgibacillus pantothenticus (Proom and Knight 1950) Heyndrickx et al. 1998. International Journal of Systematic and Evolutionary Microbiology. 49. 3. 1083–1090. 10.1099/00207713-49-3-1083. 1466-5026. 10425765. free.
  8. Shida. O.. Takagi. H.. Kadowaki. K.. Komagata. K.. 1996-10-01. Proposal for Two New Genera, Brevibacillus gen. nov. and Aneurinibacillus gen. nov.. International Journal of Systematic Bacteriology. en. 46. 4. 939–946. 10.1099/00207713-46-4-939. 0020-7713. 8863420. free.
  9. Mual. Poonam. Singh. Nitin Kumar. Verma. Ashish. Schumann. Peter. Krishnamurthi. Srinivasan. Dastager. Syed. Mayilraj. Shanmugam. 2016-05-01. Reclassification of Bacillus isronensis Shivaji et al. 2009 as Solibacillus isronensis comb. nov. and emended description of genus Solibacillus Krishnamurthi et al. 2009. International Journal of Systematic and Evolutionary Microbiology. en. 66. 5. 2113–2120. 10.1099/ijsem.0.000982. 1466-5026. 26907585. free.
  10. Gupta. Radhey S.. Patel. Sudip. Saini. Navneet. Chen. Shu. 2020-11-01. Robust demarcation of 17 distinct Bacillus species clades, proposed as novel Bacillaceae genera, by phylogenomics and comparative genomic analyses: description of Robertmurraya kyonggiensis sp. nov. and proposal for an emended genus Bacillus limiting it only to the members of the Subtilis and Cereus clades of species. International Journal of Systematic and Evolutionary Microbiology. en. 70. 11. 5753–5798. 10.1099/ijsem.0.004475. 1466-5026. 33112222. free.
  11. Web site: Genus: Neobacillus. 2021-05-20. lpsn.dsmz.de. en.
  12. Web site: GTDB - Tree. 2021-05-25. gtdb.ecogenomic.org.
  13. Kämpfer . Peter . Glaeser . Stefanie P. . McInroy . John A. . Clermont . Dominique . Lipski . André . Criscuolo . Alexis . Neobacillus rhizosphaerae sp. nov., isolated from the rhizosphere, and reclassification of Bacillus dielmonensis as Neobacillus dielmonensis comb. nov. . International Journal of Systematic and Evolutionary Microbiology . 2022 . 72 . 005636 . 10.1099/ijsem.0.005636 . 36327328.

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