''Heyndrickxia'' 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. The Gram stain is ...

rod-shaped bacteria (except for ''Heyndrickxia'' ''sporothermodurans'', which stains gram-negative) in the family ''

Bacillaceae Bacillaceae, from Latin "bacillus", meaning "little staff, wand", 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 Baci ...

'' within the order ''

Bacillales Bacillales, from Latin "bacillus", meaning "little staff, wand", are an order (biology), order of Gram-positive bacteria, placed within the Bacillota. The ''Bacillales'' are the most productive order of the phylum ''Firmicutes''. Representative ...

''. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

for this genus is '' Heyndrickxia oleronia.'' Members of ''Heyndrickxia'' were originally assigned to the genus ''

Bacillus ''Bacillus'', from Latin "bacillus", meaning "little staff, wand", 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-sh ...

.'' The

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

nature and unclear evolutionary relationships of the genus ''Bacillus'' has long been a topic in the scientific community. It was composed of many unrelated species with a diverse range of biochemical characteristics due to the vague criteria (such as the ability to form endospores under aerobic conditions) used to assign species to this genus. Multiple phylogenetic studies and comparative genomic analyses have been conducted to clarify the taxonomy of genus, resulting in the restriction of ''Bacillus'' 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 ''Bacill ...

'' and ''

Bacillus cereus ''Bacillus cereus'' is a Gram-positive bacteria, Gram-positive Bacillus, 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 o ...

'', and the establishment of many novel genera such as '' Virgibacillus, Solibacillus,

Brevibacillus ''Brevibacillus'' is a genus of Gram-positive bacteria in the family Brevibacillaceae. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnolo ...

'' and '' Ectobacillus''. The name ''Heyndrickxia'' was chosen to celebrate Professor Marc Heyndrickx (University of Gent) for his contributions to the field of microbiology and his research on ''Bacillus'' species.

Biochemical characteristics and molecular signatures

Members of the genus ''Heyndrickxia'' are aerobic,

endospore An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore (i.e., not ...

-forming bacteria. Most species are

motile Motility is the ability of an organism to move independently using metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components. Motility is observed in animals, mi ...

and generally

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

- and

oxidase In biochemistry, an oxidase is an oxidoreductase (any enzyme that catalyzes a redox reaction) that uses dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydrogen peroxid ...

-positive. The main isolation source for this genus is in dairy or dairy production facilities, such as in raw milk and feed concentrate for cattle. ''Heyndrickxia'' can survive in temperatures ranging from , but optimal growth occurs in the range of . Five

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 as exclusive for this genus in the proteins stage V sporulation protein D, N-acetyl-gamma-glutamyl-phosphate reductase, type II/IV secretion system protein, homoserine O-succinyltransferase and septation ring formation regulator EzrA which can be used as reliable distinguishing molecular signatures to demarcate ''Heyndrickxia'' species from other ''Bacillaceae'' genera and bacteria.

Taxonomy

, there are a total of 3 species with validly published names in the genus ''Heyndrickxia''. Members of this genus form a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

branch in various

phylogenetic tree A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In ...

s created based on concatenated sequences from various datasets of conserved proteins and 16S rRNA genome sequences. The monophyletic nature of this genus is also found 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 resolving parap ...

. Additionally, the non-validly published species "Bacillus obstructivis" also branches with members of ''Heyndrickxia'' as well as share the unique molecular markers specific for the genus. However, transfer of this species into the clade was not proposed due to the lack of culture strain information. This indicates the need to perform periodic analysis of the classification of this genus when more genome sequence and culture stain information becomes available. In July 2023, an article in the ''

IJSEM The ''International Journal of Systematic and Evolutionary Microbiology'' is a peer-reviewed scientific journal covering research in the field of microbial systematics that was established in 1951. Its scope covers the taxonomy, nomenclature, iden ...

'' argued '' Bacillus acidicola'', '' Bacillus pervagus'', '' Margalitia'', and '' Weizmannia'' should all be subsumed under ''Heyndrickxia''. Being a taxonomic opinion in the IJSEM, the new combination names are considered valid. GTDB release R214 does not yet include this "lumping" change.

Phylogeny

References

{{Taxonbar, from=Q107210947 Bacillaceae Bacteria genera

Biochemical characteristics and molecular signatures

Taxonomy

Phylogeny

See also

References