''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. Gram-positive bacte ...

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

'' within 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 In 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 species that contains the biological type specimen ...

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

.'' The

polyphyletic 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 ...

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 ''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 ...

'', and the establishment of many 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 positive. Under s ...

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'' f ...

Brevibacillus ''Brevibacillus'' is a genus of Gram-positive bacteria in the family Paenibacillaceae The Paenibacillaceae are a family of Gram-positive bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often con ...

'' 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 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 ...

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., no ...

-forming bacteria. Most species are

motile Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

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 t ...

- and

oxidase In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...

-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 In enzymology, a N-acetyl-gamma-glutamyl-phosphate reductase () is an enzyme that catalyzes the chemical reaction :N-acetyl-L-glutamate 5-semialdehyde + NADP+ + phosphate \rightleftharpoons N-acetyl-L-glutamyl 5-phosphate + NADPH + H+ The 3 su ...

, type II/IV secretion system protein,

homoserine O-succinyltransferase In enzymology, a homoserine O-succinyltransferase () is an enzyme that catalyzes the chemical reaction :succinyl-CoA + L-homoserine \rightleftharpoons CoA + O-succinyl-L-homoserine Thus, the two substrates of this enzyme are succinyl-CoA and ...

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 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 ...

branch in various

phylogenetic trees A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

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 breaking up 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.

References

{{Taxonbar, from=Q107210947 Bacillaceae Bacteria genera