The ''Hafniaceae'' are a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Gram-negative bacteria 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 ...

. This family is a member of the order

Enterobacterales Enterobacterales is an order of Gram-negative bacteria, Gram-negative, non-spore forming, Facultative anaerobic organism, facultatively anaerobic, rod-shaped bacteria with the class Gammaproteobacteria. The type genus of this order is ''Enterob ...

in the class Gammaproteobacteria of the phylum Pseudomonadota. Genera in this family include the type genus '' Hafnia'', along with '' Edwardsiella'' and'' Obesumbacterium''. The name ''Hafniaceae'' is derived from the Latin term ''Hafnia'', referring the type genus of the family and the suffix "-aceae", an ending used to denote a family. Together, ''Hafniaceae'' refers to a family whose nomenclatural type is the genus ''Hafnia''.

Biochemical Characteristics and Molecular Signatures

Members are catalase-positive, oxidase-negative, and negative for lysine decarboxylase. These bacteria are also able to grow on MacConkey media, and are capable of reducing nitrate. Four

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) were identified for this family in the proteins two-component system response regulator GIrR,

glucose-1-phosphate adenylyltransferase In enzymology, a glucose-1-phosphate adenylyltransferase () is an enzyme that catalysis, catalyzes the chemical reaction :ATP + alpha-D-glucose 1-phosphate \rightleftharpoons diphosphate + ADP-glucose Thus, the two substrate (biochemistry), subst ...

transcriptional activator A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. Activators are considered to have ''positive'' control over gene expression, as they function to promote gene transcription and ...

NhaR, and the hybrid sensor

histidine kinase Histidine kinases (HK) are multifunctional, and in non-animal kingdoms, typically transmembrane, proteins of the transferase class of enzymes that play a role in signal transduction across the cellular membrane. The vast majority of HKs are hom ...

/response regulator. These molecular signatures were identified through genomic analyses and serves as a reliable molecular means to distinguish members of this family from other families within the order Enterobacterales and all other bacteria.

Historical Systematics and Current Taxonomy

''Hafniaceae'', as of 2021, contains three validly published genera. Members of this family were originally members of the family '' Enterobacteriaceae'', a large phylogenetically unrelated group of species with distinct biochemical characteristics and different ecological niches. The original assignment of species into the family ''Enterobacteriaceae'' was largely based on 16S rRNA genome sequence analyses, which is known to have low discriminatory power and the results of which changes depends on the algorithm and organism information used. Despite this, the analyses still exhibited polyphyletic branching, indicating the presence of distinct subgroups within the family. In 2016, Adeolu et al. proposed the division of ''Enterobacteriaceae'' into 7 novel families based on comparative genomic analyses and the branching pattern of various phylogenetic trees constructed from conserved genome sequences, 16S rRNA sequences and multilocus sequence analyses. Molecular markers, specifically

, specific to this family were also identified as evidence supporting the division independent of phylogenetic trees.

References

Hafniaceae

Enterobacterales Gram-negative bacteria {{Enterobacterales-stub