Ectobacillus is a genus ofGram-positive (with the exception ofEctobacillus funiculus, which isGram-negative), rod-shaped bacteria in the familyBacillaceae within the orderBacillales.[3][4] The type species for this genus isEctobacillus panaciterrae.[1]
Ectobacillus is composed of species originally belonging to the genusBacillus. The genusBacillus comprises a large number of phylogenetically unrelated bacteria species with a diverse range of biochemical characteristics.[5][6] The polyphyletic nature of the genus is partly due to the vague criteria used to assign species to this genus (ie. accepting all species that are able to form endospores in aerobic conditions).[7] Comparative genomic analyses and phylogenetic studies have set out to clarify the complex taxonomic relationship of this genus, resulting in the transfer of many species into novel genera such asVirgibacillus,Solibacillus,Brevibacillus andAlteribacter.[8][9][10][3] In addition, the genusBacillus has been restricted to include only species closely related toBacillus subtilis andBacillus cereus.[11][3]
The nameEctobacillus is derived from its taxonomic position in relation toBacillus. The prefix "ecto-" (which comes from the Greek prepositionecto, and translates to "outside") and the suffix "-bacillus" (which comes from the Latin nounBacillus, referring to a rod or small staff, as well asBacillus, a bacterial genus) come together to form the nameEctobacillus, meaning "outside ofBacillus".[3]
Biochemical Characteristics and Molecular Signatures
Members of the genusEctobacillus can beaerobic orfacultatively anaerobic. They all are endospore-forming and some members are motile cells.Ectobacillus can survive in temperatures ranging from 15°C to 45°C, but optimal growth occurs in the range of 28-35°C.[3]
Analyses of genome sequences fromEctobacillus have identified fiveconserved signature indels (CSIs) that are exclusive forEctobacillus species in the proteins 3-isopropylmalate dehydratase small subunit, bacillithiol biosynthesis deacetylase BshB1, aldo or keto reductase, MBL fold metallo-hydrolase, and CYTH domain-containing protein. These CSIs can be used to demarcateEctobacillus from otherBacillceae genera in molecular terms.[3]
As of March 2025, there are a total of 5 species with validly published names in the genusEctobacillus.[1][2] Members of this clade were found to group together in a monophyletic branch in various phylogenetic trees constructed on conserved genome sequences and 16S rRNA sequences.[3] This branching pattern could also be seen in theGenome Taxonomy Database (GTDB), further supporting this classification.[12]
