Acinetobacter silvestris sp. nov. discovered in forest ecosystems in Czechia

We investigated a taxonomically novel group of the genus Acinetobacter, which included five strains isolated from soil and water samples collected in preserved forest areas in Czechia between 2013 and 2021. The whole-genome sequences of the strains were 3.1-3.2 Mb in size, with G+C contents of 38.0-38.2mol%. Core genome-based phylogenetic analysis showed that they formed a compact and deeply branched Glade within the genus. The genomic average nucleotide identity based on BLAST/digital DNA-DNA hybridization values for the novel strains were 99.2-99.6%/95.2-98.4%, whereas those between the novel strains and the type strains of the known Acinetobacter species reached <78%/<24%. The results of the genus-wide analysis of whole-cell MALDI-TOF mass spectra supported the sharp distinctness of the group. The five strains were non-glucose acidifying. nonhaemolytic, nonproteolytic and growing at 28 degrees C. but not at 32 degrees C; they assimilated acetate, benzoate, ethanol, L-histidine, 4-hydroxybenzoate, DL-lactate and malonate but not 4-aminobutyrate, L-aspartate or 2,3-butanediol; this phenotype is unique among the known Acinetobacter species. We conclude that the five strains represent a novel environmental species, for which the name Acinetobacter silvestris sp. nov. is proposed, with the type strain ANC 4999(T) (=CCM 920(T)=CCUG 7587(T)=CNCTC 8124(T)).

Automated summary

This study investigated a taxonomically novel group within the genus Acinetobacter, finding that five strains exhibited unique characteristics in terms of genome sequences, strain features, and molecular mass spectra compared to known Acinetobacter species. As a result, these five strains represent a new environmental species, proposed to be named Acinetobacter silvestris sp. nov.