Acinetobacter

Abstract

A.ci.ne.to.bac'ter. Gr. masc. adj. akinetos unable to move; N.L. masc. adj. bacter , a rod; N.L. masc. n. Acinetobacter , a non‐motile rod. Proteobacteria / Gammaproteobacteria / Pseudomonadales / Moraxellaceae / Acinetobacter Rods 0.9–1.6 × 1.5–2.5 μm, becoming spherical in the stationary phase of growth. Colonies are generally nonpigmented and are mucoid when the cells are encapsulated. Cells commonly occur in pairs. Do not form spores. Gram‐stain‐negative. Flagella are absent, and swimming motility does not occur, but cells display twitching motility associated with fimbriae. Strictly aerobic. Oxidase‐negative. Catalase‐positive. Mesophilic. Most strains do not reduce nitrate to nitrite in conventional assays. Grow well on complex media. Most strains grow in defined media containing a single carbon and energy source (most commonly acetate), using ammonium or nitrate salts or one of several common amino acids, as a source of nitrogen. The genome consists of a single circular chromosome sized 2.6−4.7 Mb and a strain‐dependent set of plasmid replicons. Widespread in nature, inhabiting diverse soil and water ecosystems and being associated with plants and animals. Some species reside on the human skin and mucosa. Several species can cause nosocomial infections; strains involved are often resistant to multiple antibiotics and can give rise to epidemics. In 2021, the genus included 73 species with correct names. DNA G + C content (mol%) : 34.9−49.6 (median: 40.2). Type species : Acinetobacter calcoaceticus Baumann et al. 1968b AL (basonym: Micrococcus calcoaceticus Beijerinck 1911) emend. Bouvet and Grimont 1986.

Proposal for Acinetobacter higginsii sp. nov. to accommodate organisms of human clinical origin previously classified as Acinetobacter genomic species 16

“…The genome sequences of GS15 and GS16 were 4.0-4.3 Mb and 4.1-4.6 Mb in size, with G+C content of 40.7-41.0 mol% and 40.7-40.9 mol%, respectively. These values fall within the range reported for the genus [1] and correspond to those of the haemolytic clade species that are phylogenetically closest to GS15 and GS16 (Table S1, Fig. 1).…”

“…The genotypic distinctness of these organisms at the strain level was verified by macrorestriction analysis of genomic DNA. Based on the tests described by Křížová et al [10], all 13 strains of GS15 and GS16 shared the general characteristics of the genus Acinetobacter [1], i.e. they were oxidase-negative, catalase-positive, and strictly aerobic Gram-stain-negative coccobacilli, incapable of dissimilative denitrification and swimming motility, and capable of transforming auxotrophic strain Acinetobacter baylyi BD413 to prototrophy in the assay of Juni [11].…”

“…Phylogenetic reconstructions based on the Acinetobacter core genome revealed the existence of several discrete clades encompassing multiple species [1,2]. One, termed the haemolytic clade [3], typically, although not exclusively, contains organisms with strong haemolytic activity on sheep blood agar and includes all known Acinetobacter strains with the gelatinase activity detectable in routine bacteriological media [1]. This clade currently includes 14 species with correct names and five provisional taxa with not yet defined nomenclatural status (Table S1, Fig.…”

“…In contrast, the other clade members have smaller genomes and moderate or low metabolic activity. The most noticeable example is Acinetobacter parvus, which has a genome as small as 2.8-3.0 Mb, is one of the catabolically least active Acinetobacter species and forms minute colonies on agar media [1,7]. A pivotal contribution to the understanding of the Acinetobacter haemolytic clade was made by Bouvet and Jeanjean in 1989 [8], who delineated five novel proteolytic genomic species (designated GS13-17), each with two to four human isolates.…”

Genomic Analysis of Two Novel Bacteriophages Infecting Acinetobacter beijerinckii and halotolerans Species

“…This study focused on the isolation and analysis of the genome sequences of two novel phages infecting non-ACB complex species, namely A. beijerinckii NIPH 838 T (phage nACB1) and A. halotolerans ANC 5766 T (phage nACB2). A. beijerinckii and A. halotolerans are members of the Acinetobacter hemolytic clade [ 9 ], which is the largest well-separated phylogroup within the genus [ 10 ]. The clade encompasses species that almost all show a strong ability to lyse sheep erythrocytes in ordinary agar media (including both A. beijerinckii and A. halotolerans ) and may include strains with gelatinase activity, whereas species outside this clade are neither hemolytic nor proteolytic, except for a few that embrace a certain proportion of weakly hemolytic strains [ 9 ].…”