Phenotypic and Chemotaxonomic characterization
Colonies of strain CAAS 2-6T on NB agar were circular, smooth and 0.8–1.2 mm in diameter. Strain CAAS 2-6T was Gram-staining-negative, aerobic, and short rod shaped, with a size of approximately 0.7 µm×0.9–1.6 µm (Fig. S3). Strain CAAS 2-6T was able to grow at 15–40 ℃ (optimally at 25–40 ℃), at pH 6.0–8.0 (optimally at pH 7.0–7.5) and in the presence of 0–6% (w/v) NaCl (optimally at 0–4%). Strain CAAS 2-6T exhibited resistance to Penicillin, Ceftazidime, and Oxacillin(= 0 cm), showed weak resistance to Ampicillin, Cefazolin, Gentamicin, Neomycin, Cephalexin, and Cefradine(≤ 1.5 cm), while being susceptible to the remaining 14 antibiotics. Differential phenotypic characteristics between strain CAAS 2-6T and its closer affinity species of the genus Acinetobacter were summarized in Table 1. The API ZYM, API 20NE and API 50CH results confirmed that the classification of strain CAAS 2-6T as a member of the genus Acinetobacter. For example, all known species within the genus Acinetobacter lack the ability to produce arginine hydrolase, chymotrypsin α-galactosidase, β-galactosidase, α-glucosidase, β-glucosidase, β-glucuronidase, N-acetyl-β-glucosaminase, α-mannosidase, and β-fucosidase. Conversely, they exhibit the ability to produce esterase and leucine-arylamidase, lipase, valine arylamidase and cystinol-arylamidase. However, strain CAAS 2-6T differed from all recognized species of genus Acinetobacter. It could be distinguishable from other species in genus Acinetobacter by the ability to ferment glucose, as well as the absence of acid phosphomonoesterase activity (Table S3).
The whole-cell fatty acid profiles of strain CAAS 2-6T and other species in the genus Acinetobacter are presented in Table 2. Strain CAAS 2-6T exhibited the similarly predominant fatty acids, including C12:0(7.0%), C16:0(25.7%), C16:0 N alcohol(6.5%), C18:1 ω9c(10.5%) and Summed Feature 3(25.8%). The detailed fatty acid profile of strain CAAS 2-6T can be found in Table 1. The polar lipid composition mainly consisted of diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), and phosphatidylcholine(PC) (Fig. S4). These profiles were similar to those of recently described strains wihin the genus Acinetobacter (Das et al. 2021, Feng et al. 2014, Malhotra et al. 2012). The analysis of chemotaxonomic properties, including fatty acid profiles and polar lipid composition, confirmed the placement of strain CAAS 2-6T within the genus Acinetobacter as a novel species.
Table 1
Fatty acid composition of strain CAAS 2-6T and its phylogenetically closest relatives Strains: 1, CAAS 2-6T; 2, A. chinensis WCHAc010005T; 3, A. sichuanensis WCHAc060041T; 4, A. chengduensis WCHAc060005T; 5, A. wuhouensis WCHA60T. All dates from this study. –, Not detected. Fatty acids present at > 5 % are highlighted in bold. Summed Feature 2 comprised C12:0 aldehyde ?, Summed Feature 3 comprised C16:1 ω7c and/or C16:1 ω6c, Summed Feature 5 comprised C18:2 ω6, 9c and/or Ante-C18:0, Summed Feature 8 comprised C18:1 ω7c.
Fatty acid | 1 | 2 | 3 | 4 | 5 |
C10:0 | 0.22 | 0.55 | 0.19 | 1.20 | 0.34 |
C12:0 | 6.96 | 12.06 | 5.61 | 13.60 | 13.68 |
Iso-C13:0 | 1.82 | – | – | 3.17 | – |
C12:0 2-OH | 0.51 | 1.75 | – | 2.05 | – |
C12:0 3-OH | 3.37 | 7.94 | – | 7.04 | 5.87 |
Iso-C14:0 | 1.29 | – | – | 1.90 | 0.72 |
C14:0 | 1.20 | 0.50 | 9.78 | 1.72 | 0.96 |
Iso-C15:0 | 3.84 | – | – | 1.98 | 0.65 |
Anteiso-C15:0 | 1.32 | – | – | 1.45 | 6.33 |
C16:1 ω7c alcohol | 1.77 | – | – | – | – |
C16:0 N alcohol | 6.45 | – | – | – | – |
Iso-C16:0 | 1.55 | – | – | 0.44 | 4.68 |
C16:0 | 25.74 | 17.90 | 25.60 | 19.17 | 14.46 |
Iso-C17:0 | 0.10 | 1.48 | 0.29 | 0.83 | 0.82 |
Iso-C17:1 ω10c | 1.06 | – | 9.13 | – | – |
C17:0 | 0.19 | – | 0.83 | 0.94 | 1.18 |
C18:3 ω6c | 2.08 | – | – | – | – |
C18:1 ω9c | 10.46 | 24.31 | – | 19.84 | 18.18 |
C18:0 | 1.06 | 0.90 | 1.53 | 2.44 | 2.86 |
C19:0 cyclo ω8c | – | – | 1.36 | – | – |
Summed Feature 2 | 0.54 | – | 12.79 | – | 0.54 |
Summed Feature 3 | 25.78 | 27.47 | 10.76 | 20.40 | 25.82 |
Summed Feature 5 | – | – | – | – | 0.22 |
Summed Feature 8 | 0.60 | 4.50 | 21.78 | – | 2.50 |
Description of A cinetobacter lentus sp. nov.
Acinetobacter lentus (len’tus. L. masc. adj. lentus, slow, delayed, referring to slow growth).
Cells are Gram-staining-negative, aerobic, non-motile, short rods (approx. 0.7 µm×0.9–1.6 µm). Growth occurs on BHI agar, R2A agar, TSA, NA and LB agar. Colonies grown on NB agar medium are circular, smooth, and 0.8–1.2 mm in diameter within 24 hours at 37 ℃. Growth occurs at 15–40 ℃ (optimally at 25–40 ℃), at pH 6.0–8.0 (optimally at pH 7.0–7.5) and in the presence of 0–6% (w/v) NaCl (optimally at 0–4%). Positive results were obtained for catalase, alkaline phosphomonoesterase, esterase(C4 and C8), leucine-arylamidase, valine arylamidase and Naphthol-AS-BI-phosphoric acid, negative results were observed for oxidase, arginine dihydrolase, urease, gelatinase, lipase(C14), cystinol- arylamidase, trypsin, chymotrypsin, acid phosphomonoesterase, α-galactosidase, β-galactosidase, β-glucuronidase, α-glucosidase, β-glucosidase, N-acetyl-β-glucosaminase, α-mannosidase and β-fucosidase. In the API 20NE system, assimilation occurred on L-arabinose, D-mannose, N-acetyl glucosamine, D-maltose, gluconate, decanoic acid, malic acid, citric acid and phenylacetic acid. In the API 50CH system, acids are produced from glucose, furctoseribose, N-acetylglucosamine, esculin, maltose, starch; are weakly produced from arbutin; and are not produced from glycerinum, erythrose, D-arabinose, L-arabinose, ribose, D-xylose, L-xylose, adonitol, β-methyl-D-xyloside, galactose, mannose, sorbose, rhamnose, dulcitol, inositol, mannitol, sorbitol, α-metyl-D-mannosidase, α-metyl-D-glucoside, amygdalin, salicoside, cellobiose, lactose, melibiose, sucrose, trehalose, inulin, melezitose, raffinose, glycogen, xylitol, geranyl, D-turanose, D-lyxose, D-tagatose, D-fucose, L-fucose, D-arabitol, L-arabitol, gluconat, 2-keto-gluconate, 5-keto-gluconate. The predominant fatty acids were identified as C12:0, C16:0 N alcohol, C16:0, C18:1 ω6c, and Summed Feature 3. Polar lipids include DPG, PG, and PC.
The type strain, CAAS 2-6T (= GDMCC 1.3951T = KCTC 8156T = JCM 36321T), was isolated from Chang'an Landfill in the Longquan Mountains, China. The DNA G + C content of the type strain is 44.41 mol%. The GenBank accession numbers for the draft genome assembly and 16S rRNA gene sequences of strain Acinetobacter lentus CAAS 2-6T are JAQIHG000000000 and OQ110573 respectively.