Molecular insight into endosulfan degradation by Ese protein from Arthrobacter: Evidence-based structural bioinformatics and quantum mechanical calculations.

Endosulfan is an organochlorine insecticide widely used for agricultural pest control. Many nations worldwide have restricted or completely banned it due to its extreme toxicity to fish and aquatic invertebrates. Arthrobacter sp. strain KW has the ability to degrade α, ß endosulfan and its intermediate metabolite endosulfate; this degradation is associated with Ese protein, a two-component flavin-dependent monooxygenase (TC-FDM). Employing in silico tools, we obtained the 3D model of Ese protein, and our results suggest that it belongs to the Luciferase Like Monooxygenase family (LLM). Docking studies showed that the residues V59, V315, D316, and T335 interact with α-endosulfan. The residues: V59, T60, V315, D316, and T335 are implicated in the interacting site with ß-endosulfan, and the residues: H17, V315, D316, T335, N364, and Q363 participate in the interaction with endosulfate. Topological analysis of the electron density by means of the Quantum Theory of Atoms in Molecules (QTAIM) and the Non-Covalent Interaction (NCI) index reveals that the Ese-ligands complexes are formed mainly by dispersive forces, where Cl atoms have a predominant role. As Ese is a monooxygenase member, we predict the homodimer formation. However, enzymatic studies must be developed to investigate the Ese protein's enzymatic and catalytic activity.

Arthrobacter horti sp. nov., isolated from mountain soil.

Gram-stain-positive, aerobic, rod-shaped strains, YJM1T and YJM12S, were isolated from Maebong Mountain, Dogok-dong, Gangnam-gu, Seoul, Republic of Korea. Strains YJM1T and YJM12S exhibited growth at 5-35 °C (optimum, 20-30 °C) and pH 6-9 (optimum, pH 7) and in 0-4 % (w/v) NaCl. Strains YJM1T and YJM12S showed highest 16S rRNA gene sequence similarity to the following members of the genus Arthrobacter: A. nanjingensis A33T (98.3 %/98.2 % similarity), A. woluwensis NBRC 107840T (98.2 %/98.1 %), A. humicola KV-653T (97.3 %), A. oryzae KV-651T (97.3 %), and A. globiformis NBRC 12137T (97.2 %). The strains grew well on Reasoner's 2A, nutrient, Mueller-Hinton, yeast-dextrose, and glucose-peptone-meat extract agars. The major polar lipids of strain YJM1T were phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylinositol. The primary respiratory quinone of strain YJM1T was MK-9(H2), and the major fatty acids of strains YJM1T and YJM12S were anteiso-C15 : 0, anteiso-C17 : 0, iso-C15 : 0, and iso-C16 : 0. The DNA G+C content, based on the whole genome sequence of strain YJM1T, was 68.3 mol%. Average nucleotide identity values and digital DNA-DNA hybridization values between strain YJM1T and the reference strains ranged from 75.0 to 92.7 % and from 21.0 to 65.3 %, respectively. Strain YJM1T exhibited antimicrobial activity against Bacillus subtilis and Escherichia coli. Considering the chemotaxonomic, phenotypic, genotypic, and phylogenetic results, we propose the strain YJM1T represents a novel species in the genus Arthrobacter and suggest the name Arthrobacter horti sp. nov. (type strain YJM1T=KACC 23300T=JCM 36483T).

Bacterial crude oil and polyaromatic hydrocarbon degraders from Kazakh oil fields as barley growth support.

Bacterial strains of the genera Arthrobacter, Bacillus, Dietzia, Kocuria, and Micrococcus were isolated from oil-contaminated soils of the Balgimbaev, Dossor, and Zaburunye oil fields in Kazakhstan. They were selected from 1376 isolated strains based on their unique ability to use crude oil and polyaromatic hydrocarbons (PAHs) as sole source of carbon and energy in growth experiments. The isolated strains degraded a wide range of aliphatic and aromatic components from crude oil to generate a total of 170 acid metabolites. Eight metabolites were detected during the degradation of anthracene and of phenanthrene, two of which led to the description of a new degradation pathway. The selected bacterial strains Arthrobacter bussei/agilis SBUG 2290, Bacillus atrophaeus SBUG 2291, Bacillus subtilis SBUG 2285, Dietzia kunjamensis SBUG 2289, Kocuria rosea SBUG 2287, Kocuria polaris SBUG 2288, and Micrococcus luteus SBUG 2286 promoted the growth of barley shoots and roots in oil-contaminated soil, demonstrating the enormous potential of isolatable and cultivable soil bacteria in soil remediation. KEY POINTS: • Special powerful bacterial strains as potential crude oil and PAH degraders. • Growth on crude oil or PAHs as sole source of carbon and energy. • Bacterial support of barley growth as resource for soil remediation.

Synthesis and characterization of faujasite zeolite membrane for selective enrichment of Arthrobacter sp. in synthetic wastewater.

This paper centers on the preparation and characterization of both a clay support and a faujasite zeolite membrane. Additionally, the study explores the development of bacterial media to assess the performance of these prepared membranes. The faujasite zeolite membrane was created using the hydrothermal method, involving the deposition of a faujasite layer to fine-tune the pore sizes of the clay support. The clay supports were crafted from clay which was sieved to particle size Φ ≤ 63 µm, and compacted with 3.0 wt.% activated carbon, then sintered at 1,000 °C. Distilled water fluxes revealed a decrease from 1,500 L m-2 h-1 to a minimum of 412 L m-2 h-1 after 180 min of filtration. Both membranes were characterized by XRF, XRD, FTIR, adsorption-desorption of nitrogen (N2), and SEM-EDS. PCR technique was used for the identification of the isolated Arthrobacter sp., and the retention of the bacteria on the clay support and the faujasite zeolite membrane were found to be 96 and 99%, respectively. The results showed that the faujasite zeolite membrane passed the clay support due to a narrow pore size of the faujasite zeolite membrane of 2.28 nm compared to 3.55 nm for the clay supports.

Infection or Contamination with Rothia, Kocuria, Arthrobacter and Pseudoglutamicibacter-a Retrospective Observational Study of Non-Micrococcus Micrococcaceae in the Clinic.

Rothia, Kocuria, Arthrobacter, and Pseudoglutamicibacter are bacterial species within the family Micrococcaeae. Knowledge of human infections due to these bacteria is limited. This study aimed to examine features of infections caused by non-Micrococcus Micrococcaeae (NMM). Findings of NMM from blood cultures and other sterile cultures from 2012 to 2021 were identified from the records of the Department of Clinical Microbiology in Region Skåne, Lund, Sweden. Medical records were retrospectively reviewed. True infection was defined as having signs of infection, no other more likely pathogen, and no other focal infection, together with two positive blood cultures or one positive blood culture and an intravascular device. A total of 197 patients with findings of NMM in blood cultures were included. Among adult patients with bacteremia, 29 patients (22%) were considered to have a true infection. Adults with true infection were significantly more likely to have malignancy (69%), leukopenia (62%), and treatment with chemotherapeutics (66%) compared to patients with contaminated samples (24%, 3%, and 8%, respectively) (P < 0.001). A total of 31 patients had findings of NMM in other sterile cultures, and infections were considered true in joints (n = 4), a pacemaker (n = 1), and peritoneal dialysis fluid (n = 1). Infections due to NMM occur but are rare. Growth of NMM in blood cultures should be suspected to be a true infection mainly in immunocompromised patients.

Arthrobacter mangrovi sp. nov., an actinobacterium isolated from the rhizosphere of a mangrove.

A novel actinobacterium, designated HIs16-36T, was isolated from the rhizosphere of a mangrove on Ishigaki Island, Okinawa, Japan, and its taxonomic position was investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain HIs16-36T was closely related to the members of the genus Arthrobacter. The highest 16S rRNA gene sequence similarity was observed with Arthrobacter crystallopoietes (98.5 %), followed by Arthrobacter globiformis (97.2 %). The peptidoglycan of strain HIs16-36T was of the A4α type, with lysine as the diagnostic diamino acid. The predominant isoprenoid quinone was MK-9(H2) and the major fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two glycolipids. These chemotaxonomic features corresponded to those of the genus Arthrobacter. Meanwhile, the differences in some phenotypic characteristics, along with the results of average nucleotide identity and digital DNA-DNA hybridization analyses, indicated that strain HIs16-36T should be distinguished from the recognized species of the genus Arthrobacter. Therefore, strain HIs16-36T represents a novel species of the genus Arthrobacter, for which the name Arthrobacter mangrovi sp. nov. is proposed. The type strain is HIs16-36T (=NBRC 112813T=TBRC 15750T).

Arthrobacter zhaoxinii sp. nov. and Arthrobacter jinronghuae sp. nov., isolated from Marmota himalayana.

Four yellow-coloured strains (zg-Y815T/zg-Y108 and zg-Y859T/zg-Y826) were isolated from the intestinal contents of Marmota himalayana and assigned to the 'Arthrobacter citreus group'. The four strains grew optimally on brain heart infusion agar with 5 % defibrinated sheep blood plate at 30 °C, pH 7.0 and with 0.5 % NaCl (w/v). Comparative analysis of their 16S rRNA genes indicated that the two strain pairs belong to the genus Arthrobacter, showing the highest similarity to Arthrobacter yangruifuii 785T (99.52 %), which was further confirmed by the 16S rRNA gene and genome-based phylogenetic analysis. The comparative genomic analysis [digital DNA-DNA hybridization, (dDDH) and average nucleotide identity (ANI)] proved that the four strains are two different species (zg-Y815T/zg-Y108, 71.7 %/96.8 %; zg-Y859T/zg-Y826, 87.3 %/98.5 %) and differ from other known species within the genus Arthrobacter (zg-Y815T, 19.6-32.3 %/77.2-88.0 %; zg-Y859T, 19.5-29.3 %/77.4-86.3 %). Strain pairs zg-Y815T/zg-Y108 and zg-Y859T/zg-Y826 had the same major cellular fatty acids (iso-C16 : 0 and anteiso-C15 : 0), with MK-8(H2) as their dominant respiratory quinone (70.6 and 61.7 %, respectively). The leading polar lipids were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylinositol. The detected amino acids and cell-wall sugars of the two new species were identical (amino acids: alanine, glutamic acid, and lysine; sugars: rhamnose, galactose, mannose, glucose, and ribose). According to the phylogenetic, phenotypic, and chemotaxonomic analyses, we concluded that the four new strains represented two different novel species in the genus Arthrobacter, for which the names Arthrobacter zhaoxinii sp. nov. (zg-Y815T= GDMCC 1.3494T = JCM 35821T) and Arthrobacter jinronghuae sp. nov. (zg-Y859T = GDMCC 1.3493T = JCM 35822T) are proposed.

Arthrobacter vasquezii sp. nov., isolated from a soil sample from Union Glacier, Antarctica.

A Gram-stain-positive, catalase-positive, non-motile bacteria, with a rod-coccus cycle (designated as EH-1B-1T) was isolated from a soil sample from Union Glacier in Ellsworth Mountains, Antarctica. Strain EH-1B-1T had an optimal growth temperature of 28 °C and grew at pH 7-10. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, C16 : 0 and anteiso-C17 : 0. The G+C content based on the whole genome sequence was 63.1 mol%. Strain EH-1B-1T was most closely related to members of the genus Arthrobacter, namely Arthrobacter subterraneus and Arthrobacter tumbae. The strain grew on tryptic soy agar, Reasoner's 2A agar, lysogeny broth agar and nutrient agar. The average nucleotide identity and digital DNA-DNA hybridization values between strain EH-1B-1T and its closest reference type strains ranged from 78 to 88 % and from 20.9 to 36.3 %, respectively. Based on phenotypic, chemotypic and genotypic evidence, it is proposed that strain EH-1B-1T represents a novel species of Arthrobacter, for which the name Arthrobacter vasquezii sp. nov. is proposed, with strain EH-1B-1T (RGM 3386T=LMG 32961T) as the type strain.

Arthrobacter caoxuetaonis sp. nov., Arthrobacter zhangbolii sp. nov. and Arthrobacter gengyunqii sp. nov., isolated from Marmota himalayana faeces from Qinghai-Tibet Plateau.

Six aerobic or facultative anaerobic, motile, Gram-stain-positive, catalase-positive and oxidase-negative strains (zg-Y453T, zg-Y324, zg-Y462T, zg-Y411, zg-Y809T and zg-Y786) were isolated from different faecal samples of Marmota himalayana from the Qinghai-Tibet Plateau. Pale yellow, round, raised and moist colonies appeared 48 h after incubation at 28 °C on brain-heart infusion plates supplemented with 5 % defibrinated sheep blood. According to the 16S rRNA gene sequence alignment, two strain pairs (zg-Y453T/zg-Y324 and zg-Y462T/zg-Y411) shared the highest similarities to Arthrobacter luteolus (99.5 and 99.2 %), and the other one (zg-Y809T/zg-Y786) to Arthrobacter citreus (99.5 %). Results of phylogenetic analysis based on the 16S rRNA gene and genome sequences showed that these six strains represented three separate species within the genus Arthrobacter. The average nucleotide identity and digital DNA-DNA hybridization values between the three novel type strains (zg-Y453T/zg-Y462T/zg-Y809T) and other known species in this genus were all below respective thresholds (70.2-81.5/19.6-24.2 %, 70.6-81.8/19.8-25.0 %, and 70.4-88.2/19.9-35.3 %). Although phylogenetically related, there were obvious chemotaxonomic and phenotypic differences: strain pair zg-Y462T/zg-Y411 had anteiso-C15 : 0 as the only major fatty acid; the three novel species had different dominant quinones, MK-8(H2) in strains zg-Y462T/zg-Y809T (74.8/81.1 %) and MK-8(H2)/MK-9(H2) (43.1/53.0 %) in zg-Y453T; similarly, the ability to reduce nitrate in strains zg-Y453T and zg-Y462T could differentiate them from zg-Y809T. All strains had diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol, but differed slightly in the types of unidentified glycolipids, phospholipids and lipids. Based on the results of these polyphasic taxonomic analyses, three novel species within the genus Arthrobacter are proposed, namely Arthrobacter caoxuetaonis sp. nov. (type strain, zg-Y453T=GDMCC 1.2809T=JCM 35173T), Arthrobacter zhangbolii sp. nov. (type strain, zg-Y462T=GDMCC 1.2880T=JCM 35170T) and Arthrobacter gengyunqii sp. nov. (type strain, zg-Y809T=GDMCC 1.2808T=JCM 35168T).

Metabolomics reveal metabolic variation caused by co-culture of Arthrobacter ureafaciens and Trichoderma harzianum and their impacts on wheat germination.

Arthrobacter ureafaciens DnL1-1 is a bacterium used for atrazine degradation, while Trichoderma harzianum LTR-2 is a widely used biocontrol fungus. In this study, a liquid co-cultivation of these two organisms was initially tested. The significant changes in the metabolome of fermentation liquors were investigated based on cultivation techniques (single-cultured and co-cultured DnL1-1 and LTR-2) using an UPLC-QTOF-MS in an untargeted metabolomic approach. Principle components analysis (PCA) and partial least squares discriminant analysis (PLS-DA) supervised modelling revealed modifications of the metabolic profiles in fermentation liquors as a function of interactions between different strains. Compared with pure-cultivation of DnL1-1, 51 compounds were altered during the cocultivation, with unique and significant differences in the abundance of organic nitrogen compounds (e.g. carnitine, acylcarnitine 4:0, acylcarnitine 5:0, 3-dehydroxycarnitine and O-acetyl-L-carnitine) and trans-zeatin riboside. Nevertheless, compared with pure-cultivation of LTR-2, the abundance of 157 compounds, including amino acids, soluble sugars, organic acids, indoles and derivatives, nucleosides, and others, changed significantly in the cocultivation. Among them, the concentration of tryptophan, which is a precursor to indoleacetic acid, indoleacetic acid, aspartic acid, and L-glutamic acid increased while that of most soluble sugars decreased upon cocultivation. The fermentation filtrates of co-cultivation of LTR-2 and DnL1-1 showed significant promoting effects on germination and radicle length of wheat. A subsequent experiment demonstrated synergistic effects of differential metabolites caused by co-cultivation of DnL1-1 and LTR-2 on wheat germination. Comprehensive metabolic profiling may provide valuable information on the effects of DnL1-1 and LTR-2 on wheat growth.

Characterization of Arthropeptide B, an Antifungal Cyclic Tetrapeptide from Arthrobacter humicola.

Disease suppressive composts are known, yet little information on the potential role of specific microbial antagonist within are available. Arthrobacter humicola isolate M9-1A has been obtained from a compost prepared from marine residues and peat moss. The bacterium is a non-filamentous actinomycete with antagonistic activity against plant pathogenic fungi and oomycetes sharing its ecological niche in agri-food microecosystems. Our objective was to identify and characterize compounds with antifungal activity produced by A. humicola M9-1A. Arthrobacter humicola culture filtrates were tested for antifungal activity in vitro and in vivo and a bioassay-guided approach was used to identify potential chemical determinants of its observed activity against molds. The filtrates reduced the development of lesions of Alternaria rot on tomatoes and the ethyl acetate extract inhibited growth of Alternaria alternata. A compound, arthropeptide B [cyclo-(L-Leu, L-Phe, L-Ala, L-Tyr)], was purified from the ethyl acetate extract of the bacterium. Arthropeptide B is a new chemical structure reported for the first time and has shown antifungal activity against A. alternata spore germination and mycelial growth.

First report of Arthrobacter woluwensis causing brown blotch disease on white button mushroom (Agaricus bisporus).

Agaricus bisporus is one of the most commonly grown edible fungi in the world. In December 2021, brown blotch disease (2% incidence) was observed on the cap of A. bisporus, growing in a mushroom cultivation base in Guangxi, China. Initially, brown blotches (1-1.3 cm) appeared on the cap of A. bisporus, which expanded gradually as the cap grew. After two days, the infection penetrated inner tissues of fruiting bodies, and blotches were dark brown. For the isolation of causative agent(s), internal tissue samples of the infected stipes (5×5×5 mm) were sterilized in 75% ethanol for 30 s, rinsed three times with sterile deionized water (SDW), then, mashed in the sterile 2 ml Eppendorf tubes, 1000 µl SDW was added and the suspension was diluted into seven concentrations (10-1~10-7). Each suspension (120 µl) was spread on Luria Bertani (LB) medium and incubated for 24 hours at 28 °C. Morphological examination of the isolates was referred to Liu et al (2022). The dominant single colonies were whitish-grayish, smooth, convex. The cells were Gram-positive, non-flagellated, nonmotile, no pods or endospores formed, and no fluorescent pigments production on King's B medium (Solarbio). Amplified 16S rRNA (1351 bp; OP740790) of five colonies using universal primers 27f/1492r (Liu et al., 2022), exhibited 99.26% identity with Arthrobacter (Ar.) woluwensis. The partial sequences of the ATP synthase subunit beta gene (atpD) (677 bp; OQ262957), RNA polymerase subunit beta gene (rpoB) (848 bp; OQ262958), preprotein translocase subunit SecY gene (secY) (859 bp; OQ262959) and elongation factor Tu gene (tuf) (831 bp; OQ262960) genes of colonies were amplified using the method of Liu et al (2018), also exhibited more than 99% similarities to Ar. woluwensis. The biochemical tests for isolates (n=3) were performed via bacterial micro-biochemical reaction tubes (Hangzhou Microbial Reagent Co., LTD), and the results showed the same biochemical characteristics as Ar. woluwensis (Positive for esculin hydrolysis, urea, gelatinase, catalase, sorbitol, gluconate, salicin and arginine. Negative for citrate, nitrate reduction and rhamnose) (Funke et al., 1996). The isolates were identified as Ar. woluwensis based on morphological characteristics, biochemical tests and phylogenetic analysis. Pathogenicity tests were performed with bacterial suspensions (1 × 109 CFU/ml) after growing for 36 h in LB Broth at 28 °C, 160 rpm. 30 µl bacterial suspension was added to the cap and tissue of young A. bisporus. SDW was added as a negative control. All treatments were incubated at 20 °C and 80-85% humidity. The experiment was repeated three times with five caps and five tissues of young A. bisporus each time. Brown blotches were observed on all the parts of the inoculated caps and tissues after 24 h of inoculation. At 48 h, the inoculated caps turned dark brown while the infected tissues changed from brown to black and expanded to the entire tissue block giving a severely rotten appearance and foul odor. This disease symptoms were similar to those observed in the original samples. There were no lesions in the control group. After the pathogenicity test, the pathogen was re-isolated from the infected caps and tissues based on morphological characteristics, 16S rRNA sequences, and biochemical results, fulfilling Koch's postulates. Arthrobacter spp. are very widely distributed in the environment (Kim et al., 2008). To date, two studies have confirmed Arthrobacter spp. as a pathogen of edible fungi (Bessette, 1984; Wang et al., 2019). However, this is the first report of Ar. woluwensis causing brown blotch disease on A. bisporus. Our finding could contribute to developing phytosanitary and control treatments for this disease.

Phytoremediation of PAH compounds by microbial communities in sodic soil.

The PAH degrading microbial consortium was collected from sodic soil of the nursery of Guru Jambheshwar University of Science and Technology, Hisar, Haryana (India). And the soil was artificially amended with phenanthrene and naphthalene to isolate the PAHs degrading microbial consortium. The diversity of microbial consortium was analyzed using the NGS (Next Generation Sequencing) based metagenomic approach. The result of diversity analysis showed species Tepidanaerobacter syntrophicus, Sphingomonas oliophenolica, Arthrobacter psychrochitinipnius, Bifidobacterium bombi, Nocardiodies islandensis, Rhodovibrio sodomensis, Thiorhodococus pfennigii, Aeromicrobium ponti, Steroidobacter dentrificans, Actinomaduria maheshkhaliensis, Dactylosporangium maewongense, Pelotomaculum isophthalicicum, and Nocardioides islandensis were present in the consortium. Moreover, Sphingomonas, Arthrobacter, Sphingobium, Azospirillium, Thirohodococcus, and Pelotomaculum were the prominent pollutant degrader genera in the microbial consortium. Since the bioremediation of these pollutants occurs with a significant reduction in toxicity, the study's perspective is to use this type of consortium for bioremediation of specifically contaminated soil.

The present work's novelty was to find the helpful microbial consortium for the bioremediation of toxic compounds such as naphthalene and phenanthrene. In this study, the degradation of such compounds was done by the various communities of genera like Bifidobacterium, Conexibacter, Sterodobacter, Rhodovibrio, Arthrobacter, Actinomadura, and Euzebya, which are rarely described in the earlier researches. Therefore, this study will enhance the quality of future research.

Arthrobacter rhizosphaerae sp. nov., isolated from wheat rhizosphere.

Gram-stain-positive, aerobic, non-spore-forming strains CCNWLXL 1-35T, CCNWLXL 12-2 and CCNWLXL 21-a, were isolated from wheat rhizosphere from Yangling, Shaanxi Province, China. Comparison of the 16S rRNA gene sequences showed that they belonged to the genus Arthrobacter and were closely related to Arthrobacter globiformis NBRC 12137T (97.95% similarity). Genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed these strains constituted a single species. The major fatty acids was anteiso-C15:0. The polar lipids consist of diphosphatidylglycerol, phsophatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and glycolipid. The predominant menaquinone was MK-9. The peptidoglycan type was A4α. Thus, these strains were classified as representing a novel species in the genus Arthrobacter, for which the name Arthrobacter rhizosphaerae sp. nov. is proposed. The type strain is CCNWLXL 1-35T (=JCM 34638T, =CCTCC AB 2021087T) and additional strains are CCNWLXL 12-2 (=JCM 35018, =CCTCC AB 2021546), CCNWLXL 21-a (=JCM 35019, =CCTCC AB 2021545).

Arthrobacter sunyaminii sp. nov. and Arthrobacter jiangjiafuii sp. nov., new members in the genus Arthrobacter.

Four novel bacterial strains (zg-ZUI122T/zg-ZUI10 and zg-ZUI227T/zg-ZUI100) were isolated from the intestinal contents of Marmota himalayana and characterized using a polyphasic approach. Cells were Gram-stain- and catalase-positive, urease- and oxidase-negative. Strains grew optimally at 28-30 °C, pH 7.0, with 0.5 % NaCl (w/v). A comparative analysis of 16S rRNA gene sequences revealed that strain pairs zg-ZUI122T/zg-ZUI10 and zg-ZUI227T/zg-ZUI100 belonged to the genus Arthrobacter and were most closely related to Arthrobacter citreus DSM 20133T, with similarities of 99.6 and 99.5 %, respectively. This was further confirmed by phylogenetic analyses based on the 16S rRNA gene and genome sequences. The digital DNA-DNA hybridization and average nucleotide identity values between the two new type strains (zg-ZUI122T and zg-ZUI227T) and other species in the genus Arthrobacter were 20.0-24.4/77.2-83.4% and 19.9-25.1/77.1-83.4%, all below the thresholds. The major cellular fatty acids detected in the two novel species included iso-C15 : 0 and anteiso-C15 : 0; the predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol. MK-8(H2) (77.3%) was the predominant respiratory quinone detected in strain zg-ZUI122T, while MK-8(H2) (53.7%) and MK-9(H2) (46.3%) were detected in strain zg-ZUI227T. The shared cell-wall amino acids detected in the two novel species were alanine, glutamic acid and lysine; the shared whole cell wall sugars consisted of galactose, mannose and ribose. All these analyses concluded that these four strains represent two different novel species in the genus Arthrobacter, for which the names Arthrobacter sunyaminii sp. nov. (zg-ZUI122T = GDMCC 1.2502T = KCTC 49677T) and Arthrobacter jiangjiafuii sp. nov. (zg-ZUI227T = GDMCC 1.2500T = KCTC 49676T) are proposed.

Arthrobacter polaris sp. nov., a new cold-adapted member of the family Micrococcaceae isolated from Antarctic fellfield soil.

An aerobic, Gram-stain-positive and non-spore-forming strain, designated C1-1T, was isolated from a fellfield soil sample collected from frost-sorted polygons on Jane Col, Signy Island, Maritime Antarctic. Cells with a size of 0.65-0.9×1.2-1.7 µm have a flagellar motile apparatus and exhibit a rod-coccus growth cycle. Optimal growth conditions were observed at 15-20 °C, pH 7.0 and NaCl concentration up to 0.5 % (w/v) in the medium. The 16S rRNA gene sequence of C1-1T showed the highest pairwise similarity of 98.77 % to Arthrobacter glacialis NBRC 113092T. Phylogenetic trees based on the 16S rRNA and whole-genome sequences revealed that strain C1-1T belongs to the genus Arthrobacter and is most closely related to members of the 'Arthrobacter psychrolactophilus group'. The G+C content of genomic DNA was 58.95 mol%. The original and orthologous average nucleotide identities between strain C1-1T and A. glacialis NBRC 113092T were 77.15 % and 77.38 %, respectively. The digital DNA-DNA relatedness values between strain C1-1T and A. glacialis NBRC 113092T was 21.6 %. The polar lipid profile was composed mainly of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and an unidentified glycolipid. The predominant cellular fatty acids were anteiso-C15 : 0 (75 %) and anteiso-C17 : 0 (15.2 %). Menaquinone MK-9(H2) (86.4 %) was the major respiratory quinone in strain C1-1T. The peptidoglycan type was determined as A3α (l-Lys-l-Ala3; A11.6). Based on all described phylogenetic, physiological and chemotaxonomic characteristics, we propose that strain C1-1T (=DSM 112353T=CCM 9148T) is the type strain of a novel species Arthrobacter polaris sp. nov.

Arthrobacter cavernae sp. nov., a novel actinobacterium isolated from sediment of karst cave.

A novel, Gram-stain-positive, aerobic, non-endospore-forming, non-motile and rod-shaped bacterium designated PO-11T was isolated from sediment of karst cave collected in Libo county, Guizhou Province, PR China. The isolate grew optimally on R2A agar at 25 °C, pH 8.0 and with 0.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that PO-11T belonged to the genus Arthrobacter and was most closely related to Arthrobacter methylotrophus TGAT (98.3 % sequence similarity), Arthrobacter alkaliphilus LC6T (97.7 %) and Arthrobacter ramosus CCM1646T (97.1 %). Genome sequencing revealed a genome size of 4 073 119 bp and the genomic DNA G+C content was 66.16 mol%. Its DNA-DNA relatedness values with A. methylotrophus TGAT, A. alkaliphilus LC6T and A. ramosus CCM1646T were 23.0, 22.9 and 23.2 %, respectively. The main fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The major respiratory quinone was MK-9(H2). The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, glycolipid, phosphatidylethanolamine, phosphatidylinositol and unidentified lipids. Thus, based on phylogenetic and phenotypic and chemotaxonomic data, strain PO-11T represents a novel species of the genus Arthrobacter, for which the name Arthrobacter cavernae sp. nov. is proposed. The type strain is strain PO-11T (=CCTCC AB 2021070T=LMG 32459T).

Bioremediation potential of hexavalent chromium-resistant Arthrobacter globiformis 151B: study of the uptake of cesium and other alkali ions.

Cesium (Cs+) enters environments largely because of global release into the environment from weapons testing and accidents such as Fukushima Daiichi and Chernobyl nuclear waste. Even at low concentrations, Cs+ is highly toxic to ecological receptors because of its physicochemical similarity to macronutrient potassium (K+). We investigated the uptake and accumulation of Cs+ by Arthrobacter globiformis strain 151B in reference to three similar alkali metal cations rubidium (Rb+), sodium (Na+), and potassium (K+). The impact of hexavalent chromium (Cr+6) as a co-contaminant was also evaluated. A. globiformis 151B accumulated Cs+ and Cr6+ in a time-dependent fashion. In contrast, the uptake and accumulation of Rb+ did not exhibit any trends. An exposure to Cs+, Rb+, and Cr+6 triggered a drastic increase in K+ and Na+ uptake by the bacterial cells. That was followed by the efflux of K+ and Na+, suggesting a Cs+ "substitution." Two-dimensional gel-electrophoresis of bacterial cell proteomes with the following mass-spectrometry of differentially expressed bands revealed that incubation of bacterial cells with Cs+ induced changes in the expression of proteins involved in the maintenance of cellular homeostasis and reactive oxygen species removal. The ability of A. globiformis 151B to mediate the uptake and accumulation of cesium and hexavalent chromium suggests that it possesses wide-range bioremediation potential.

Construction of automated high-throughput screening method for finding efficient 3-ketosteroid 1,2-dehydrogenating strains.

Dehydrogenation reaction at C1(2) positions is typical and representative of industrial production of steroid drugs. Anti-inflammatory activity can be doubled when the nucleus of the anti-inflammatory steroid hormone drug introduces double bonds at the C1(2) positions. Arthrobacter simplex is currently the most widely studied and used strain for C1(2) dehydrogenation. Therefore, breeding Arthrobacter simplex with high-efficiency dehydrogenation ability is of great significance. In order to obtain high-efficiency strains, the research proposed a new screening strategy based on image process technique: firstly, a color reaction between 2,4-dinitrophenylhydrazine (DNPH) and 9α-hydroxyandrost-4-ene-3,17-dione (9α-OH-AD) was established to characterize the dehydrogenation ability of the strain; secondly, the color data of strains mutated by atmospheric and room temperature plasma (ARTP) in the "color reaction" were automated and analyzed for dehydrogenation ability prediction using optimized support vector machine model. Result showed that the prediction accuracy reached as high as 96% in verification experiments. After a series of mutagenesis, including breaking the bottleneck of a single mutation in ARTP, the dominant strain ARLU-146 was finally obtained from 5168 strains. Its initial conversion rate was 0.8059 g/L/h, with a conversion of 94.41% at 24 h, compared to the original strain ASP which increased the transformation rate by more than 10%. By further process optimization, a high conversion (94.34% within 20 h) with high substrate (85 g/L cortisone acetate) was achieved. According to literature research, it is the highest conversion at this substrate concentration. KEY POINTS: • A high-throughput screening method was developed by using image processing and machine learning technique. • "Mutation bottleneck" of single ARTP mutagenesis was surpassed by complex mutagenesis. • A high substrate (85 g/L CA) and high transformation rate craft (94.34% within 20 h) were built.

Arthrobacter terrae sp. nov., a psychrophilic actinobacterium with multi copies of capA gene isolated from Antarctic soil.

A Gram-staining-positive, non-spore-forming, non-flagellated, ellipsoidal, strain Z1-20 T belonging to the genus Arthrobacter was isolated from a soil sample collected from the Zhongshan station, Antarctic. Phylogenetic analysis of the 16S rRNA gene sequences and phylogenetic analysis revealed that strain Z1-20 T formed a unique single cluster in the genus Arthrobacter and shared high 16S rRNA sequence similarities of 97.1% and 96.9% with A. glacialis HLT2-12-2 T and A. psychrochitiniphilus GP3T, respectively. Values of Digital DNA-DNA hybridization (dDDH) between strain Z1-20 T against A. glacialis HLT2-12-2 T and A. psychrochitiniphilus GP3T were 20.3% and 13.8%, respectively. Average nucleotide identity (ANI) score between strain Z1-20 T against A. glacialis HLT2-12-2 T and A. psychrochitiniphilus GP3T were 72.5% and 72.1%, respectively. Genes for the synthesis of the osmoprotectant glycine betaine and higher copies of capA gene encoding cold shock protein were found in genome of Z1-20 T that may help Z1-20 T in cold-adaptation. Strain Z1-20 T comprised lysine as the diagnostic diamino acid. Based on the results of phylogenetic, phenotypic and chemotaxonomic features, strain Z1-20 T represents a novel species of a novel taxon of genus Arthrobacter, for which the name Arthrobacter terrae gen. nov., sp. nov. is proposed.