Arenimonas taoyuanensis sp. nov., a novel bacterium isolated from rice-field soil in China

Microbial diversity alteration reveals biomarkers of contamination in soil-river-lake continuum

Microbial communities inhabiting soil-water-sediment continuum in coastal areas provide important ecosystem services. Their adaptation in response to environmental stressors, particularly mitigating the impact of pollutants discharged from human activities, has been considered for the development of microbial biomonitoring tools, but their use is still in the infancy. Here, chemical and molecular (16S rRNA gene metabarcoding) approaches were combined in order to determine the impact of pollutants on microbial assemblages inhabiting the aquatic network of a soil-water-sediment continuum around the Ichkeul Lake (Tunisia), an area highly impacted by human activities. Samples were collected within the soil-river-lake continuum at three stations in dry (summer) and wet (winter) seasons. The contaminant pressure index (PI), which integrates Polycyclic aromatic hydrocarbons (PAHs), alkanes, Organochlorine pesticides (OCPs) and metal contents, and the microbial pressure index microgAMBI, based on bacterial community structure, showed significant correlation with contamination level and differences between seasons. The comparison of prokaryotic communities further revealed specific assemblages for soil, river and lake sediments. Correlation analyses identified potential "specialist" genera for the different compartments, whose abundances were correlated with the pollutant type found. Additionally, PICRUSt analysis revealed the metabolic potential for pollutant transformation or degradation of the identified "specialist" species, providing information to estimate the recovery capacity of the ecosystem. Such findings offer the possibility to define a relevant set of microbial indicators for assessing the effects of human activities on aquatic ecosystems. Microbial indicators, including the detection of "specialist" and sensitive taxa, and their functional capacity, might be useful, in combination with integrative microbial indices, to constitute accurate biomonitoring tools for the management and restoration of complex coastal aquatic systems.

Arenimonas fontis sp. nov., a bacterium isolated from Chukotka hot spring, Arctic region, Russia

A moderately thermophilic, neutrophilic, aerobic, Gram-negative bacterium, strain 3729k^T, was isolated from a thermal spring of the Chukotka Peninsula, Arctic region, Russia. It grew chemoorganoheterotrophically, utilizing proteinaceous substrates, including highly rigid keratins as well as various polysaccharides (glucomannan, locust bean gum, gum guar and xanthan gum). The major fatty acids of strain 3729k^T were iso-C_15 : 0 (60.9%), iso-C_17 : 0 (12.0%), C_16 : 0 (9.9%) and iso-C_16 : 0 (7.4%). Isoprenoid quinones were Q-8 (95%) and Q-9 (5%). The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine and three unidentified polar lipids. Strain 3729k^T was inhibited by chloramphenicol, neomycin, novobiocin, kanamycin, tetracycline, ampicillin and polymyxin B, but resistant to rifampicin, vancomycin and streptomycin. At the same time, strain 3729k^T inhibited growth of Micrococcus luteus and its genome possessed genes for antimicrobial activity against Gram-positive bacteria (a single putative bacteriocin and several secreted lysozymes and peptidoglycan lytic transglycosylases). The DNA G+C content was 69.8 mol%. 16S rRNA gene sequence-based phylogenetic analysis placed strain 3729k^T into a distinct species/genus-level branch within the family Xanthomonadaceae (Proteobacteria). Phylogenetic analysis of 120 conservative protein sequences of all Xanthomonadaceae with validly published names and publicly available genomic sequences supported a species-level position of strain 3729k^T within the genus Arenimonas. Pairwise ANI values between strain 3729k^T and other Arenimonas species were of 75-80 %, supporting the proposal of a novel species. Accordingly, Arenimonas fontis sp. nov., with the type strain 3729k^T (=VMK В-3232^Т=DSM 105847^T), was proposed.

Changes in microbial communities during the removal of natural and synthetic glucocorticoids in three types of river-based aquifer media

Glucocorticoids in sewage treatment plant effluent discharged into rivers could influence microbial community structure in river-based aquifer media and affect groundwater quality. The effect of representative natural and synthetic glucocorticoids, namely, hydrocortisone (CRL) and dexamethasone (DEX), on the microbial communities in three types of river-based aquifer media was evaluated. The aquifer media was taken from the Beijing Chaobai River (BJ), Hebei Hutuo River (HB), and Tianjin Duliujian River (TJ) and they exhibited different physicochemical and biological properties. The attenuation rates of CRL were 0.175, 0.119, and 0.096 day^-1 and for DEX were 0.222, 0.151, and 0.113 day^-1 in the media from BJ, HB, and TJ, respectively. All the attenuation rates followed first-order kinetics. The biodiversity decreased significantly with CRL and DEX amendment. The microbial community composition differed in relation to the type of aquifer media and glucocorticoids, especially for BJ at the phylum level. In BJ, the major bacterial genus was Bacillus and in HB it was Rhodobacter. However, in TJ, three bacterial genera (Methylophilus, Methylobacillus, and Methylotenera) and Candidatus_Nitrososphaera were predominant in the microflora. All these genera were able to degrade both CRL and DEX. Distance-based redundancy analysis revealed that total organic carbon (TOC), the type of glucocorticoid, and the pH were the main factors explaining the variations in microbial community composition.

Arenimonas terrae sp. nov., isolated from orchard soil

A Gram-stain-negative, strictly aerobic bacterial strain, designated R29^T, was isolated from orchard soil in Hwasun, South Korea. Cells were non-motile rods with catalase and oxidase activities. Growth was observed at 15-40 °C (optimum, 30 °C) and pH 7.0-9.0. Ubiquinone-8 was identified as the predominant isoprenoid quinone. Major polar lipids consisted of phosphatidylethanolamine, six phospholipids, an unidentified aminolipid and two unidentified polar lipids. Strain R29^T contained iso-C_15 : 0, iso-C_16 : 0 and summed feature 9 (comprising iso-C_17 : 1 ω9c/10-methyl-C_16 : 0) as major cellular fatty acids. The G+C content of the genomic DNA calculated from the whole-genome sequence was 69.8 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that R29^T was most closely related to Arenimonas daejeonensis T7-07^T and Arenimonas malthae CC-JY-1^T with sequence similarities of 98.0 and 96.9 %, respectively The average nucleotide identity and in silico DNA-DNA hybridization values between R29^T and the type strains of A. daejeonensis and A. malthae were 87.0 % and 31.6 % and 83.4 % and 26.1 %, respectively. On the basis of the phenotypic, chemotaxonomic and molecular features, strain R29^T represents a novel species of the genus Arenimonas, for which the name Arenimonas terrae sp. nov. is proposed. The type strain is R29^T (=KACC 19896^T=JCM 33216^T).

Responses and successions of sulfonamides, tetracyclines and fluoroquinolones resistance genes and bacterial community during the short-term storage of biogas residue and organic manure under the incubator and natural conditions

Biogas residue and organic manure are frequently used for crop planting. However, the evaluation of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and bacterial community before their applications to fields is still lacking. This study monitored the variations of bacteria resistant to sulfadiazine, tetracycline and norfloxacin, 57 resistance genes for sulfonamides, tetracyclines and fluoroquinolones as well as the bacterial community during the 28-day aerobic storage of biogas residue and organic manure by using viable plate counts, high-throughput qPCR and Illumina MiSeq sequencing methods. Then two storage conditions, incubator (25 °C) and natural environment, were used to assess the responses of ARB and ARGs to the environmental factors. Results showed that a total of 35 and 21 ARGs were detected in biogas residue and organic manure, respectively. ARB and ARGs were enriched up to 8.01-fold in biogas residue after the 28-day storage, but varied in a narrow range during the storage of organic manure. Compared with the incubator condition, the proliferation of ARB and ARGs in biogas residue under the natural condition was relatively inhibited by the varied and complicated environmental factors. However, we found that there was no significant difference of ARB and ARGs in organic manure between the incubator and natural conditions. Bacterial community was also shifted during the storage of biogas residue, especially Bacteroidetes_VC2.1_Bac22, Aequorivita, Luteimonas and Arenimonas. Network analysis revealed that the relationship in biogas residue was much more complicated than that in organic manure, which ultimately resulted in large successions of ARB and ARGs during the short-term storage of biogas residue. Therefore, we suggest that further measures should be taken before the application of biogas residue to fields.

Arenimonas caeni sp. nov., isolated from activated sludge

A Gram-stain-negative, non-spore-forming, motile and rod-shaped strain, z29^T, was isolated from the active sludge of a municipal wastewater treatment plant at Wuhu, Anhui, PR China. Phylogenetic analysis of the 16S rRNA gene revealed that strain z29^T is most closely related to the genus Arenimonas, showing the highest similarity to Arenimonas donghaensis HO3-R19^T (97.14 %), Arenimonas aestuarii S2-21^T (96.46 %), Arenimonas daejeonensis T7-07^T (96.24 %) and Arenimonas taoyuanensis YN2-31A^T (96.23 %). The only respiratory quinone of strain z29^T was ubiquinone 8 (Q-8). The major cellular fatty acids (>10 %) were iso-C15 : 0, iso-C16 : 0 and summed feature 9 (iso-C17 : 1ω9c and/or C16 : 010-methyl). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. The genomic DNA G+C content was 70.2 mol%. Genomic comparison between strain z29^T and Arenimonas donghaensis HO3-R19^T revealed 83.72 % average nucleotide identity. Based on the phenotypic and chemotaxonomic results together with phylogenetical analysis, strain z29^T is classified as representing a novel species of the genus Arenimonas, for which the name Arenimonas caeni sp. nov. is proposed. The type strain is z29^T (=JCM 32091^T=CCTCC AB 2017067^T).

Arenimonas halophila sp. nov., isolated from soil

A Gram-staining-negative, aerobic, non-motile, rod-shaped bacterium, designated CAU 1453^T, was isolated from soil and its taxonomic position was investigated using a polyphasic approach. Strain CAU 1453^T grew optimally at 30 °C and at pH 6.5 in the presence of 1 % (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that CAU 1453^T represented a member of the genus Arenimonas and was most closely related to Arenimonas donghaensis KACC 11381^T (97.2 % similarity). CAU 1453^T contained ubiquinone-8 (Q-8) as the predominant isoprenoid quinone and iso-C15 : 0 and iso-C16 : 0 as the major cellular fatty acids. The polar lipids consisted of diphosphatidylglycerol, a phosphoglycolipid, an aminophospholipid, two unidentified phospholipids and two unidentified glycolipids. CAU 1453^T showed low DNA-DNA relatedness with the most closely related strain, A. donghaensis KACC 11381^T (26.5 %). The DNA G+C content was 67.3 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, CAU 1453^T represents a novel species of the genus Arenimonas, for which the name Arenimonas halophila sp. nov. is proposed. The type strain is CAU 1453^T (=KCTC 62235^T=NBRC 113093^T).

Arenimonas soli sp. nov., isolated from saline-alkaline soil

A Gram-staining-negative, non-motile, aerobic bacterial strain, designated Y3L17T, was isolated from the saline-alkaline soil of a farmland, Hangjin Banner, Inner Mongolia, northern China. Y3L17T could grow at 15-45 °C (optimum 35 °C), pH 6.0-10.0 (optimum pH 8.0) and with 0-4 % (w/v) NaCl (optimum 0 %). The results of phylogenetic analysis based on the 16S rRNA gene and gyrB gene sequences revealed that Y3L17T tightly clustered with strains of members of the genus Arenimonas, sharing the highest 16S rRNA gene similarities with Arenimonas aestuarii S2-21T (99.5 %) and Arenimonas donghaensis HO3-R19T (98.2 %), and lower similarities (<97 %) with all the other type strains of species of this genus. However, Y3L17T shared only 92.62 % gyrB gene similarities with A. aestuarii S2-21T. The DNA-DNA hybridization values of Y3L17T with A. aestuariiS2-21T and A. donghaensis HO3-R19T were 20.1±2.5 and 18.2±3.2 %, respectively. Y3L17T contained phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, five unknown phospholipids and one unknown lipid as the major polar lipids. Ubiquinone-8 (Q-8) was the predominant respiratory quinone, while iso-C15 : 0, iso-C17 : 0ω9c and iso-C11 : 0 3-OH were the major cellular fatty acids. Its genomic DNA G+C content was 65.4 mol%. On the basis of its phenotypic, phylogenetic and genotypic characteristics, Y3L17T represents a novel species within the genus Arenimonas, for which the name Arenimonas soli sp. nov. is proposed, the type strain is Y3L17T (=CGMCC 1.15905T =KCTC 52420T).