Isoptericola dokdonensis sp. nov., isolated from soil

Assessing hydrocarbon degradation capacity of Isoptericola peretonis sp. nov. and related species: a comparative study

Since the beginning of their production and use, fossil fuels have affected ecosystems, causing significant damage to their biodiversity. Bacterial bioremediation can provide solutions to this environmental problem. In this study, the new species Isoptericola peretonis sp. nov. 4D.3T has been characterized and compared to other closely related species in terms of hydrocarbon degradation and biosurfactant production by in vitro and in silico analyses. Biosurfactants play an important role in microbial hydrocarbon degradation by emulsifying hydrocarbons and making them accessible to the microbial degradation machinery. The tests performed showed positive results to a greater or lesser degree for all strains. In the synthesis of biosurfactants, all the strains tested showed biosurfactant activity in three complementary assays (CTAB, hemolysis and E24%) and rhamnolipid synthesis genes have been predicted in silico in the majority of Isoptericola strains. Regarding hydrocarbon degradation, all the Isoptericola strains analyzed presented putative genes responsible for the aerobic and anaerobic degradation of aromatic and alkane hydrocarbons. Overall, our results highlight the metabolic diversity and the biochemical robustness of the Isoptericola genus which is proposed to be of interest in the field of hydrocarbon bioremediation.

Isoptericola haloaureus sp. nov., a dimorphic actinobacterium isolated from mangrove sediments of southeast India, implicating biosaline agricultural significance through nitrogen fixation and salt tolerance genes

Strain MP-1014T, an obligate halophilic actinobacterium, was isolated from the mangrove soil of Thandavarayancholanganpettai, Tamil Nadu, India. A polyphasic approach was utilized to explore its phylogenetic position completely. The isolate was Gram-positive, filamentous, non-motile, and coccoid in older cultures. Ideal growth conditions were seen at 30 °C and pH 7.0, with 5% NaCl (W/V), and the DNA G + C content was 73.3%. The phylogenic analysis of this strain based upon 16S rRNA gene sequence revealed 97-99.8% similarity to the recognized species of the genus Isoptericola. Strain MP-1014T exhibits the highest similarity to I. sediminis JC619T (99.7%), I. chiayiensis KCTC19740T (98.9%), and subsequently to I. halotolerans KCTC19646T (98.6%), when compared with other members within the Isoptericola genus (< 98%). ANI scores of strain MP-1014T are 86.4%, 84.2%, and 81.5% and dDDH values are 59.7%, 53.6%, and 34.8% with I. sediminis JC619T, I. chiayiensis KCTC19740T and I. halotolerans KCTC19646T respectively. The major polar lipids of the strain MP-1014T were phosphatidylinositol, phosphatidylglycerol, diphosphotidylglycerol, two unknown phospholipids, and glycolipids. The predominant respiratory menaquinones were MK9 (H4) and MK9 (H2). The major fatty acids were anteiso-C15:0, anteiso-C17:0, iso-C14:0, C15:0, and C16:0. Also, initial genome analysis of the organism suggests it as a biostimulant for enhancing agriculture in saline environments. Based on phenotypic and genetic distinctiveness, the strain MP-1014 T represents the novel species of the genus Isoptericola assigned Isoptericola haloaureus sp. nov., is addressed by the strain MP-1014 T, given its phenotypic, phylogenetic, and hereditary uniqueness. The type strain is MP-1014T [(NCBI = OP672482.1 = GCA_036689775.1) ATCC = BAA 2646T; DSMZ = 29325T; MTCC = 13246T].

Isoptericola luteus sp. nov., a novel yellow bacterium isolated from soil

An aerobic, non-motile, Gram-stain-positive bacterium, designated strain NEAU-Y5T, was isolated from a soil sample collected from Northeast Agricultural University, Heilongjiang province. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NEAU-Y5T belonged to the genus and showed high 16S rRNA sequence similarity to Isoptericola variabilis (98.9 %), Isoptericola nanjingensis (98.9 %), Isoptericola cucumis (98.5 %), Isoptericola hypogeus (98.5 %), Isoptericola dokdonensis (98.5 %), Isoptericola jiangsuensis (98.3 %), and Isoptericola halalbus (98.1 %), followed by other members of the genus Isoptericola (<98 %), and phylogenetically clustered with I. dokdonensis and I. jiangsuensis. Strain NEAU-Y5T was found to grow at 4-40 °C (optimum, 28 °C), pH 6.0-12.0 (optimum, pH 7.0), and tolerated 0-6 % NaCl (w/v). The cell-wall peptidoglycan type was l-Lys-d-Asp. The whole-cell hydrolysates contained glucose, galactose, and ribose. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, and glucosamine unknown phospholipid. Major fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. The predominant menaquinone was MK-9(H4). The DNA G+C content was 73.4 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between strain NEAU-Y5T and the type strains of the genus Isoptericola ranged from 18.6 to 23.5 % and from 77.3 to 81.6 %, respectively. Based on morphological, physiological, chemotaxonomic, and phylogenetic data, as well as digital DNA-DNA hybridization and average nucleotide identity values, the novel strain NEAU-Y5T could be differentiated from its closest relatives. Therefore, the strain represents a novel species of the genus Isoptericola, for which the name Isoptericola luteus sp. nov. is proposed. The type strain is NEAU-Y5T (=CCTCC AA 2019087T=DSM 110637T).

Isoptericola croceus sp. nov., a novel actinobacterium isolated from saline-alkali soil

A novel actinomycete, designated strain q2^T, was isolated from the saline-alkaline soil, collected from Daqing, Heilongjiang province, China. The results of phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain q2^T belongs to the genus Isoptericola, and showed the highest sequence similarity to Isoptericola halotolerans KCTC 19046^T (98.48%) and Isoptericola chiayiensis KCTC 19740^T (98.13%), respectively. The average nucleotide identity values between strain q2^T and other members of the genus Isoptericola were lower than 95% recommended for distinguishing novel prokaryotic species. Cells of strain q2^T were Gram-staining-positive, aerobic, non-motile, rod-shaped and non-spore-forming. Colonies of strain q2^T were golden-yellow pigmented, tidy edged and smooth surfaced. Growth occurred at 15-37 °C (optimum, 29 °C), pH 7.0-10.0 (optimum, pH 8.0). The predominant respiratory quinones were MK-9(H₄) and MK-9(H₂). The main detected polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, and phosphatidylinositol mannoside. The peptidoglycan compositions were L-alanine, D-aspartic, L-glutamic acid and L-lysine (type A4α). The major cellular fatty acids (> 10%) were anteiso-C_15:0, iso-C_15:0, and anteiso-C_17:0. The G+C content of the genomic DNA was determined to be 69.7%. Based on the phenotypic, physiological, genotypic, and phylogenetic data, strain q2^T represents a novel species of the genus Isoptericola, for which the name Isoptericola croceus sp. nov. is proposed. The type strain is q2^T (= GDMCC 1.2923^T = KCTC 49759^T).

Genome information of the cellulolytic soil actinobacterium Isoptericola dokdonensis DS-3 and comparative genomic analysis of the genus Isoptericola

The actinobacterial group is regarded as a reservoir of biologically active natural products and hydrolytic enzymes with the potential for biomedical and industrial applications. Here, we present the complete genome sequence of Isoptericola dokdonensis DS-3 isolated from soil in Dokdo, small islets in the East Sea of Korea. This actinomycete harbors a large number of genes encoding carbohydrate-degrading enzymes, and its activity to degrade carboxymethyl cellulose into glucose was experimentally evaluated. Since the genus Isoptericola was proposed after reclassification based on phylogenetic analysis, strains of Isoptericola have been continuously isolated from diverse environments and the importance of this genus in the ecosystem has been suggested by recent culturomic or metagenomic studies. The phylogenic relationships of the genus tended to be closer among strains that had been isolated from similar habitats. By analyzing the properties of published genome sequences of seven defined species in the genus, a large number of genes for carbohydrate hydrolysis and utilization, as well as several biosynthetic gene clusters for secondary metabolites, were identified. Genomic information of I. dokdonensis DS-3 together with comparative analysis of the genomes of Isoptericola provides insights into understanding this actinobacterial group with a potential for industrial applications.

Isoptericola sediminis sp. nov., Isolated from Chilika Lagoon

A yellow-colored, Gram-stain-positive, rod shaped, non-motile bacterium, designated as strain JC619^T, was isolated from the sediment of Chilika lagoon, India. Strain JC619^T shows highest 16S rRNA gene sequence similarity (99.08%) with Isoptericola chiayiensis KCTC 19740^T followed by Isoptericola halotolerans KCTC 19046^T (98.6%) and other members of the genus Isoptericola (< 98%). NaCl is required for growth of strain JC619^T and tolerates up to 18% (w/v) and pH up to 10. Strain JC619^T grows optimally at temperature 30 °C, NaCl concentration of 3% (w/v), and at pH 7.5. The genome size of strain JC619^T is 3.2 Mb with G+C content of 73.0 mol%. ANI scores of strain JC619^T are 81.9% and 80.1% and dDDH values are 24.4% and 22.7% with I. chiayiensis KCTC 19740^T and I. halotolerans KCTC 19046^T, respectively. Respiratory quinones are MK-9(H4) and MK-9(H2). Predominant fatty acids (> 10%) are anteiso-C_15:0, iso-C_16:0, and iso-C_15:0. Major polar lipids of strain JC619^T are phosphatidylglycerol, phosphatidylinositolmannoside, diphosphatidylglycerol, and phosphatidylinositol. Strain JC619^T is catalase positive but cytochrome oxidase negative and reduces nitrate. The genomic distinction of strain JC619^T with its nearest related species of the genus Isoptericola is well supported with chemotaxonomic characteristics and differential physiological properties. Therefore, strain JC619^T represents a new species under the genus Isoptericola for which Isoptericola sediminis sp. nov. is proposed. Type strain is JC619^T (=KCTC 49244^T =NBRC 114063^T).

Isoptericola halalbus sp. nov., a halotolerant actinobacterium isolated from saline lake sediment

A novel Gram-stain-positive bacterium, designated CFH 91151^T, was isolated from sediment collected from a saline lake in Yuncheng, Shanxi Province, PR China. Cells of strain CFH 91151^T were rod-or v-shaped, aerobic, non-motile, non-spore-forming and halotolerant. Results of 16S rRNA gene sequence analysis revealed that strain CFH 91151^T was closely related to Isoptericola variabilis MX5^T and Isoptericola nanjingensis H17^T (98.7 and 98.4% sequence similarity, respectively). The strain grew at 4-45 °C, pH 5.0-9.0 and with 0-14.0 % (w/v) NaCl. Cells were positive for catalase, nitrate was not used and H₂S was not produced. Major cellular fatty acids were anteiso-C_15 : 0 (62.76 %), anteiso-C_17 : 0 (12.09 %) and iso-C_15 : 0 (9.46 %). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, two unidentified phospholipids and three unidentified glycolipids. The menaquinone was MK-9 (H4). The genome size was 4.10 Mbp with a G+C content of 72.4 mol%. The average amino acid identity (ANI) and in silico DNA-DNA hybridization (DDH) values between CFH 91151^T and the other species of the genus Isoptericola were found to be low (ANIm <87.19 %, ANIb <84.38 % and DDH <29.30 %). Based on physiological properties, chemotaxonomic characteristics and low ANI and DDH results, strain CFH 91151^T is considered to represent a novel species, for which the name Isoptericola halalbus sp. nov. is proposed. The type strain is CFH 91151^T (=DSM 105976^T=KCTC 49061^T).

A strategy for securing unique microbial resources – focusing on Dokdo islands-derived microbial resources

This review focuses on the state of research on the microbial resources of Dokdo, Korea, as a strategy for securing national microbial resources. In the Korean peninsula, studies aimed at securing microbial resources are carried out across diverse natural environments, especially in the Dokdo islands. Until 2017, a total of 61 novel microbial genera, species, or newly recorded strains have been reported. Among these, 10 new taxa have had their whole genome sequenced and published, in order to find novel useful genes. Additionally, there have been multiple reports of bacteria with novel characteristics, including promoting plant growth or inducing systemic resistance in plants, calcite-forming ability, electrical activation, and production of novel enzymes. Furthermore, fundamental studies on microbial communities help to secure and define microbial resources in the Dokdo islands. This study will propose several tactics, based on ecological principles, for securing more microbial resources to cope with the current increase in international competition for biological resources.

Isoptericola cucumis sp. nov., isolated from the root tissue of cucumber (Cucumis sativus)

A Gram-stain-positive, aerobic organism, showing an irregular cell morphology, was isolated from the root tissue of cucumber (Cucumis sativus) and investigated in detail for its taxonomic position. On the basis of the 16S rRNA gene sequence analysis, strain AP-38T was shown to be most closely related to Isoptericola variabilis (99.1 %) and Isoptericola nanjingensis (98.9 %). The 16S rRNA gene sequence similarity to all other species of the genus Isoptericola was ≤98.5 %. DNA-DNA relatedness to Isoptericola variablis DSM 10177T and Isoptericola nanjingensis DSM 24300T was 31(reciprocal 41 %) and 34 (reciprocal 34 %), respectively. The diagnostic diamino acid of the peptidoglycan was l-lysine. The quinone system contained predominantly menaquinones MK-9(H4) and MK-9(H2). In the polar lipid profile, major compounds were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two phosphatidylinositol mannosides. The polyamine pattern contained the major components spermidine and spermine and significant amounts of tyramine. In the fatty acid profile, anteiso-C15 : 0 and iso-C15 : 0 were present in major amounts. These data support the allocation of the strain to the genus Isoptericola. The results of physiological and biochemical characterization additionally provide phenotypic differentiation of strain AP-38T from I. variabilis and I. nanjingensis. AP-38T represents a novel species of the genus Isoptericola, for which we propose the name Isoptericola cucumis sp. nov., with AP-38T (= LMG 29223T=CCM 8653T) as the type strain.

Isoptericola nanjingensis sp. nov., a mineral-weathering bacterium

A Gram-positive-staining, non-motile, rod- or coccoid-shaped actinobacterium, designated strain H17T, was isolated from a soil sample from Nanjing, Jiangsu Province, PR China. The organism grew optimally at 30 °C, pH 7.0 and with 3 % NaCl (w/v). Strain H17T contained L-Lys-D-Asp as the cell-wall peptidoglycan type and galactose, xylose and mannose as the whole-cell sugars. The major fatty acids were anteiso-C15:0 and iso-C15:0. The total polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phospholipids, phosphatidylinositol, phosphoglycolipid, one unidentified glycolipid and one unidentified lipid. The menaquinone was MK9(H4). Mycolic acids were not detected. The DNA G+C content was 72.4 mol%. Phylogenetic analysis of this strain based on 16S rRNA gene sequences revealed 97.8-99.6 % similarity to recognized species of the genus Isoptericola. The low level of DNA-DNA relatedness to other species of the genus Isoptericola and the many phenotypic properties that distinguished strain H17T from recognized species of this genus demonstrated that isolate H17T should be classified as representing a novel species of the genus Isoptericola. The name Isoptericola nanjingensis sp. nov. is proposed for this novel species. The type strain is H17T (=DSM 24300T=CCTCC AB 2011005T).

Isoptericola jiangsuensis sp. nov., a chitin-degrading bacterium

A Gram-positive-staining, non-motile, rod- or coccoid-shaped bacterium, strain CLGT, was isolated from beach sand from Lianyungang, Jiangsu Province, PR China. The organism grew optimally at 30 °C and pH 7.0. Strain CLGT contained l-Lys–d-Asp as the peptidoglycan type and galactose, rhamnose and xylose as the whole-cell sugars. It contained anteiso-C15 : 0 and iso-C15 : 0 as the major fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phospholipid, phosphatidylinositol, three phosphoglycolipids and one unidentified lipid. The DNA G+C content was 70.3 mol%. The 16S rRNA gene sequence similarity of strain CLGT with Isoptericola dokdonensis DS-3T was 99.4 % but the DNA–DNA relatedness between strain CLGT and I. dokdonensis DS-3T was 58.7 %. There were also many phenotypic properties that distinguished strain CLGT from recognized species of the genus Isoptericola. The results showed that strain CLGT represents a novel species of the genus Isoptericola, for which the name Isoptericola jiangsuensis sp. nov. is proposed. The type strain is CLGT (=DSM 21863T=CCTCC AB208287T).

Luteimicrobium subarcticum gen. nov., sp. nov., a new member of the suborder Micrococcineae

A novel Gram-stain-positive bacterium, designated R19-04T, was isolated from a soil sample from Rishiri Island, Japan, and its taxonomic position was investigated by a polyphasic approach. Cells of strain R19-04T exhibited a rod–coccus cycle. The peptidoglycan type of the isolate was A4α; lysine was the diagnostic diamino acid. The predominant menaquinone was MK-8(H2) and the major fatty acid was anteiso-C15 : 0. The polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content was 72.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain R19-04T represented a novel member of the suborder Micrococcineae. Its nearest phylogenetic neighbours were the members of the genus Oerskovia, with 16S rRNA gene sequence similarity of 97.0–97.1 %. However, strain R19-04T was clearly distinguishable from members of the genus Oerskovia and phylogenetically related genera in terms of chemotaxonomic characteristics. On the basis of the chemotaxonomic and phylogenetic characteristics, a novel genus and species are proposed, Luteimicrobium subarcticum gen. nov., sp. nov. The type strain of Luteimicrobium subarcticum is R19-04T (=NBRC 105647T =DSM 22413T).