Ferruginibacter albus sp. nov., isolated from a mountain soil, and Mucilaginibacter robiniae sp. nov., isolated from a black locust flower, Robinia pseudoacacia

Two bacterial strains, designated KIS38-8T and F39-2T, were isolated from a mountain soil sample and a black locust flower (Robinia pseudoacacia) in Republic of Korea, respectively. The phylogenetic tree based on 16S rRNA gene sequences showed that strain KIS38-8T was classified into the genus Ferruginibacter with the highest sequence similarity to Ferruginibacter lapsinanis HU1-HG42T (96.6 %), and strain F39-2T was grouped into the genus Mucilaginibacter with the highest sequence similarity to Mucilaginibacter daejeonensis Jip 10T (97.6 %). Orthologous average nucleotide identity and digital DNA–DNA hybridization values between strain KIS38-8T and closely related Ferruginibacter strains were less than 72 and 19 %, respectively, while those values between strain F39-2T and closely related Mucilaginibacter strains were less than 73 and 21 %, respectively. The DNA G+C contents of strain KIS38-8T and F39-2T were 36.4 and 41.4 mol%, respectively. On the basis of the phenotypic and genotypic evidence, strains KIS38-8T and F39-2T are considered to represent novel species of the genus Ferruginibacter and Mucilaginibacter , respectively, for which the names Ferruginibacter albus sp. nov. (type strain KIS38-8T=KACC 17328T=NBRC 113101T) and Mucilaginibacter robiniae sp. nov. (type strain F39-2T=KACC 19733T=JCM 33062T) have been proposed.

Mucilaginibacter aquatilis sp. nov., Mucilaginibacter arboris sp. nov., and Mucilaginibacter ginkgonis sp. nov., novel bacteria isolated from freshwater and tree bark

Three Gram-stain-negative, strictly aerobic, non-motile and rod-shaped bacterial strains, designated as HME9299^T, HMF7410^T and HMF7856^T, were isolated from freshwater and tree bark collected in Yong-in, Republic of Korea. Strains HME9299^T, HMF7410^T and HMF7856^T exhibited the highest 16S rRNA gene sequence similarities of 97.2, 94.4 and 96.4 % to Mucilaginibacter daejeonensis Jip 10^T, Mucilaginibacter terrae CCM 8645^T and Mucilaginibacter phyllosphaerae PP-F2F-G21^T, respectively. Among themselves, the values were 94.1-95.7 %. Phylogenetic analysis of the 16S rRNA gene sequences of the three isolates revealed that they belonged to the genus Mucilaginibacter within the family Sphingobacteriaceae. The predominant fatty acids of three strains were summed feature 3 (comprising C_16 : 1  ω7c and/or C_16 : 1  ω6c) and iso-C_15 : 0. Strain HME9299^T contained a relatively large amount of C_16 : 1  ω5c. The predominant respiratory quinone was menaquinone-7. The genome sizes of strains HME9299^T, HMF7410^T and HMF7856^T were 4.33, 4.16 and 3.68 Mbp, respectively, and their DNA G+C contents were 41.6, 38.4 and 43.9 mol%, respectively. Based on the results of the phenotypic, genotypic, chemotaxonomic and phylogenetic investigation, three novel species, Mucilaginibacter aquatilis sp. nov, Mucilaginibacter arboris sp. nov. and Mucilaginibacter ginkgonis sp. nov., are proposed. The type strains are HME9299^T (=KCTC 42122^T=DSM 29146^T), HMF7410^T (=KCTC 62464^T=NBRC 113227^T) and HMF7856^T (=KCTC 72782^T=NBRC 114275^T), respectively.

Bacterial response to sharp geochemical gradients caused by acid mine drainage intrusion in a terrace: Relevance of C, N, and S cycling and metal resistance

A unique terrace with sharp gradient of environmental conditions was selected to study the microbial response and survival strategies to the extreme environments introduced by acid mine drainage (AMD) contamination. A combination of geochemical analyses, metagenomic sequencing, ex-situ microcosm setups, and statistical analyses were used to investigate the environment-microbe interactions. The microbial communities and metabolic potentials along the terrace were studied by focusing on the genes associated with important biogeochemical processes (i.e., C, N, S cycling and metal resistance). Results show that the variations of geochemical parameters substantially shaped the indigenous microbial communities. Sharp environmental gradients also impacted the microbial metabolic potentials, especially for C, N, and S cycling. Although the relative abundances of carbon fixing genes did not significantly vary along the environmental gradients, the taxa for carbon fixation varied significantly in more contaminated fields versus less contaminated fields, indicating the effects of AMD contamination on the autotrophic microbial communities. AMD input also influenced the N cycling, especially for nitrogen fixation and dissimilatory nitrate reduction to ammonium (DNRA). In addition, ex situ experiments were undertaken to evaluate the effects of AMD contamination on nitrogen fixation rates. Random Forest (RF) analysis indicated that nitrate, pH, total N, TOC exhibited positive correlations with the rates of nitrogen fixation while total Fe, Fe(III), and sulfate showed negative effects. Two co-occurrence networks at taxonomic and genomic levels indicated that geochemical parameters such as pH, TOC, total N, total S, and total Fe substantially influenced the innate microbial communities and their metabolic potentials. The current study provides an understanding for microbial response to AMD contamination and lays the foundation for future potential AMD bioremediation.

Mucilaginibacter hurinus sp. nov., isolated from briquette warehouse soil

A novel bacterial strain, designated ZR32^T, was isolated from briquette warehouse soil in Ulsan (Korea). The strain was aerobic, showing pink-colored colonies on R2A agar. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain ZR32^T was closely related to Mucilaginibacter soli R9-65^T (97.0%), Mucilaginibacter gynuensis YC7003^T (96.9%), and Mucilaginibacter lutimaris BR-3^T (96.8%). The values of DNA-DNA relatedness related two highest strains M. soli R9-65^T and M. gynuensis YC7003^T were 31.2 ± 6.9% and 19.7 ± 0.3%, respectively. Its genome size was 3.9 Mb, comprising 3402 predicted genes. The DNA G+C content of strain ZR32^T was 43.0 mol%. The major cellular fatty acids (> 5% of total) were summed feature 3 (C_16:1ω6c and/or C_16:1ω7c), C_16:0, C_16:1ω5c, iso-C_15:0, iso-C_17:0 3-OH, and C_17:1ω9c. The major respiratory quinine was menaquinone-7 (MK-7). The major polar lipids were phosphatidylethanolamine, two unidentified phospholipids, one unidentified sphingolipid, and one unidentified polar lipid. Strain ZR32^T showed distinctive characteristics such as the temperature and pH for growth ranges, being positive for β-glucosidase, salicin production, negative for N-acetyl-glucosamine assimilation, being resistant to carbenicillin and piperacillin to related species. On the basis of phenotypic, chemotaxonomic, and phylogenetic data, strain ZR32^T represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter hurinus sp. nov. is proposed. The type strain is ZR32^T (= KCTC 62193 = CCTCC AB 2017285).

Pigments from Soil Bacteria and Their Therapeutic Properties: A Mini Review

Advancement in research on dyes obtained from natural sources e.g., plants, animals, insects and micro-organisms is widening the application of natural dyes in various fields. The natural dyes substituted their synthetic analogs at the beginning of twentieth century due to their improved quality, value, ease of production, ease of dyeing and some other factors. This era of dominance ended soon when toxic effects of synthetic dyes were reported. In the last few decades, pigments from micro-organisms especially soil derived bacteria is replacing dyes from other natural sources because of the increasing demand for safe, non-toxic, and biodegradable natural product. Apart from application in agriculture practices, cosmetics, textile, food and paper industries, bacterial pigments have additional biological activities e.g., anti-tumor, anti-fungal, anti-bacterial, immunosuppressive anti-viral, and many more which make them a potential candidate for pharmaceutical industry. Optimization of culture conditions and fermentation medium is the key strategies for large scale production of these natural dyes. An effort has been done to give an overview of pigments obtained from bacteria of soil origin, their dominance over dyes from other sources (natural and synthetic) and applications in the medical world in the underlying study.

Description of Hymenobacter daejeonensis sp. nov., isolated from grass soil, based on multilocus sequence analysis of the 16S rRNA gene, gyrB and tuf genes

A polyphasic taxonomic study was carried out on strains PB105^T and PB108 isolated from a grass soil in Korea. The cells of the strains were Gram-stain negative, non-spore-forming, non-motile, and rod-shaped. Comparative 16S rRNA gene sequence studies showed a clear affiliation of these strains with Bacteroidetes, which showed high pairwise sequence similarities with Hymenobacter algoricola VUG-A23a^T (99.2%), Hymenobacter fastidiosus VUG-A124a^T (97.4%), and Hymenobacter daecheongensis Dae14^T (96.9%). The phylogenetic analysis based on 16S rRNA gene sequences showed that the strains formed a clear phylogenetic lineage with the genus Hymenobacter. The major fatty acids were identified as C_15:0 iso, C_15:0 anteiso, C_16:1 ω5c, C_15:0 iso 3-OH, C_17:0 iso 3-OH, summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c/t), and summed feature 4 (C_17:1 anteiso B and/or C_17:1 iso I). The major cellular polar lipids were identified as phosphatidylethanolamine, an unidentified aminolipid, and two unidentified lipids. The respiratory quinone was identified as MK-7 and the genomic DNA G+C content was determined to be 64.5 mol% for strain PB105^T and 64.1 mol% for strain PB108. DNA-DNA hybridization value of type strain PB105^T with H. algoricola VUG-A23a^T was 32.3% (reciprocal 39.2). Based on the combined genotypic and phenotypic data, we propose that strains PB105^T and PB108 represent a novel species of the genus Hymenobacter, for which the name Hymenobacter daejeonensis sp. nov. is proposed. The type strain is PB105^T (= KCTC 52579^T = JCM 31885^T).