Leucobacter weissii sp. nov., an isolate from activated sludge once described as first representative of the peptidoglycan variation B2δ, and emended description of the genus Leucobacter

Leucobacter tenebrionis sp. nov., isolated from the gut of Tenebrio molitor

A novel Gram-stain-positive bacterium, designated NB10T, was isolated from the gut of Tenebrio molitor. The isolate was rod-shaped, aerobic, non-motile and non-spore-forming. Colonies of strain NB10T were light yellow, circular and smooth. Phylogenetic analysis based on 16S rRNA gene sequence comparisons indicated that the isolate was related to the genus Leucobacter. Its closest relatives were Leucobacter holotrichiae T14T (97.8 % 16S rRNA gene sequence similarity), Leucobacter zeae CC-MF41T (97.0%) and Leucobacter salsicius M1-8T (96.4%). The DNA G+C content of strain NB10T was 68.8 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization values among strain NB10T and the selected Leucobacter species were ≤83.8 % (ANI-blast), 87.6 % (ANI-MUMmer) and 29.6%, which were below the recommended cutoff values for species delineation. The predominant cellular fatty acids were anteiso-C15 : 0 (39.0%), anteiso-C17 : 0 (35.5%) and iso-C16 : 0 (17.0%). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and glycolipids. The predominant respiratory quinones were MK-11 and MK-10. The cell wall amino acids were Gly, Glu, Tr, Ala, and DAB. Based on these phylogenetic and phenotypic results, strain NB10T can be clearly distinguished from all of the recognized species of the genus Leucobacter and is considered to represent a novel species of that genus. The name Leucobacter tenebrionis sp. nov. is proposed, with the type strain NB10T (=MCCC 1K07072T=KCTC 49728T).

Leucobacter allii sp. nov. and Leucobacter rhizosphaerae sp. nov., isolated from rhizospheres of onion and garlic, respectively

Three bacterial strains, H21R-40^T and H21R-36 from garlic (Allium sativum) and H25R-14^T from onion (Allium cepa), were isolated from plant rhizospheres sampled in the Republic of Korea. Results of 16S rRNA gene sequence analysis revealed the highest sequence similarity of strain H21R-40^T to Leucobacter celer subsp. astrifaciens CBX151^T (97.3 %) and Leucobacter triazinivorans JW-1^T (97.2 %), and strain H25R-14^T to Leucobacter insecticola HDW9B^T (98.8 %) and Leucobacter humi Re6^T (98.4 %), while the sequence similarity between strains H21R-40^T and H21R-36 was 99.8 %. According to the phylogenomic tree, strains H21R-40^T with H21R-36 formed an independent clade separable from other Leucobacter species within the genus Leucobacter and strain H25R-14^T clustered with Leucobacter insecticola HDW9B^T, Leucobacter coleopterorum HDW9A^T and Leucobacter viscericola HDW9C^T. Strains H21R-40^T and H21R-36 had orthologous average nucleotide identity (OrthoANI) and digital DNA-DNA hybridization (dDDH) values (98.1 % and 86.9 %, respectively) higher than the threshold ranges for species delineation (95-96 % and 70 %, respectively). The OrthoANI and dDDH values between two strains (H21R-40^T and H25R-14^T) and the type strains of species of the genus Leucobacter were lower than 81 and 24 %, respectively. The peptidoglycan type of three strains was type B1. The major menaquinones and major polar lipids of the strains were MK-11 and MK-10, and diphosphatidylglycerol, phatidylglycerol and an unidentified glycolipid, respectively. The major fatty acids (more than 10 % of the total fatty acids) of strains H21R-40^T and H21R-36 were anteiso-C_15 : 0, anteiso-C_17 : 0 and iso-C_16 : 0, and those of strain H25R-14^T were anteiso-C_15 : 0 and iso-C_16 : 0. The phenotypic, chemotaxonomic and genotypic data obtained in this study showed that the strains represent two novel species of the genus Leucobacter, named Leucobacter allii sp. nov. (H21R-40^T and H21R-36) and Leucobacter rhizosphaerae sp. nov. (H25R-14^T). The respective type strains are H21R-40^T (=DSM 114348^T=JCM 35241^T=KACC 21839^T=NBRC 115481^T) and H25R-14^T (=DSM 114346^T=JCM 35239^T=KACC 21837^T=NBRC 115479^T).

Keystone microbial taxa organize micropollutant-related modules shaping the microbial community structure in estuarine sediments

The fluctuation of environmental conditions drives the structure of microbial communities in estuaries, highly dynamic ecosystems. Microorganisms inhabiting estuarine sediments play a key role in ecosystem functioning. They are well adapted to the changing conditions, also threatened by the presence of pollutants. In order to determine the environmental characteristics driving the organization of the microbial assemblages, we conducted a seasonal survey along the Adour Estuary (Bay of Biscay, France) using 16S rRNA gene Illumina sequencing. Microbial diversity data were combined with a set of chemical analyses targeting metals and pharmaceuticals. Microbial communities were largely dominated by Proteobacteria (41 %) and Bacteroidota (32 %), showing a strong organization according to season, with an important shift in winter. The composition of microbial communities showed spatial distribution according to three main areas (upstream, middle, and downstream estuary) revealing the influence of the Adour River. Further analyses indicated that the microbial community was influenced by biogeochemical parameters (C_org/N_org and δ¹³C) and micropollutants, including metals (As, Cu, Mn, Sn, Ti, and Zn) and pharmaceuticals (norfloxacin, oxolinic acid and trimethoprim). Network analysis revealed specific modules, organized around keystone taxa, linked to a pollutant type, providing information of paramount importance to understand the microbial ecology in estuarine ecosystems.

Leucobacter chinensis sp. nov., with plant growth-promoting potential isolated from field soil after seven-years continuous maize cropping

A novel Gram-stain-positive, aerobic, non-motile and rod-shaped bacterium, designated strain NC76-1^T, was isolated from soil from a field that had undergone seven years continuous maize cropping from Liuba town located in Zhangye city, Gansu province, PR China. Colonies of strain NC76-1^T were white, opaque and circular with a convex shape. The isolate was found to be able to grow at 10-40 °C (optimum 30 °C), pH 6.0 to 12.0 (optimum 7.0-8.0) and with 0-5.0 % (w/v) NaCl (optimum 0%). On the basis of the results of 16S rRNA gene sequence analysis, the strain fell within the clade of the genus Leucobacter, showing the highest sequence similarities with Leucobacter iarius 40^T (97.4%), Leucobacter aridicollis CIP 108388^T (97.0%), Leucobacter chromiireducens subsp. solipictus TAN 31504^T (96.7%) and Leucobacter denitrificans M1T8B10^T (96.7%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between NC76-1^T and its closest relatives, L. iarius 40^T, L. aridicollis CIP 108388^T, L. chromiireducens subsp. solipictus TAN 31504^T and L. denitrificans M1T8B10^T were ≤73.5 % and 20.3%, respectively. The genomic DNA G+C content of NC76-1^T was 61.5 mol%. It presented MK-11 as the predominant menaquinone. The major cellular fatty acids were anteiso-C_15 : 0 (49.2 %) and iso-C_16 : 0 (35.7%). The major polar lipids were found to be diphosphatidyglycerol, phosphatidylglycerol, phosphatidylethanolamine, aminoglycolipid, five glycolipid and one unidentified lipids. The cell wall amino acids were 2,4-diaminobutyric acid, alanine, glutamic acid, glycine and threonine. On the basis of the phylogenetic, phenotypic and chemotaxonomic characteristics, strain NC76-1^T is concluded to represent a novel species within the genus Leucobacter, for which the name Leucobacter chinensis sp. nov. is proposed. The type strain is NC76-1^T (GDMCC 1.2286^T= JCM 34651^T).

Leucobacter soli sp. nov., from soil amended with humic acid

A Gram-positive, non-spore-forming actinobacterium (IMT-300^T) was isolated from soil amended with humic acid in Malvern, AL, USA. This soil has been used for 50+years for the cultivation of earthworms for use as fish bait. Based on 16S rRNA gene sequence similarity studies, strain IMT-300^T was shown to belong to the genus Leucobacter and was closely related to the type strain of 'Leucobacter margaritiformis' L1^T (97.8%). Similarity to all other type strains of Leucobacter species was lower than 97.2 %. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the IMT-300^T genome assembly and those of the closest relative Leucobacter type strain were 81.4 and 23.3 % (Leucobacter chironomi), respectively. The peptidoglycan of strain IMT-300^T contained l-2,4-diaminobutyric acid as the diagnostic diamino acid. In addition, glycine, d- and l-alanine and d-glutamic acid were found. The peptidoglycan type represents a variant of B2δ (B11). The major quinones were menaquinones MK-10 and MK-11. The polar lipid profile consisted of the major lipids diphosphatidylglycerol, phosphatidylglycerol and moderate to minor amounts of two unidentified phospholipids, two unidentified glycolipids and an unidentified aminophospholipid. The polyamine pattern contained major amounts of spermidine and spermine. Strain IMT-300^T contained the major fatty acids C_15 : 0 anteiso, C_16 : 0 iso and C_17 : 0 anteiso, like other members of the genus Leucobacter. The results of ANI and dDDH analyses and physiological and biochemical tests allowed a genotypic and phenotypic differentiation of strain IMT-300^T from the most closely related Leucobacter species. Strain IMT-300^T represents a novel Leucobacter species, for which we propose the name Leucobacter soli sp. nov., with the type strain IMT-300^T (CIP 111803^T=DSM 110505^T=CCM 9020^T=LMG 31600^T).

Streptomonospora litoralis sp. nov., a halophilic thiopeptides producer isolated from sand collected at Cuxhaven beach

Strain M2^T was isolated from the beach of Cuxhaven, Wadden Sea, Germany, in course of a program to attain new producers of bioactive natural products. Strain M2^T produces litoralimycin and sulfomycin-type thiopeptides. Bioinformatic analysis revealed a potential biosynthetic gene cluster encoding for the M2^T thiopeptides. The strain is Gram-stain-positive, rod shaped, non-motile, spore forming, showing a yellow colony color and forms extensively branched substrate mycelium and aerial hyphae. Inferred from the 16S rRNA gene phylogeny strain M2^T affiliates with the genus Streptomonospora. It shows 96.6% 16S rRNA gene sequence similarity to the type species Streptomonospora salina DSM 44593 ^T and forms a distinct branch with Streptomonospora sediminis DSM 45723 ^T with 97.0% 16S rRNA gene sequence similarity. Genome-based phylogenetic analysis revealed that M2^T is closely related to Streptomonospora alba YIM 90003 ^T with a digital DNA-DNA hybridisation (dDDH) value of 26.6%. The predominant menaquinones of M2^T are MK-10(H₆), MK-10(H₈), and MK-11(H₆) (> 10%). Major cellular fatty acids are iso-C_16:0, anteiso C_17:0 and C_18:0 10-methyl. The polar lipid profile consisted of diphosphatidylglycerol phosphatidyl glycerol, phosphatidylinositol, phosphatidylcholine, phosphatidylethanolamine, three glycolipids, two unknown phospholipids, and two unknown lipids. The genome size of type strain M2^T is 5,878,427 bp with 72.1 mol % G + C content. Based on the results obtained from phylogenetic and chemotaxonomic studies, strain M2^T (= DSM 106425 ^T = NCCB 100650 ^T) is considered to represent a novel species within the genus Streptomonospora for which the name Streptomonospora litoralis sp. nov. is proposed.

Leucobacter chromiisoli sp. nov., isolated from chromium-containing chemical plant soil

A Gram-stain-positive, rod-shaped, aerobic, non-motile, non-sporulating bacterial strain, designated CSA1^T, was isolated from chromium-containing soil sampled at a chemical plant. Growth of strain CSA1^T occurred at pH 6-10 (optimum, pH 7), 15-45 °C (optimum, 30 °C) and in the presence of 0.5-6.5 % (w/v) NaCl (optimum, 2 %). The 16S rRNA gene sequence of strain CSA1^T revealed the highest similarity to Leucobacter ruminantium A2^T (97.5 %), Leucobacter tardus K 70/01^T (97.3 %), Leucobacter humi Re6^T (96.6 %), Leucobacter kyeonggiensis F3-P9^T (96.2 %), Leucobacter zeae CC-MF41^T (96.1 %) and Leucobacter weissii S27^T (96.0 %). The draft genome of CSA1^T was approximately 3 350 931 bp in size with a G+C content of 70.6 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among strain CSA1^T and the selected Leucobacter species were 74.0-79.2 % (ANIb), 84.3-87.1 % (ANIm) and 21.5-25.4 % (dDDH), which are below the recommended cutoff values for species delineation. The major fatty acids were anteiso-C_15 : 0, iso-C_16 : 0 and anteiso-C_17 : 0. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid. The predominant menaquinones were MK-11, MK-8 and MK-6. The cell-wall amino acids were 2,4-diaminobutyric acid, alanine, glycine, glutamic acid and threonine. From the phenotypic, chemotaxonomic and molecular features, strain CSA1^T was considered to represent a novel species of the genus Leucobacter, for which the name Leucobacter chromiisoli sp. nov. is proposed. The type strain is CSA1^T (=JCM 34359^T=CGMCC 1.18746^T).

Leucobacter coleopterorum sp. nov., Leucobacter insecticola sp. nov., and Leucobacter viscericola sp. nov., isolated from the intestine of the diving beetles, Cybister brevis and Cybister lewisianus, and emended description of the genus Leucobacter

Three novel bacterial strains, HDW9A^T, HDW9B^T, and HDW9C^T, isolated from the intestine of the diving beetles Cybister lewisianus and Cybister brevis, were characterized as three novel species using a polyphasic approach. The isolates were Gram-staining-positive, strictly aerobic, non-motile, and rod-shaped. They grew optimally at 30°C (pH 7) in the presence of 0.5% (wt/vol) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that they belong to the genus Leucobacter and are closely related to L. denitrificans M1T8B10^T (98.4-98.7% sequence similarity). Average nucleotide identity (ANI) values among the isolates were 76.4-84.1%. ANI values for the isolates and the closest taxonomic species, L. denitrificans KACC 14055^T, were 72.3-73.1%. The isolates showed ANI values of < 76.5% with all analyzable Leucobacter strains in the EzBioCloud database. The genomic DNA G + C content of the isolates was 60.3-62.5%. The polar lipid components were phosphatidylglycerol, diphosphatidylglycerol, and other unidentified glycolipids, phospholipids, and lipids. The major cellular fatty acids were anteiso-C_15:0, iso-C_16:0, and anteiso-C_17:0. MK-10 was the major respiratory quinone, and MK-7 and MK-11 were the minor respiratory quinones. The whole-cell sugar components of the isolates were ribose, glucose, galactose, and mannose. The isolates harbored L-2,4-diaminobutyric acid, L-serine, L-lysine, L-aspartic acid, glycine, and D-glutamic acid within the cell wall peptidoglycan. Based on phylogenetic, phenotypic, chemotaxonomic, and genotypic analyses, strains HDW9A^T, HDW9B^T, and HDW9C^T represent three novel species within the genus Leucobacter. We propose the name Leucobacter coleopterorum sp. nov. for strain HDW9A^T (= KACC 21331^T = KCTC 49317^T = JCM 33667^T), the name Leucobacter insecticola sp. nov. for strain HDW9B^T (= KACC 21332^T = KCTC 49318^T = JCM 33668^T), and the name Leucobacter viscericola sp. nov. for strain HDW9C^T (= KACC 21333^T = KCTC 49319^T = JCM 33669^T).

Leucobacter muris sp. nov., isolated from the nose of a laboratory mouse

A Gram-stain-positive, rod-shaped, aerobic, non-motile, white, opaque bacterial isolate, designated 924/12^T, was isolated from the nose of a laboratory mouse in Düsseldorf, Germany. The 16S rRNA gene sequence analyses indicated the phylogenetic position of the strain within the genus Leucobacter. Similarity levels over 97 % were recorded between the 16S rRNA gene sequence of strain 924/12^T and the type strains of the species Leucobacter chironomi DSM 19883^T (99.5 %), followed by Leucobacter celersubsp. astrifaciens CBX151^T (97.6 %), Leucobacter celersubsp. celer NAL101^T (97.5 %), 'Leucobacter kyeonggiensis' F3-P9 (97.5 %), Leucobacter zeae CC-MF41^T (97.3 %), Leucobacter chromiiresistens JG31^T (97.1 %), Leucobacter triazinivorans JW-1^T (97.1 %), Leucobacter corticis 2 C-7^T (97.0 %) and Leucobacter aridicolis CIP108388^T (97.0 %). DNA-DNA hybridization and whole genomic comparison, mandatory to taxonomically separate strain 924/12^T from the type strain of L. chironomi, revealed similarity values of 40.4 and 30.8 %, respectively, thus below the threshold of 70 % recommended differentiating between species. The cell-wall amino acids of the novel isolate were diaminobutyric acid, alanine, glycine, threonine and glutamic acid. The major fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, glycolipid and one unknown lipid, whereas the predominant menaquinones were MK-11 and MK-10. The genomic DNA G+C content of strain 924/12^T was 70.6 mol%. Phylogenetic analyses based on the 16S rRNA gene sequences and the phenotypical differences between strain 924/12^T and the other closely related type strains of the genus Leucobacter indicated that strain 924/12^T represents a novel species within the genus Leucobacter, family Microbacteriaceae, for which the name Leucobacter muris sp. nov. is proposed. The type strain is 924/12^T (=DSM 101948^T=CCM 8761^T).