Search

The phylum Actinobacteria includes important human pathogens like Mycobacterium tuberculosis and Corynebacterium diphtheriae and renowned producers of secondary metabolites of commercial interest, yet only a small part of its diversity is represented by sequenced genomes. Here, we present 824 actinobacterial isolate genomes in the context of a phylum-wide analysis of 6,700 genomes including public isolates and metagenome-assembled genomes (MAGs). We estimate that only 30%-50% of projected actinobacterial phylogenetic diversity possesses genomic representation via isolates and MAGs. A comparison of gene functions reveals novel determinants of host-microbe interaction as well as environment-specific adaptations such as potential antimicrobial peptides. We identify plasmids and prophages across isolates and uncover extensive prophage diversity structured mainly by host taxonomy. Analysis of >80,000 biosynthetic gene clusters reveals that horizontal gene transfer and gene loss shape secondary metabolite repertoire across taxa. Our observations illustrate the essential role of and need for high-quality isolate genome sequences.

Granulicella arctica sp. nov., Granulicella mallensis sp. nov., Granulicella tundricola sp. nov. and Granulicella sapmiensis sp. nov., novel acidobacteria from tundra soil. Editorial: Acidobacteria - Towards Unraveling the Secrets of a Widespread, Though Enigmatic, Phylum Keywords: Acidobacteriota; phototrophy; phosphorus removal; niche adaptation; drought resistance; host-association; thermophile EN Acidobacteriota phototrophy phosphorus removal niche adaptation drought resistance host-association thermophile 1 4 4 06/28/22 20220624 NES 220624 The bacterial phylum, I Acidobacteriota i (Oren and Garrity, [40]) (formerly I Acidobacteria i ) is a diverse and ubiquitous group of environmental bacteria originally discovered in the late 1990s (Kuske et al., [31]; Ludwig et al., [33]). Acidobacteriota, phosphorus removal, drought resistance, phototrophy, niche adaptation, host-association, thermophile. [Extracted from the article]

Although climate change is expected to increase the extent of drylands worldwide, the effect of drought on the soil microbiome is still insufficiently understood as for dominant but little characterized phyla like the Acidobacteria. In the present study the active acidobacterial communities of Namibian soils differing in type, physicochemical parameters, and land use were characterized by high-throughput sequencing. Water content, pH, major ions and nutrients were distinct for sandy soils, woodlands or dry agriculture on loamy sands. Soils were repeatedly sampled over a 2-year time period and covered consecutively a strong rainy, a dry, a normal rainy and a weak rainy season. The increasing drought had differential effects on different soils. Linear modeling of the soil water content across all sampling locations and sampling dates revealed that the accumulated precipitation of the preceding season had only a weak, but statistically significant effect, whereas woodland and irrigation exerted a strong positive effect on water content. The decrease in soil water content was accompanied by a pronounced decrease in the fraction of active Acidobacteria (7.9–0.7%) while overall bacterial community size/cell counts remained constant. Notably, the strongest decline in the relative fraction of Acidobacteria was observed after the first cycle of rainy and dry season, rather than after the weakest rainy season at the end of the observation period. Over the 2-year period, also the β-diversity of soil Acidobacteria changed. During the first year this change in composition was related to soil type (loamy sand) and land use (woodland) as explanatory variables. A total of 188 different acidobacterial sequence variants affiliated with the " Acidobacteriia ," Blastocatellia , and Vicinamibacteria changed significantly in abundance, suggesting either drought sensitivity or formation of dormant cell forms. Comparative physiological testing of 15 Namibian isolates revealed species-specific and differential responses in viability during long-term continuous desiccation or drying-rewetting cycles. These different responses were not determined by phylogenetic affiliation and provide a first explanation for the effect of drought on soil Acidobacteria. In conclusion, the response of acidobacterial communities to water availability is non-linear, most likely caused by the different physiological adaptations of the different taxa present. [ABSTRACT FROM AUTHOR]

Acidobacteria occur in a large variety of ecosystems worldwide and are particularly abundant and highly diverse in soils. In spite of their diversity, only few species have been characterized to date which makes Acidobacteria one of the most poorly understood phyla among the domain Bacteria. We used a culture-independent niche modeling approach to elucidate ecological adaptations and their evolution for 4,154 operational taxonomic units (OTUs) of Acidobacteria across 150 different, comprehensively characterized grassland soils in Germany. Using the relative abundances of their 16S rRNA gene transcripts, the responses of active OTUs along gradients of 41 environmental variables were modeled using hierarchical logistic regression (HOF), which allowed to determine values for optimum activity for each variable (niche optima). By linking 16S rRNA transcripts to the phylogeny of full 16S rRNA gene sequences, we could trace the evolution of the different ecological adaptations during the diversification of Acidobacteria. This approach revealed a pronounced ecological diversification even among acidobacterial sister clades. Although the evolution of habitat adaptation was mainly cladogenic, it was disrupted by recurrent events of convergent evolution that resulted in frequent habitat switching within individual clades. Our findings indicate that the high diversity of soil acidobacterial communities is largely sustained by differential habitat adaptation even at the level of closely related species. A comparison of niche optima of individual OTUs with the phenotypic properties of their cultivated representatives showed that our niche modeling approach (1) correctly predicts those physiological properties that have been determined for cultivated species of Acidobacteria but (2) also provides ample information on ecological adaptations that cannot be inferred from standard taxonomic descriptions of bacterial isolates. These novel information on specific adaptations of not-yet-cultivated Acidobacteria can therefore guide future cultivation trials and likely will increase their cultivation success. [ABSTRACT FROM AUTHOR]

In this study, electrochemically active microbial biofilms were cultivated and studied at continuously alternating electrode potentials. Compared to cultivation and operation at a single constant potential, this method enhanced microbial turnover and maximum current densities. Electrochemically active microbial biofilms were cultivated in a multi‐carbon source culture for several biofilm generations and were subsequently fed with real, domestic wastewater. Compared to constant potential cultivation, average (N=12) biofilm limiting current density at +0.2 V vs. Ag/AgCl increased from 0.350±0.101 to 0.508±0.099 mA cm−2 with a significant reduction in the time required until the maximum current output was reached from 2.01±0.79 to 1.36±0.71 d. The relative increase in maximum current density and decrease in the time required to reach it are similar. The relative differences of higher over lower values are both approximately 45 %. Biofilm community analysis showed a dominance of Geobacteraceae spp. in the electrochemically active biofilms, which is in accordance with the formal potentials derived from cyclic voltammetry. The overall increase in performance is related to the selection of electrochemically active microorganisms, which exhibit local maxima in their electron transfer kinetics between −0.3 and −0.2 V vs. Ag/AgCl. [ABSTRACT FROM AUTHOR]

This study focuses on improving the treatment capacity and current output of electrochemically active microorganisms (EAM) during real wastewater treatment. A multi-carbon-source artificial wastewater consisting of several carbon sources, which represent typical fermentation and hydrolysis products derived from the otherwise myriad wastewater constituents, was developed as a more realistic simulation thereof. An electrochemically preselected inoculum was obtained by means of re-suspension of a well-established EAM biofilm, which was subsequently used to inoculate sterile electrodes. Repeating this procedure yielded increasingly enriched and conditioned biofilms with improved performance. After cultivation in the complex artificial medium, highly efficient fourth generation EAM biofilms were fed real wastewater (i. e. effluent after primary settling) and outperformed those cultivated using a single substrate (i. e. acetate) in terms of current output and chemical oxygen demand (COD) degradation rates. [ABSTRACT FROM AUTHOR]

The decomposition of dead mammalian tissue involves a complex temporal succession of epinecrotic bacteria. Microbial activity may release different cadaveric volatile organic compounds which in turn attract other key players of carcass decomposition such as scavenger insects. To elucidate the dynamics and potential functions of epinecrotic bacteria on carcasses, we monitored bacterial communities developing on still-born piglets incubated in different forest ecosystems by combining high-throughput Illumina 16S rRNA sequencing with gas chromatography-mass spectrometry of volatiles. Our results show that the community structure of epinecrotic bacteria and the types of cadaveric volatile compounds released over the time course of decomposition are driven by deterministic rather than stochastic processes. Individual cadaveric volatile organic compounds were correlated with specific taxa during the first stages of decomposition which are dominated by bacteria. Through best-fitting multiple linear regression models, the synthesis of acetic acid, indole and phenol could be linked to the activity of Enterobacteriaceae, Tissierellaceae and Xanthomonadaceae, respectively. These conclusions are also commensurate with the metabolism described for the dominant taxa identified for these families. The predictable nature of in situ synthesis of cadaveric volatile organic compounds by epinecrotic bacteria provides a new basis for future chemical ecology and forensic studies. [ABSTRACT FROM AUTHOR]

Despite their high phylogenetic diversity and abundance in soils worldwide, Acidobacteria represent an enigmatic bacterial phylum. Four novel Acidobacteria strains were isolated from Namibian semiarid savannah soils using low-nutrient cultivation media and extended incubation periods. 16S rRNA gene sequence analyses placed the isolates within Acidobacteria subdivision 4. Sequence identities with their closest relatives Aridibacter famidurans and Blastocatella fastidiosa were ≤94.9%. The Gram-negative, non-motile, rod-shaped, aerobic, and chemoorganotrophic bacteria grew at minimum doubling times of 5–14 h and formed tiny white to pinkish colonies. Major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, and phosphatidylglycerol. The major isoprenoid quinone was MK-8. The major fatty acid methyl esters comprised iso -C 15:0 , iso -C 15:1 H/C 13:0 3-OH, and C 16:1 ω 7 c /C 16:1 ω 6 c . Based on a polyphasic taxonomic characterization, strain Ac_18_E7 T (=DSM 26557 T = LMG 28656 T ) represented a novel species and genus, Tellurimicrobium multivorans gen. nov., sp. nov. The other strains constituted three independent species of the novel genus Stenotrophobacter gen. nov., Stenotrophobacter terrae sp. nov. (Ac_28_D10 T = DSM 26560 T = LMG 28657 T ), S. roseus sp. nov. (Ac_15_C4 T = DSM 29891 T = LMG 28889 T ), and S. namibiensis sp. nov. (Ac_17_F2 T = DSM 29893 T = LMG 28890 T ). These isolates doubled the number of established species and permitted the description of higher taxa of Acidobacteria subdivision 4. The family Blastocatellaceae fam. nov. is proposed in order to summarize the currently known oligotrophic, slightly acidophilic to neutrophilic mesophiles from arid soils. The superordinated order Blastocatellales ord. nov. and Blastocatellia classis nov. also include the terrestrial species Pyrinomonas methylaliphatogenes and the anoxygenic photoheterotrophic species Chloracidobacterium thermophilum from microbial mats. [ABSTRACT FROM AUTHOR]

Highlights • Only 2 out of 46 acidobacterial strains representing 7 subdivisions contain brGDGTs. • Strains of SDs 1, 3, 4, and 6 produce their building block, i.e. iso -diabolic acid. • Iso -diabolic acid occurs in a (mono) ether-bound form in SD 4 Acidobacteria. • The gene cluster responsible for the formation of this ether bond is identified. • Methylation of iso -diabolic acid occurs at C-5 and C-6 as observed for brGDGTs. Abstract 13,16-Dimethyl octacosanedioic acid (iso -diabolic acid) is a major membrane-spanning lipid of subdivisions (SDs) 1, 3 and 4 of the Acidobacteria, a highly diverse phylum within the Bacteria. It has been suggested that these lipids are potential building blocks for the orphan bacterial glycerol dialkyl glycerol tetraethers (GDGT) that occur widely in a variety of environmental settings. Here, we expand the knowledge on the occurrence of iso -diabolic acid in Acidobacteria by examining the lipid composition of six strains belonging to SDs 6, 8, 10, and 23 of the Acidobacteria, not previously analyzed for these lipids. In addition, we examined 12 new strains belonging to SDs 1, 3 and 4. Acid hydrolysis of total cell material released iso -diabolic acid in substantial quantities (25–39% of all fatty acids) from the strains of SDs 1 and 3 (except “ Candidatus Solibacter usitatus”), and, for the first time, strains of SD 6 (6–25%), but not from SDs 8, 10, and 23. The monoglycerol ether derivative of iso -diabolic acid was only dominantly present in SD 4 strains (17–34%), indicating that the occurrence of ether-bound iso -diabolic acid is mainly restricted to SD 4 species. Methylated iso -diabolic acid derivatives were encountered in SDs 1, 3, 4, and 6, but only SD 4 species produced 5-methyl iso -diabolic acid derivatives, whereas the other SDs formed 6-methyl iso -diabolic acids. This suggests that the position of methylation of iso -diabolic acid may be controlled by the phylogenetic affiliation within the Acidobacteria and thus may not be a direct but an indirect response environmental to environmental conditions as inferred from the bacterial GDGT distributions in soil, peat and rivers. [ABSTRACT FROM AUTHOR]

Two new strains JP48 T and JP55 affiliated with the acidobacterial class Terriglobia have been isolated from fen soil sampled in the Fichtelgebirge Mountains near Bayreuth, Germany. Both strains were Gram-stain-negative, non-motile, non-spore-forming rods that divide by binary fission, segregate exopolysaccharide-like material and form capsules. Strains JP48 T and JP55 grew at 4-36 °C (optimum at 27 °C), pH 3.6-7.3 (optimum at pH 4.6-5.5) and with NaCl concentrations of 0-3% (optimum at 1.0%; w/v). Strains JP48 T and JP55 grew aerobically on a wide range of organic substrates including mono- and oligosaccharides, amino acids and short-chained fatty acids. MK-8 was identified as the major respiratory quinone. The major fatty acids for strains JP48 T and JP55 were iso -C 15 : 0 , C 16 : 1  ω7c, C 16 : 0 and iso -diabolic acid. Phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, lysophophatidylethanolamine, phosphatidylcholine, unidentified glyco- and glycophospholipids, and unidentified high mass lipid species were the major polar membrane lipids. The G+C content of strains JP48 T and JP55 was 57.4 and 57.2 mol%, respectively. The genomes of strains JP48 T and JP55 contained nine potential secondary metabolite regions encoding for the compound classes NRPS(-like), T3PKS, terpene, or lanthipeptide class IV. Phylogenetic reconstruction and 16S rRNA gene sequence similarities of 98.3 and 96.9% identified Edaphobacter dinghuensis DHF9 T and Edaphobacter lichenicola DSM 104462 T as the most closely related type strains to strains JP48 T and JP55. Based on their phenotype, phylogeny and chemotaxonomy, we propose the novel species Edaphobacter paludis sp. nov. (type strain JP48 T =DSM 109919 T =CECT 30269 T ; additional strain JP55=DSM 109920=CECT 30268) within the class Terriglobia of the phylum Acidobacteriota .

Strain 0141_2 T was isolated from a temperate grassland soil in Germany and was found to be affiliated with the order Solirubrobacterales . It is most closely related to Baekduia soli BR7-21 T , with 98.1 % 16S rRNA gene sequence similarity. Cells are rod-shaped, non-motile, stain Gram-positive and can have multiple vesicles in the cell surface. Polyhydroxybutyrate is accumulated within the cells. Catalase- and oxidase-positive. It is a mesophilic aerobe and grows best around neutral to slightly acidic pH in R2A medium. The major fatty acids are C 18 : 1  ω 9 c , iso-C 16 : 0 , C 18 : 0 , C 16 : 0 , C 16 : 1  ω 7 c and C 17 : 1  ω 8 c . Diphosphatidylglycerol is present. The predominant respiratory quinone is MK-7(H 4 ). Meso-diaminopimelic acid is the diagnostic diamino acid in the cell-wall peptidoglycan. The G+C content of genomic DNA is 72.9 mol%. Based on the results of phenotypic, chemotaxonomic, genomic and phylogenetic analysis, we propose the novel species Baekduia alba sp. nov. with the type strain 0141_2 T (=DSM 104299 T =LMG 30000 T =CECT 9239 T ).

The order Solirubrobacterales is a deep-branching lineage within the phylum Actinomycetota . Most representatives have been isolated from terrestrial environments. A strain isolated from a grassland soil was found to be affiliated with this order and therefore characterized by a polyphasic approach. Cells of strain 0166_1 T are Gram-positive, short rods, non-motile, non-spore-forming and divide by binary fission. A surface layer with protrusions covers the majority of the cells. Strain 0166_1 T grows optimally around neutral to slightly alkaline pH (pH 7.1-7.9) and at temperatures between 24-36 °C in SSE/HD 1 : 10 medium. It grows optimally with 0-0.5% NaCl (w/v) but can withstand concentrations up to 5 %. The major fatty acids are C 18 : 1  ω9 c , C 16 : 1  ω 7 c , C 17 : 0 cyclo ω 7 c , C 18 : 1  ω7 c methyl and C 19 : 0 cyclo ω 9 c . The major polar lipids are diphosphatidylglycerol, two unidentified phospholipids and one unidentified glycolipid. MK-7(H4) and MK-7(H2) are the predominant respiratory quinones. meso -2,6-Diaminopimelic acid is the diagnostic diamino acid in the cell-wall peptidoglycan. The G+C content for strain 0166_1 T is 72.8 mol%. 16S rRNA gene sequence analysis indicated that this bacterium was related to Conexibacter arvalis KV-962 T and Conexibacter stalactiti YC2-25 T with 95.5 and 95.2 % sequence similarity, respectively. Based on the phenotypic, genomic and phylogenetic data, we propose the novel species Capillimicrobium parvum sp. nov. (type strain 0166_1 T =DSM 104329 T =LMG 29999 T =CECT 9240 T ) of the novel genus Capillimicrobium gen. nov. within the novel family Capillimicrobiaceae fam. nov.

Members of the metabolically diverse order Nitrosomonadales inhabit a wide range of environments. Two strains affiliated with this order were isolated from soils in Germany and characterized by a polyphasic approach. Cells of strains 0125&#95;3 T and Swamp67 T are Gram-negative rods, non-motile, non-spore-forming, non-capsulated and divide by binary fission. They tested catalase-negative, but positive for cytochrome c -oxidase. Both strains form small white colonies on agar plates and grow aerobically and chemoorganotrophically on SSE/HD 1 : 10 medium, preferably utilizing organic acids and proteinaceous substrates. Strains 0125&#95;3 T and Swamp67 T are mesophilic and grow optimally without NaCl addition at slightly alkaline conditions. Major fatty acids are C 16 : 1   ω 7 c , C 16 : 0 and C 14 : 0 . The major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyglycerol. The predominant respiratory quinone is Q-8. The G+C content for 0125&#95;3 T and Swamp67 T was 67 and 66.1 %, respectively. The 16S rRNA gene analysis indicated that the closest relatives (<91 % sequence similarity) of strain 0125&#95;3 T were Nitrosospira multiformis ATCC 25196 T , Methyloversatilis universalis FAM5 T and Denitratisoma oestradiolicum AcBE2-1 T , while Nitrosospira multiformis ATCC 25196 T , Nitrosospira tenuis Nv1 T and Nitrosospira lacus APG3 T were closest to strain Swamp67 T . The two novel strains shared 97.4 % 16S rRNA gene sequence similarity with one another and show low average nucleotide identity of their genomes (83.8 %). Based on the phenotypic, chemotaxonomic, genomic and phylogenetic analysis, we propose the two novel species Usitatibacter rugosus sp. nov (type strain 0125&#95;3 T =DSM 104443 T =LMG 29998 T =CECT 9241 T ) and Usitatibacter palustris sp. nov. (type strain Swamp67 T =DSM 104440 T =LMG 29997 T =CECT 9242 T ) of the novel genus Usitatibacter gen. nov., within the novel family Usitatibacteraceae fam. nov.

A novel acidophilic member of the phylum Actinobacteria was isolated from an acidic, metal-contaminated stream draining from an abandoned underground coal mine (Trongol mine), situated close to Curanilahue, Biobío Region, Chile. The isolate (USS-CCA1 T ) was demonstrated to be a heterotroph that catalysed under aerobic conditions the oxidation of ferrous iron and the reduction of ferric iron under anaerobic conditions, but not the oxidation of sulfur nor hydrogen. USS-CCA1 T is a Gram-positive, motile, short rod-shaped, mesophilic bacterium with a temperature growth optimum at 30 °C (range 20-39 °C). It was categorized as an extreme acidophile growing between 1.7 and 4.5 and optimally at pH 3.0. The G+C content of the chromosomal DNA of the isolate was 74.1 mol%, which is highly related to Aciditerrimonas ferrireducens IC-180 T , (the most closely related genus; 94.4 % 16S rRNA gene identity), and higher than other acidophilic actinobacteria. The isolate (USS-CCA1 T ) was shown to form a distinct 16S rRNA clade from characterized acidophilic actinobacteria, well separated from the genera Acidimicrobium , Ferrimicrobium , Ferrithrix , 'Acidithrix' and Aciditerrimonas . Genomic indexes (ANIb, DDH, AAI, POCP) derived from the USS-CCA1 T draft genome sequence (deposited at DDBJ/ENA/GenBank under the accession WJHE00000000) support assignment of the isolate to a new species and a new genus within the Acidimicrobiaceae family. Isolate USS-CCA1 T is the designated type strain of the novel species Acidiferrimicrobium australe (=DSM 106828 T ,=RGM 2506 T ).

Acidobacteria constitute a globally widespread phylum and mainly inhabit soil environments. Despite their high abundance and activity, only 60 species from seven of the 26 acidobacterial subdivisions (sds; corresponding to class level) are (validly) described. Thus, only a low number of higher taxonomic ranks is currently distinguished within the Acidobacteria. Additionally, the distribution of the known acidobacterial species within the described families of the Acidobacteriaceae (sd1), Bryobacteraceae (sd3), Blastocatellaceae (sd4), Pyrinomonadaceae (sd4), Holophagaceae (sd8) and Acanthopleuribacteraceae (sd8) is extremely biased as most strains are affiliated with the Acidobacteriaceae. Members of this family are characteristic for acidic soils. In contrast, culture-independent analysis of microbial communities worldwide revealed that sd6 Acidobacteria prevail in soils with neutral pH. To improve the existing acidobacterial taxonomy, we here formally describe the first family within sd6 Acidobacteria, the Vicinamibacteraceae. Members of the Vicinamibacteraceae are aerobic, neutrophilic, psychrotolerant to mesophilic chemoheterotrophs. Their cells stain Gram-negative, do not form capsules or spores, and are non-motile. They occur as single cells or in aggregates and divide by binary fission. Growth occurs on sugars or complex proteinaceous compounds. MK-8 is the major quinone. Major fatty acids are iso-C15 : 0, summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), C18 : 1ω7c or ω9c, iso-C17 : 1ω9c, C16 : 0 and iso-C17 : 0. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol are the major polar lipids. Unidentified glycolipids or unknown phospholipids might also be present. The G+C content of the DNA ranges from 64.7 to 65.9 mol%. Within the Vicinamibacteraceae fam. nov., Vicinamibacter and Luteitalea are the only genera described so far.

A novel slow-growing bacterium, designated strain AW1220 T , was isolated from agricultural floodplain soil sampled at Mashare (Kavango region, Namibia) by using a high-throughput cultivation approach. Strain AW1220 T was characterized as a Gram-negative, non-motile, rod-shaped bacterium. Occasionally, some cells attained an unusual length of up to 35 µm. The strain showed positive responses for catalase and cytochrome-c oxidase and divided by binary fission and/or budding. The strain had an aerobic chemoorganoheterotrophic metabolism and was also able to grow under micro-oxic conditions. Colonies were small and pink pigmented. Strain AW1220 T was found to be a mesophilic, neutrophilic and non-halophilic bacterium. Cells accumulated polyphosphate intracellularly and mainly utilized complex protein substrates for growth. 16S rRNA gene sequence comparisons revealed that strain AW1220 T belonged to the class Gemmatimonadetes (=group 1). Its closest relatives were found to be Gemmatimonas aurantiaca T-27 T (90.9 % gene sequence similarity), Gemmatimonas phototrophica AP64 T (90.8 %) and Longimicrobiumterrae CB-286315 T (84.2 %). The genomic G+C content was 73.3 mol%. The major fatty acids were iso-C15 : 0, C16 : 1ω7c and/or iso-C15 : 0 2-OH, iso-C17 : 1ω9c, iso-C15 : 0 3-OH and C16 : 0. The predominant respiratory quinone was MK-9, albeit minor amounts of MK-8 and MK-10 are also present. The polar lipids comprised major amounts of phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol and one unidentified phosphoglycolipid. On the basis of its polyphasic characterization, strain AW1220 T represents a novel genus and species of the class Gemmatimonadetes for which the name Roseisolibacter agri gen. nov., sp. nov. is proposed, with the type strain AW1220 T (=DSM 104292 T =LMG 29977 T ).

Members of the class Blastocatellia are frequently found in soils with a neutral and (slightly) basic pH where they constitute an important fraction of the microbial community. A novel representative of the class Blastocatellia was isolated from a Ghanaian soil and was characterized in detail. Cells of strain A24&#95;SHP&#95;-5&#95;238 T were non-motile rods that divided by binary fission and formed orange to salmon-coloured colonies on agar plates. Strain A24&#95;SHP&#95;-5&#95;238 T tolerated pH values of pH 6.0-9.0 (best growth at pH 7.0-8.5) and temperature values of 8-45 °C (best growth at 33-40 °C). It grew chemo-organoheterotrophically on several sugars, a few amino acids, organic acids and different complex protein substrates. In addition, strain A24&#95;SHP&#95;-5&#95;238 T was able to use nitrate as an alternative electron acceptor in the absence of oxygen. Major fatty acids of A24&#95;SHP&#95;-5&#95;238 T were iso-C15 : 0, summed feature 1 (C13 : 0 3-OH/iso-C15 : 1 H), summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), anteiso-C17 : 0 and anteiso-C15 : 0. The major quinone was MK-8, and the DNA G+C content was 53.5 mol%. The closest described phylogenetic relatives were Aridibacter famidurans A22&#95;HD&#95;4H T and Aridibacter kavangonensis Ac&#95;23&#95;E3 T with a 16S rRNA gene sequence identity of 97.6 and 97.2 %, respectively. The DNA-DNA hybridization values (<28.5 %) confirmed that A24&#95;SHP&#95;-5&#95;238 T represents a novel species within the genus Aridibacter. Based on its morphological, physiological and molecular characteristics, we propose the novel species Aridibacter nitratireducens sp. nov. (type strain A24&#95;SHP&#95;-5&#95;238 T = DSM 102177 T = CECT 9235 T ).

A novel slow-growing bacterial strain designated as AW305T was isolated from an agricultural floodplain soil located in Mashare, Kavango region, Namibia. Cells stained Gram-negative, were non-motile, non-spore-forming, coccoid to rod-shaped and did not form a capsule. Colonies were yellow-pigmented, but flexirubin-type pigments were not detected. AW305T had an aerobic chemo-organoheterotrophic metabolism, using a narrow spectrum of carbon sources for growth, with preference for complex protein substrates, organic acids and amino acids. AW305T was able to grow at 15-40 °C, pH 5.3-8.3 and in the presence of up to 0.25 % (w/v) NaCl. 16S rRNA gene sequence comparison showed that AW305T belonged to the genus Flaviaesturariibacter (family Chitinophagaceae). Its closest relatives were Flaviaesturariibacter amylovorans GCR0105T (97.0 %), Flavisolibacter ginsengiterrae Gsoil 492T (93.6 %) and Flavisolibacter ginsengisoli Gsoil 643T (93.2 %). DNA-DNA hybridization experiments corroborated that AW305T represents an independent genomospecies. The genomic DNA G+C content was 57.6 mol%. Major fatty acids were iso-C15 : 1 G, iso-C15 : 0, C16 : 1ω5c, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The predominant respiratory quinone was MK-7, albeit minor amounts of MK-6 were also detected. The polar lipids comprised major amounts of phosphatidylethanolamine and minor amounts of two unidentified lipids, an unidentified phospholipid, an unidentified glycolipid and an unidentified aminoglycophospholipid. On the basis of the polyphasic characterization, strain AW305T represents a novel species of the genus Flaviaesturariibacter for which the name Flaviaesturariibacter luteus sp. nov. is proposed, with the type strain AW305T (=DSM 100282T=LMG 29416T).

The phylum Acidobacteria represents one of the highly diverse but poorly characterized phylogenetic groups of the domain Bacteria. The taxonomically described acidobacteria belong to 27 genera and 49 species, which represent subdivisions 1, 3, 4, 6, 8, 10 and 23 of this phylum. However, the corresponding family ranks have been defined only for some of these characterized micro-organisms. Here, we suggest the establishment of a novel family, Bryobacteraceae fam. nov., to accommodate taxonomically described members of subdivision 3 Acidobacteria. This family is characterized by Gram-stain-negative, non-spore-forming and non-motile rods, which divide by binary fission. Members of this family are mildly acidophilic, mesophilic, aerobic and facultatively anaerobic chemoheterotrophs that utilize various sugars and polysaccharides. The major fatty acids are iso-C15 : 0 and C16 : 1ω7c; the cells also contain significant amounts of 13,16-dimethyloctacosanedioic (iso-diabolic) acid. Currently, the family comprises the genera Bryobacter and Paludibaculum.

Three novel strains of the phylum Acidobacteria (Ac&#95;11&#95;E3T, Ac&#95;12&#95;G8T and Ac&#95;16&#95;C4T) were isolated from Namibian semiarid savanna soils by a high-throughput cultivation approach using low-nutrient growth media. 16S rRNA gene sequence analysis placed all three strains in the order Blastocatellales of the class Blastocatellia (Acidobacteria subdivision 4). However, 16S rRNA gene sequence similarities to their closest relative Pyrinomonas methylaliphatogenes K22T were ≤90 %. Cells of strains Ac&#95;11&#95;E3T, Ac&#95;12&#95;G8T and Ac&#95;16&#95;C4T were Gram-staining-negative and non-motile and divided by binary fission. Ac&#95;11&#95;E3T and Ac&#95;16&#95;C4T formed white colonies, while those of Ac&#95;12&#95;G8T were orange-yellowish. All three strains were aerobic chemoorganoheterotrophic mesophiles with a broad pH range for growth. All strains used a very limited spectrum of carbon and energy sources for growth, with a preference for complex proteinaceous substrates. The major respiratory quinone was MK-8. The major shared fatty acid was iso-C15 : 0. The DNA G+C contents of strains Ac&#95;11&#95;E3T, Ac&#95;12&#95;G8T and Ac&#95;16&#95;C4T were 55.9 mol%, 66.9 mol% and 54.7 mol%, respectively. Based on these characteristics, the two novel genera Brevitaleagen. nov. and Arenimicrobiumgen. nov. are proposed, harboring the novel species Brevitaleaaridisoli sp. nov. (Ac&#95;11&#95;E3T=DSM 27934T=LMG 28618T), Brevitalea deliciosa sp. nov. (Ac&#95;16&#95;C4T=DSM 29892T=LMG 28995T) and Arenimicrobium luteum sp. nov. (Ac&#95;12&#95;G8T=DSM 26556T=LMG 29166T), respectively. Since these novel genera are only distantly related to established families, we propose the novel family Pyrinomonadaceaefam. nov. that accommodates the proposed genera and the genus Pyrinomonas(Crowe et al., 2014).

Members of the phylum Acidobacteria are abundant in a wide variety of soil environments. Despite this, previous cultivation attempts have frequently failed to retrieve representative phylotypes of Acidobacteria, which have, therefore, been discovered by culture-independent methods (13175 acidobacterial sequences in the SILVA database version 123; NR99) and only 47 species have been described so far. Strain Ac&#95;5&#95;C6T represents the first isolate of the globally widespread and abundant subdivision 6 Acidobacteria and is described in the present study. Cells of strain Ac&#95;5&#95;C6T were Gram-stain-negative, immotile rods that divided by binary fission. They formed yellow, extremely cohesive colonies and stable aggregates even in rapidly shaken liquid cultures. Ac&#95;5&#95;C6T was tolerant of a wide range of temperatures (12-40 °C) and pH values (4.7-9.0). It grew chemoorganoheterotrophically on a broad range of substrates including different sugars, organic acids, nucleic acids and complex proteinaceous compounds. The major fatty acids of Ac&#95;5&#95;C6T were iso-C17 : 1 ω9c, C18 : 1 ω7c and iso-C15 : 0. Summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), iso-C17 : 0 and C16 : 0 were also detected. Phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and an unidentified glycolipid were identified as polar lipids. The major quinone was MK-8. The DNA G+C content of Ac&#95;5&#95;C6T was 65.9 mol%. With 16S rRNA gene sequence similarities of 83-84 %, the closest described relatives were Acidicapsa borealis KA1T, Acidobacterium capsulatum 161T, Granulicella pectinovorans TPB6011T, Occallatibacter riparius 277T and Paludibaculum fermentans P105T. According to the morphological, physiological and molecular characteristics, the novel genus Vicinamibacter gen. nov., and the novel species, Vicinamibacter silvestris sp. nov. (type strain Ac&#95;5&#95;C6T = DSM 29464T = LMG 29035T) are proposed.

A novel aerobic, chemo-organoheterotrophic bacterium, strain Ac&#95;26&#95;B10T, was isolated from a semiarid savannah soil collected in northern Namibia (Mashare, Kavango region). Based on analysis of its nearly full-length 16S rRNA gene sequence, the isolate belongs to the genus Terriglobus (family Acidobacteriaceae, order Acidobacteriales, class Acidobacteria) and shares 98.3 and 96.9 % 16S rRNA gene sequence similarity with its closest relatives, Terriglobus tenax DRP 35T and T. aquaticus O3SUJ4T. Cells were Gram-negative, coccoid to rod-shaped, non-motile and divided by binary fission. Strain Ac&#95;26&#95;B10T showed weak catalase activity and, in contrast to the other described species of the genus Terriglobus, was oxidase-positive. Compared with the already established species of the genus Terriglobus, the novel strain used a larger range of sugars and sugar alcohols for growth, lacked α-mannosidase activity and exhibited a higher temperature optimum of growth. DNA–DNA hybridization studies with its closest phylogenetic relative, T. tenax DSM 28898T, confirmed that strain Ac&#95;26&#95;B10T represents a distinct genomospecies. Its most abundant fatty acids were iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. Dominant polar lipids were phosphatidylethanolamine and diphosphatidylglycerol. The predominant menaquinone was MK-8; minor amounts of MK-7 and MK-8(H2) were also recorded. The G+C content of the genomic DNA was 58.5 mol%. On the basis of our polyphasic analysis, Ac&#95;26&#95;B10T represents a novel species of the genus Terriglobus, for which the name Terriglobus albidus sp. nov. is proposed. The type strain is Ac&#95;26&#95;B10T ( = DSM 26559T = LMG 27984T).

Acidobacteria constitute an abundant fraction of the soil microbial community and are currently divided into 26 subdivisions. Most cultivated members of the Acidobacteria are affiliated with subdivision 1, while only a few representatives of subdivisions 3, 4, 8, 10 and 23 have been isolated and described so far. Two novel isolates of subdivision 4 of the Acidobacteria were isolated from subtropical savannah soils and are characterized in the present work. Cells of strains A22&#95;HD&#95;4H(T) and Ac&#95;23&#95;E3(T) were immotile rods that divided by binary fission. Colonies were pink and white, respectively. The novel strains A22&#95;HD&#95;4H(T) and Ac&#95;23&#95;E3(T) were aerobic mesophiles with a broad range of tolerance towards pH (4.0-9.5 and 3.5-10.0, respectively) and temperature (15-44 and 12-47 °C, respectively). Both showed chemo-organoheterotrophic growth on some sugars, the amino sugar N-acetylgalactosamine, a few amino acids, organic acids and various complex protein substrates. Major fatty acids of A22&#95;HD&#95;4H(T) and Ac&#95;23&#95;E3(T) were iso-C(15 : 0), summed feature 1 (C(13 : 0) 3-OH/iso-C(15 : 1) H), summed feature 3 (C(16 : 1)ω7c/C(16 : 1)ω6c) and anteiso-C(17 : 0). The major quinone was MK-8; in addition, MK-7 occurred in small amounts. The DNA G+C contents of A22&#95;HD&#95;4H(T) and Ac&#95;23&#95;E3(T) were 53.2 and 52.6 mol%, respectively. The closest described relative was Blastocatella fastidiosa A2-16(T), with 16S rRNA gene sequence identity of 93.2 and 93.3%, respectively. Strains A22&#95;HD&#95;4H(T) and Ac&#95;23&#95;E3(T) displayed 16S rRNA gene sequence similarity of 97.4% to each other. On the basis of the low DNA-DNA hybridization value, the two isolates represent different species. Based on morphological, physiological and molecular characteristics, the new genus Aridibacter gen. nov. is proposed, with two novel species, the type species Aridibacter famidurans sp. nov. (type strain A22&#95;HD&#95;4H(T) = DSM 26555(T) = LMG 27985(T)) and a second species, Aridibacter kavangonensis sp. nov. (type strain Ac&#95;23&#95;E3(T) = DSM 26558(T) = LMG 27597(T))., (© 2014 IUMS.)