Aurantibacillus circumpalustris gen. nov., sp. nov., the first characterized representative of the Bacteroidota candidate family env.OPS 17 and proposal of Aurantibacillaceae fam. nov.

16S rRNA sequence types associated with the candidate family env.OPS 17 have been reported from various environments, but no representatives have been characterized and validly named. Bacteria of env.OPS 17 are affiliated with the order Sphingobacteriales and were first detected more than two decades ago in the vicinity of a thermal spring in Yellowstone National Park. Strain Swamp196T, isolated from the soil surrounding a swamp in Northern Germany, is the first characterized representative of candidate family env.OPS 17. Cells of strain Swamp196T are rod-shaped, non-motile, non-spore-forming, non-capsulated and stain Gram-negative. Colonies are small and orange-coloured. The strain is mesophilic and grows under aerobic or microaerophilic conditions. It grows chemo-organotrophically over a narrow range of pH and exclusively on proteinaceous substrates. The major cellular fatty acids are iso-C15 : 0, iso-C15 : 1 ω10c, C18 : 1 ω9c and C16 : 1 ω7c and the major polar lipids are two unidentified aminophospholipids, one unidentified aminolipid and one unidentified lipid. The predominant respiratory quinone is MK-7. The DNA G+C content of genomic DNA is 35.5 mol%. Strain Swamp196T is related to Pedobacter cryophilus AR-3-17T, Arcticibacter pallidicorallinus Hh36T and Pedobacter daechungensis Dae 13T with 16S rRNA gene sequence similarity of 84.1, 83.8 and 83.5 %, respectively. Based on our phenotypic, genomic and phylogenetic analysis, we propose the novel species Aurantibacillus circumpalustris sp. nov (type strain Swamp196T=DSM 105849T=CECT 30420T) of the novel genus Aurantibacillus gen. nov. and the novel family Aurantibacillaceae fam. nov.

Baekduia alba sp. nov., a novel representative of the order Solirubrobacterales isolated from temperate grassland soil.

Strain 0141_2T 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 BR7-21T, 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 C18 : 1 ω9c, iso-C16 : 0, C18 : 0, C16 : 0, C16 : 1 ω7c and C17 : 1 ω8c. Diphosphatidylglycerol is present. The predominant respiratory quinone is MK-7(H4). 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_2T (=DSM 104299T=LMG 30000T=CECT 9239T).

Capillimicrobium parvum gen. nov., sp. nov., a novel representative of Capillimicrobiaceae fam. nov. within the order Solirubrobacterales, isolated from a grassland soil.

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_1T 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_1T 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 C18 : 1 ω9c, C16 : 1 ω7c, C17 : 0 cyclo ω7c, C18 : 1 ω7c methyl and C19 : 0 cyclo ω9c. 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_1T is 72.8 mol%. 16S rRNA gene sequence analysis indicated that this bacterium was related to Conexibacter arvalis KV-962T and Conexibacter stalactiti YC2-25T 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_1T=DSM 104329T=LMG 29999T=CECT 9240T) of the novel genus Capillimicrobium gen. nov. within the novel family Capillimicrobiaceae fam. nov.

Usitatibacter rugosus gen. nov., sp. nov. and Usitatibacter palustris sp. nov., novel members of Usitatibacteraceae fam. nov. within the order Nitrosomonadales isolated from soil.

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_3T and Swamp67T 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_3T and Swamp67T are mesophilic and grow optimally without NaCl addition at slightly alkaline conditions. Major fatty acids are C16 : 1 ω7c, C16 : 0 and C14 : 0. The major polar lipids are diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyglycerol. The predominant respiratory quinone is Q-8. The G+C content for 0125_3T and Swamp67T was 67 and 66.1 %, respectively. The 16S rRNA gene analysis indicated that the closest relatives (<91 % sequence similarity) of strain 0125_3T were Nitrosospira multiformis ATCC 25196T, Methyloversatilis universalis FAM5T and Denitratisoma oestradiolicum AcBE2-1T, while Nitrosospira multiformis ATCC 25196T, Nitrosospira tenuis Nv1T and Nitrosospira lacus APG3T were closest to strain Swamp67T. 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_3T=DSM 104443T=LMG 29998T=CECT 9241T) and Usitatibacter palustris sp. nov. (type strain Swamp67T=DSM 104440T=LMG 29997T=CECT 9242T) of the novel genus Usitatibacter gen. nov., within the novel family Usitatibacteraceae fam. nov.

Terricaulis silvestris gen. nov., sp. nov., a novel prosthecate, budding member of the family Caulobacteraceae isolated from forest soil.

The family Caulobacteraceae comprises prosthecate bacteria with a dimorphic cell cycle and also non-prosthecate bacteria. Cells of all described species divide by binary fission. Strain 0127_4T was isolated from forest soil in Baden Württemberg (Germany) and determined to be the first representative of the family Caulobacteraceae which divided by budding. Cells of strain 0127_4T were Gram-negative, rod-shaped, prosthecate, motile by means of a polar flagellum, non-spore-forming and non-capsulated. The strain formed small white colonies and grew aerobically and chemo-organotrophically utilizing organic acids, amino acids and proteinaceous substrates. 16S rRNA gene sequence analysis indicated that this bacterium was related to Aquidulcibacter paucihalophilus TH1-2T and Asprobacter aquaticus DRW22-8T with 91.3 and 89.7% sequence similarity, respectively. Four unidentified glycolipids were detected as the major polar lipids and, unlike all described members of the family Caulobacteraceae, phosphatidylglycerol was absent. The major fatty acids were summed feature 8 (C18 : 1ω7c/C18 : 1ω6c), summed feature 9 (iso-C17 : 1ω9c/C16 : 0 10-methyl), C16 : 0 and summed feature 3 (C16 : 1 ω6c/C16 : 1 ω7c). The major respiratory quinone was Q-10. The G+C content of the genomic DNA was 63.5 %. Based on the present taxonomic characterization, strain 0127_4T represents a novel species of a new genus, Terricaulis silvestris gen. nov., sp. nov. The type strain of Terricaulis silvestris is 0127_4T (=DSM 104635T=CECT 9243T).

Roseisolibacter agri gen. nov., sp. nov., a novel slow-growing member of the under-represented phylum Gemmatimonadetes.

A novel slow-growing bacterium, designated strain AW1220T, was isolated from agricultural floodplain soil sampled at Mashare (Kavango region, Namibia) by using a high-throughput cultivation approach. Strain AW1220T 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 AW1220T 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 AW1220T belonged to the class Gemmatimonadetes (=group 1). Its closest relatives were found to be Gemmatimonas aurantiaca T-27T (90.9 % gene sequence similarity), Gemmatimonas phototrophica AP64T (90.8 %) and Longimicrobiumterrae CB-286315T (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 AW1220T 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 AW1220T (=DSM 104292T=LMG 29977T).

Function of bacterial community dynamics in the formation of cadaveric semiochemicals during in situ carcass decomposition.

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.

Flaviaesturariibacter luteus sp. nov., isolated from an agricultural floodplain soil, and emended description of the genus Flaviaesturariibacter.

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).

Aridibacter nitratireducens sp. nov., a member of the family Blastocatellaceae, class Blastocatellia, isolated from an African soil.

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_SHP_-5_238T were non-motile rods that divided by binary fission and formed orange to salmon-coloured colonies on agar plates. Strain A24_SHP_-5_238T 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_SHP_-5_238T was able to use nitrate as an alternative electron acceptor in the absence of oxygen. Major fatty acids of A24_SHP_-5_238T 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_HD_4HT and Aridibacter kavangonensis Ac_23_E3T with a 16S rRNA gene sequence identity of 97.6 and 97.2 %, respectively. The DNA-DNA hybridization values (<28.5 %) confirmed that A24_SHP_-5_238T 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_SHP_-5_238T = DSM 102177T = CECT 9235T).

Parviterribacter kavangonensis gen. nov., sp. nov. and Parviterribacter multiflagellatus sp. nov., novel members of Parviterribacteraceae fam. nov. within the order Solirubrobacterales, and emended descriptions of the classes Thermoleophilia and Rubrobacteria and their orders and families.

Two Gram-type-positive, non-spore-forming bacteria, strains D16/0/H6T and A22/0/F9_1T, were isolated from Namibian semiarid savannah soils. 16S rRNA gene sequence analysis revealed 96.6 % identity between the two strains and placed them within the order Solirubrobacterales of the class Thermoleophilia. The closest phylogenetic relatives with validly published names were several strains of the genus Solirubrobacter and the species Conexibacter arvalis, with pairwise sequence similarities of ≤ 94.0 %. Cells of strain D16/0/H6T were ovoid to rod-shaped, whereas strain A22/0/F9_1T formed regular rods. Cells of both strains were motile and divided by binary fission. Colonies were pink and white to pale yellowish/brownish, respectively. Strains D16/0/H6T and A22/0/F9_1T were aerobic, chemoheterotrophic mesophiles with broad temperature (13-43 and 17-43 °C, respectively) and pH (pH 4.5-8.5 and 5.0-9.5) ranges for growth. Complex proteinaceous substrates and glucose were the preferred carbon and energy sources. Strain A22/0/F9_1T also grew on various carboxylic acids. For both strains, the peptidoglycan diamino acid was meso-2,6-diaminopimelic acid. The major quinone was MK-8. As a minor compound, MK-7 occurred in strain D16/0/H6T; strain A22/0F9_1T also contained MK-7, MK-7(H2) and MK-8(H2). Major fatty acids of strain D16/0/H6T were 10-methyl C17 : 0, iso-C16 : 0 and C18 : 1ω9c. Strain A22/0F9_1T contained C18 : 1ω9c, C17 : 1ω8c, C17 : 1ω6c and iso-C16 : 0 as major components. The DNA G+C contents of strains D16/0/H6T and A22/0/F9_1T were 72.8 and 74.0 mol%, respectively. Based on these characteristics, the two isolates are assigned to novel species of the new genus Parviterribacter gen. nov., the type species Parviterribacter kavangonensis sp. nov. (type strain D16/0/H6T = DSM 25205T = LMG 26950T) and a second species Parviterribacter multiflagellatus sp. nov. (type strain A22/0/F9_1T = DSM 25204T = LMG 26949T). As the novel genus and species cannot be clearly assigned to an established family within the order Solirubrobacterales, the novel family Parviterribacteraceae fam. nov. is proposed. Emended descriptions of the classes Thermoleophilia and Rubrobacteria and their orders and families are also provided.

The first representative of the globally widespread subdivision 6 Acidobacteria,Vicinamibacter silvestris gen. nov., sp. nov., isolated from subtropical savannah soil.

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_5_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_5_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_5_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_5_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_5_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_5_C6T = DSM 29464T = LMG 29035T) are proposed.

Brevitalea aridisoli, B. deliciosa and Arenimicrobium luteum, three novel species of Acidobacteria subdivision 4 (class Blastocatellia) isolated from savanna soil and description of the novel family Pyrinomonadaceae.

Three novel strains of the phylum Acidobacteria (Ac_11_E3T, Ac_12_G8T and Ac_16_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_11_E3T, Ac_12_G8T and Ac_16_C4T were Gram-staining-negative and non-motile and divided by binary fission. Ac_11_E3T and Ac_16_C4T formed white colonies, while those of Ac_12_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_11_E3T, Ac_12_G8T and Ac_16_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_11_E3T=DSM 27934T=LMG 28618T), Brevitalea deliciosa sp. nov. (Ac_16_C4T=DSM 29892T=LMG 28995T) and Arenimicrobium luteum sp. nov. (Ac_12_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).

Terriglobus albidus sp. nov., a member of the family Acidobacteriaceae isolated from Namibian semiarid savannah soil.

A novel aerobic, chemo-organoheterotrophic bacterium, strain Ac_26_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_26_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. DNA­DNA hybridization studies with its closest phylogenetic relative, T. tenax DSM 28898T, confirmed that strain Ac_26_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_26_B10T represents a novel species of the genus Terriglobus, for which the name Terriglobus albidus sp. nov. is proposed. The type strain is Ac_26_B10T ( = DSM 26559T = LMG 27984T).

Touching the (almost) untouchable: a minimally invasive workflow for microbiological and biomolecular analyses of cultural heritage objects.

Microbiological and biomolecular approaches to cultural heritage research have expanded the established research horizon from the prevalent focus on the cultural objects' conservation and human health protection to the relatively recent applications to provenance inquiry and assessment of environmental impacts in a global context of a changing climate. Standard microbiology and molecular biology methods developed for other materials, specimens, and contexts could, in principle, be applied to cultural heritage research. However, given certain characteristics common to several heritage objects-such as uniqueness, fragility, high value, and restricted access, tailored approaches are required. In addition, samples of heritage objects may yield low microbial biomass, rendering them highly susceptible to cross-contamination. Therefore, dedicated methodology addressing these limitations and operational hurdles is needed. Here, we review the main experimental challenges and propose a standardized workflow to study the microbiome of cultural heritage objects, illustrated by the exploration of bacterial taxa. The methodology was developed targeting the challenging side of the spectrum of cultural heritage objects, such as the delicate written record, while retaining flexibility to adapt and/or upscale it to heritage artifacts of a more robust constitution or larger dimensions. We hope this tailored review and workflow will facilitate the interdisciplinary inquiry and interactions among the cultural heritage research community.

Novel isolates double the number of chemotrophic species and allow the first description of higher taxa in Acidobacteria subdivision 4.

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 5-14h 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-C15:0, iso-C15:1H/C13:0 3-OH, and C16:1ω7c/C16:1ω6c. 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.