Whole-Genome Sequencing of Corallococcus sp. Strain EGB Reveals the Genetic Determinants Linking Taxonomy and Predatory Behavior.

Corallococcus sp. strain EGB is a Gram-negative myxobacteria isolated from saline soil, and has considerable potential for the biocontrol of phytopathogenic fungi. However, the detailed mechanisms related to development and predatory behavior are unclear. To obtain a comprehensive overview of genetic features, the genome of strain EGB was sequenced, annotated, and compared with 10 other Corallococcus species. The strain EGB genome was assembled as a single circular chromosome of 9.4 Mb with 7916 coding genes. Phylogenomics analysis showed that strain EGB was most closely related to Corallococcus interemptor AB047A, and it was inferred to be a novel species within the Corallococcus genus. Comparative genomic analysis revealed that the pan-genome of Corallococcus genus was large and open. Only a small proportion of genes were specific to strain EGB, and most of them were annotated as hypothetical proteins. Subsequent analyses showed that strain EGB produced abundant extracellular enzymes such as chitinases and ß-(1,3)-glucanases, and proteases to degrade the cell-wall components of phytopathogenic fungi. In addition, 35 biosynthetic gene clusters potentially coding for antimicrobial compounds were identified in the strain EGB, and the majority of them were present in the dispensable pan-genome with unexplored metabolites. Other genes related to secretion and regulation were also explored for strain EGB. This study opens new perspectives in the greater understanding of the predatory behavior of strain EGB, and facilitates a potential application in the biocontrol of fungal plant diseases in the future.

Global Geographic Diversity and Distribution of the Myxobacteria.

Bacteria are globally distributed in various environments on earth, but a global view of the geographic diversity and distribution of a single taxon is lacking. The Earth Microbiome Project (EMP) has established a global collection of microbial communities, providing the possibility for such a survey. Myxococcales is a bacterial order with a potent ability to produce diverse natural products and have wide application potential in agriculture, biomedicine, and environmental protection. In this study, through a comparative analysis of the EMP data and public information, we determined that myxobacteria account for 2.34% of the total bacterial operational taxonomic units (OTUs), and are one of the most diverse bacterial groups on Earth. Myxococcales OTUs are globally distributed and prefer nonsaline soil and sediments, followed by saline environments, but rarely appear in host-associated environments. Myxobacteria are among the least-investigated bacterial groups. The presently cultured and genome-sequenced myxobacteria are most likely environmentally widespread and abundant taxa, and account for approximately 10% and 7% of the myxobacterial community (>97% similarity), respectively. This global panoramic view of the geographic distribution and diversity of myxobacteria, as well as their cultured and genome-sequenced information, will enable us to explore these important bioresources more reasonably and efficiently. The diversity and distribution of myxobacteria beyond the EMP data are further discussed. IMPORTANCE The diversity and distribution of bacteria are crucial for our understanding of their ecological importance and application potential. Myxobacteria are fascinating prokaryotes with multicellular behaviors and a potent capacity for producing secondary metabolites, and have a wide range of potential applications. The ecological importance of myxobacteria in major ecosystems is becoming established, but the global geographic diversity and distribution remain unclear. From a global survey we revealed that Myxococcales OTUs are globally distributed and prefer nonsaline soil and sediments, followed by saline environments, but rarely appear in host-associated environments. The global panoramic view of the geographic distribution and diversity of myxobacteria, as well as their cultured and genome-sequenced information, will enable us to explore these important bioresources more reasonably and efficiently.

Opinions 100, 101 and 102.

The International Committee on Systematics of Prokaryotes has formally made final decisions, taking into account the conclusions of the Judicial Commission, on three pending Requests for an Opinion, thereby allowing the corresponding Opinions to be issued. According to Opinion 100, the request for the recognition of strain A1-86 (=DSM 17629=NCIMB 14373) as the neotype strain of Eubacterium rectale (Hauduroy et al. 1937) Prévot 1938 (Approved Lists 1980) is denied, ruling that a neotype does not need to be designated for E. rectale because strain VPI 0990 (=ATCC 33656=CIP 105953) is considered to be a duplicate isolate of the same strain as VPI 0989 (=ATCC 25578) and may serve as its nomenclatural type. Opinion 101 approves the request that strain ATCC 25946 (=DSM 14877) serves as the type strain of Melittangium lichenicola instead of strain ATCC 25944, formally correcting the Approved Lists of Bacterial Names. Opinion 102 concludes that strain Cc m8 (=DSM 14697=CIP 109128=JCM 12621) is an established neotype strain for the species Myxococcus macrosporus, replacing the designated type strain Windsor M271, and that strain Mx s8 (=DSM 14675=JCM 12634) is an established neotype strain for the species Myxococcus stipitatus, replacing the designated type strain Windsor M78, with some additional considerations about the nature of the type material replaced and about the name Corallococcus (Myxococcus) macrosporus.

Diazotrophic Anaeromyxobacter Isolates from Soils.

Biological nitrogen fixation is an essential reaction in a major pathway for supplying nitrogen to terrestrial environments. Previous culture-independent analyses based on soil DNA/RNA/protein sequencing could globally detect the nitrogenase genes/proteins of Anaeromyxobacter (in the class Deltaproteobacteria), commonly distributed in soil environments and predominant in paddy soils; this suggests the importance of Anaeromyxobacter in nitrogen fixation in soil environments. However, direct experimental evidence is lacking; there has been no research on the genetic background and ability of Anaeromyxobacter to fix nitrogen. Therefore, we verified the diazotrophy of Anaeromyxobacter based on both genomic and culture-dependent analyses using Anaeromyxobacter sp. strains PSR-1 and Red267 isolated from soils. Based on the comparison of nif gene clusters, strains PSR-1 and Red267 as well as strains Fw109-5, K, and diazotrophic Geobacter and Pelobacter in the class Deltaproteobacteria contain the minimum set of genes for nitrogenase (nifBHDKEN). These results imply that Anaeromyxobacter species have the ability to fix nitrogen. In fact, Anaeromyxobacter PSR-1 and Red267 exhibited N2-dependent growth and acetylene reduction activity (ARA) in vitro Transcriptional activity of the nif gene was also detected when both strains were cultured with N2 gas as a sole nitrogen source, indicating that Anaeromyxobacter can fix and assimilate N2 gas by nitrogenase. In addition, PSR-1- or Red267-inoculated soil showed ARA activity and the growth of the inoculated strains on the basis of RNA-based analysis, demonstrating that Anaeromyxobacter can fix nitrogen in the paddy soil environment. Our study provides novel insights into the pivotal environmental function, i.e., nitrogen fixation, of Anaeromyxobacter, which is a common soil bacterium.IMPORTANCEAnaeromyxobacter is globally distributed in soil environments, especially predominant in paddy soils. Current studies based on environmental DNA/RNA analyses frequently detect gene fragments encoding nitrogenase of Anaeromyxobacter from various soil environments. Although the importance of Anaeromyxobacter as a diazotroph in nature has been suggested by culture-independent studies, there has been no solid evidence and validation from genomic and culture-based analyses that Anaeromyxobacter fixes nitrogen. This study demonstrates that Anaeromyxobacter harboring nitrogenase genes exhibits diazotrophic ability; moreover, N2-dependent growth was demonstrated in vitro and in the soil environment. Our findings indicate that nitrogen fixation is important for Anaeromyxobacter to survive under nitrogen-deficient environments and provide a novel insight into the environmental function of Anaeromyxobacter, which is a common bacterium in soils.

Bioprospecting of indigenous myxobacteria from Iran and potential of Cystobacter as a source of anti-MDR compounds.

Drug resistance is a critical issue in future clinical treatment. Methicillin-resistant Staphylococcus aureus (MRSA) is among the pathogens that need indispensable drug-discovery efforts. The myxobacteria are a unique group of bacteria that have recently been regarded for their potency to produce new drugs with high chemical diversity and unusual mode of actions. The present study was conducted to isolate and screen myxobacteria for the first time from Iran habitats and evaluate their antibacterial activity against the multidrug-resistant strain of S. aureus. Out of 62 soil and rotten plant samples, 51 myxobacteria were isolated. The isolates belonged to Myxococcus, Corallococcus, Pyxidicoccus, and Cystobacter genera based on morphology and 16S rRNA gene sequencing. Secondary metabolites of the selected strains were screened for activity on MDR strain with resistance to multiple antibiotic classes. The semi-purified fraction from Cystobacter sp. UTMC 4086 showed potent activity against MDR S. aureus with minimum inhibitory effect at 5 ≥ µg per mL compared with vancomycin (5 µg per mL) as well as no toxicity against Artemia salina. Hence, the strain Cystobacter sp. UTMC 4086 can be a valuable candidate for antibiotic discovery against MRSA and its metabolites can be subjected to further purification and analysis aimed at the identification of the effective chemical entity.

Predatory Organisms with Untapped Biosynthetic Potential: Descriptions of Novel Corallococcus Species C. aberystwythensis sp. nov., C. carmarthensis sp. nov., C. exercitus sp. nov., C. interemptor sp. nov., C. llansteffanensis sp. nov., C. praedator sp. nov., C. sicarius sp. nov., and C. terminator sp. nov.

Corallococcus spp. are common soil-dwelling organisms which kill and consume prey microbes through the secretion of antimicrobial substances. Two species of Corallococcus have been described previously (Corallococcus coralloides and Corallococcus exiguus). A polyphasic approach, including biochemical analysis of fatty acid methyl esters, substrate utilization, and sugar assimilation assays, was taken to characterize eight Corallococcus species strains and the two type strains. The genomes of all strains, including that of C. exiguus DSM 14696T (newly reported here), shared an average nucleotide identity below 95% and digital DNA-DNA hybridization scores of less than 70%, indicating that they belong to distinct species. In addition, we characterized the prey range and antibiotic resistance profile of each strain, illustrating the diversity of antimicrobial activity and, thus, the potential for drug discovery within the Corallococcus genus. Each strain gave a distinct profile of properties, which together with their genomic differences supports the proposal of the eight candidate strains as novel species. The eight candidates are as follows: Corallococcus exercitus sp. nov. (AB043AT= DSM 108849T = NBRC 113887T), Corallococcus interemptor sp. nov. (AB047AT= DSM 108843T = NBRC 113888T), Corallococcus aberystwythensis sp. nov. (AB050AT = DSM 108846T = NBRC 114019T), Corallococcus praedator sp. nov. (CA031BT= DSM 108841T = NBRC 113889T), Corallococcus sicarius sp. nov. (CA040BT= DSM 108850T = NBRC 113890T), Corallococcus carmarthensis sp. nov. (CA043DT= DSM 108842T = NBRC 113891T), Corallococcus llansteffanensis sp. nov. (CA051BT= DSM 108844T = NBRC 114100T), and Corallococcus terminator sp. nov. (CA054AT= DSM 108848T = NBRC 113892T).IMPORTANCECorallococcus is a genus of predators with broad prey ranges, whose genomes contain large numbers of gene clusters for secondary metabolite biosynthesis. The physiology and evolutionary heritage of eight Corallococcus species strains were characterized using a range of analyses and assays. Multiple metrics confirmed that each strain belonged to a novel species within the Corallococcus genus. The strains exhibited distinct patterns of drug resistance and predatory activity, which mirrored their possession of diverse sets of biosynthetic genes. The breadth of antimicrobial activities observed within the Corallococcus genus highlights their potential for drug discovery and suggests a previous underestimation of both their taxonomic diversity and biotechnological potential. Taxonomic assignment of environmental isolates to novel species allows us to begin to characterize the diversity and evolution of members of this bacterial genus with potential biotechnological importance, guiding future bioprospecting efforts for novel biologically active metabolites and antimicrobials.

Automated identification of Myxobacterial genera using Convolutional Neural Network.

The Myxococcales order consist of eleven families comprising30 genera, and are featured by the formation of the highest level of differential structure aggregations called fruiting bodies. These multicellular structures are essential for their resistance in ecosystems and is used in the primitive identification of these bacteria while their accurate taxonomic position is confirmed by the nucleotide sequence of 16SrRNA gene. Phenotypic classification of these structures is currently performed based on the stereomicroscopic observations that demand personal experience. The detailed phenotypic features of the genera with similar fruiting bodies are not readily distinctive by not particularly experienced researchers. The human examination of the fruiting bodies requires high skill and is error-prone. An image pattern analysis of schematic images of these structures conducted us to the construction of a database, which led to an extractable recognition of the unknown fruiting bodies. In this paper, Convolutional Neural Network (CNN) was considered as a baseline for recognition of fruiting bodies. In addition, to enhance the result the classifier, part of CNN is replaced with other classifiers. By employing the introduced model, all 30 genera of this order could be recognized based on stereomicroscopic images of the fruiting bodies at the genus level that not only does not urge us to amplify and sequence gene but also can be attained without preparation of microscopic slides of the vegetative cells or myxospores. The accuracy of 77.24% in recognition of genera and accuracy of 88.92% in recognition of suborders illustrate the applicability property of the proposed machine learning model.

Reclassification of 'Polyangium brachysporum' DSM 7029 as Schlegelella brevitalea sp. nov.

Strain DSM 7029, isolated from a soil sample in Greece, can produce antitumour glidobactins, and has been found, as a heterologous host, to produce useful nonribosomal peptide synthetase-polyketide synthase hybrid molecules known as epothilones. This strain was originally named 'Polyangium brachysporum' of the family Polyangiaceae and the order Myxococcales. However, phylogenetic analysis of the 16S rRNA gene sequence of strain DSM 7029 indicated that it was clustered with members of Schlegelella. Significant growth occurred at 25-42 °C, pH 5.0-10.0 and in the presence of 0-0.2 % (w/v) NaCl. The predominant ubiquinone was Q-8. The major fatty acids were C16 : 1ω7c/C16 : 1ω6c, C16 : 0 and C18 : 1ω7c. The G+C content of genomic DNA was 67.51 mol%. The strain was clearly distinguishable from other neighbouring Schlegelella members and genera Caldimonas and Zhizhongheella, using phylogenetic analysis, fatty acid composition data and a range of physiological and biochemical characteristics and genome analysis. Therefore, strain DSM 7029 represents a novel species of the genus Schlegelella, for which the name Schlegelella brevitalea sp. nov. is proposed.

Analysis of the Genome and Metabolome of Marine Myxobacteria Reveals High Potential for Biosynthesis of Novel Specialized Metabolites.

Comparative genomic/metabolomic analysis is a powerful tool to disclose the potential of microbes for the biosynthesis of novel specialized metabolites. In the group of marine myxobacteria only a limited number of isolated species and sequenced genomes is so far available. However, the few compounds isolated thereof so far show interesting bioactivities and even novel chemical scaffolds; thereby indicating a huge potential for natural product discovery. In this study, all marine myxobacteria with accessible genome data (n = 5), including Haliangium ochraceum DSM 14365, Plesiocystis pacifica DSM 14875, Enhygromyxa salina DSM 15201 and the two newly sequenced species Enhygromyxa salina SWB005 and SWB007, were analyzed. All of these accessible genomes are large (~10 Mb), with a relatively small core genome and many unique coding sequences in each strain. Genome analysis revealed a high variety of biosynthetic gene clusters (BGCs) between the strains and several resistance models and essential core genes indicated the potential to biosynthesize antimicrobial molecules. Polyketides (PKs) and terpenes represented the majority of predicted specialized metabolite BGCs and contributed to the highest share between the strains. BGCs coding for non-ribosomal peptides (NRPs), PK/NRP hybrids and ribosomally synthesized and post-translationally modified peptides (RiPPs) were mostly strain specific. These results were in line with the metabolomic analysis, which revealed a high diversity of the chemical features between the strains. Only 6-11% of the metabolome was shared between all the investigated strains, which correlates to the small core genome of these bacteria (13-16% of each genome). In addition, the compound enhygrolide A, known from E. salina SWB005, was detected for the first time and structurally elucidated from Enhygromyxa salina SWB006. The here acquired data corroborate that these microorganisms represent a most promising source for the detection of novel specialized metabolites.

A polyphasic approach leads to seven new species of the cellulose-decomposing genus Sorangium, Sorangium ambruticinum sp. nov., Sorangium arenae sp. nov., Sorangium bulgaricum sp. nov., Sorangium dawidii sp. nov., Sorangium kenyense sp. nov., Sorangium orientale sp. nov. and Sorangium reichenbachii sp. nov.

Seventy-three strains of Sorangium have been isolated from soil samples collected from all over the world. The strains were characterized using a polyphasic approach and phenotypic, genotypic and chemotype analyses clarified their taxonomic relationships. 16S rRNA, xynB1, groEL1, matrix-assisted laser desorption/ioniziation time-of-flight mass spectrometry and API-ZYM analyses were conducted. In addition, from selected representative strains, fatty acids, quinones and phospholipids were analysed. In silico DNA-DNA hybridization and DNA-DNA hybridization against the current type species of Sorangiumcellulosum strain Soce 1871T (DSM 14627T) completed the analyses. Finally, our study revealed seven new species of Sorangium: Sorangium ambruticinum (Soce 176T; DSM 53252T, NCCB 100639T, sequence accession number ERS2488998), Sorangium arenae (Soce 1078T; DSM 105768T, NCCB 100643T, ERS2489002), Sorangium bulgaricum (Soce 321T; DSM 53339T, NCCB 100640T, ERS2488999), Sorangium dawidii (Soce 362T; DSM 105767T, NCCB 100641T, ERS2489000), Sorangium kenyense (Soce 375T; DSM 105741T, NCCB 100642T, ERS2489001), Sorangium orientale (Soce GT47T; DSM 105742T, NCCB 100638T, ERS2501484) and Sorangium reichenbachii (Soce 1828T; DSM 105769T, NCCB 100644T, ERS2489003).

Simulacricoccus ruber gen. nov., sp. nov., a microaerotolerant, non-fruiting, myxospore-forming soil myxobacterium and emended description of the family Myxococcaceae.

A non-fruiting group of myxobacteria was previously speculated to exist in nature based on metagenomics data containing uncultured members of the order Myxococcales. Here, we describe a myxobacterial strain, designated MCy10636T, which was isolated from a German soil sample collected in 2013. It exhibits swarming characteristics but atypically produces myxospores in the absence of fruiting bodies. The novel strain stains Gram-negative and Congo-red-negative and is characterized mesophilic, neutrophilic, chemoheterotrophic and microaerotolerant. Branched-chain fatty acids are the predominant cellular fatty acids over the straight-chain type, and contain the major fatty acids iso-C17 : 0 2-OH, C16 : 1, iso-C17 : 0 and iso-C15 : 0. Based on blastn results, the 16S rRNA gene sequence reveals similarity (97 %) to Aggregicoccus edonensis MCy1366T, (97 %) Myxococcus macrosporus DSM 14697T, (96 %) Corallococcus coralloides DSM2259T and Corallococcus exiguus Cc e167T. Phylogenetic analysis showed a novel lineage of MCy10636T in the family Myxococcaceae, suborder Cystobacterineae. Based on polyphasic taxonomic characterization, we propose that this unusual, non-fruiting, myxospore-forming and microaerotolerant myxobacterial strain, MCy10636T, represents a novel genus and species, Simulacricoccus ruber gen. nov., sp. nov. (DSM 106554T=NCCB 100651T).

Correlating chemical diversity with taxonomic distance for discovery of natural products in myxobacteria.

Some bacterial clades are important sources of novel bioactive natural products. Estimating the magnitude of chemical diversity available from such a resource is complicated by issues including cultivability, isolation bias and limited analytical data sets. Here we perform a systematic metabolite survey of ~2300 bacterial strains of the order Myxococcales, a well-established source of natural products, using mass spectrometry. Our analysis encompasses both known and previously unidentified metabolites detected under laboratory cultivation conditions, thereby enabling large-scale comparison of production profiles in relation to myxobacterial taxonomy. We find a correlation between taxonomic distance and the production of distinct secondary metabolite families, further supporting the idea that the chances of discovering novel metabolites are greater by examining strains from new genera rather than additional representatives within the same genus. In addition, we report the discovery and structure elucidation of rowithocin, a myxobacterial secondary metabolite featuring an uncommon phosphorylated polyketide scaffold.

Nannocystis konarekensis sp. nov., a novel myxobacterium from an Iranian desert.

An orange-coloured myxobacterium, MNa11734T, was isolated from desert in Iran. MNa11734T had rod-shaped vegetative cells, moved by gliding and was bacteriolytic. No real fruiting body formation could be observed, but sporangioles were produced on water agar. The strain was mesophilic, strictly aerobic and chemoheterotrophic. 16S rRNA gene analyses revealed that MNa11734T belonged to the family Nannocystaceae, genus Nannocystis and was closely related to Nannocystis pusilla Na p29T (DSM 14622T) and Nannocystis exedens Na e1T (DSM 71T), with 97.8 and 97.6 % 16S rRNA gene sequence similarity, respectively. Laboratory-measured DNA-DNA hybridization showed only 9.5/15.7 % (reciprocal) similarity between the novel strain and N. pusilla Na p29T, and 14.1/20.4 % between the strain and N. exedens Na e1T, whereas DNA-DNA hybridization estimates derived from draft genome sequences were 21.8-23.0 % and 22.2-23.7 %, respectively, depending on the calculation method. The G+C content of DNA from Nannocystis konarekensis MNa11734T was 73.3 mol%, for N. pusilla Nap29T it was 71.8 mol% and for N. exedens Nae1T it was 72.2 mol%. The major fatty acids of the new strain were C16 : 1 (56.2 %), iso-C17 : 0 (14.4 %), C14 : 0 (8.2 %), C16 : 0 (6.6 %) and iso-C15 : 0 (5.9 %). Strain MNa11734T exhibited phylogenetic and physiological similarities to the two other species of Nannocystis, i.e. N. pusilla and N. exedens, but the differences were sufficient enough to represent a novel species, for which the name Nannocystiskonarekensis sp. nov. is proposed. The type strain is MNa11734T (=DSM 104509T=NCCB 100618T).

Unravelling the Complete Genome of Archangium gephyra DSM 2261T and Evolutionary Insights into Myxobacterial Chitinases.

Family Cystobacteraceae is a group of eubacteria within order Myxococcales and class Deltaproteobacteria that includes more than 20 species belonging to 6 genera, that is, Angiococcus, Archangium, Cystobacter, Hyalangium, Melittangium, and Stigmatella. Earlier these members have been classified based on chitin degrading efficiency such as Cystobacter fuscus and Stigmatella aurantiaca, which are efficient chitin degraders, C. violaceus a partial chitin degrader and Archangium gephyra a chitin nondegrader. Here we report the 12.5 Mbp complete genome of A. gephyra DSM 2261T and compare it with four available genomes within the family Cystobacteraceae. Phylogeny and DNA-DNA hybridization studies reveal that A. gephyra is closest to Angiococcus disciformis, C. violaceus and C. ferrugineus, which are partial chitin degraders of the family Cystobacteraceae. Homology studies reveal the conservation of approximately half of the proteins in these genomes, with about 15% unique proteins in each genome. The total carbohydrate-active enzymes (CAZome) analysis reveals the presence of one GH18 chitinase in the A. gephyra genome whereas eight copies are present in C. fuscus and S. aurantiaca. Evolutionary studies of myxobacterial GH18 chitinases reveal that most of them are likely related to Terrabacteria and Proteobacteria whereas the Archangium GH18 homolog shares maximum similarity with those of chitin nondegrading Acidobacteria.

Myxobacteria in high moor and fen: An astonishing diversity in a neglected extreme habitat.

Increasing antibiotic resistances of numerous pathogens mean that myxobacteria, well known producers of new antibiotics, are becoming more and more interesting. More than 100 secondary metabolites, most of them with bioactivity, were described from the order Myxococcales. Especially new myxobacterial genera and species turned out to be reliable sources for novel antibiotics and can be isolated from uncommon neglected habitats like, for example, acidic soils. Almost nothing is known about the diversity of myxobacteria in moors, except some information from cultivation studies of the 1970s. Therefore, we evaluated the myxobacterial community composition of acidic high moor and fen both with cultivation-independent 16S rRNA clone bank analysis and with cultivation. Phylogenetic analyses of clone sequences revealed a great potential of undescribed myxobacteria in high moor and fen, whereby all sequences represent unknown taxa and were detected exclusively by cultivation-independent analyses. However, many clones were assigned to sequences from other cultivation-independent studies of eubacterial diversity in acidic habitats. Cultivation revealed different strains exclusively from the genus Corallococcus. Our study shows that the neglected habitat moor is a promising source and of high interest with regard to the cultivation of prospective new bioactive secondary metabolite producing myxobacteria.

Vitiosangium cumulatum gen. nov., sp. nov. and Vitiosangium subalbum sp. nov., soil myxobacteria, and emended descriptions of the genera Archangium and Angiococcus, and of the family Cystobacteraceae.

Bacterial strains MCy10943T and MCy10944T were isolated in 2014 from dried Nepalese soil samples collected in 2013 from Phukot, Kalikot, Western Nepal, and Godawari, Lalitpur, Central Nepal. The novel organisms showed typical myxobacterial growth characteristics, which include swarming colony and fruiting body formation on solid surfaces, and a predatory ability to lyse micro-organisms. The strains were aerobic, mesophilic, chemoheterotrophic and showed resistance to various antibiotics. The major cellular fatty acids common to both organisms were C17 : 0 2-OH, iso-C15 : 0, C16 : 1 and iso-C17 : 0. The G+C content of the genomic DNA was 72-75 mol%. Phylogenetic analysis showed that the strains belong to the family Cystobacteraceae, suborder Cystobacterineae, order Myxococcales. The 16S rRNA gene sequences of both strains showed 97-98 % similarity to Archangium gephyra DSM 2261T andCystobacter violaceus DSM 14727T, and 96.7-97 % to Cystobacter fuscus DSM 2262T and Angiococcus disciformis DSM 52716T. Polyphasic taxonomic characterization suggested that strains MCy10943T and MCy10944T represent two distinct species of a new genus, for which the names Vitiosangium cumulatum gen. nov., sp. nov. and Vitiosangium subalbum sp. nov. are proposed. The type strain of Vitiosangium cumulatum is MCy10943T (=DSM 102952T=NCCB 100600T) while that for Vitiosangium subalbum is MCy10944T (=DSM 102953T=NCCB 100601T). In addition, emended descriptions of the genera Archangium and Angiococcus, and of the family Cystobacteraceaeare provided.

Racemicystis persica sp. nov., a myxobacterium from soil.

A novel myxobacterium, strain MSr11462T, was isolated in 2015 from a soil sample collected form Kish Island beach, Persian Gulf, Iran. It displayed general myxobacterial features like Gram-negative staining, rod-shaped vegetative cells, gliding on solid surfaces, microbial lytic activity, fruiting-body-like aggregates and myxospore-like structures. The strain was mesophilic, aerobic and showed a chemoheterotrophic mode of nutrition. It was resistant to many antibiotics like gentamycin, polymyxin, fusidic acid and trimethoprim, and the key fatty acids of whole-cell hydrolysates were iso-C15 : 0, C16 : 0, iso-C17 : 0, C18 : 1, iso-C17 : 1 2-OH, C18 : 1 2-OH, iso-C15 : 0 OAG (O-alkylglycerol) and C16 : 1 OAG. The 16S rRNA gene sequence showed highest similarity (98.6 %) to Racemicystis crocea strain MSr9521T (GenBank accession no. KT591707). The phylogenetic analysis based on 16S rRNA gene sequences and matrix-assisted laser-desorption/ionization time-of-flight (MALDI-TOF) spectroscopy data supports a novel species of the family Polyangiaceae and the genus Racemicystis. DNA-DNA hybridization showed only about 50 % similarity between the novel strain and the phylogenetically closest species, Racemicystis. crocea MSr9521T. On the basis of a comprehensive taxonomic study, we propose a novel species, Racemicystis persica sp. nov., for strain MSr11462T (=DSM 103165T=NCCB 100606T).

Racemicystis crocea gen. nov., sp. nov., a soil myxobacterium in the family Polyangiaceae.

A novel bacterial strain designated MSr9521T was isolated in 2014 from a soil sample collected in 1986 from the Philippines. The novel bacterium shows myxobacterial characteristics that include pseudoplasmodial swarming, fruiting body formation and predatory ability to lyse microorganisms. The strain is chemoheterotrophic, mesophilic and aerobic. Major fatty acids are C18:1, C17:1 2-OH and iso-C15:0, and also contains trace amounts of omega-3/-6 polyunsaturated fatty acids. The G+C content of the genomic DNA is 70.4 mol%. The 16S rRNA gene sequence shows 95-96 % closest similarity to Sorangium cellulosum DSM 14627T, Polyangium fumosum Pl fu5T, Jahnella thaxteri Pl t4T and Byssovorax cruenta By c2T. The molecular phylogenetic analysis shows that the novel isolate forms a novel branch in the family Polyangiaceae, suborder Sorangiineae. Polyphasic taxonomic characterization suggests that the strain MSr9521T represents a novel species of a new genus in the family Polyangiaceae, for which the name Racemicystis crocea gen. nov., sp. nov. is proposed. The type strain of Racemicystis crocea is MSr9521T (=DSM 100773T=NCCB 100574T).

Comparison of myxobacterial diversity and evaluation of isolation success in two niches: Kiritimati Island and German compost.

Myxobacteria harbor an enormous potential for new bioactive secondary metabolites and therefore the isolation of in particular new groups is of great interest. The diversity of myxobacteria present in two ecological habitats, namely sand from Kiritimati Island and German compost, was evaluated by both cultivation-based and cultivation-independent methods. Phylogenetic analyses of the strains in comparison with 16S rRNA gene sequences from cultured and uncultured material in GenBank revealed a great potential of undescribed myxobacteria in both sampling sites. Several OTUs (operational taxonomic units) represent unknown taxa and were detected by clone bank analyses, but not by cultivation. Clone bank analyses indicated that the myxobacterial community is predominantly indigenous. The 16S rDNA libraries from the two samples were generated from total community DNA with myxobacterial specific forward and universal reverse primer sets. The clones were partially sequenced. Cultivation was successful for exclusively bacteriolytic, but not for cellulolytic myxobacteria and revealed 42 strains from the genera Corallococcus, Myxococcus, and Polyangium. The genera of Myxococcaceae family were represented by both approaches. But, even in this well studied family, as well as in the suborders Sorangiineae and Nannocystineae, a considerable number of clones were assigned to, if any, uncultivated organisms. Our study shows an overrepresentation of the genera Myxococcus spp. and Corallococcus spp. with standard cultivation methods. However, high deficits are demonstrated in the cultivation success of the myxobacterial diversity detected by exclusively cultivation-independent approaches. Especially, clades which are exclusively represented by clones are of high interest with regard to the cultivation of new bioactive secondary metabolite producers.

Reclassification of Angiococcus disciformis, Cystobacter minus and Cystobacter violaceus as Archangium disciforme comb. nov., Archangium minus comb. nov. and Archangium violaceum comb. nov., unification of the families Archangiaceae and Cystobacteraceae, and emended descriptions of the families Myxococcaceae and Archangiaceae.

The species Archangium gephyra, Angiococcus disciformis, Cystobacter minus and Cystobacter violaceus are currently classified in three different genera of the order Myxococcales. The 16S rRNA gene sequences of the respective type strains show a similarity higher than 98.4 % and form a tight phylogenetic group. A dendrogram calculating the similarity of MALDI-TOF spectra confirmed the close relatedness of the four species that grouped in a monophyletic cluster in the neighbourhood of other species of the genus Cystobacter. The type strains shared similar fatty acid patterns of high complexity with iso-C15 : 0, C16 : 1ω5c and iso-C14 : 0 3-OH as the major components. The vegetative cells of these species are uniformly long needle-shaped rods, and the myxospores are short rods, ovoid or irregularly spherical thus differing from the myxospores of species related to Cystobacter fuscus, the type species of this genus. Some enzymic and hydrolysing reactions of the type strains are described. As a result of the high relatedness and similarity of the four species, it is proposed to place them into one genus, and due to phylogenetic and morphological distinctness, the species should be classified in a genus distinct from the genus Cystobacter as Archangium gephyra (type strain M18T = DSM 2261T = ATCC 25201T = NBRC 100087T), Archangium disciforme comb. nov. (type strain CMU 1T = DSM 52716T = ATCC 33172T), Archangium minus comb. nov. (proposed neotype strain Cb m2 = DSM 14751 = JCM 12627) and Archangium violaceum comb. nov. (type strain Cb vi61T = DSM 14727T = CIP 109131T = JCM 12629T). Since the family ArchangiaceaeJahn 1924 AL has priority over the family CystobacteraceaeMcCurdy 1970 AL, it is proposed to assign the genera Archangium, Anaeromyxobacter, Cystobacter, Hyalangium, Melittangium and Stigmatella to the family Archangiaceae. Emended descriptions of the families Myxococcaceae and Archangiaceae are also provided.