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Two myxobacterial strains (KH5-1 T and NO1) were isolated from the activated sludge tanks treating municipal sewage wastewater in Japan. These strains were recognised as myxobacteria based on their phenotypic characteristics of swarming colonies and fruiting bodies. Phylogenetic analyses using the 16S rRNA gene revealed that strains KH5-1 T and NO1 were affiliated with the genus Corallococcus, with the closest neighbours being Corallococcus exercitus AB043A T (99.77% and 99.84%, respectively). Genome comparisons using orthologous average nucleotide identity (orthoANI) and digital DNA-DNA hybridisation similarity (dDDH) with strains KH5-1 T and NO1 and their phylogenetically close relatives in Corallococcus spp. were below the thresholds. The major cellular fatty acids of strains KH5-1 T and NO1 were iso-C 15:0 (31.9%, 30.0%), summed feature 3 (comprising C 16:1 ω7c and/or C 1 6:1 ω6c) (20.2%, 17.7%), and iso-C 17:0 (12.1%, 14.8%), and the major respiratory quinone was found to be menaquinone (MK)-8. Based on the phenotypic, chemotaxonomic, and phylogenetic evidence, strains KH5-1 T and NO1 represent a new species in the genus Corallococcus, for which the proposed name is Corallococcus caeni sp. nov. The type strain is KH5-1 T (= NCIMB 15510 T  = JCM 36609 T )., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aim: Corallococcus species are diverse in the natural environment with 10 new Corallococcus species having been characterized in just the last 5 years. As well as being an abundant myxobacterial genus, they produce several secondary metabolites, including Corallopyronin, Corramycin, Coralmycin, and Corallorazine. We isolated a novel strain Corallococcus spp RDP092CA from soil in South Wales, UK, using Candida albicans as prey bait and characterized its predatory activities against pathogenic bacteria and yeast., Methods and Results: The size of the RDP092CA genome was 8.5 Mb with a G + C content of 71.4%. Phylogenetically, RDP092CA is closely related to Corallococcus interemptor, C. coralloides, and C. exiguus. However, genome average nucleotide identity and digital DNA-DNA hybridization values are lower than 95% and 70% when compared to those type strains, implying that it belongs to a novel species. The RDP092CA genome harbours seven types of biosynthetic gene clusters (BGCs) and 152 predicted antimicrobial peptides. In predation assays, RDP092CA showed good predatory activity against Escherichia coli, Pseudomonas aeruginosa, Citrobacter freundii, and Staphylococcus aureus but not against Enterococcus faecalis. It also showed good antibiofilm activity against all five bacteria in biofilm assays. Antifungal activity against eight Candida spp. was variable, with particularly good activity against Meyerozyma guillermondii DSM 6381. Antimicrobial peptide RDP092CA_120 exhibited potent antibiofilm activity with >50% inhibition and >60% dispersion of biofilms at concentrations down to 1 μg/ml., Conclusions: We propose that strain RDP092CA represents a novel species with promising antimicrobial activities, Corallococcus senghenyddensis sp. nov. (=NBRC 116490T =CCOS 2109T), based on morphological, biochemical, and genomic features., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

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.

Myxobacteria represent a viable source of chemically diverse and biologically active secondary metabolites. The myxochelins are a well-studied family of catecholate-type siderophores produced by various myxobacterial strains. Here, we report the discovery, isolation, and structure elucidation of three new myxochelins N1-N3 from the terrestrial myxobacterium Corallococcus sp. MCy9049, featuring an unusual nicotinic acid moiety. Precursor-directed biosynthesis (PDB) experiments and total synthesis were performed in order to confirm structures, improve access to pure compounds for bioactivity testing, and to devise a biosynthesis proposal. The combined evaluation of metabolome and genome data covering myxobacteria supports the notion that the new myxochelin congeners reported here are in fact frequent side products of the known myxochelin A biosynthetic pathway in myxobacteria.

Myxobacteria are one of the most promising secondary metabolites producers. However, they are difficult to isolate and cultivate. To obtain more myxobacteria and know the effects of environmental factors on myxobacterial community, we characterized myxobacterial communities in Dinghushan acidic forest soils of pH 3.6-4.5 with culture-dependent and -independent techniques, and analyzed environmental factors shaping myxobacterial communities. A total of 21 myxobacteria were isolated using standard cultivation methods, including eleven isolates of Corallococcus, nine isolates of Myxococcus and one isolate of Archangium, and contained three potential novel species. In addition, a total of 67 unknown myxobacterial operational taxonomic units (OTUs) were obtained using high-throughput sequencing method. The abundance of Myxococcales account for 0.9-2.2% of bacterial communities, and Sorangium is the most abundant genus (60.1%) in Myxococcales. Correlation analysis demonstrated that bacterial diversity and soil pH are the key factors shaping myxobacterial community. These results revealed an abundant myxobacterial community which is shaped by other bacteria and pH in Dinghushan acidic forest soils., Competing Interests: The authors have declared that no competing interests exist.

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 N 2 -dependent growth and acetylene reduction activity (ARA) in vitro Transcriptional activity of the nif gene was also detected when both strains were cultured with N 2 gas as a sole nitrogen source, indicating that Anaeromyxobacter can fix and assimilate N 2 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. IMPORTANCE Anaeromyxobacter 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, N 2 -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., (Copyright © 2020 American Society for Microbiology.)

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.

Quinolinic acid (QUIN) is a neurotoxin, gliotoxin, and proinflammatory molecule involved in the pathogenesis of several neurological diseases. Myxobacteria have been known as a rich source of secondary metabolites with diverse structures and mode of actions. In this study, we examined the potential neuroprotective effects of myxobacterial extracts on QUIN-induced excitotoxicity in primary human neurons. For this purpose, primary cultures of human neurons were pre-incubated with myxobacterial extracts and subsequently treated with QUIN at a pathophysiological concentration of 550 nM. The results showed that some myxobacterial extracts can significantly attenuate formation of reactive oxygen species (ROS), nitric oxide (NO) production, and extracellular lactate dehydrogenase (LDH) activity of human neurons. Moreover, myxobacterial extracts were also able to reduce neuronal nitric oxide synthase (nNOS) activity. Some extracts prevented cell death by reducing the activation of poly (ADP-ribose) polymerase (PARP1) by QUIN, therefore by maintaining NAD + levels. In addition, myxobacterial extracts ameliorated oxidative stress by increasing the intracellular levels of glutathione after treatment with QUIN. The results showed that extracts of Stigmatella sp. UTMC 4072 and Archangium sp. UTMC 4070 and were the most effective in reducing QUIN-induced excitotoxicity in primary human neurons. Due to their antioxidative activity, myxobacterial extracts represent an underexplored source of potential new drugs for the treatment of neurodegenerative diseases.

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 MCy10636 T , 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 MCy1366 T , (97 %) Myxococcus macrosporus DSM 14697 T , (96 %) Corallococcus coralloides DSM2259 T and Corallococcus exiguus Cc e167 T . Phylogenetic analysis showed a novel lineage of MCy10636 T in the family Myxococcaceae, suborder Cystobacterineae. Based on polyphasic taxonomic characterization, we propose that this unusual, non-fruiting, myxospore-forming and microaerotolerant myxobacterial strain, MCy10636 T , represents a novel genus and species, Simulacricoccus ruber gen. nov., sp. nov. (DSM 106554 T =NCCB 100651 T ).

An orange-coloured myxobacterium, MNa11734 T , was isolated from desert in Iran. MNa11734 T 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 MNa11734 T belonged to the family Nannocystaceae, genus Nannocystis and was closely related to Nannocystis pusilla Na p29 T (DSM 14622 T ) and Nannocystis exedens Na e1 T (DSM 71 T ), 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 p29 T , and 14.1/20.4 % between the strain and N. exedens Na e1 T , 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 MNa11734 T was 73.3 mol%, for N. pusilla Nap29 T it was 71.8 mol% and for N. exedens Nae1 T 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 MNa11734 T 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 MNa11734 T (=DSM 104509 T =NCCB 100618 T ).

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., (© 2017 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

Myxobacteria, a group of antimicrobial producing bacteria, have been successfully cultured and characterized from ten soil samples collected from different parts of Slovakia. A total of 79 myxobacteria belonging to four genera (Myxococcus, Corallococcus, Sorangium, and Polyangium) were isolated based on aspects of their life cycle. Twenty-five of them were purified, fermented, and screened for antimicrobial activities against 11 test microorganisms. Results indicated that crude extracts showed more significant activities against Gram-positive than against Gram-negative bacteria or fungi. Based on a higher degree and broader range of antimicrobial production, the two most potential extracts (K9-5, V3-1) were selected for HPLC fractionation against Micrococcus luteus and Staphylococcus aureus and LC/MS analysis of potential antibiotic metabolites. The analysis resulted in the identification of polyketide-peptide antibiotics, namely corallopyronin A and B (K9-5) and myxalamid B and C (V3-1), which were responsible for important Gram-positive activity in the observed strains. A sequence similarity search through BLAST revealed that these strains showed the highest sequence similarity to Corallococcus coralloides (K9-5, NCBI accession number KX256198) and Myxococcus xanthus (V3-1, NCBI accession number KX256197). Although screening of myxobacteria is laborious, due to difficulties in isolating cultures, this research represented the first report covering the isolation and cultivation of this challenging bacterial group from Slovakian soils as well as the screening of their antimicrobial activity, cultural identification, and secondary metabolite identification.

Epothilones are cytotoxic macrolactones having auspicious anti-tumorous activities, but merely produced by rare Sorangium strains. Here, we have focused on the epothilone gene cluster from special niche bacterial strain, S. cellulosum So0157-2. Therefore, we have isolated a high pH tolerant S. cellulosum strain So0157-2 and characterized the epothilones gene cluster and its flanks by cosmid/fosmid libraries preparation and sequencing. The assembly spanned 94,459 bp and consisted of 56,019 bp core region. Remarkably, the core as well as upstream 420 bp and downstream 315 bp were highly conserved, while further neighboring regions varied extremely. Transposase traces were identified near the core of clusters, supporting that the transposon-mediated transgenesis is a naturally evolved strategy for the cluster's dissemination. A predicted neighboring esterase gene was identified as a potential epothilone-resistance gene preventing self-toxicity. Novel modification or regulatory genes, a multi-position-cyclo releasing gene and their relationship with corresponding analogs were identified in strain So0157-2. These findings open the door to discover additional, naturally evolved epothilone-related genes for significant applications in industrial as well as clinical sector.

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.

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).

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).

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., (© 2015 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

Bacteria have been by far the most promising resource for antibiotics in the past decades and will in all undoubtedly remain an important resource of innovative bioactive natural products in the future. Actinobacteria have been screened for many years, whereas the Myxobacteria have been underestimated in the past. Even though Actinobacteria belong to the Gram-positive and Myxobacteria to the Gram-negative bacteria both groups have a number of similar characters, as they both have huge genomes with in some cases more than 10kB and a high GC content and they both can differentiate and have often cell cycles including the formation of spores. Actinobacteria have been used for the antibiotic research for many years, hence it is often discussed whether this resource has now been exhaustively exploited but most of the screening programs from pharmaceutical companies were basing on the cultivation mainly of members of the genus Streptomyces or Streptomyces like strains (e.g., some Saccharopolyspora, Amycolatopsis or Actinomadura species) by use of standard methods so that many of the so called "neglected" Actinobacteria were overlooked the whole time. The present review gives an overview on the state of the art regarding new bioactive compounds with a focus on the marine habitats. Furthermore, the evaluation of Myxobacteria in our ongoing search for novel anti-infectives is highlighted.

Plant-based sediment microbial fuel cells (PMFCs) couple the oxidation of root exudates in living rice plants to current production. We analysed the composition of the microbial community on anodes from PMFC with natural rice field soil as substratum for rice by analysing 16S rRNA as an indicator of microbial activity and diversity. Terminal restriction fragment length polymorphism (TRFLP) analysis indicated that the active bacterial community on anodes from PMFCs differed strongly compared with controls. Moreover, clones related to Deltaproteobacteria and Chloroflexi were highly abundant (49% and 21%, respectively) on PMFCs anodes. Geobacter (19%), Anaeromyxobacter (15%) and Anaerolineae (17%) populations were predominant on anodes with natural rice field soil and differed strongly from those previously detected with potting soil. In open circuit (OC) control PMFCs, not allowing electron transfer, Deltaproteobacteria (33%), Betaproteobacteria (20%), Chloroflexi (12%), Alphaproteobacteria (10%) and Firmicutes (10%) were detected. The presence of an electron accepting anode also had a strong influence on methanogenic archaea. Hydrogenotrophic methanogens were more active on PMFC (21%) than on OC controls (10%), whereas acetoclastic Methanosaetaceae were more active on OC controls (31%) compared with PMFCs (9%). In conclusion, electron accepting anodes and rice root exudates selected for distinct potential anode-reducing microbial populations in rice soil inoculated PMFC., (© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.)

A novel myxobacterium, MCy1366(T) (Ar1733), was isolated in 1981 from a soil sample collected from a region near Tokyo, Japan. 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 such as cephalosporin C, kanamycin, gentamicin, hygromycin B, polymyxin and bacitracin, and the key fatty acids of whole cell hydrolysates were iso-C15 : 0, iso-C17 : 0 and iso-C17 : 0 2-OH. The genomic DNA G+C content of the novel strain was 65.6 mol%. The 16S rRNA gene sequence showed highest similarity (97.60 %) to 'Stigmatella koreensis' strain KYC-1019 (GenBank accession no. EF112185). Phylogenetic analysis based on 16S rRNA gene sequences and MALDI-TOF MS data revealed a novel branch in the family Myxococcaceae. DNA-DNA hybridization showed only 28 % relatedness between the novel strain and the closest recognized species, Corallococcus exiguus DSM 14696(T) (97 % 16S rRNA gene sequence similarity). A recent isolate from a soil sample collected in Switzerland, MCy10622, displayed 99.9 % 16S rRNA gene sequence similarity with strain MCy1366(T) and showed almost the same characteristics. Since some morphological features like fruiting-body-like aggregates were barely reproducible in the type strain, the newly isolated strain, MCy10622, was also intensively studied. On the basis of a comprehensive taxonomic study, we propose a novel genus and species, Aggregicoccus edonensis gen. nov., sp. nov., for strains MCy1366(T) and MCy10622. The type strain of the type species is MCy1366(T) ( = DSM 27872(T) = NCCB 100468(T))., (© 2015 Prof. Dr. Rolf Muller, Department of Pharmaceutical Biotechnology, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany.)

Objective: Purpose of this work was to screen myxobacteria from soils and study their biological activities towards pathogenic bacteria, tumor cells and insects., Methods: Through inactivated E. coli and filter paper inducing methods, we isolated and purified myxobacteria from soil samples. Then we identified these purified strains based on morphological observation, physiological and biochemical characteristics, and the 16S rDNA sequences homologous analysis. By plate diffusion experiments, oral toxicity tests and tetrazolium assays, we investigated the biological activities of the myxobacterial culture supernatant., Results: We isolated 35 myxobacterial strains and classified them as 4 genera: Myxococcus (9), Corallococcus (9), Nannocystis (11) and Sorangium (6). Eight purified myxobacteria were identified and named. Cytotoxicity tests show that strain C. macrospores S22 had potent and broad-spectrum cytotoxic effect on tumor cell lines including B16, 4T1, HeLa and HCT-116, so did the strains M. fulvus S51, C. exiguus S22 and M. Xanthus S55. Additionally, C. macrospores S22 also shows inhibitory activity to pathogenic bacteria Bacillus subtillis and Candida albicans., Conclusion: Myxobacteria are widely distributed in natural soils. C. macrosporus has potent toxicity against cancer cells and pathogenic bacteria; and C. exiguus with antitumor activity. The myxobacterial strains are promising resources for discovery and development of new active natural products and drugs.

A bacterial strain designated SBNa008(T) was isolated from a Philippine soil sample. It exhibited the general characteristics associated with myxobacteria, such as swarming of Gram-negative vegetative rod cells, fruiting body and myxospore formation and predatory behaviour in lysing micro-organisms. The novel strain was characterized as mesophilic, chemoheterotrophic and aerobic. The major fatty acids were C(20:4)ω6,9,12,15 all cis (arachidonic acid), iso-C(15 : 0), C(17 : 1) 2-OH and iso-C(15 : 0) dimethylacetal. Interestingly, SBNa008(T) contained diverse fatty acids belonging to the commercially valuable polyunsaturated omega-6 and omega-3 families, and a highly conjugated dihydroxylated C28 steroid. The G+C content of the genomic DNA was 67.3 mol%. The 16S rRNA gene sequence revealed 95-96% similarity to sequences derived from clones of uncultured bacteria and 94-95% similarity to cultured members of the suborder Sorangiineae. Phylogenetic analysis revealed that strain SBNa008(T) formed a novel lineage in the suborder Sorangiineae. Based on a polyphasic taxonomic characterization, we propose that strain SBNa008(T) represents a novel genus and species, Minicystis rosea gen. nov., sp. nov. The type strain of Minicystis rosea is SBNa008(T) ( =DSM 24000(T) =NCCB 100349(T))., (© 2014 IUMS.)

Two myxobacterial strains (designated B00001(T) and B00002(T)) were isolated from forest soil samples collected from Yakushima Island, Kagoshima, Japan. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains B00001(T) and B00002(T) respectively formed independent branches within the suborders Cystobacterineae and Sorangiineae and were most closely related to Cystobacter armeniaca DSM 14710(T) (90.4% similarity) and Byssovorax cruenta DSM 14553(T) (91.3%). Neither strain showed typical features of myxobacteria such as bacteriolytic action or fruiting body formation, but both had high DNA G+C contents (66.3-68.3 mol%). Swarming motility was observed in strain B00002(T) only. Cells of both strains were vegetative, chemoheterotrophic, mesophilic, strictly aerobic, Gram-negative, motile rods, and both strains exhibited esterase lipase (C8), leucine arylamidase, naphthol-AS-BI-phosphohydrolase and β-galactosidase activities. Strain B00001(T) contained MK-7 as the predominant respiratory quinone and the major fatty acid was iso-C15:0. In contrast, strain B00002(T) contained MK-8 as the major cellular quinone and the major fatty acids were C16 : 1ω5c and iso-C17 : 0. Based on the phenotypic and genotypic data presented, strains B00001(T) and B00002(T) represent novel genera and species, for which we propose the names Vulgatibacter incomptus gen. nov., sp. nov. and Labilithrix luteola gen. nov., sp. nov., respectively. The type strains of Vulgatibacter incomptus and Labilithrix luteola are B00001(T) ( = NBRC 109945(T) = DSM 27710(T)) and B00002(T) ( = NBRC 109946(T) = DSM 27648(T)), respectively. The new genera are assigned to the new families Vulgatibacteraceae fam. nov. and Labilitrichaceae fam. nov., respectively. In addition, Anaeromyxobacteraceae fam. nov., is proposed to accommodate the genus Anaeromyxobacter, which is related to the genus Vulgatibacter., (© 2014 IUMS.)

Objective: We isolated Myxobacteria strains from soil samples collected from Guangzhou, identified the strain and studied the antitumor activity., Methods: We isolated Myxobacteria strains from soil samples through inactivated E. coli inducing method, identified the strain according to morphological observation, physiological and biochemical characteristics, and the homologous analysis of 16S rRNA sequences of nucleotides. The antitumor spectrum and the corresponding IC50 of the active component separated from the culture was analyzed. Confocal laser scanning microscope was used to examine the growth inhibitory effect of the active component on B16 cells., Results: We isolated a Myxobacteria strain and identified as Myxococcus macrosporus STXZ54. The active component termed SGF5 showed cytostatic activity against B16, Hela, 4T1, Hep-3B with IC50 values of 10 microg/mL, and HCT-116 cell with IC50 values of 70 microg/mL. Subcellular structure of B16 cells were abnormal observed by confocal laser scanning microscope. Combining the apoptosis and necrosis assay result it is likely that SGF5 can induce apoptosis of B16 cells., Conclusion: The active component separated from the culture of Myxococcus macrosporus STXZ54 has a significant antitumor activity tested by cytotoxicity assay, which was worth exploiting as potential antitumor drugs.

Large-scale surveys show that the anti-tumour compounds known as epothilones are produced by only a small proportion of Sorangium strains, thereby greatly hampering the research and development of these valuable compounds. In this study, to investigate the niche diversity of epothilone-producing Sorangium strains, we re-surveyed four soil samples where epothilone producers were previously found. Compared with the < 2.5% positive strains collected from different places, epothilone producers comprised 25.0-75.0% of the Sorangium isolates in these four positive soil samples. These sympatric epothilone producers differed not only in their 16S rRNA gene sequences and morphologies but also in their production of epothilones and biosynthesis genes. A further exploration of 14 soil samples collected from a larger area around a positive site showed a similar high positive ratio of epothilone producers among the Sorangium isolates. The present results suggest that, in an area containing epothilone producers, the long-term genetic variations and refinements resulting from selective pressure form a large reservoir of epothilone-producing Sorangium strains with diverse genetic compositions., (© 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)

Although many molecular ecological surveys have been conducted, there is little concerning the details of specific bacterial groups, resulting in an incomplete understanding of the microorganismal composition and community structures in the environment. Myxobacteria are micropredators that are metabolically active in the soil microbial food web and have typically been considered minority components of soil bacterial communities. In this study, we surveyed the percentage of myxobacteria in a single soil sample via pyrosequencing on combined universal libraries of the V3-V4 and V6-V8 hypervariable regions of the 16S rRNA gene. Surprisingly, myxobacteria accounted for 4.10% of the bacterial community and 7.5% of the total operational taxonomic units at the 3% similarity level in the soil, containing almost all of the cultivated myxobacterial families or genera. To testify the appearance of myxobacteria in soil niches, we retrieved myxobacteria-related 16S rRNA gene sequences of 103 high-throughput sequencing data sets obtained from public databases. The results indicated that myxobacteria-related sequences were among the predominant groups in these data sets accounting for 0.4-4.5% of bacterial communities. The abundance of myxobacterial communities were correlated with site temperature, carbon-to-nitrogen ratio and pH values. Based on these results, we discussed the survival strategies of myxobacterial community in soil., (© 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.)

The rubber oxygenase (RoxA) of Xanthomonas sp. strain 35Y (RoxA(Xsp)) is so far the only known extracellular c-type diheme cytochrome that is able to cleave poly(cis-1,4-isoprene). All other rubber-degrading bacteria described are Gram positive and employ a nonheme protein (latex-clearing protein [Lcp]) for the postulated primary attack of polyisoprene. Here, we identified RoxA orthologs in the genomes of Haliangium ochraceum, Myxococcus fulvus, Corallococcus coralloides, and Chondromyces apiculatus. The roxA orthologs of H. ochraceum (RoxA(Hoc)), C. coralloides BO35 (RoxA(Cco)), and M. fulvus (RoxA(Mfu)) were functionally expressed in a ΔroxA Xanthomonas sp. 35Y background. All RoxA orthologs oxidatively cleaved polyisoprene, as revealed by restoration of clearing-zone formation and detection of 12-oxo-4,8-dimethyltrideca-4,8-diene-1-al (ODTD) as a cleavage product. RoxA(Xsp), RoxA(Mfu), and RoxA(Cco) were purified and biochemically characterized. The optimal temperature of RoxA(Cco) and RoxA(Mfu) was between 22 and 30°C. All RoxA orthologs as isolated showed an oxidized UV-visible spectrum. Chemical reduction of RoxA(Cco) and RoxA(Mfu) indicated the presence of two slightly different heme centers with absorption maxima between 549 and 553 nm, similar to RoxA(Xsp). Sequence analysis and modeling of the three-dimensional structures of the RoxA orthologs revealed a high degree of similarity to the recently solved RoxA(Xsp) structure and included several conserved residues, notably, W302, F317, and a MauG motif at about H517. Lcp-like sequences were not detected in the genomes of the Xanthomonas sp. 35Y, H. ochraceum, M. fulvus, and C. coralloides. No RoxA orthologs were found in Gram-positive bacteria, and this first description of functional RoxA in Gram-negative bacteria other than Xanthomonas proves that RoxA is more common among rubber degraders than was previously assumed.

Fifty-eight terrestrial and salt-tolerant myxobacteria were isolated from the saline-alkaline soils collected from Xinjiang, China. Based on the morphologies and the 16S rRNA gene sequences, these isolates were assigned into 6 genera, Myxococcus, Cystobacter, Corallococcus, Sorangium, Nannocystis and Polyangium. All the strains grew better with 1% NaCl than without NaCl. Some Myxococcus strains were able to grow at 2% NaCl concentration, suggesting that these strains may be particular type of terrestrial myxobacteria.

Objective: We isolated myxobacteria and explored their diversity from the rhizosphere soils of some medicinal plants., Methods: We used the helper bacteria baiting technique to isolate myxobacteria from the rhizosphere soils collected in South China Botanical Garden and Nanling National Forest Park. The myxobacteria were identified by morphological characteristics and 16S rDNA gene sequences analysis., Results: A total of 50 strains were isolated from 22 soil samples, which were identified into 7 genera, Myxococcus (18), Corallococcus (11), Cystobacter (7), Archangium (8), Stigmatella (1), Chondromyces (4) and Pyxidicoccus (1). The dominant genera were Myxococcus and Corallococcus., Conclusion: Environmental factors were associated with the diversity of myxobactria. Myxobacteria better adapt in high organic matter content and neutral pH environments. The strains of Myxococcus and Corallococcus had a good adaptability for different pH. Meanwhile, the dependence of the strains of Myxococcus and Cystobacter on organic carbon content was not too obvious, and they can also be found in the poor soils. Our findings provided an important scientific base for the development and utilization of myxobacteria resources.

Objective: We isolated myxobacteria in saline-alkaline soils of Xinjiang using a prey-predator strategy where the prey bacteria can induce the predator myxobacteria to form visible fruiting body, and evaluated intrinsic relationships between prey and predator myxobacteria., Methods: Sixteen bacteria with inductive effects of fruiting body formation were obtained, and then used as preys to isolate the myxobacteria., Results: A total of 55 myxobacteria strains were isolated from 25 soil samples, which were identified to the genera of Myxococcus, Corallococcus, Pyxidicoccus, Cystobacter, and Nannocystis. Besides, 6 unpurified isolates were believed to be myxobacteria. All the 16 prey bacteria had preferable inductive effects on Myxococcus spp., whereas Pyxidicoccus spp. and Cystobacter spp. were only induced by Gram-positive strains., Conclusion: The prey-predator strategy provided a new and more effective way to isolate myxobacteria.

A myxobacterial strain, designated SYR-2(T), was obtained from a mud sample from an estuarine marsh alongside the Yoshino River, Shikoku, Japan. It had rod-shaped vegetative cells and formed bacteriolytic enlarging colonies or so-called 'swarms' in the agar media. Fruiting-body-like globular to polyhedral cell aggregates and myxospore-like spherical to ellipsoidal cells within them were observed. Those features coincided with the general characteristics of myxobacteria. The strain was mesophilic and strictly aerobic. Growth of SYR-2(T) was observed at 18-40 °C (optimum, 30-35 °C), pH 5.5-8.3 (optimum, pH 7.0-7.5) and with 0.0-2.5 % (w/v) NaCl (optimum, 0.2-1.0 %). Both Mg(2+) and Ca(2+) were essential cations for the growth. The predominant fatty acids were iso-C15 : 0 (43.8 %), iso-C17 : 0 (22.4 %) and iso-C16 : 0 (9.6 %). A C20 : 4 fatty acid [arachidonic acid (4.3 %)], iso-C19 : 0 (1.5 %) and anteiso-acids [ai-C15 : 0 (0.5 %), ai-C17 : 0 (0.3 %)] were also detected. The G+C content of the DNA was 69.7 mol%. The strain contained menaquinone-7 (MK-7) as the major respiratory quinone. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain SYR-2(T) belonged to the suborder Nannocystineae, order Myxococcales in the class Deltaproteobacteria, and the strain was most closely related to two type strains of marine myxobacteria, Enhygromyxa salina SHK-1(T) and Plesiocystis pacifica SIR-1(T), with 96.5 % and 96.0 % similarities, respectively. These characteristics determined in this polyphasic study suggested that strain SYR-2(T) represents a novel species in a new genus of myxobacteria. The name Pseudenhygromyxa salsuginis gen. nov., sp. nov. is proposed to accommodate this isolate, and the type strain of Pseudenhygromyxa salsuginis is SYR-2(T) ( = NBRC 104351(T) = DSM 21377(T)).

Phylogenetic analysis of the groEL1 and xynB1 gene sequences from Sorangium cellulosum strains isolated in Korea previously revealed the existence of at least 5 subgroups (A-E). In the present study, we used sequence analysis of polymerase chain reaction-amplified biosynthetic genes of strains from the 5 subgroups to indicate correlations between S. cellulosum subgroups and their secondary metabolic gene categories. We detected putative biosynthetic genes for disorazol, epothilone, ambruticin, and soraphen in group A, group C, group D, and group E strains, respectively. With the exception of KYC3204, culture extracts from group A, group B, and group C strains exhibited no noticeable antimicrobial inhibitory activities. By contrast, culture extracts from group D strains inhibited the growth of Candida albicans, whereas culture extracts from group E strains inhibited the growth of C. albicans and Staphylococcus aureus. High performance liquid chromatography analysis of the culture extracts from the strains of each subgroup revealed unique peak patterns. Our findings indicate the existence of at least 5 subgroups of S. cellulosum strains, each of which has the potential to produce a unique set of secondary metabolites.

The study compares the bacteriological quality on Asian seabass (Lates calcarifer) between ice and salt storage methods. The main objectives of the study were to identify different bacteria constituents and quantitative bacterial load in Asian seabass when preserved with ice and sea salt. For the purpose of this study, Asian seabass was stored in two different conditions of ice-chilled and salted for 2 days. All fish samples were analyzed by performing bacteriological analysis and the isolated bacteria were identified by using API identification system. In case of the quantity of bacteria in the flesh, Chilling and salting had no significant difference to the quantity of bacteria on fish flesh. As for the skin, salt-preserved fish showed higher quantity of bacteria than ice-preserved fish. Acinetobacter baumannii and Pseudomonas fluorescens had been identified from skin sample of ice-chilled fish. Besides P. fluorescens and A. baumannii other isolates identified include Vibrio and Myxobacteria. All bacteria were cocci-shaped except a few bacilli. In term of bacteria number and morphological characteristics, ice-chilled preserved fish was better than salt preserved fish. Overall, less number of bacteria was observed in both ice-chilled and sea salt preserved fish. The result of this study indicated that the quick preservation is a very important factor to control bacterial load in the preserved fish.

Myxobacteria are common in terrestrial habitats and well known for their formation of fruiting bodies and production of secondary metabolites. We studied a cluster of myxobacteria consisting only of sequences of marine origin (marine myxobacteria cluster, MMC) in sediments of the North Sea. Using a specific PCR, MMC sequences were detected in North Sea sediments down to 2.2 m depth, but not in the limnetic section of the Weser estuary and other freshwater habitats. In the water column, this cluster was only detected on aggregates up to a few meters above the sediment surface, but never in the fraction of free-living bacteria. A quantitative real-time PCR approach revealed that the MMC constituted up to 13% of total bacterial 16S rRNA genes in surface sediments of the North Sea. In a global survey, including sediments from the Mediterranean Sea, the Atlantic, Pacific and Indian Ocean and various climatic regions, the MMC was detected in most samples and to a water depth of 4300 m. Two fosmids of a library from sediment of the southern North Sea containing 16S rRNA genes affiliated with the MMC were sequenced. Both fosmids have a single unlinked 16S rRNA gene and no complete rRNA operon as found in most bacteria. No synteny to other myxobacterial genomes was found. The highest numbers of orthologues for both fosmids were assigned to Sorangium cellulosum and Haliangium ochraceum. Our results show that the MMC is an important and widely distributed but largely unknown component of marine sediment-associated bacterial communities.

A novel starch-degrading myxobacterium designated NOSO-4(T) (new organism of the Sorangiineae strain 4) was isolated in 1995 from a soil sample containing plant residues, collected in Lucknow, Uttar Pradesh, India. The novel bacterium shows typical myxobacterial characteristics such as gram-negative, rod-shaped vegetative cells, swarming colonies, fruiting body-like aggregates and bacteriolytic activity. The strain is mesophilic, strictly aerobic and chemoheterotrophic. Based on 16S rRNA gene sequences, NOSO-4(T) shows highest similarity (96.2 %) with the unidentified bacterial strain O29 (accession no. FN554397), isolated from leek (Allium porrum) rhizosphere, and to the myxobacteria Jahnella thaxteri (88.9 %) and Chondromyces pediculatus (88.5 %). Major fatty acids are C(17 : 1) 2-OH, C(20 : 4)ω6 (arachidonic acid), and the straight-chain fatty acids C(17 : 0), C(15 : 0) and C(16 : 0). The genomic DNA G+C content of the novel isolate is 66.8 mol%. It is proposed that strain NOSO-4(T) represents a novel species in a new genus, i.e. Sandaracinus amylolyticus gen. nov., sp. nov., but also belongs to a new family, Sandaracinaceae fam. nov. The type strain of the type species, S. amylolyticus sp. nov., is NOSO-4(T) ( = DSM 53668(T) = NCCB 100362(T)).

Objective: To isolate myxobacteria and investigate their diversity in saline-alkaline soils from Akesu in Xinjiang., Methods: Conventional culture-dependent methods, e. g. baiting technique, water agar, soil extract agar and mineral agar, were used to isolate myxobacteria from 25 soil samples collected from Akesu areas of Xinjiang. Combining with physicochemical properties (acidity/alkalinity, salt concentration, vegetation and geographical locations) of the soil samples, myxobacterial diversity was studied., Results: In total 58 strains were isolated, and identified as belonging to 6 different genera, i.e. Myxococcus, Cystobacter, Corallococcus, Sorangium, Nannocystis and Polyangium of Myxococcales. The most frequent genus isolated was Myxococcus which may better adapt in harsh environments. Different myxobacterial diversity was detected in different habitat., Conclusion: Myxobacteria diversity was low in saline-alkaline soils of Akesu in Xinjiang.

Microorganisms are globally dispersed and are able to proliferate in any habitat that supports their lifestyles, which, however, has not yet been explored in any specific microbial taxon. The social myxobacteria are considered typical soil bacteria because they have been identified in various terrestrial samples, a few in coastal areas, but none in other oceanic environments. To explore the prevalence of marine myxobacteria and to investigate their phylogenetic relationships with their terrestrial counterparts, we established myxobacteria-enriched libraries of 16S rRNA gene sequences from four deep-sea sediments collected at depths from 853 to 4675 m and a hydrothermal vent at a depth of 204 m. In all, 68 different myxobacteria-related sequences were identified from randomly sequenced clones of the libraries of different samples. These myxobacterial sequences were diverse but phylogenetically similar at different locations and depths. However, they were separated from terrestrial myxobacteria at high levels of classification. This discovery indicates that the marine myxobacteria are phylogeographically separated from their terrestrial relatives, likely because of geographic separation and environment selection.

Three myxobacterial strains, designated SWB004, SWB005 and SWB006, were obtained from beach sand samples from the Pacific Ocean and the North Sea. The strains were cultivated in salt water containing media and subjected to studies to determine their taxonomic status, the presence of genes for the biosynthesis of polyketides and antibiotic production. 16S rDNA sequence analysis revealed the type strain Enhygromyxa salina SHK-1(T) as their closest homolog, displaying between 98% (SWB005) and 99% (SWB004 and SWB006) sequence similarity. All isolates were rod-shaped cells showing gliding motility and fruiting body formation as is known for myxobacteria. They required NaCl for growth, with an optimum concentration of around 2% [w/v]. The G + C-content of genomic DNA ranged from 63.0 to 67.3 mol%. Further, the strains were analyzed for their potential to produce polyketide-type structures. PCR amplified ketosynthase-like gene fragments from all three isolates enhances the assumption that these bacteria produce polyketides. SWB005 was shown to produce metabolites with prominent antibacterial activity, including activity towards methicillin resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE).

3-O-alpha-D-ribofuranosyl epothilone A (epothiloneoside A) is a major component of glycosylated epothilones in Sorangium cellulosum strain So0157-2. The production and glycosylation ratios of epothiloneoside A in both solid and liquid culture conditions with various pH values and carbon sources were studied. The results showed that glycosylation occurs whenever epothilones are produced, regardless of changes in pH values, production time curves, and different carbon sources. We suggest that glycosylation is a stable process, paralleling the biosynthesis of epothilones in the So0157-2 strain.

A bacterial strain designated SBKo001(T) was isolated from a forest soil sample from Mt Makiling in Laguna, Philippines. It shows the general characteristics associated with myxobacteria, such as swarming of Gram-negative, rod-shaped vegetative cells, fruiting body formation and bacteriolytic activity. The strain is mesophilic, strictly aerobic and chemoheterotrophic and also exhibits resistance to various antibiotics. Major fatty acids are iso-C(15 : 0), C(17 : 1) 2-OH and C(20 : 4) (arachidonic acid). The G+C content of the genomic DNA is 69.2 mol%. A reference strain, NOSO-1 (=DSM 53757), isolated from the Etosha Basin in Namibia, shares nearly the same characteristics with SBKo001(T). The identical 16S rRNA gene sequences of the two strains show 94 % identity to strains of the cellulose-degrading Byssovorax and Sorangium species. Phylogenetic analysis reveals a novel branch diverging from the Polyangiaceae, Sorangiineae, Myxococcales. Their uniqueness in morphological growth stages, unusual fatty acid profile, broad-spectrum antibiotic resistance and branch divergence from the Polyangiaceae imply that strains SBKo001(T) and NOSO-1 not only represent a novel genus and species, proposed here as Phaselicystis flava gen. nov., sp. nov., but also belong to a new family, Phaselicystidaceae fam. nov. The type strain of Phaselicystis flava is SBKo001(T) (=DSM 21295(T) =NCCB 100230(T)).

Versaphilic Anaeromyxobacter dehalogenans strains implicated in hexavalent uranium reduction and immobilization are present in the fractured saprolite subsurface environment at the U.S. Department of Energy Integrated Field-Scale Subsurface Research Challenge (IFC) site near Oak Ridge, TN. To provide insight into the in situ distribution of Anaeromyxobacter strains in this system with a nonuniform groundwater flow, 16S rRNA gene-targeted primers and linear hybridization (TaqMan) probes were designed for Oak Ridge IFC Anaeromyxobacter isolates FRC-D1 and FRC-W, along with an Anaeromyxobacter genus-targeted probe and primer set. Multiplex quantitative real-time PCR (mqPCR) was applied to samples collected from Oak Ridge IFC site areas 1 and 3, which are not connected by the primary groundwater flow paths; however, transport between them through cross-plane fractures is hypothesized. Strain FRC-W accounted for more than 10% of the total quantifiable Anaeromyxobacter community in area 1 soils, while strain FRC-D1 was not detected. In FeOOH-amended enrichment cultures derived from area 1 site materials, strain FRC-D1 accounted for 30 to 90% of the total Anaeromyxobacter community, demonstrating that this strain was present in situ in area 1. The area 3 total Anaeromyxobacter abundance exceeded that of area 1 by 3 to 5 orders of magnitude, but neither strain FRC-W- nor FRC-D1-like sequences were quantifiable in any of the 33 area 3 groundwater or sediment samples tested. The Anaeromyxobacter community in area 3 increased from <10(5) cells/g sediment outside the ethanol biostimulation treatment zone to 10(8) cells/g sediment near the injection well, and 16S rRNA gene clone library analysis revealed that representatives of a novel phylogenetic cluster dominated the area 3 Anaeromyxobacter community inside the treatment loop. The combined applications of genus- and strain-level mqPCR approaches along with clone libraries provided novel information on patterns of microbial variability within a bacterial group relevant to uranium bioremediation.

Myxobacteria produce a range of structurally novel natural products which exhibit unusual or unique modes of action, attracting significant interest from both the academic and drug discovery communities. Efforts to discover new strains with the potential to biosynthesize novel molecules have revealed that myxobacterial diversity and natural products are far from exhausted. We describe here a general, nonselective approach to unearth further myxobacterial strains, in order to mine them for compounds with potential as medicines. Sample collection from locations world-wide has shown that environments which exhibit significant biological complexity yield the highest probability of isolating novel myxobacterial strains. Here, we illustrate the details of simple and efficient strain purification techniques, which lead systematically to the identification of new and promising myxobacteria. Compound identification is then facilitated by molecular biological approaches, coupled with sophisticated high resolution mass spectrometry, statistical analysis, and bioassays.

Epothilone and its analogs are a potent new class of anticancer compounds produced by myxobacteria. Thus, in an effort to identify new myxobacterial strains producing epothilone and its analogs, cellulose-degrading myxobacteria were isolated from Korean soils, and 13 strains carrying epothilone biosynthetic gene homologs were screened using a polymerase chain reaction. A migration assay revealed that Sorangium cellulosum KYC3013, 3016, 3017, and 3018 all produced microtubule-stabilizing compounds, and an LCMS/ MS analysis showed that S. cellulosum KYC3013 synthesized epothilone A.

Aims: Efficient strain dereplication is of great value during the generation of bacterial strain collections for industrial screening. We evaluated the utilization of the RNase P RNA gene (rnpB) sequence as a tool for molecular dereplication of myxobacteria., Methods and Results: 16S rDNA (approx. 1 x 5 kbp) and rnpB (approx. 0 x 3 kbp) sequences were obtained and aligned. From 50 strains, we obtained 20 different sequences for the 16S rDNA and 24 for rnpB. Intersequence similarity was lower for rnpB than for 16S rDNA., Conclusions: rnpB allows the rapid discrimination of similar strains, with a higher resolution power as compared with 16S rRNA gene sequencing. It not only gives better discrimination, but is also faster and cheaper than 16S rDNA sequencing., Significance and Impact of the Study: Myxobacteria isolation and cultivation require time and experience. The application of rnpB sequencing to early myxobacterial strain dereplication may help in the generation of diverse strain libraries of these bacteria.

A recombinant plasmid, pRP-GFP, harboring the green fluorescent protein (GFP) gene from the broad-host-range mobilizable plasmid pRK415 of the RK2 family was constructed and transferred by conjugation from Escherichia coli S17-1 to Sorangium cellulosum So ce90. The results of Southern blot analysis showed that the plasmid replicated autonomously without being integrated into the chromosome of the bacterium. In pRP-GFP, gfp was driven by a So ce90 DNA fragment called EpoPro, which is an 890-bp DNA segment spanning from -890 to -1 relative to the start codon (GTG) of epoA, a gene that encodes EPOS A, which is presumed to be involved in the initiation of epothilone biosynthesis. The GFP in the transformed S. cellulosum So ce90 was detected by fluorescence microscopy, which suggests that the EpoPro fragment had the function of promoter. Because the green fluorescent bacilli could be directly observed by fluorescence microscopy, the stable expression of GFP was rapid and convenient for conjugation screening in addition to the antibiotic resistance genes within the constructed plasmid. This is the first report on an exogenous plasmid that can be stably maintained as an extrachromosomal element in S. cellulosum.

Acetate is the most abundant intermediate of organic matter degradation in anoxic rice field soil and is converted to CH(4) and/or CO(2). Aceticlastic methanogens are the primary microorganisms dissimilating acetate in the absence of sulfate and reducible ferric iron. In contrast, very little is known about bacteria capable of assimilating acetate under methanogenic conditions. Here, we identified active acetate-assimilating microorganisms by using a combined approach of frequent label application at a low concentration and comparative RNA-stable isotope probing with (13)C-labeled and unlabeled acetate. Rice field soil was incubated anaerobically at 25 degrees C for 12 days, during which (13)C-labeled acetate was added at a concentration of 500 muM every 3 days. (13)C-labeled CH(4) and CO(2) were produced from the beginning of the incubation and accounted for about 60% of the supplied acetate (13)C. RNA was extracted from the cells in each sample taken and separated by isopycnic centrifugation according to molecular weight. Bacterial and archaeal populations in each density fraction were screened by reverse transcription-PCR-mediated terminal restriction fragment polymorphism analysis. No differences in the bacterial populations were observed throughout the density fractions of the unlabeled treatment. However, in the heavy fractions of the (13)C treatment, terminal restriction fragments (T-RFs) of 161 bp and 129 bp in length predominated. These T-RFs were identified by cloning and sequencing of 16S rRNA as from a Geobacter sp. and an Anaeromyxobacter sp., respectively. Apparently these bacteria, which are known as dissimilatory iron reducers, were able to assimilate acetate under methanogenic conditions, i.e., when CO(2) was the predominant electron acceptor. We hypothesize that ferric iron minerals with low bioavailability might have served as electron acceptors for Geobacter spp. and Anaeromyxobacter spp. under these conditions.

Epizootic bovine abortion (EBA), also known as "foothill abortion", is a vector borne disease of beef cattle that graze in the mountainous regions of California, southern Oregon and western Nevada transmitted by the argasid tick Ornithodoros coriaceus. Recently, the putative agent of EBA was identified as a novel Deltaproteobacter in the order Myxococcales. In this study, a TaqMan real-time PCR (TM-PCR) protocol specific to the putative EBA agent was developed. The new real-time TM-PCR assay functioned sensitively and specifically to detect pathogen DNA in field-collected O. coriaceus ticks. The assay had an analytical sensitivity of a single plasmid copy and, when evaluated with a collection of tick-borne pathogens, yielded a positive PCR-result only for the agent of EBA. Use of the TM-PCR represents an effective tool for rapid and highly sensitive assessment of environmental risk and spatial and statistical analysis to highlight areas where there may be increased risk for EBA in susceptible cattle.

Six red-pigmented strains of the Alphaproteobacteria with optimal growth between 45 and 54 degrees C were previously isolated from coloured biofilms in two fine-paper machines and one pulp dryer. The strains were found to be resistant to 15 p.p.m. 2,2-dibromo-3-nitrilopropionamide, a common industrial biocide. 16S RNA gene sequence similarity of the isolates was 99.7-100 %. Ribotyping using the restriction enzymes PvuII and EcoRI showed that four of the isolates (C-lvk-R2A-1, C-lvk-R2A-2(T), C-R2A-52d and C-R2A-5d) belong to a single species. 16S rRNA gene-based phylogenetic analysis revealed that, together with Rhodobacter blasticus ATCC 33485(T), the isolates form a deep line of descent (94.7-94.9 % sequence similarity) within the family Rhodobacteraceae loosely affiliated with the Rhodobacter/Paracoccus clade. The isolates were strictly aerobic and oxidase-positive (catalase was weakly positive) and utilized a wide range of substrates including pentoses, hexoses, oligosaccharides and sugar alcohols. The predominant constituents in their cellular fatty acid profiles were C(19 : 0) cyclo omega8c (39-44 %), C(18 : 0) (21-24 %) and C(16 : 0) (21-23 %). Fatty acids present in smaller amounts included C(18 : 1)omega7c, C(10 : 0) 3-OH, C(18 : 1)omega7c 11-methyl, C(20 : 2)omega6,9c and C(17 : 0) cyclo, amongst others. Polar lipids included diphosphatidylglycerol, phosphatidylcholine and an unidentified aminolipid, but not phosphatidylethanolamine. Carotenoid pigments were synthesized but bacteriochlorophyll a was not. The polyamine patterns consisted of the major compounds putrescine, spermidine and sym-homospermidine. The major respiratory lipoquinone was ubiquinone Q-10. The DNA G+C content was 69.4-70.2 mol%. On the basis of the phylogenetic and phenotypic evidence, the biofilm isolates were classified in a new genus, Rubellimicrobium gen. nov.; four of the isolates are assigned to the type species, Rubellimicrobium thermophilum gen. nov., sp. nov. Strain C-lvk-R2A-2(T) (=CCUG 51817(T) = DSM 16684(T) = HAMBI 2421(T)) is the type strain of Rubellimicrobium thermophilum.

The diversity of myxobacteria in a soil niche was explored using culture-dependent and -independent methods. Conventional cultivation for bacteriolytic myxobacteria produced six types of myxobacteria, which were identified as two Myxococcus spp., two Corallococcus spp., a Cystobacter sp. and a Nannocysts sp. Hybridization analysis of the soil bacterial 16S rRNA gene library with myxobacteria-specific probes revealed that myxobacteria accounted for less than 1% in the bacterial community. A Cystobacterineae 16S rRNA genes-rich library was further established from the soil DNA by polymerase chain reaction amplification with a Cystobacterineae-specific primer combined with a universal bacterial primer. Screening of the special library using Cystobacterineae- and Sorangineae-specific probes produced approximately 45% and 3% positive signals respectively. Sixty-four positive clones were randomly selected for sequencing. Except three repeats, the sequences were diverse ranging from 0.3% to 21.3%, and homologous with the known myxobacteria at 77.6-99.8%, including 57 in Cystobacterineae, one close to Nannocystis and three much more distant from the known myxobacteria. The sequences in the Cystobacterineae can further be divided into at least 12 groups, of which most were unreported. The results suggest that myxobacteria in nature are much more diverse than were ever known, even in one soil niche.