Genomic convergence between Akkermansia muciniphila in different mammalian hosts.

BACKGROUND: Akkermansia muciniphila is a member of the human gut microbiota where it resides in the mucus layer and uses mucin as the sole carbon, nitrogen and energy source. A. muciniphila is the only representative of the Verrucomicrobia phylum in the human gut. However, A. muciniphila 16S rRNA gene sequences have also been found in the intestines of many vertebrates. RESULTS: We detected A. muciniphila-like bacteria in the intestines of animals belonging to 15 out of 16 mammalian orders. In addition, other species belonging to the Verrucomicrobia phylum were detected in fecal samples. We isolated 10 new A. muciniphila strains from the feces of chimpanzee, siamang, mouse, pig, reindeer, horse and elephant. The physiology and genome of these strains were highly similar in comparison to the type strain A. muciniphila MucT. Overall, the genomes of the new strains showed high average nucleotide identity (93.9 to 99.7%). In these genomes, we detected considerable conservation of at least 75 of the 78 mucin degradation genes that were previously detected in the genome of the type strain MucT. CONCLUSIONS: The low genomic divergence observed in the new strains may indicate that A. muciniphila favors mucosal colonization independent of the differences in hosts. In addition, the conserved mucus degradation capability points towards a similar beneficial role of the new strains in regulating host metabolic health.

Luteolibacter luteus sp. nov., isolated from stream bank soil.

A non-motile, Gram-stain-negative, rod-shaped and yellow-colored bacterium, designated G-1-1-1T was obtained from soil sampled at Gwanggyo stream bank, Gyeonggi-do, Republic of Korea. Cells were aerobic, catalase positive, grew optimally at 25-30 °C and hydrolysed aesculin and casein. A phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain G-1-1-1T formed a lineage within the genus Luteolibacter. The closest members were Luteolibacter flavescens GKXT (97.7% sequence similarity) and Luteolibacter arcticus MC 3726T (97.3%). The sequence similarities with other members of the genus Luteolibacter were ≤ 93.9%. The genome of strain G-1-1-1T was 6,412,079 bp long with 5176 protein-coding genes. The diagnostic amino acid of cell-wall peptidoglycan of strain G-1-1-1T was meso-diaminopimelic acid. The only respiratory quinone was menaquinone-9 and the principal polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and unidentified phospholipids. The predominant cellular fatty acids were iso-C14:0, C16:1 ω9c, C16:0, C14:0 and anteiso-C15:0. The DNA G + C content was 61.0 mol%. The anti-SMASH analysis of whole genome showed eight putative biosynthetic gene clusters responsible for various secondary metabolites. Based on genomic, chemotaxonomic, phenotypic and phylogenetic analyses, strain G-1-1-1T represents a novel species in the genus Luteobacter, for which the name Luteolibacter luteus sp. nov. is proposed. The type strain is G-1-1-1T (= KACC 21614T = NBRC 114341T).

Luteolibacter ambystomatis sp. nov., isolated from the skin of an Anderson's salamander (Ambystoma andersoni).

A bacterial strain designated 32AT was isolated from the skin of an Anderson's salamander (Ambystoma andersoni) and subjected to a comprehensive taxonomic study. The strain was Gram-stain-negative, rod-shaped, non-motile, oxidase- and urease-negative, and catalase-positive. 16S rRNA gene sequence comparisons placed the strain in the genus Luteolibacter with highest sequence similarities to Luteolibacter pohnpeiensis A4T-83T (95.2%), Luteolibacter gellanilyticus CB-286403T (95.1%) and Luteolibacter cuticulihirudinis E100T (94.9%). Genomic sequence analysis revealed a size of 5.3 Mbp, a G+C-content of 62.2 mol% and highest ANI values with Luteolibacter luteus (71.2%), Luteolibacter yonseiensis (71.4%) and L. pohnpeiensis (69.5%). In the polyamine pattern, 1,3-diaminopropane and spermidine were predominant. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The quinone system was composed of the major menaquinones MK-9 and MK-10. Major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, the unidentified aminolipid AL2, the unidentified phospholipid PL2 and the unidentified aminophospholipid APL1. The fatty acid profile contained major amounts of iso-C14:0, iso-C16:0, C16 : 0 and C16 : 1 ω9c. In addition, C14 : 0, C15:0, anteiso-C15 : 0, summed feature 2 (C14 : 0 3OH and/or iso-C16 : 0 I), and the hydroxylated fatty acids iso-C14 : 0 3OH, iso-C16 : 0 3OH and C16 : 0 3-OH were detected. Physiologically, strain 32AT is distinguishable from its next relatives. Based on phylogenetic, genomic, physiological and chemotaxonomic data, strain 32AT represents a novel species of the genus Luteolibacter for which we propose the name Luteolibacter ambystomatis sp. nov. The type strain is 32AT (=CCM 9141T=LMG 32214T).

Characterization of sponge-associated Verrucomicrobia: microcompartment-based sugar utilization and enhanced toxin-antitoxin modules as features of host-associated Opitutales.

Bacteria of the phylum Verrucomicrobia are ubiquitous in marine environments and can be found as free-living organisms or as symbionts of eukaryotic hosts. Little is known about host-associated Verrucomicrobia in the marine environment. Here we reconstructed two genomes of symbiotic Verrucomicrobia from bacterial metagenomes derived from the Atlanto-Mediterranean sponge Petrosia ficiformis and three genomes from strains that we isolated from offshore seawater of the Eastern Mediterranean Sea. Phylogenomic analysis of these five strains indicated that they are all members of Verrucomicrobia subdivision 4, order Opitutales. We compared these novel sponge-associated and seawater-isolated genomes to closely related Verrucomicrobia. Genomic analysis revealed that Planctomycetes-Verrucomicrobia microcompartment gene clusters are enriched in the genomes of symbiotic Opitutales including sponge symbionts but not in free-living ones. We hypothesize that in sponge symbionts these microcompartments are used for degradation of l-fucose and l-rhamnose, which are components of algal and bacterial cell walls and therefore may be found at high concentrations in the sponge tissue. Furthermore, we observed an enrichment of toxin-antitoxin modules in symbiotic Opitutales. We suggest that, in sponges, verrucomicrobial symbionts utilize these modules as a defence mechanism against antimicrobial activity deriving from the abundant microbial community co-inhabiting the host.

Regional community assembly drivers and microbial environmental sources shaping bacterioplankton in an alpine lacustrine district (Pyrenees, Spain).

Microbial communities in natural ecosystems are subject to strong ecological rules. The study of local communities along a regional metacommunity can reveal patterns of community assembly, and disentangle the underlying ecological processes. In particular, we seek drivers of community assembly at the regional scale using a large lacustrine dataset (>300 lakes) along the geographical, limnological and physico-chemical gradients in the Pyrenees. By using high throughput amplicon sequencing of the 16S rRNA gene, and inferring environmental sources of bacterial immigrants, we showed that surface aquatic bacterial assemblages were strongly influenced by terrestrial populations from soil, biofilms or sediments, and primarily selected by a pH-alkalinity gradient. Indeed, source proportions explained 27% of the community variation, and chemistry 15% of the total variation, half of it shared with the sources. Major taxonomic groups such as Verrucomicrobia, Actinobacteria and Bacteroidetes showed higher aquatic affinities than Parcubacteria, Gammaproteobacteria, Alphaproteobacteria or Betaproteobacteria, which may be recruited and selected through different hydrographic habitats. A regional fingerprint was observed with lower alpha diversity and higher beta diversity in the central Pyrenees than in both ends. We suggest an ecological succession process, likely influenced by complex interactions of environmental source dispersal and environmental filtering along the mountain range geography.

Oceanipulchritudo coccoides gen. nov., sp. nov., isolated from marine sediment within the family Puniceicoccaceae.

A Gram-stain-negative, aerobic coccus, designated CK1056T, was isolated from coastal sediment of Xiaoshi Island, Weihai, PR China. Strain CK1056T was found to grow at 15-37 °C (optimum, 30 °C), with 0.5-6.5 % (w/v) NaCl (optimum, 3.5 %) and displayed alkaliphilic growth within the pH range of pH 6.5-10.0 (optimum, pH 8.0). The major fatty acids identified were iso-C15 : 0 and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The main polar lipids consisted of aminophosphoglycolipid and phosphatidylethanolamine. The predominant respiratory quinone was MK-7. The G+C content of the genomic DNA was 54.0 mol%. The result of the 16S rRNA gene sequence analysis confirmed the affiliation of this micro-organism to the family Puniceicoccaceae, with Coraliomargarita akajimensis KCTC 12865T as its closest relative with only 88.0 % sequence similarity. From the taxonomic data obtained in this study, we propose that the new marine isolate be placed into a novel species within a novel genus in the family Puniceicoccaceae, phylum Verrucomicrobia, for which the name Oceanipulchritudo coccoides gen. nov., sp. nov. is proposed. The type strain is CK1056T (=KCTC 72798T=MCCC 1H00425T).

Oleiharenicola lentus sp. nov., isolated from irrigation water.

Bacterial strain TWA-58T, isolated from irrigation water in Taiwan, was characterized using a polyphasic taxonomy approach. Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of 92 protein clusters indicated that strain TWA-58T formed a phylogenetic lineage in the genus Oleiharenicola of the family Opitutaceae. Strain TWA-58T was most closely related to Oleiharenicola alkalitolerans NVTT with a 96.7 % 16S rRNA gene sequence similarity. Strain TWA-58T showed 75.2 % average nucleotide identity, 70.9 % average amino acid identity and 21.0 % digital DNA-DNA hybridization identity with O. alkalitolerans NVTT. Cells were Gram-stain-negative, aerobic, motile, coccoid-shaped and formed transparent colonies. Optimal growth occurred at 25 °C, pH 6, and 0 % NaCl. The major fatty acids of strain TWA-58T were iso-C15 : 0 and anteiso-C15 : 0. The predominant hydroxy fatty acid was iso-C13 : 0 3-OH. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and two unidentified aminophospholipids. The major isoprenoid quinone was MK-7. Genomic DNA G+C content of strain TWA-58T was 65.3 mol%. On the basis of phenotypic and genotypic properties and phylogenetic inference, strain TWA-58T should be classified in a novel species of the genus Oleiharenicola, for which the name Oleiharenicola lentus sp. nov. is proposed. The type strain is TWA-58T (=BCRC 81161T=LMG 31019T=KCTC 62872T).

Phragmitibacter flavus gen. nov., sp. nov. a new member of the family Verrucomicrobiaceae.

The Gram-stain-negative, aerobic, non-motile, oxidase- and catalase-positive, rod-shaped yellow-coloured bacterial strain MG-N-17T was isolated from a water sample of Lake Ferto/Neusiedler See (Hungary). Results of phylogenetic analysis based on the 16S rRNA gene sequence revealed that the strain forms a distinct linage within the family Verrucomicrobiaceae of the phylum Verrucomicrobia, and its closest relatives are Verrucomicrobium spinosum DSM 4136T (94.38 %) and Roseimicrobium gellanilyticum DC2a-G7T (91.55 %). The novel bacterial strain prefers a weak alkaline environment and grows optimally between 22-28 °C in the absence of NaCl. The major isoprenoid quinones are MK-10, MK-11, MK-12 and MK-9. The major cellular fatty acids are anteiso-C15 : 0, C16 : 0, C16 : 1ω5c and iso-C14 : 0. The polar lipid profile contains phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and four unidentified glycolipids. The assembled draft genome of strain MG-N-17T had 44 contigs with an N50 value 348255 nt, 56.5× genome coverage, total length of 5 910 933 bp and G+C content of 56.9 mol%. Strain MG-N-17T (=DSM 106674T=NCAIM B.02643T) is proposed as the type strain of a new genus and species in the family Verrucomicrobiaceae, for which the name Phragmitibacter flavus gen. nov., sp. nov. is proposed.

Rariglobus hedericola gen. nov., sp. nov., belonging to the Verrucomicrobia, isolated from a temperate freshwater habitat.

The bacterial strain 53C-WASEF was isolated from a small freshwater ditch located in Eugendorf, Austria. Phylogenetic reconstructions with 16S rRNA gene sequences and genome based, with amino acid sequences obtained from 105 single copy genes, suggested that the strain represents a new genus and a new species within the family Opitutaceae, which belongs to the class Opitutae of the phylum Verrucomicrobia. Comparisons of the 16S rRNA gene sequence of strain 53C-WASEF with those of related type strains revealed a highest sequence similarity of 93.5 % to Nibricoccus aquaticus and of 92.9 % to Geminisphaera colitermitum. Interestingly, phylogentic trees indicated the latter as being the closest known relative of the new strain. Phenotypic, chemotaxonomic and genomic traits were investigated. Cells were observed to be small, spherical, motile and unpigmented, and grew chemoorganotrophically and aerobically. The respiratory quinone was MK-7, the predominant fatty acids were anteiso-C15 : 0, C16 : 1ω5c and C16 : 0. The identified polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Genome sequencing revealed genes putatively encoding for flagella synthesis and cellulose degradation. The genome size was 4.1 Mbp and the G+C content 60.6 mol%. For the new genus and the new species, we propose the name Rariglobus hedericola gen. nov., sp. nov. (=CIP 111665T=DSM 109123T).

An Akkermansia muciniphila subtype alleviates high-fat diet-induced metabolic disorders and inhibits the neurodegenerative process in mice.

The prevalence of obesity and diabetes, and their complicating mental disorders, severely affect public health. This study aimed to investigate the long-term effects of an Akkermansia muciniphila subtype (A. muciniphilasub) on high-fat diet-induced obesity and diabetes, and to evaluate whether this subtype can alleviate their complicated mental disorders. Whole genome sequencing and short chain fatty acid production analysis in supernatant of pure culture were performed. Female adult C57BL/6 mice were fed a high-fat diet or a normal chow diet and were gavaged with A. muciniphilasub or phosphate-buffered saline daily for 10 months. Body weight, food consumption and blood glucose were measured. At the end of the treatment period, all mice were subjected to the Y-maze test, sucrose preference test, analyses of serum, fecal microbiota analysis and histological examination. This A. muciniphilasub had 278 unique genes compared to the type strain (A. muciniphila ATCC BAA-835) and produced short chain fatty acids both. A. muciniphilasub administration significantly reduced body weight gain and improved the spatial memory of high-fat diet-fed mice. A. muciniphilasub increased Nissl bodies in neurons of the hippocampus, and restored the high-fat diet-inhibited tryptophan metabolism. The high-fat diet led to decreased serum 5-hydroxytryptamine and induced depression, which were not alleviated by A. muciniphilasub. A. muciniphilasub increased the relative fecal abundance of Bifidobacterium, and was negatively correlated with the fecal abundance of Bacteroides. The present study demonstrated the beneficial effects of this A. muciniphilasub on body weight, blood glucose control and the alleviation of the memory decay caused by a high-fat diet in mice.

Coraliomargarita sinensis sp. nov., isolated from a marine solar saltern.

A Gram-stain negative, spherical, obligately aerobic bacterium, designated strain WN38T, was isolated from a marine solar saltern on the coast of Weihai, China. Optimal growth occurred at 33 °C, pH 7.0-7.5 and in the presence of 3-4 % (w/v) NaCl. The genome of strain WN38T was found to contain the genes necessary for arsenate reductase and related proteins, indicating that it may have potential in bioremediation of heavy metal polluted environments. Comparative 16S rRNA gene sequence analysis showed that strain WN38T represented a member of the genus Coraliomargarita, and was related most closely to Coraliomargarita akajimensis KCTC 12865T (95.7 %). Pairwise sequence similarities to all other type strains of species were below 90 %. Genome-based calculations (average nucleotide identity, genome-to-genome distance and DNA G+C percentage) and results of pairwise amino acid identity (AAI >60 %) and percentage of conserved proteins (POCP >50 %) also indicated clearly that strain WN38T represents a novel species within this genus. Different phenotypic analyses, such as the detection of a quinone system composed of the sole respiratory quinone was menaquinone-7 (MK-7) and a fatty acid profile with iso-C14 : 0, C18 : 0 and C18 : 1ω9c as major components, supported this finding at the same time as contributing to a comprehensive characterization of strain WN38T. On the basis of its phenotypic and genotypic properties, strain WN38T represents a novel species of the genus Coraliomargarita, for which the name Coraliomargaritasinensis sp. nov. is proposed. The type strain is WN38T (=KCTC 62602T=MCCC 1H00313T).

Nibricoccus aquaticus gen. nov., sp. nov., a new genus of the family Opitutaceae isolated from hyporheic freshwater.

A yellow-coloured, Gram-strain-negative, non-motile, cocci-shaped, strictly aerobic bacterium, designated HZ-65T, was isolated from hyporheic freshwater in the Republic of Korea. Strain HZ-65T grew at 15-37 °C (optimum, 25-30 °C), pH 5.5-9.0 (optimum, pH 7.0) and 0-0.5 % NaCl (w/v; optimum at 0 % NaCl). Phylogenetic analysis based on the 16S rRNA gene showed that strain HZ-65T is a member of family Opitutaceae and is closely related to Opitutus terrae PB90-1T (94.0 % similarity), Cephaloticoccus primus CAG34T (93.0 %), and Cephaloticoccus capnophilus CV41T (92.7 %), while the similarities to other Opitutaceae-type strains were lower than 90.0 %. The DNA G+C content was 62.2 mol% and the quinone present was menaquinone-7. The predominant fatty acids were iso-C14 : 0, anteiso-C15 : 0, C16 : 0, and iso-C16 : 0, representing 70 % of the total fatty acids. The major polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Analysis of the HZ-65T genome revealed the presence of 300 genes that are involved in carbohydrate-active enzymes, which indicates the metabolic potential to degrade polysaccharides. The phenotypic, chemotaxonomic, genetic, and phylogenetic properties suggest that strain HZ-65T represents a novel species in a new genus within the family Opitutaceae, for which the name Nibricoccus aquaticus gen. nov., sp. nov., is proposed. The type strain of Nibricoccus aquaticus is HZ-65T (KACC 19333T=NBRC 112907T).

Akkermansia muciniphila and its role in regulating host functions.

Akkermansia muciniphila is an intestinal bacterium that was isolated a decade ago from a human fecal sample. Its specialization in mucin degradation makes it a key organism at the mucosal interface between the lumen and host cells. Although it was isolated quite recently, it has rapidly raised significant interest as A. muciniphila is the only cultivated intestinal representative of the Verrucomicrobia, one of the few phyla in the human gut that can be easily detected in phylogenetic and metagenome analyses. There has also been a growing interest in A. muciniphila, due to its association with health in animals and humans. Notably, reduced levels of A. muciniphila have been observed in patients with inflammatory bowel diseases (mainly ulcerative colitis) and metabolic disorders, which suggests it may have potential anti-inflammatory properties. The aims of this review are to summarize the existing data on the intestinal distribution of A. muciniphila in health and disease, to provide insight into its ecology and its role in founding microbial networks at the mucosal interface, as well as to discuss recent research on its role in regulating host functions that are disturbed in various diseases, with a specific focus on metabolic disorders in both animals and humans.

Luteolibacter gellanilyticus sp. nov., a gellan-gum-degrading bacterium of the phylum Verrucomicrobia isolated from miniaturized diffusion chambers.

A novel chemo-organoheterotrophic bacterium, strain CB-286403T, was isolated from a Mediterranean forest soil, collected at Sierra de Tejeda, Almijara and Alhama Natural Park, Spain, by using the Diffusion Sandwich System, a device with 384 miniature diffusion chambers. The 16S rRNA gene sequence analyses identified the isolate as a member of the genus Luteolibacter where the type strains Luteolibacterpohnpeiensis A4T-83T (GenBank acc. no. AB331895), Luteolibacteryonseiensis EBTL01T (JQ319003), Luteolibacterluojiensis DR4-30T (JN630810) and Luteolibacteralgae A5J-41-2T (AB331893) were the closest relatives with similarities of 97.0, 96.3, 96.3 and 94.5 %, respectively. The novel isolate was characterized as a Gram-stain-negative, non-motile, short-rod-shaped bacterium. The strain showed a positive response for catalase and cytochrome-c oxidase, divided by binary fission and/or budding, and exhibited an aerobic metabolism. Strain CB-286403T showed a mesophilic and neutrophilic growth range and showed a nutritional preference for simple sugars and complex protein substrates. Major fatty acids included iso-C14 : 0, C16 : 0, C16 : 1ω7c/iso-C15 : 0 2-OH and anteiso-C15 : 0. The predominant respiratory quinone was MK-9. Polar lipids comprised major amounts of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol and minor amounts of three unidentified lipids, a glycolipid, a phospholipid and a phosphoglycolipid. Based on a polyphasic taxonomic characterization, strain CB-286403T represents a novel species of the genus Luteolibacter, for which the name Luteolibacter gellanilyticus sp. nov. is proposed. The type strain is CB-286403T (=DSM 28998T=CECT 8659T).

Ruficoccus amylovorans gen. nov., sp. nov., an amylolytic and nitrate-reducing diazotroph of the family Puniceicoccaceae.

A novel amylolytic, nitrate-reducing and diazotrophic bacterium, designated strain CC-MHH0563T, isolated from a fermenter was assessed for its taxonomic status using a polyphasic approach. Cells of strain CC-MHH0563T were Gram-staining-negative, catalase- and oxidase-positive, mesophilic and aerobic cocci, which produced reddish nondiffusible pigments. Growth was observed at 15-37 °C (optimal 25 °C), pH 6.0-8.0 (optimal pH 7.0) and salinity of 0-3 % (w/v). Strain CC-MHH0563T showed highest pairwise 16S rRNA gene sequence similarity to members of the genera Cerasicoccus(89.3-89.5 %), Coraliomargarita (87.8 %), Pelagicoccus(85.8-86.4 %) and Puniceicoccus (87.9 %), and established a discrete taxonomic lineage during phylogenetic analysis. The major fatty acids found in strain CC-MHH0563T were C14 : 0, anteiso-C15 : 0, C16 : 0, C17 : 0, C18 : 0 and C18 : 1ω9c. The polar lipid profile consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, two unknown aminolipids and two unknown aminophospholipids. The polyamine pattern showed a predominance of spermidine and a minor amount of cadaverine. The DNA G+C content was 57.4 mol% and the predominant quinone system was menaquinone-7. The low 16S rRNA gene sequence similarity values (<90.0 %) and a distinct phylogenetic clustering clearly distinguished strain CC-MHH0563T from other representatives of the family Puniceicoccaceae. Based on the discrete phylogenetic, phenotypic and chemotaxonomic traits together with the results of comparative 16S rRNA gene sequence analysis, strain CC-MHH0563T is considered to represent a novel genus and species of the family Puniceicoccaceae, for which the name Ruficoccus amylovorans gen. nov., sp. nov. is proposed. The type strain of the type species is CC-MHH0563T (=BCRC 80918T=JCM 31066T).

Luteolibacter flavescens sp. nov., isolated from deep seawater.

A novel Gram-stain-negative, rod-shaped, non-motile strain, designated GKXT, was isolated from deep seawater. Strain GKXT was able to grow at 20-35 °C (optimum, 25 °C), pH 5.5-9.5 (optimum, 7.5) and 0-4.0 % (w/v) NaCl (optimum, 1.0 %). The major fatty acids were C16 : 1ω9c (15.4 %), C16 : 0 (18.4 %), C14 : 0 (12.0 %), iso-C14 : 0 (30.1 %) and anteiso-C15 : 0 (5.7 %). Strain GKXT contained phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid as the main polar lipids. The only isoprenoid quinone was menaquinone-9. The diagnostic amino acids of the cell-wall peptidoglycan contained meso-diaminopimelic acid. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain GKXT belonged to the genus Luteolibacter in the family Verrucomicrobiaceae. The 16S rRNA gene sequence of this strain showed 98.0, 93.5 and 93.3 % sequence similarity, respectively, with those of Luteolibacter arcticus MC 3726T, L.uteolibacter pohnpeiensisA4T-83T and L.uteolibacter cuticulihirudinis E100T. DNA-DNA hybridization value of strain GKXT with L. arcticus MC 3726T was 33.1 %. The G+C content of the genomic DNA was 59.5 mol%. On the basis of the genotypic, phenotypic, phylogenetic and chemotaxonomic characteristics, strain GKXT was proposed to represent a novel species of the genus Luteolibacter, named Luteolibacter flavescens sp. nov. (type strain GKXT=MCCC 1K03193T=KCTC 52361T).

Effect of Macondo Prospect 252 Oil on Microbiota Associated with Pelagic Sargassum in the Northern Gulf of Mexico.

The environmental impact of major oil spills on marine microorganisms has yet to be thoroughly investigated using molecular biology techniques. The Deepwater Horizon (DWH) drilling rig explosion of 2010 affected an approximately 176,000 km2 surface area of the Gulf of Mexico (GOM) when an estimated 210 million gallons of oil from the Macondo Prospect spilled into the environment. Pelagic Sargassum, a complex of two surface drifting species (Sargassum natans and Sargassum fluitans) of marine brown macroalgae and a critically important habitat in the GOM ecosystem, was suffused by Macondo Prospect 252 oil released during the DWH event. Using 16S rRNA PCR and Roche 454 pyrosequencing, the effect of the oil on the bacterial population associated with pelagic Sargassum and contiguous waters was examined by comparing sequence data generated from samples collected from oiled and non-oiled locations in the northern GOM. Sequence data showed similar microbial composition in Sargassum regardless of exposure to oil primarily dominated by five phyla; Proteobacteria, Bacteroidetes, Actinobacteria, Verrucomicrobia, and unclassified bacteria. The microbial composition in water samples was significantly less diverse than for Sargassum and consisted primarily of Proteobacteria, Firmicutes, and Bacteroidetes. Due to the evenly distributed abundance of microbial species on oiled and non-oiled pelagic Sargassum, study findings indicate that DWH spilled oil had minimal effect on the composition and diversity of the microbial community associated with Sargassum and contiguous waters. However, higher abundances of Sulfitobacter and one species of Psychrobacter were found in oiled water samples when compared to non-oiled water samples indicating some effect of DHW oil in the microbial composition of seawater. Though there are a number of marine studies using molecular biology approaches, this is the first molecular examination of the impact of the DWH oil spill on bacterial communities associated with pelagic Sargassum and contiguous waters from the GOM.

Distinct bacterial communities across a gradient of vegetation from a preserved Brazilian Cerrado.

The Cerrado biome in the Sete Cidades National Park, an Ecological Reserve in Northeastern Brazil, has conserved its native biodiversity and presents a variety of plants found in other savannas in Brazil. Despite this finding the soil microbial diversity and community structure are poorly understood. Therefore, we described soil bacterial diversity and distribution along a savanna vegetation gradient taking into account the prevailing environmental factors. The bacterial composition was retrieved by sequencing a fragment of the 16S ribosomal RNA gene. The bacterial operational taxonomic units (OTUs) were assigned to 37 different phyla, 96 classes, and 83 genera. At the phylum level, a core comprised by Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, Verrucomicrobia and Planctomycetes, was detected in all areas of Cerrado. 'Cerrado stricto sensu' and 'Cerradao' share more similarities between edaphic properties and vegetation and also present more similar bacterial communities, while 'Floresta decidual' and 'Campo graminoide' show the largest environmental differences and also more distinct bacterial communities. Proteobacteria (26%), Acidobacteria (21%) and Actinobacteria (21%) were the most abundant phyla within the four areas. All the samples present similar bacteria richness (alpha diversity) and the observed differences among them (beta diversity) were more related to the abundance of specific taxon OTUs compared to their presence or absence. Total organic C, N and P are the main abiotic factors structuring the bacterial communities. In summary, our findings show the bacterial community structure was clearly different across the Cerrado gradient, but that these environments share a bacterial phylum-core comprising Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia and Planctomycetes with other Brazilian savannas.

Molecular diversity of bacterial endosymbionts associated with dagger nematodes of the genus Xiphinema (Nematoda: Longidoridae) reveals a high degree of phylogenetic congruence with their host.

Bacterial endosymbionts have been detected in some groups of plant-parasitic nematodes, but few cases have been reported compared to other groups in the phylum Nematoda, such as animal-parasitic or free-living nematodes. This study was performed on a wide variety of plant-parasitic nematode families and species from different host plants and nematode populations. A total of 124 nematode populations (previously identified morphologically and molecularly) were screened for the presence of potential bacterial endosymbionts using the partial 16S rRNA gene and fluorescence in situ hybridization (FISH) and confocal microscopy. Potential bacterial endosymbionts were only detected in nematode species belonging to the genus Xiphinema and specifically in the X. americanum group. Fifty-seven partial 16S rRNA sequences were obtained from bacterial endosymbionts in this study. One group of sequences was closely related to the genus 'Candidatus Xiphinematobacter' (19 bacterial endosymbiont sequences were associated with seven nematode host species, including two that have already been described and three unknown bacterial endosymbionts). The second bacterial endosymbiont group (38 bacterial endosymbiont sequences associated with six nematode species) was related to the family Burkholderiaceae, which includes fungal and soil-plant bacterial endosymbionts. These endosymbionts were reported for the first time in the phylum Nematoda. Our findings suggest that there is a highly specific symbiotic relationship between nematode host and bacterial endosymbionts. Overall, these results were corroborated by a phylogeny of nematode host and bacterial endosymbionts that suggested that there was a high degree of phylogenetic congruence and long-term evolutionary persistence between hosts and endosymbionts.

Evaluation and update of cutoff values for methanotrophic pmoA gene sequences.

The functional pmoA gene is frequently used to probe the diversity and phylogeny of methane-oxidizing bacteria (MOB) in various environments. Here, we compared the similarities between the pmoA gene and the corresponding 16S rRNA gene sequences of 77 described species covering gamma- and alphaproteobacterial methanotrophs (type I and type II MOB, respectively) as well as methanotrophs from the phylum Verrucomicrobia. We updated and established the weighted mean pmoA gene cutoff values on the nucleotide level at 86, 82, and 71 % corresponding to the 97, 95, and 90 % similarity of the 16S rRNA gene. Based on these cutoffs, the functional gene fragments can be entirely processed at the nucleotide level throughout software platforms such as Mothur or QIIME which provide a user-friendly and command-based alternative to amino acid-based pipelines. Type II methanotrophs are less divergent than type I both with regard to ribosomal and functional gene sequence similarity and GC content. We suggest that this agrees with the theory of different life strategies proposed for type I and type II MOB.