Identification of novel long chain N-acylhomoserine lactones of chain length C20 from the marine phototrophic bacterium Rhodovulum sulfidophilum.

Gram-negative bacterial quorum sensing is mainly regulated by an extracellularly produced N-acylhomoserine lactone (AHL). AHL consists of a lactone ring and an acyl chain, which generally varies from C4 to C18 in length and affords species-specific variety. In this study, we developed an ultra-high performance liquid chromatography tandem mass spectrometry system and detected two kinds of long chain AHLs with chain length C20 from the reverse-phase thin layer chromatography-fractionated cultured supernatant of the marine photosynthetic bacterium Rhodovulum sulfidophilum. By fragmentation search analysis to detect compounds with a homoserine lactone ring moiety for data dependent acquisition, a minor AHL, presumed to be 3-OH-C18-homoserine lactone (HSL), was also found. Among the detected C20-HSLs, 3-OH-C20-HSL was structurally identified and 3-OH-C20:1-HSL was strongly suggested. To our knowledge, this is the first report to show a novel AHL with the longest C20 acyl side chain found to date. ABBREVIATIONS: AGC: automatic gain control; AHL: N-acylhomoserine lactone; CD: cyclodextrin; CID: collision induced dissociation; DDA: data dependent acquisition; EPI: enhanced product ion; FISh: fragment ion search; HCD: high energy collisional dissociation; HSL: homoserine lactone; IT: injection time; LC: liquid chromatography; MS: mass spectrometry; PRM: parallel reaction monitoring; RP: reverse phase; SRM: selected reaction monitoring; TLC: thin layer chromatography; UHPLC: ultra high performance liquid chromatography.

Epigenetic profile of Japanese supercentenarians: a cross-sectional study.

BACKGROUND: Centenarians and supercentenarians with exceptional longevity are excellent models for research towards improvements of healthy life expectancy. Extensive research regarding the maintenance and reduction of epigenetic age has provided insights into increasing healthy longevity. To this end, we explored the epigenetic signatures reflecting hallmarks of exceptional healthy longevity, including avoidance of age-related diseases and cognitive functional decline. METHODS: In this cross-sectional study, we enrolled Japanese non-centenarians (eligible participants aged 20-80 years) from the Tohoku Medical Megabank Community-Based Cohort Study and centenarians and supercentenarians (aged 101-115 years) from the Tokyo Centenarian Study and the Japanese Semi-supercentenarian Study. We assessed participants' whole-blood DNA methylation profiles and then developed sex-specific and non-specific first-generation epigenetic clocks by elastic net regression, calculated individuals' epigenetic ages, and assessed their age acceleration. We also screened for age-related CpG sites in non-centenarians by epigenome-wide linear regression analyses and ANOVA. We subsequently investigated which CpG sites in centenarians and supercentenarians had DNA methylation patterns following the age-related findings obtained from non-centenarians and which did not. We further characterised CpG sites with hypermethylation or hypomethylation in the centenarians and supercentenarians using enrichment and protein-protein interaction network analyses. FINDINGS: We enrolled 421 non-centenarians (231 [55%] women and 190 [45%] men; age range 20-78 years), recruited between May 20, 2013, and March 31, 2016, and 94 centenarians and supercentenarians (66 women [70%] and 28 [30%] men; age range 101-115 years), recruited between Jan 20, 2001, and April 17, 2018. Non-sex-specific epigenetic clock showed the highest accuracy (r=0·96) based on which centenarians and supercentenarians had negative epigenetic age acceleration. Epigenome-wide association analyses further showed that centenarians and supercentenarians had younger-than-expected epigenetic states (DNA methylation profiles similar to those of non-centenarians) for 557 CpG sites enriched in cancer-related and neuropsychiatric-related genes, whereas these individuals had advanced (or older) epigenetic states for 163 CpG sites represented by genes related to TGF-ß signalling, which is involved in anti-inflammatory responses and known to contribute to healthy ageing. INTERPRETATION: These results indicate that exceptionally healthy longevity depends not only on maintaining young epigenetic states but also on advanced states of specific epigenetic regions. FUNDING: The Japan Agency for Medical Research and Development, KDDI Research, and Keio University. TRANSLATION: For the Japanese translation of the abstract see Supplementary Materials section.

DNA Methylation Abnormalities and Altered Whole Transcriptome Profiles after Switching from Combustible Tobacco Smoking to Heated Tobacco Products.

BACKGROUND: The use of heated tobacco products (HTP) has increased exponentially in Japan since 2016; however, their effects on health remain a major concern. METHODS: Tsuruoka Metabolome Cohort Study participants (n = 11,002) were grouped on the basis of their smoking habits as never smokers (NS), past smokers (PS), combustible tobacco smokers (CS), and HTP users for <2 years. Peripheral blood mononuclear cells were collected from 52 participants per group matched to HTP users using propensity scores, and DNA and RNA were purified from the samples. DNA methylation (DNAm) analysis of the 17 smoking-associated DNAm biomarker genes (such as AHRR, F2RL3, LRRN3, and GPR15), as well as whole transcriptome analysis, was performed. RESULTS: Ten of the 17 genes were significantly hypomethylated in CS and HTP users compared with NS, among which AHRR, F2RL3, and RARA showed intermediate characteristics between CS and NS; nonetheless, AHRR expression was significantly higher in CS than in the other three groups. Conversely, LRRN3 and GPR15 were more hypomethylated in HTP users than in NS, and GPR15 expression was markedly upregulated in all the groups when compared with that in NS. CONCLUSIONS: HTP users (switched from CS <2 years) display abnormal DNAm and transcriptome profiles, albeit to a lesser extent than the CS. However, because the molecular genetic effects of long-term HTP use are still unknown, long-term molecular epidemiologic studies are needed. IMPACT: This study provides new insights into the molecular genetic effects on DNAm and transcriptome profiles in HTP users who switched from CS.

Evaluation of short-term epigenetic age fluctuation.

Considerable effort has been spent on lowering and maintaining the epigenetic age. However, the extent to which epigenetic age fluctuates under normal conditions is poorly understood. Therefore, we analyzed methylation data from monocytes and peripheral blood mononuclear cells collected from two Japanese men. The ranges of the Pan-tissue, Skin and blood, and DNAm PhenoAge epigenetic age during 3 months were ≥ 5.62, ≥ 3.04, and ≥ 8.23 years, and the maximum daily changes were 5.21, 3.20, and 6.53 years, respectively. These fluctuations were not suppressed by correcting for cell-type composition. Although the underlying biological mechanism remains unclear, there was a nonnegligible degree of age fluctuation which should inform personalized clinical applications.

Low MICA Gene Expression Confers an Increased Risk of Graves' Disease: A Mendelian Randomization Study.

Background: Expression of natural killer group 2 member D (NKG2D) ligand (NKG2DL) plays a major role as a "danger signal" on stressed cells to promote removal of the latter by NKG2D-expressing cytotoxic lymphocytes. NKG2DL expression has been found in peripheral immune cells as well, such as in macrophages; however, the effect of this expression is yet to be determined. Methods: We determined instrumental variables (IVs; R2 <0.01 in linkage disequilibrium), explaining the major variance in major histocompatibility complex class I chain-related protein A (MICA) and B (MICB) gene expression levels from the expression-quantitative trait locus (eQTL) of NKG2DLs based on the RNA-seq analysis of peripheral blood mononuclear cells (PBMCs) from 381 Japanese. Simultaneously, the target outcomes were filtered by PheWAS from 58 health risks, using a community-based cohort study composed of 44,739 Japanese residents. Finally, we estimated the causal effect of gene expression levels on the outcomes using the Mendelian randomization approach. Results: We determined nine and four IVs, explaining 87.6% and 33.0% of MICA and MICB gene expression levels, respectively. In the association test, we identified 10 or 13 significant outcomes associated with the MICA or MICB eQTLs, respectively, as well as the causal effect of MICA expression on Graves' disease (GD) (p = 4.2 × 10-3; odds ratio per 1 S.D. difference in the expression: 0.983 [confidence interval: 0.971-0.995]), using the weighted median estimator, without significant pleiotropy (p > 0.05), and the results were consistent across the sensitivity analyses. Conclusions: Our study provide novel evidence associating NKG2DL expression with GD, an autoimmune thyroiditis; direction of the effect indicated the immunoregulatory role of MICA expression in PBMCs, suggesting the importance of further functional assays in inflammatory diseases.

Longitudinal DNA methylation dynamics as a practical indicator in clinical epigenetics.

BACKGROUND: One of the fundamental assumptions of DNA methylation in clinical epigenetics is that DNA methylation status can change over time with or without interplay with environmental and clinical conditions. However, little is known about how DNA methylation status changes over time under ordinary environmental and clinical conditions. In this study, we revisited the high frequency longitudinal DNA methylation data of two Japanese males (24 time-points within three months) and characterized the longitudinal dynamics. RESULTS: The results showed that the majority of CpGs on Illumina HumanMethylation450 BeadChip probe set were longitudinally stable over the time period of three months. Focusing on dynamic and stable CpGs extracted from datasets, dynamic CpGs were more likely to be reported as epigenome-wide association study (EWAS) markers of various traits, especially those of immune- and inflammatory-related traits; meanwhile, the stable CpGs were enriched in metabolism-related genes and were less likely to be EWAS markers, indicating that the stable CpGs are stable both in the short-term within individuals and under various environmental and clinical conditions. CONCLUSIONS: This study indicates that CpGs with different stabilities are involved in different functions and traits, and thus, they are potential indicators that can be applied for clinical epigenetic studies to outline underlying mechanisms.

Extracellular production of an RNA aptamer by ribonuclease-free marine bacteria harboring engineered plasmids: a proposal for industrial RNA drug production.

Natural noncoding small RNAs have been shown to be involved in a number of cellular processes as regulators. Using the mechanisms thus elucidated, artificial small interfering RNAs (siRNAs), ribozymes, and RNA aptamers are also expected to be potential candidates for RNA therapeutic agents. However, current techniques are too costly for industrial production of these RNAs for use as drugs. Here, we propose a new method for in vivo production of artificial RNAs using the marine phototrophic bacterium Rhodovulum sulfidophilum. Using engineered plasmids and this bacterium, which produces extracellular nucleic acids in nature, we developed a method for extracellular production of a streptavidin RNA aptamer. As the bacterium does not produce any RNases in the culture medium, at least within the cultivation period tested, the designed RNA itself is produced and retained in the culture medium of the bacterium without any specific mechanism for protection against degradation by nucleases. Here, we report that the streptavidin RNA aptamer is produced in the culture medium and retains its specific function. This is the first demonstration of extracellular production of a functional artificial RNA in vivo, which will pave the way for inexpensive production of RNA drugs.

Distribution of Phototrophic Purple Nonsulfur Bacteria in Massive Blooms in Coastal and Wastewater Ditch Environments.

The biodiversity of phototrophic purple nonsulfur bacteria (PNSB) in comparison with purple sulfur bacteria (PSB) in colored blooms and microbial mats that developed in coastal mudflats and pools and wastewater ditches was investigated. For this, a combination of photopigment and quinone profiling, pufM gene-targeted quantitative PCR, and pufM gene clone library analysis was used in addition to conventional microscopic and cultivation methods. Red and pink blooms in the coastal environments contained PSB as the major populations, and smaller but significant densities of PNSB, with members of Rhodovulum predominating. On the other hand, red-pink blooms and mats in the wastewater ditches exclusively yielded PNSB, with Rhodobacter, Rhodopseudomonas, and/or Pararhodospirillum as the major constituents. The important environmental factors affecting PNSB populations were organic matter and sulfide concentrations and oxidation‒reduction potential (ORP). Namely, light-exposed, sulfide-deficient water bodies with high-strength organic matter and in a limited range of ORP provide favorable conditions for the massive growth of PNSB over co-existing PSB. We also report high-quality genome sequences of Rhodovulum sp. strain MB263, previously isolated from a pink mudflat, and Rhodovulum sulfidophilum DSM 1374T, which would enhance our understanding of how PNSB respond to various environmental factors in the natural ecosystem.

Characterization of extracellular DNA production and flocculation of the marine photosynthetic bacterium Rhodovulum sulfidophilum.

The marine photosynthetic bacterium Rhodovulum sulfidophilum produces extracellular nucleic acids involved in its flocculation. Previously, we showed that the RNA fraction of these extracellular nucleic acids released into the culture medium contains mainly non-aminoacylated fully mature-sized tRNAs and fragments of 16S and 23S rRNAs. Here, we report the characterization of extracellular DNA itself and its production during cultivation. No differences were detected in nucleotide sequence between the intracellular DNA and extracellular soluble DNA on Southern blotting. Whole intracellular DNA seemed to be released from the cell. The bacterial floc was degraded by deoxyribonuclease or ribonuclease treatment, indicating that at least the extracellular DNA and RNAs in the floc are involved in the maintenance of the floc. When cultivated in nutritionally rich medium, the bacteria formed small flocs and produced large amounts of extracellular DNA, which were solubilized in the medium. In nutritionally poor medium, however, huge flocs of cells appeared and almost no extracellular soluble DNA was observed in the medium. As the floc was degraded by deoxyribonuclease treatment, it seems likely that the extracellular soluble DNA observed in the rich medium may be incorporated into the large floc and play a role in floc maintenance in poor medium. Addition of an inhibitor of quorum sensing, alpha-cyclodextrin, inhibited huge floc maintenance in the nutritionally poor medium. In the presence of alpha-cyclodextrin, the floc was rapidly degraded and extracellular soluble DNA production increased.

Extracellular tRNAs of the marine photosynthetic bacterium Rhodovulum sulfidophilum are not aminoacylated.

The marine photosynthetic bacterium Rhodovulum sulfidophilum produces nucleic acids extracellularly. We have identified these extracellular RNAs as fully mature sized tRNAs and fragments of 16S and 23S rRNAs. Most of the tRNAs have mature 3'-terminal CCA sequences. In the present study we found that these extracellular tRNAs were not aminoacylated, although almost all intracellular tRNAs are aminoacylated.

Extracellular nucleic acids of the marine bacterium Rhodovulum sulfidophilum and recombinant RNA production technology using bacteria.

Extracellular nucleic acids of high molecular weight are detected ubiquitously in seawater. Recent studies have indicated that these nucleic acids are, at least in part, derived from active production by some bacteria. The marine bacterium Rhodovulum sulfidophilum is one of those bacteria. Rhodovulumsulfidophilum is a non-sulfur phototrophic marine bacterium that is known to form structured communities of cells called flocs, and to produce extracellular nucleic acids in culture media. Recently, it has been revealed that this bacterium produces gene transfer agent-like particles and that this particle production may be related to the extracellular nucleic acid production mechanism. This review provides a summary of recent physiological and genetic studies of these phenomena and also introduces a new method for extracellular production of artificial and biologically functional RNAs using this bacterium. In addition, artificial RNA production using Escherichia coli, which is related to this topic, will also be described.

Involvement of the response regulator CtrA in the extracellular DNA production of the marine bacterium Rhodovulum sulfidophilum.

The marine bacterium Rhodovulum sulfidophilum is a nonsulfur phototrophic bacterium, which is known to produce extracellular nucleic acids in soluble form in culture medium. In the present paper, constructing the response regulator ctrA-deficient mutant of R. sulfidophilum, we found that this mutation causes a significant decrease in the extracellular DNA production. However, by the introduction of a plasmid containing the wild type ctrA gene into the mutant, the amount of extracellular DNA produced was recovered. This is the first and clear evidence that the extracellular DNA production is actively controlled by the CtrA in R. sulfidophilum.

Spermidine inhibits transient and stable ribosome subunit dissociation.

Recent light-scattering experiments and sucrose density gradient centrifugational analyses suggested that the 70S ribosome undergoes RRF- and EF-G-triggered transient subunit dissociation that is followed by IF3-induced stable dissociation. However, the experimental conditions did not include the ubiquitous cellular polyamine spermidine, which is required for efficient translation. We found that when spermidine was present, the transient dissociation was inhibited. Moreover, the published experiments used ribosome concentrations that were far lower than the physiological concentration. We found that when spermidine and higher ribosome concentrations were included in the experimental conditions, only very limited stable subunit dissociation was observed. These results suggest that neither transient nor stable dissociation occurs under physiological conditions applied here.

Cell-free translation systems for protein engineering.

Cell-free translation systems have developed significantly over the last two decades and improvements in yield have resulted in their use for protein production in the laboratory. These systems have protein engineering applications, such as the production of proteins containing unnatural amino acids and development of proteins exhibiting novel functions. Recently, it has been suggested that cell-free translation systems might be used as the fundamental basis for cell-like systems. We review recent progress in the field of cell-free translation systems and describe their use as tools for protein production and engineering.

The gene transfer agent-like particle of the marine phototrophic bacterium Rhodovulum sulfidophilum.

Gene transfer agents (GTAs) are shaped like bacteriophage particles but have many properties that distinguish them from bacteriophages. GTAs play a role in horizontal gene transfer in nature and thus affect the evolution of prokaryotic genomes. In the course of studies on the extracellular production of designed RNAs using the marine bacterium Rhodovulum sulfidophilum, we found that this bacterium produces a GTA-like particle. The particle contains DNA fragments of 4.5 kb, which consist of randomly fragmented genomic DNA from the bacterium. This 4.5-kb DNA production was prevented while quorum sensing was inhibited. Direct observation of the particle by transmission electron microscopy revealed that the particle resembles a tailed phage and has a head diameter of about 40 nm and a tail length of about 60 nm. We also identified the structural genes for the GTA in the genome. Translated amino acid sequences and gene positions are closely related to those of the genes that encode the Rhodobacter capsulatus GTA. This is the first report of a GTA-like particle from the genus Rhodovulum. However, gene transfer activity of this particle has not yet been confirmed. The differences between this particle and other GTAs are discussed.

Complete Genome Sequence of Rhodovulum sulfidophilum DSM 2351, an Extracellular Nucleic Acid-Producing Bacterium.

Rhodovulum sulfidophilum DSM 2351 is the nonsulfur photosynthetic bacterium that efficiently releases nucleic acids into the extracellular milieu, which leads to flocculation. In this study, we determined the complete genome sequence of R. sulfidophilum DSM 2351, which will provide new insights into the mechanism of its unique nucleic acid release.

Short hairpin RNAs of designed sequences can be extracellularly produced by the marine bacterium Rhodovulum sulfidophilum.

Previously, we proposed a new method for production of RNA aptamers using the marine bacterium Rhodovulum sulfidophilum. A streptavidin RNA aptamer (an RNA which binds to streptavidin) was extracellularly produced by this bacterium containing engineered plasmid. The aptamer had full biological function. As a next step we attempted to produce another functional RNA, short hairpin RNAs (shRNAs) using this bacterial system. We have designed two types of shRNAs targeted to the luciferase gene. Here we report that shRNAs are successfully produced extracellularly by this system. Even if the shRNA has a long stem-loop structure which is thought to interfere with transcription in bacterial cells, the yield of the shRNA is almost the same as that of the streptavidin RNA aptamer. During the course of these experiments, we also found a new type of RNA processing for the double-stranded region of the shRNA.

Artificial RNA aptamer production by the marine bacterium Rhodovulum sulfidophilum: improvement of the aptamer yield using a mutated transcriptional promoter.

Noncoding small RNAs and artificial RNA aptamers are now expected to be potential candidates for RNA therapeutic agents. We previously proposed a unique method for economical production of these RNAs using the marine phototrophic bacterium Rhodovulum sulfidophilum. This bacterium does not produce any ribonucleases but does produce extracellular nucleic acids in the culture medium in nature. Using this bacterium and an engineered plasmid containing the rrn promoter for the RNA expression, we developed a method for production of the streptavidin RNA aptamer in the culture medium. However, the yield of this RNA product in the culture medium by this method was not enough for practical use. In the present paper, we improved the yield of this product by modification of the -35 region of the rrn promoter so as to escape from the Fis protein control and the use of a new vector plasmid. Using this system, the extracellular RNA aptamer of approximately 200 ng and the total RNA aptamer (both extra- and intracellular form) of about 20 µg from 1 L culture were accomplished by constitutive expression of the gene.

In vitro and in vivo production and purification of circular RNA aptamer.

RNA aptamers are potential candidates for RNA therapeutics. They must be clinically modified for medical applications because they are vulnerable to indigenous ribonucleases. Since circular RNA molecules without any chemical modification are much more stable than linear ones in a cell extract, we report the production of a circular form of streptavidin RNA aptamer both in vitro and in vivo. Circularization was accomplished by self-splicing permuted intron-exon sequences derived from T4 bacteriophage gene td. This sequence was producible in both Escherichia coli cells and in vitro. The circularized streptavidin RNA aptamer retained its binding of streptavidin and was stabile in HeLa cell extracts compared to the linear form of the streptavidin aptamer. The self-spliced circular RNA from the transcribed permuted intron-exon transcripts in E. coli cells was purified from a total RNA fraction using the solid-phase DNA probe method following anion exchange chromatography that excluded gel electrophoresis. This study provides an alternative method for designing and purifying useful RNA aptamers.

In vivo circular RNA production using a constitutive promoter for high-level expression.

The permuted intron-exon (PIE) method based on group I intron self-splicing is the only methodology currently available for production of circular RNA in vivo. Here, we report improvement of the circular RNA expression method based on an induction-free vector system utilizing the highly efficient constitutive lpp promoter.