Identification of a TonB-Dependent Receptor Involved in Lanthanide Switch by the Characterization of Laboratory-Adapted Methylosinus trichosporium OB3b.

Two methanol dehydrogenases (MDHs), MxaFI and XoxF, have been characterized in methylotrophic and methanotrophic bacteria. MxaFI contains a calcium ion in its active site, whereas XoxF contains a lanthanide ion. Importantly, the expression of MxaFI and XoxF is inversely regulated by lanthanide bioavailability, i.e., the "lanthanide switch." To reveal the genetic and environmental factors affecting the lanthanide switch, we focused on two Methylosinus trichosporium OB3b mutants isolated during routine cultivation. In these mutants, MxaF was constitutively expressed, but lanthanide-dependent XoxF1 was not, even in the presence of 25 µM cerium ions, which is sufficient for XoxF expression in the wild type. Genotyping showed that both mutants harbored a loss-of-function mutation in the CQW49_RS02145 gene, which encodes a TonB-dependent receptor. Gene disruption and complementation experiments demonstrated that CQW49_RS02145 was required for XoxF1 expression in the presence of 25 µM cerium ions. Phylogenetic analysis indicated that CQW49_RS02145 was homologous to the Methylorubrum extorquens AM1 lanthanide transporter gene (lutH). These findings suggest that CQW49_RS02145 is involved in lanthanide uptake across the outer membrane. Furthermore, we demonstrated that supplementation with cerium and glycerol caused severe growth arrest in the wild type. CQW49_RS02145 underwent adaptive laboratory evolution in the presence of cerium and glycerol ions, resulting in a mutation that partially mitigated the growth arrest. This finding implies that loss-of-function mutations in CQW49_RS02145 can be attributed to residual glycerol from the frozen stock. IMPORTANCE Lanthanides are widely used in many industrial applications, including catalysts, magnets, and polishing. Recently, lanthanide-dependent metabolism was characterized in methane-utilizing bacteria. Despite the global demand for lanthanides, few studies have investigated the mechanism of lanthanide uptake by these bacteria. In this study, we identify a lanthanide transporter in Methylosinus trichosporium OB3b and indicate the potential interaction between intracellular lanthanide and glycerol. Understanding the genetic and environmental factors affecting lanthanide uptake should not only help improve the use of lanthanides for the bioconversion of methane into valuable products like methanol but also be of value for developing biomining to extract lanthanides under neutral conditions.

Dendrimer porphyrins as the oxygen sensor for intracellular imaging to suppress interaction towards biological molecules.

Optical methods using phosphorescence quenching by oxygen are suitable for the measurement of oxygen concentration within cells. In cells, however, the dyes such as Pt-porphyrins interact with biological components so that their optical properties are changed. Therefore, the absolute oxygen concentration determination in cells is difficult. To suppress this interaction, we focussed on porphyrin-cored dendrimers (dendrimer-porphyrins) and synthesized 2nd-4th generation dendrimer-porphyrins with various surface functional groups (G2-G4, ARG, αGLU and γGLU). These dendrimer-porphyrins showed oxygen sensing property and the change of their spectroscopic properties by biomolecules was supressed. Additionally, the dendrimer-porphyrins were accumulated in cells even in the presence of serum, so oxygen concentration imaging without the effect of serum starvation was also achieved.

Methane Hydroxylation with Water as an Electron Donor under Light Irradiation in the Presence of Reconstituted Membranes Containing both Photosystem†II and a Methane Monooxygenase.

Methane/methanol conversion is one of the most important chemical reactions. Methane monooxygenases from methanotrophs are enzymes that catalyze methane/methanol conversion under mild conditions. Here we report the reconstitution of purified photosystem II (PSII) from Thermosynechococcus elongatus BP-1 into the membrane fraction containing particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b. Photoinduced hydroxylation of methane to methanol was successfully achieved by using the PSII-reconstituted membrane containing pMMO under light irradiation. This result indicates that the sequential redox chain from PSII through the quinone pool to pMMO can be constructed and that water can serve as the electron donor for methane hydroxylation under irradiation with light. pMMO in the membrane fraction produced hydrogen peroxide as a byproduct when an electron donor was added for methane hydroxylation, whereas under light irradiation conditions the PSII-reconstituted membrane containing pMMO did not generate hydrogen peroxide. Optimization of the electron-transfer rate can easily be achieved with this system by tuning the light intensity.

Specific Interaction between Redox Phospholipid Polymers and Plastoquinone in Photosynthetic Electron Transport Chain.

Redox phospholipid polymers added in culture media are known to be capable of extracting electrons from living photosynthetic cells across bacterial cell membranes with high cytocompatibility. In the present study, we identify the intracellular redox species that transfers electrons to the polymers. The open-circuit electrochemical potential of an electrolyte containing the redox polymer and extracted thylakoid membranes shift to positive (or negative) under light irradiation, when an electron transport inhibitor specific to plastoquinone is added upstream (or downstream) in the photosynthetic electron transport chain. The same trend is also observed for a medium containing living photosynthetic cells of Synechococcus elongatus PCC7942. These results clearly indicate that the phospholipid redox polymers extract photosynthetic electrons mainly from plastoquinone.

The effect of a prostaglandin E1 derivative on the symptoms and quality of life of patients with lumbar spinal stenosis.

BACKGROUND: Quality of life (QOL) is a concern for patients with lumbar spinal stenosis (LSS). In this study, QOL was examined using the 5-item EuroQol (EQ-5D). METHODS: QOL and activities of daily living (ADL) were surveyed for 91 patients who visited 18 medical institutions in our prefecture and were diagnosed with LSS-associated intermittent claudication. A second survey was performed after ≥6 weeks for 79 of the subjects to evaluate therapy with limaprost (an oral prostaglandin E1 derivative) or etodolac (an NSAID). Symptoms, maximum walking time, QOL, ADL items, and relationships among these variables were investigated for all 91 patients. Leg pain, leg numbness, and low back pain while walking were surveyed by use of VAS scores (0-100). RESULTS: Leg pain, leg numbness, and low back pain while walking (VAS ≥25) were present in 83.5, 62.6, and 54.9 % of the patients in the first survey, and approximately half of the patients had a maximum walking time <15 min. The mean EQ-5D utility value for QOL was 0.59 ± 0.12. This value was significantly associated with maximum walking time (p = 0.030) based on classification of patients into groups with walking times <7.5, 7.5-15, 15-30, and >30 min, showing that maximum walking time affected health-related QOL. Of the 79 patients who completed the second survey, 56 had taken limaprost and 23 (control group) had received etodolac. Limaprost improved possible walking time, reduced ADL interference, and significantly increased the EQ-5D utility score, whereas no significant changes occurred in the control group. Maximum walking time was prolonged by ≥10 min and the EQ-5D utility value was improved by ≥0.1 points in significantly more patients in the limaprost group than in the control group. CONCLUSION: According to the findings of this survey, at an average of 8 weeks after administration limaprost improved symptoms, QOL, and ADL in LSS patients whereas treatment with an NSAID reduced pain but did not have any other effects.

Switching Between Methanol Accumulation and Cell Growth by Expression Control of Methanol Dehydrogenase in Methylosinus trichosporium OB3b Mutant.

Methanotrophs have been used to convert methane to methanol at ambient temperature and pressure. In order to accumulate methanol using methanotrophs, methanol dehydrogenase (MDH) must be downregulated as it consumes methanol. Here, we describe a methanol production system wherein MDH expression is controlled by using methanotroph mutants. We used the MxaF knockout mutant of Methylosinus trichosporium OB3b. It could only grow with MDH (XoxF) which has a cerium ion in its active site and is only expressed by bacteria in media containing cerium ions. In the presence of 0 µM copper ion and 25 µM cerium ion, the mutant grew normally. Under conditions conducive to methanol production (10 µM copper ion and 0 µM cerium ion), cell growth was inhibited and methanol accumulated (2.6 µmol·mg-1 dry cell weight·h-1). The conversion efficiency of the accumulated methanol to the total amount of methane added to the reaction system was ~0.3%. The aforementioned conditions were repeatedly alternated by modulating the metal ion composition of the bacterial growth medium.

[Clinical analysis of precaution against atrial fibrillation following cardiac surgery: landiolol or amiodarone?].

Atrial fibrillation following cardiac surgery remains as a most common complication. Tachycardia with atrial fibrillation just after the operation could lead to cardiac deterioration. Although we have to control tachycardia, we often have great difficulties in managing these arrhythmias. Many reports have showed landiolol, ultra short-acting beta1 blocker, and amiodarone were effective against postoperative atrial fibrillation. However there has been no report on comparison between these 2 drugs. As excessively sympathetic activity might cause atrial fibrillation, landiolol was introduced into our therapy concomitant with the sedative. Our investigation confirmed that both landiolol and amiodarone were effective in preventing atrial fibrillation, and that the timing of transition from intravenous administration to oral intake was acceptable. When landiolol was administered, enough attention should be paid to the patients whose left ventricular function was low. The patients in whom atrial fibrillation occurred under landiolol therapy showed tendency of lower heart rate in comparison with the patients under amiodarone therapy.

Positively charged base surrogate for highly stable "base pairing" through electrostatic and stacking interactions.

"Base pairs" of cationic dyes (p-methylstilbazole) were incorporated into oligodeoxyribonucleotides (ODNs). This "base pair" greatly stabilized the duplex through electrostatic and stacking interactions. The melting temperature of modified ODN was higher than those of neutral dyes and native base pairs. Further stabilization of the duplex was observed when the number of cationic dyes increased.

Real-time monitoring of intracellular redox changes in Methylococcus capsulatus (Bath) for efficient bioconversion of methane to methanol.

This study aimed to develop a novel method for real-time monitoring of the intracellular redox states in a methanotroph Methylococcus capsulatus, using Peredox as a genetically encoded fluorescent sensor of the NADH:NAD+ ratio. As expected, the fluorescence derived from the Peredox-expressing M. capsulatus transformant increased by supplementation of electron donor compounds (methane and formate), while it decreased by specifically inhibiting the methanol oxidation reaction. Electrochemical measurements confirmed that the Peredox fluorescence reliably represents the intracellular redox changes. This study is the first to construct a reliable redox-monitoring method for methanotrophs, which will facilitate to develop more efficient methane-to-methanol bioconversion processes.

High resolution imaging of intracellular oxygen concentration by phosphorescence lifetime.

Optical methods using phosphorescence quenching by oxygen are suitable for sequential monitoring and non-invasive measurements for oxygen concentration (OC) imaging within cells. Phosphorescence intensity measurement is widely used with phosphorescent dyes. These dyes are ubiquitously but heterogeneously distributed inside the whole cell. The distribution of phosphorescent dye is a major disadvantage in phosphorescence intensity measurement. We established OC imaging system for a single cell using phosphorescence lifetime and a laser scanning confocal microscope. This system had improved spatial resolution and reduced the measurement time with the high repetition rate of the laser. By the combination of ubiquitously distributed phosphorescent dye with this lifetime imaging microscope, we can visualize the OC inside the whole cell and spheroid. This system uses reversible phosphorescence quenching by oxygen, so it can measure successive OC changes from normoxia to anoxia. Lower regions of OC inside the cell colocalized with mitochondria. The time-dependent OC change in an insulin-producing cell line MIN6 by the glucose stimulation was successfully visualized. Assessing the detailed distribution and dynamics of OC inside cells achieved by the presented system will be useful to understanding a physiological and pathological oxygen metabolism.

Specific surface modification of the acetylene-linked glycolipid vesicle by click chemistry.

A novel glycolipid with a terminal acetylene was synthesized and used to prepare unilamellar vesicles. Using these vesicles, a convenient method was developed for the specific modification of the vesicle surface using the photoresponsive copper complex [Cu(OH(2))(cage)] as the catalyst for a click reaction.

Alternative approach for aortic valve replacement: in mediastinal deviation after right lobectomy.

A 71-year-old man on hemodialysis and with a history of right lobectomy was referred for aortic valve replacement. Chest computed tomography revealed counterclockwise rotation of the heart through its longitudinal axis.We approached the aortic valve through median sternotomy. Accordingly, we transected the sternum at the level of the 3rd intercostal space and extended the skin incision approximately 2 inches perpendicular to the midline. After partial transection of the sternum, 3 spreaders were placed: the 1st, in the upper sternum; the 2nd, in the lower sternum; and the 3rd, between the ribs. These devices yielded excellent exposure of the ascending aorta. In addition, the relatively central shift of the ascending aorta contributed to the exposure of the right atrium and the right upper pulmonary vein. Subsequently, aortic valve replacement was performed in the usual fashion, and the patient experienced no postoperative respiratory complications. Aortic valve surgery with T-shaped sternotomy and without thoracotomy is an alternative technique in a patient who has a secondary deviation after lobectomy.