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A Gram-stain-negative, long-rod shaped, and facultatively anaerobic bacterium, designated as strain M1T, was isolated from the marine sediment of Jeju Island, South Korea. Strain M1T was found to be catalase- and oxidase-positive, light yellow-pigmented, non-motile, and non-flagellated, growing optimally at 30 °C, pH 7.0, and in the presence of 3% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain M1T belongs to the genus Draconibacterium and is closely related to Draconibacterium orientale FH5T (97.2%), Draconibacterium sediminis JN14CK-3 T (96.5%), “Draconibacterium filum” F2T (96.5%) and Draconibacterium mangrovi GM2-18 T (96.3% sequence similarity). The values for digital DNA-DNA hybridization ranged from 37.6 to 38.3% against D. orientale FH5T, D. sediminis KN14CK-3 T, and D. mangrovi GM2-18 T, clearly indicating that strain M1T represents a distinct species of the genus Draconibacterium. Strain M1T has a 40.0% G + C content estimated by genome sequence, menaquinone 7 as the sole respiratory quinone, C15:0 anteiso and C15:0 iso as the major fatty acids, and phosphatidylethanolamine, an unidentified phospholipid, and unidentified lipids as the polar lipids. Based on the polyphasic characteristics, it is suggested that strain M1T be assigned to the genus Draconibacterium as the type strain of a novel species, for which the name Draconibacterium halophilum sp. nov. is proposed. The type strain is M1T (= KCTC 72809 T = VTCC 910107 T).

Listeria monocytogenes is a food-borne pathogen with the ability to grow at low temperatures down to − 0.4 °C. Maintaining cytoplasmic membrane fluidity by changing the lipid membrane composition is important during growth at low temperatures. In Listeria monocytogenes, the dominant adaptation effect is the fluidization of the membrane by shortening of fatty acid chain length. In some strains, however, an additional response is the increase in menaquinone content during growth at low temperatures. The increase of this neutral lipid leads to fluidization of the membrane and thus represents a mechanism that is complementary to the fatty acid-mediated modification of membrane fluidity. This study demonstrated that the reduction of menaquinone content for Listeria monocytogenes strains resulted in significantly lower resistance to temperature stress and lower growth rates compared to unaffected control cultures after growth at 6 °C. Menaquinone content was reduced by supplementation with aromatic amino acids, which led to a feedback inhibition of the menaquinone synthesis. Menaquinone-reduced Listeria monocytogenes strains showed reduced bacterial cell fitness. This confirmed the adaptive function of menaquinones for growth at low temperatures of this pathogen.

A novel endophytic actinomycete with antagonistic activity against various phytopathogenic fungi, designated strain p1417T, was isolated from the root of cattail (Typha angustifolia L.) collected from Yunnan Province, Southwest China. A polyphasic taxonomic study was carried out to establish the taxonomic status of this strain. Strain p1417T was found to have morphological and chemotaxonomic characteristics typical of the genus Streptomyces. The diamino acid present in the cell wall was LL-diaminopimelic acid. Xylose and arabinose occurred in whole cell hydrolysates. The menaquinones were identified as MK-9(H8), MK-9(H6) and MK-9(H4). The polar lipid profile was found to contain diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The major fatty acids were found to be iso-C16:0, anteiso-C15:0, iso-C15:0 and C16:0. The genomic DNA G + C content of strain p1417T based on the genome sequence was 72.0 mol%. Based on 16 S rRNA gene, five housekeeping genes and whole genome sequences analysis, strain p1417T was most closely related to Streptomyces flavofungini JCM 4753T (99.4% 16 S rRNA gene sequence similarity), Streptomyces alboflavus JCM 4615T (98.8%) and Streptomyces aureoverticillatus JCM 4347T (98.2%). However, the average nucleotide identity values, the digital DNA–DNA hybridization values and the multilocus sequence analysis evolutionary distances between this strain and its closely related strains showed that it belonged to one distinct species. In addition, these results were also supported by differences in the phenotypic and chemotaxonomic characteristics between strain p1417T and three closely related type strains. Therefore, it is concluded that strain p1417T represents a novel species of the genus of Streptomyces, for which the name Streptomyces typhae sp. nov. is proposed. The type strain is p1417T (= CCTCC AA 2019091T = DSM 110636T).

Supplemental Digital Content is available in the text., Objective Alzheimer disease is characterized by progressive decline in cognitive function due to neurodegeneration induced by accumulation of Aβ and hyperphosphorylated tau protein. This study was conducted to explore the protective effect of vitamin K2 against Aβ42-induced neurotoxicity. Methods Alzheimer disease transgenic Drosophila model used in this study was amyloid beta with the arctic mutation expressed in neurons. Alzheimer disease flies were treated with vitamin K2 for 28 days after eclosion. Aβ42 level in brain was detected by ELISA. Autophagy-related genes and NDUFS3, the core subunit of mitochondrial complex I, were examined using real-Time PCR (RT-PCR) and western blot analysis. Results Vitamin K2 improved climbing ability (P = 0.0105), prolonged lifespan (P

A Gram-stain-negative, non-motile, yellow-pigmented and non-spore forming rod-shaped bacterium, designated strain BN140078T, was isolated from farmland soil, Chungbuk, Republic of Korea. It was able to grow aerobically at 10–40 °C (optimum 28 °C), pH 5.5–7.5 (optimum pH 7.0) and with 0–2.0% (w/v) NaCl concentration (optimum 1.0%) on Reasoner’s 2A (R2A) agar medium. Comparative 16S rRNA gene sequence analysis showed that the strain BN140078T had 96.9%, 96.5% and 96.1% 16S rRNA gene similarities with Chitinophaga ginsengihumi KACC 17604T, Chitinophaga rupis KACC 14521T and Chitinophaga japonensis KACC 12057T, respectively. The predominant respiratory quinone was menaquinone MK-7 and the major fatty acids (≥ 5%) were C16:1 ω5c, iso-C15:0, iso-C17:0 3-OH and Summed Feature 3 (C16:1 ω7c and/or C16:1 ω6c). The polar lipids were composed of phosphatidylethanolamine, four unidentified amino lipids and six unidentified lipids. The genomic DNA G+C content was 49.5 mol%. The genome of strain BN140078T comprises a number of biosynthetic gene clusters for secondary metabolites, in particular those for non-ribosomal peptide products. The polyphasic taxonomic study clearly distinguished this strain from its closest phylogenetic neighbors. Thus, we propose that the BN140078T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga agrisoli sp. nov. was proposed. The type strain is BN140078T (=KCTC 62555T = CCTCC AB 2018162T).

A polyphosphate-producing bacterium, YG09T, was isolated from the rhizosphere of Salvia miltiorrhiza. Its colonies were 2.0–3.0 mm in diameter, smooth, circular, convex and yellow after growth on R2A at 28 °C for 72 h, with aerobic, Gram-stain-negative, non-motile and rod-shaped bacteria. The strain was found to grow at 10–40 °C (optimum 37 °C), pH 5.5–8.0 (optimum 6.0), with 0–0.6% (w/v) NaCl (optimum 0). Chemotaxonomic analysis showed menaquinone-7 as the only quinone present; C15: 1 iso G, C15: 1 iso, C16: 0, C16: 0 3OH, C17: 0 iso 3OH, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) as the major fatty acids (> 5%), and phosphatidylethanolamine, three unidentified phospholipids, four unidentified polar lipids, three unidentified aminolipids, and one unidentified amino phospholipid as the polar lipids. The DNA G + C content was 44.6 mol%. The 16S rRNA gene sequences of the isolate showed highest similarities to Panacibacter ginsenosidivorans Gsoil 1550T (93.6%), Filimonas endophytica SR2-06T (93.4%), Parasegetibacter terrae SGM2-10T (92.8%), and Arvibacter flaviflagrans C-1-16T (92.7%), within the family Chitinophagaceae of the phylum Bacteroidetes. The ANI values between strain YG09T and Panacibacter ginsenosidivoran Gsoil 1550T, Filimonas endophytica SR2-06T and Filimonas lacunae YT21T were 69.4, 68.3 and 68.7%, respectively. Based on phenotypic, genotypic and phylogenetic analyses, strain YG09T represents a novel genus in the family Chitinophagaceae, for which the name Foetidibacter luteolus gen. sp. nov. is proposed. The type strain is Foetidibacter luteolus YG09T (= MCCC 1K04042T = KCTC 72595T).

A Gram-stain-negative, non-motile, aerobic, rod-shaped and reddish-pigmented bacterium, designated 8A47T, was isolated from a marine solar saltern located in Wendeng, PR China. The novel strain 8A47T grows at 20–42 °C, pH 7.0–9.0, and in the presence of 2.0–14.0% (w/v) NaCl. Optimal growth was observed at 37–40 °C, pH 7.5–8.0, and with 4.0–6.0% (w/v) NaCl. The phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 8A47T formed an evolutionary lineage with members of the genus Rhodohalobacter. Strain 8A47T exhibited high level of similarity to Rhodohalobacter barlenses MCCC 1K03442T (94.7%) and Rhodohalobacter halophilus JZ3C29T (93.5%). The major fatty acids were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), C16:0 and iso-C15:0. The sole respiratory quinone was MK-7. The polar lipids of the new isolate consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified lipid, two unidentified phospholipids and three unidentified glycolipids and. The genomic DNA G + C content of the strain 8A47T was 47.7 mol%. Based on its phenotypic, chemotaxonomic, genotypic and genomic characteristics presented in this study, strain 8A47T is considered to represent a novel species of the genus Rhodohalobacter, for which the name Rhodohalobacter mucosus sp. nov. is proposed. The type strain is 8A47T (= KCTC 62603T = MCCC 1H00329T).

A Gram-stain-negative, aerobic, non-motile, yellow-pigmented rod-shaped and alginate-degrading bacterium, designated B1N29T, was isolated from the gut of the abalone Haliotis rubra obtained in Weihai, China. Strain B1N29T was found to grow at 4–35 ℃ (optimum, 25 ℃), at pH 6.5–9.0 (optimum, 7.0–7.5) and in the presence of 0.5–9% (w/v) NaCl (optimum, 2%). Cells were positive for oxidase and catalase activity. The 16S rRNA-based phylogenetic analysis revealed that the nearest phylogenetic neighbors of strain B1N29T were Tamlana carrageenivorans KCTC 62451T (98.2%) and Tamlana agarivorans KCTC 22176T (97.7%). Based on the phylogenomic analysis, the average nucleotide identity (ANI) values between strain B1N29T and the neighbor strains were 79.2 and 79.0%, respectively; the digital DNA–DNA hybridization (dDDH) values between strain B1N29T and its two closest neighbors were 22.8 and 23.0%, respectively. Menaquinone-6 (MK-6) was detected as the sole respiratory quinone. The dominant cellular fatty acids were iso-C15:0, iso-C17:0 3-OH, anteiso-C15:0 and iso-C15:1 G. The polar lipids included phosphatidylethanolamine, one aminophospholipid, seven aminolipids and five unidentified lipids. Based on the phylogenetic and phenotypic characteristics, strain B1N29T is considered to represent a novel species of the genus Tamlana, for which the name Tamlana haliotis sp. nov. is proposed. The type strain is B1N29T (= KCTC 72683T = MCCC 1H00394T).

A novel actinobacterium, designated ASO4wetT, was isolated from the unidentified sponge (SO4) in the deep sea collected of the North Atlantic Ocean. Study of 16S rRNA gene sequences indicated that strain ASO4wetT is a member of the genus Streptomyces and showed the closest similarities to Streptomyces karpasiensis K413T (98.87 %), Streptomyces glycovorans YIM M 10366T (98.38 %), and Streptomyces abyssalis YIM M 10400T (97.53 %). Strain ASO4wetT contained MK-9(H8) as the predominant menaquinone and the major fatty acids are iso-C16:0, anteiso-C15:0, and iso-C15:0. Polyphasic taxonomy was carried out between strain ASO4wetT and its phylogenetically closely related Streptomyces strains, which further elucidated their relatedness and revealed that strain ASO4wetT could be distinguished from currently known Streptomyces species. Strain ASO4wetT clearly represents a novel species in genus Streptomyces. We propose the name Streptomyces bathyalis sp. nov., with the type strain ASO4wetT (= DSM 106605T = NCCB 100657T). Analysis of the whole-genome sequence of S. bathyalis revealed that genome size is 7,377,472 bp with 6332 coding sequences.

A Gram-stain-negative, rod-shaped, non-motile, aerobic, yellow-pigmented, marine bacterium (designated strain 176CP5-101 T) was isolated from a sponge Hymeniacidon sinapium from Cheongpo beach, Taean in Republic of Korea. The strain was able to grow at pH 6.8–8.5 (optimum at pH 7.5), in 1–7% (w/v) NaCl (optimum at 3%, w/v) and at 10–30 °C (optimum at 30 °C). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 176CP5-101 T belonged to the family Flavobacteriaceae and was most closely related to Flagellimonas aquimarina KCTC 52351 T (97.1%), F. algicola KACC 19790 T (97.0%), F. pacifica KCTC 52762 T (96.9%), F. eckloniae KCCM 42307 T (96.4%), F. flava KCTC 22665 T (96.0%), and F. maritima KCTC 32464 T (95.4%). Average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain 176CP5-101 T and F. aquimarina KCTC 52351 T were, respectively, 79.9% and 22.1%, indicating that 176CP5-101 T is a novel species of the genus Flagellimonas. The DNA G + C content of the genomic DNA was 37.8 mol%. Menaquinone with six isoprene units (MK-6) was the major respiratory quinone, and the major polar lipids were phosphatidylethanolamine (PE), unidentified aminophospholipid, and unidentified lipids. The fatty acids are mainly (> 5%) defined iso-C15:0, iso-C15:0 3-OH, iso-C15:1 G, iso-C17:0 3-OH, and C16:1 ω7c and/or C16:1 ω6c (summed feature 3). Phenotypic, phylogenetic, genomic, and chemotaxonomic characteristics showed that strain 176CP5-101 T represents a novel species of the genus Flagellimonas, for which the name Flagellimonas hymeniacidonis sp. nov. is proposed. The type strain is 176CP5-101 T (= KACC 19892 T = LMG 31316 T).

In calcific aortic valve disease (CAVD) progressive valvular calcification causes aortic valve dysfunction. CAVD has several risk factors such as age and dyslipidemia. Vitamin K was shown to inhibit vascular calcification in mice and valvular calcification in patients with CAVD. We studied the effect of menaquinone 4 (MK4/vitamin K2) on valvular calcification in the hypercholesterolemic mouse model of CAVD. LDLr −/− ApoB 100/100 male mice were fed with a Western diet for 5 months, with (n = 10) or without (n = 10) added 0.2 mg/g MK4. Body weight gain was followed weekly. Morphology of aortic valves and liver was assessed with immunohistochemistry. Plasma cholesterol levels and cytokines from hepatic tissue were assessed in the end of the study. Hepatic gene expression of lipid metabolism regulating genes were assessed after 18 h diet. MK4 exacerbated the lipoprotein lipid profile without affecting aortic valve morphology in hypercholesterolemic LDLr −/− ApoB 100/100 mice. The MK4-containing WD diet increased plasma levels of LDL and triglycerides, hepatic steatosis, and mRNA expression of genes required for triglyceride and cholesterol synthesis. MK4 diminished levels of several cytokines and chemokines in liver, including IL-6, TNFα and MCP1, as measured by hepatic cytokine array. Consequently, MK4 may exert non-beneficial effects on circulating lipid levels, especially in hypercholesterolemic individuals.

Background Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with a high prevalence worldwide, especially among overweight and obese populations. T2DM is multifactorial with several genetic and acquired risk factors that lead to insulin resistance. Mounting evidence indicates that alteration of gut microbiome composition contribute to insulin resistance and inflammation. However, the precise link between T2DM and gut microbiome role and composition remains unknown. Methods We evaluated the metabolic capabilities of the gut microbiome of twelve T2DM and six healthy individuals through shotgun metagenomics using MiSeq platform. Results We identified no significant differences in the overall taxonomic composition between healthy and T2DM subjects when controlling for differences in diet. However, results showed that T2DM enriched in metabolic pathways involved in menaquinone (vitamin K2) superpathway biosynthesis (PWY-5838) as compared to healthy individuals. Covariance analysis between the bacterial genera and metabolic pathways displaying difference in abundance (analysis of variance P6.5%) exhibit high abundance of genes involved in lysine biosynthesis and low abundance of genes involved in creatinine degradation as compared to T2DM with lower HbA1c (

An aerobic, Gram-negative, non-motile, non-spore-forming, rod-shaped, and pale yellow-colored bacterial strain, designated TS118T, was isolated from a sand sample obtained from a coastal sand dune after exposure to 3 kGy of gamma radiation. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate was a member of the genus Spirosoma and most closely related to Spirosoma metallicum PR1014kT (95.1% similarity). The genome of strain TS118T is constituted by one chromosome (5,691,492 bp) and one plasmid (28,440 bp) and has a G + C content of 52.7%. The genome contains 4641 protein coding sequences (CDSs), 38 tRNAs, and 11 rRNAs. The predominant fatty acids of strain TS118T were C16:1 ω5c, iso-C15:0, C16:0, summed feature 3 (C16:1 ω6c and/or C16:1 ω7c), and iso-C17:0 3-OH. The major polar lipids were phosphatidylethanolamine, an unidentified amino lipid and an unidentified aminophospholipid. The main respiratory quinone was menaquinone-7 (MK-7). The novel strain showed resistance to gamma radiation with a D10 value (i.e., the dose required to reduce the bacterial population by tenfold) of 4.3 kGy. Based on the phylogenetic, physiological, and chemotaxonomic characteristics, strain TS118T represents a novel species, for which the name Spirosoma taeanense sp. nov. is proposed. The type strain is TS118T (=KCTC 72898T =JCM 34024T).

An alkaliphilic actinomycete, designated HAJB-30 T, was isolated from a soda alkali-saline soil in Heilongjiang, Northeast China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain HAJB-30 T was most closely related to type strains of the genus Phytoactinopolyspora with sequence similarities ranging between 93.5 and 98.9%. Strain HAJB-30 T grew at pH 8.0–11.0 (optimum pH 9.5–10.0) and in the presence of 0–7.0% NaCl (optimum 1.0–3.0%). Whole-cell hydrolysates of the isolate contained LL-diaminopimelic acid as the diagnostic diamino acid and mannose and rhamnose as diagnostic sugars. The major fatty acids identified were iso-C14:0, iso-C15:0, anteiso-C15:0, iso-C16:0 and anteiso-C17:0, while the menaquinone was MK-9(H4). The genome (6,589,901 bp), composed of 50 contigs, had a G + C content of 66.8%. Out of the 6074 predicted genes, 6020 were protein-coding genes, and 54 were ncRNAs. Digital DNA–DNA hybridization (dDDH) estimation and average nucleotide identity (ANI) of strain HAJB-30 T against genomes of the type strains of related species in the same family ranged between 19.7 and 22.0% and between 71.5 and 76.8%, respectively. From these results, it was concluded that strain HAJB-30 T possesses sufficient characteristics differentiated from all recognized Phytoactinopolyspora species, it is considered to be a novel species for which the name Phytoactinopolyspora limicola sp. nov. is proposed. The type strain is HAJB-30 T (= CGMCC 4.7591 T, = JCM 33694 T).

OBJECTIVE To investigate the immunosuppressive effect of vitamin K2 against mitogen-activated peripheral blood mononuclear cells (PBMCs) of rheumatoid arthritis (RA) patients. MATERIALS AND METHODS Concanavalin A-stimulated PBMC culture procedure was used to evaluate the pharmacodynamics of vitamin K2 in vitro. Methotrexate was set up as the positive control. The proliferation of PBMCs was detected by MTT assay. Relationship between IC50 values of drugs on PBMC proliferation and patient-related factors including laboratory data was analyzed by nonparametric Spearman correlation test. RESULTS Vitamin K2 inhibited the proliferation of mitogen-activated PBMCs of RA patients with an IC50 value of 3,288.47 ± 4,910.02 ng/mL (mean ± SD). There was a significant correlation between IC50 values of vitamin K2 and patient-related factors of RA patients (p

A previous study reported that the

A novel bacterium of the genus Pontibacter, designated GY10130

A Gram-stain-negative, rod-shaped bacterial strain DH6

A polyphasic study was designed to resolve the taxonomic position of isolate MGRD01-02

The human gut microbiome plays a crucial role in skeletal homeostasis. The synbiotic consortium or Defined Microbial Assemblage™ (DMA™) food product, SBD111, consisting of probiotic microbes and prebiotic fibers was designed to promote bone health based on its capacity to produce short chain fatty acids (SCFA), the presence of genes for vitamin K2 production, and its ability to degrade plant fibers. A 28-day repeated administration study was performed to evaluate the oral toxicity of SBD111 in female rats (age/weight at study start: 5-7 weeks/120-180 g) administered levels of 0, 2.0 x 10

Two strictly aerobic, Gram-staining-positive, non-spore-forming, regular rod-shaped (approximately 0.7 × 1.9 mm) bacteria (HY170

Background The study and application of microbial consortia are topics of interest in the fields of metabolic engineering and synthetic biology. In this study, we report the design and optimisation of Elizabethkingia meningoseptica and Escherichia coli co-culture, which bypass certain limitations found during the molecular modification of E. meningoseptica, such as resistance to many antibiotics and fewer available molecular tools. Results The octaprenyl pyrophosphate synthase from E. meningoseptica sp. F2 (EmOPPS) was expressed, purified, and identified in the present study. Then, owing to the low vitamin K2 production by E. coli or E. meningoseptica sp. F2 monoculture, we introduced the E. meningoseptica and E. coli co-culture strategy to improve vitamin K2 biosynthesis. We achieved production titres of 32 mg/L by introducing vitamin K2 synthesis-related genes from E. meningoseptica sp. F2 into E. coli, which were approximately three-fold more than the titre achieved with E. meningoseptica sp. F2 monoculture. This study establishes a foundation for further engineering of MK-n (n = 4, 5, 6, 7, 8) in a co-cultivation system of E. meningoseptica and E. coli. Finally, we analysed the surface morphology, esterase activity, and membrane permeability of these microbial consortia using scanning electron microscopy, confocal laser scanning microscopy, and flow cytometry, respectively. The results showed that the co-cultured bacteria were closely linked and that lipase activity and membrane permeability improved, which may be conducive to the exchange of substances between bacteria. Conclusions Our results demonstrated that co-culture engineering can be a useful method in the broad field of metabolic engineering of strains with restricted molecular modifications.

Vitamin K2, a natural fat-soluble vitamin, is a potent neuroprotective molecule, owing to its antioxidant effect, but its mechanism has not been fully elucidated. Therefore, we stimulated SH-SY5Y cells with 6-hydroxydopamine (6-OHDA) in a proper dose-dependent manner, followed by a treatment of vitamin K2. In the presence of 6-OHDA, cell viability was reduced, the mitochondrial membrane potential was decreased, and the accumulation of reactive oxygen species (ROS) was increased. Moreover, the treatment of 6-OHDA promoted mitochondria-mediated apoptosis and abnormal mitochondrial fission and fusion. However, vitamin K2 significantly suppressed 6-OHDA-induced changes. Vitamin K2 played a significant part in apoptosis by upregulating and downregulating Bcl-2 and Bax protein expressions, respectively, which inhibited mitochondrial depolarization, and ROS accumulation to maintain mitochondrial structure and functional stabilities. Additionally, vitamin K2 significantly inhibited the 6-OHDA-induced downregulation of the MFN1/2 level and upregulation of the DRP1 level, respectively, and this enabled cells to maintain the dynamic balance of mitochondrial fusion and fission. Furthermore, vitamin K2 treatments downregulated the expression level of p62 and upregulated the expression level of LC3A in 6-OHDA-treated cells via the PINK1/Parkin signaling pathway, thereby promoting mitophagy. Moreover, it induced mitochondrial biogenesis in 6-OHDA damaged cells by promoting the expression of PGC-1α, NRF1, and TFAM. These indicated that vitamin K2 can release mitochondrial damage, and that this effect is related to the participation of vitamin K2 in the regulation of the mitochondrial quality-control loop, through the maintenance of the mitochondrial quality-control system, and repair mitochondrial dysfunction, thereby alleviating neuronal cell death mediated by mitochondrial damage.

A Gram-stain positive, aerobic, rod-shaped actinobacterial strain designated as JXJ CY 27-2

Supplementation with calcium (Ca) and/or vitamin D (vitD) is key to the management of osteoporosis. Other supplements like vitamin K2 (VitK2) and magnesium (Mg) could contribute to the maintenance of skeletal health. This narrative review summarizes the most recent data on Ca, vitD, vitK2 and Mg supplementation and age-related bone and muscle loss. Ca supplementation alone is not recommended for fracture prevention in the general postmenopausal population. Patients at risk of fracture with insufficient dietary intake and absorption could benefit from calcium supplementation, but it needs to be customized, taking into account possible side-effects and degree of adherence. VitD supplementation is essential in patients at risk of fracture and/or vitD deficiency. VitK2 and Mg both appear to be involved in bone metabolism. Data suggest that VitK2 supplementation might improve bone quality and reduce fracture risk in osteoporotic patients, potentially enhancing the efficacy of Ca ± vitD. Mg deficiency could negatively influence bone and muscle health. However, data regarding the efficacy of vitK2 and Mg supplementation on bone are inconclusive.

Two Gram-stain-positive, rod-shaped, endospore-forming bacteria, designated 12200R-189T and 14171R-81T were isolated from the rhizosphere of tomato plants. The 16S rRNA gene sequence similarity between strains 12200R-189T and 14171R-81T were 97.2%. Both strains showed the highest 16S rRNA gene sequence similarities to Paenibacillus sacheonensis SY01T (96.3% and 98.0%, respectively). The genome of strain 12200R-189T was approximately 6.7 Mb in size with 5,750 protein-coding genes (CDSs) and the G + C content was 58.1 mol%, whereas that of strain 14171R-81T comprised one chromosome of 7.0 Mb and two plasmids (0.2 Mb each) with 6,595 CDSs and the G + C content was 54.5 mol%. Comparative genome analysis revealed that average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among 12200R-189T, 14171R-81T, and other closely related species were below the cut-off levels 95% and 70%, respectively. Strain 12200R-189T grew at a temperature range of 15-40°C, pH 6.0-9.0, and 0-3% NaCl (w/v), whereas strain 14171R-81T grew at a temperature range of 10-37°C, pH 6.0-8.0, and 0-1% NaCl (w/v). Menaquinone-7 (MK-7) was the only isoprenoid quinone detected in both strains. The predominant cellular fatty acids (> 10%) were iso-C15:0, anteiso-C15:0, and iso-C16:0. The polar lipids of strain 12200R-189T were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), aminophospholipid (APL), phospholipid (PL), phosphatidylglycolipid (PGL), and four aminophosphoglycolipids (APGLs) and those of strain 14171R-81T were DPG, PG, PE, APL, three PLs, two PGLs, and three APGLs. Based on phylogenetic, genomic, phenotypic, and chemotaxonomic analyses, strains 12200R-189T and 14171R-81T represent two novel species of the genus Paenibacillus, for which the names Paenibacillus lycopersici sp. nov. and Paenibacillus rhizovicinus sp. nov. are proposed. The type strains are 12200R-189T (= KACC 19916T = CCTCC AB 2020027T) and 14171R-81T (= KACC 19915T = CCTCC AB 2020026T).

A shiny dark yellow pigmented, Gram-stain-negative, rod-shaped, non-motile bacterium, designated as strain JC631T, was isolated from the sediment ecosystem of Chilika lagoon, India. Strain JC631T tolerates up to pH 10 and NaCl up to 3% (w/v). MK6 is the only respiratory quinone. Predominant (> 10%) cellular fatty acids are anteiso-C11:0, anteiso-C13:0, and anteiso-C15:0. Major polar lipids are phosphatidylethanolamine, phosphatidylcholine, a few unidentified phospholipids, and a few unidentified aminolipids. 16S rRNA gene sequencing showed that strain JC631T shared the highest sequence identity (98.7%) with Arenibacter latericius KMM 426T followed by Arenibacter certesii CCUG 48006T (98.6%) and other members of the genus Arenibacter (

Abiraterone acetate (AA) is an inhibitor of androgen biosynthesis, though this cannot fully explain its efficacy against androgen-independent prostate cancer. Here, we demonstrate that androgen deprivation therapy depletes androgen-utilizing Corynebacterium spp. in prostate cancer patients and that oral AA further enriches for the health-associated commensal, Akkermansia muciniphila. Functional inferencing elucidates a coinciding increase in bacterial biosynthesis of vitamin K2 (an inhibitor of androgen dependent and independent tumor growth). These results are highly reproducible in a host-free gut model, excluding the possibility of immune involvement. Further investigation reveals that AA is metabolized by bacteria in vitro and that breakdown components selectively impact growth. We conclude that A. muciniphila is a key regulator of AA-mediated restructuring of microbial communities, and that this species may affect treatment response in castrate-resistant cohorts. Ongoing initiatives aimed at modulating the colonic microbiota of cancer patients may consider targeted delivery of poorly absorbed selective bacterial growth agents., Abiraterone acetate (AA) is indicated for the treatment of patients with metastatic castrate-resistant prostate cancer. Here, the authors show that, in prostate cancer patients, orally administered AA remodels the gut microbiome and promotes the enrichment of the commensal bacterium Akkermansia muciniphila at the expense of androgen-utilizing Corynebacterium species.

BACKGROUND: Vascular calcification, a risk factor for cardiovascular disease, is common among patients with CKD and is an independent contributor to increased vascular stiffness and vascular risk in this patient group. Vitamin K is a cofactor for proteins involved in prevention of vascular calcification. Whether or not vitamin K supplementation could improve arterial stiffness in patients with CKD is unknown. METHODS: To determine if vitamin K supplementation might improve arterial stiffness in patients in CKD, we conducted a parallel-group, double-blind, randomized trial in participants aged 18 or older with CKD stage 3b or 4 (eGFR 15–45 ml/min per 1.73 m(2)). We randomly assigned participants to receive 400 μg oral vitamin K2 or matching placebo once daily for a year. The primary outcome was the adjusted between-group difference in carotid-femoral pulse wave velocity at 12 months. Secondary outcomes included augmentation index, abdominal aortic calcification, BP, physical function, and blood markers of mineral metabolism and vascular health. We also updated a recently published meta-analysis of trials to include the findings of this study. RESULTS: We included 159 randomized participants in the modified intention-to-treat analysis, with 80 allocated to receive vitamin K and 79 to receive placebo. Mean age was 66 years, 62 (39%) were female, and 87 (55%) had CKD stage 4. We found no differences in pulse wave velocity at 12 months, augmentation index at 12 months, BP, B-type natriuretic peptide, or physical function. The updated meta-analysis showed no effect of vitamin K supplementation on vascular stiffness or vascular calcification measures. CONCLUSIONS: Vitamin K2 supplementation did not improve vascular stiffness or other measures of vascular health in this trial involving individuals with CKD. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Vitamin K therapy to improve vascular health in patients with chronic kidney disease, ISRCTN21444964 (www.isrctn.com)

Although it is known that inflammation is involved in Parkinson's disease (PD) pathogenesis and vitamin K2 (VK2) has anti-inflammatory effects, to date few studies have been reported on the relationship between VK2 and PD development. Herein we presented a case-control study involving 93 PD patients and 95 healthy controls. Overall, the serum VK2 level of PD patients (3.49 ± 1.68 ng/ml) was significantly lower than that of healthy controls (5.77 ± 2.71 ng/ml). When the PD patients were stratified by disease progression, we observed that the serum VK2 level of late stage patients was further decreased to 3.15 ± 1.18 ng/ml while the serum VK2 level of early stage patients was 3.92 ± 2.09 ng/ml. Furthermore, the curve analysis showed that the serum VK2 level decreased gradually with the increment of PD Hoehn-Yahr (H-Y) stage. We also confirmed the dysregulated inflammatory responses and coagulation cascades in PD patients by public dataset, which are associated to the decreased VK2 level. In summary, we found the serum VK2 level in PD patients is lower than that in healthy controls. The decrease of VK2 level may be related to the occurrence and progression of PD by loosening the regulation of inflammatory responses and coagulation cascades signal.

The filamentous actinomycete that produces the antibiotic GE23077 was isolated by the Lepetit Research Group from a soil sample collected in Thailand, and it was classified as a member of the genus Actinomadura on the basis of its morphology and cell-wall composition. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain formed a distinct monophyletic line within the genus Actinomadura, and it was most closely related to Actinomadura bangladeshensis DSM 45347T (99.31 % similarity) and Actinomadura mexicana DSM 44485T (98.94 %). The GE23077-producing strain formed an extensively branched, non-fragmented vegetative mycelium; no pseudosporangia were formed and the arthrospores were organized in slightly twisted chains. The cell wall contained meso-2,6-diaminopimelic acid and the diagnostic sugar was madurose. The predominant menaquinone was MK-9(H6), with minor amounts of MK-9(H8) and MK-9(H4). The diagnostic phospholipids were phosphatidylinositol and diphosphatidylglycerol. The major cellular fatty acids were C16 : 0 and tuberculostearic acid (10-methyloctadecanoic acid), followed by minor amounts of C18:1ω9c, C16:1ω7c and 10-methylheptadecanoic acid. The genomic DNA G+C content was 71.77 mol%. Significant differences in the morphological, chemotaxonomic and biochemical data, and the low DNA–DNA relatedness between the GE23077-producing strain and closely related type strains clearly demonstrate that it represents a novel species of the genus Actinomadura , for which the name Actinomadura lepetitiana sp. nov. is proposed. The type strain is NRRL B-65521T(=LMG 31258T=DSM 109019T).

A bacterial strain designated NYYP31T was isolated from the leaves of an annual halophytes, Suaeda corniculata Bunge, collected from the southern edge of the Gurbantunggut desert, north-west China. Strain NYYP31T was Gram-staining negative, strictly aerobic, rod-shaped, non-motile, and non-spore-forming. Growth was observed at 4–42 °C, at pH 5.0–10.0, in the presence of up to 8% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences and coding sequences of 92 protein clusters showed that strain NYYP31T should be assigned to the genus Sphingobacterium. 16S rRNA gene sequence similarity analysis showed that strain NYYP31T was most closely related to the type strain of Sphingobacterium daejeonense (97.9%) and Sphingobacterium lactis (97.7%). The predominant isoprenoid quinone was MK-7. The major fatty acids were identified as iso-C15:0, iso-C17:0 3-OH and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The polar lipids were phosphatidylethanolamine, two unidentified phospholipids, three unidentified lipids, three unidentified amino phospholipids, and two unidentified glycolipids. The genomic DNA G + C content was 36.4 mol%. The average nucleotide identity (ANI) values for strain NYYP31T to the type strains of S. daejeonense and S. lactis were 77.9 and 74.1%, respectively, which were below the cut-off level (95–96%) for species delineation. Based on the above results, strain NYYP31T represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium endophyticum sp. nov. is proposed. The type strain is NYYP31T (= CGMCC 1.16979T = NBRC 114258T).

Antibiotic resistance continues to spread at an alarming rate, outpacing the introduction of new therapeutics and threatening to globally undermine health care. There is a crucial need for new strategies that selectively target specific pathogens while leaving the majority of the microbiome untouched, thus averting the debilitating and sometimes fatal occurrences of opportunistic infections. To address these challenges, we have adopted a unique strategy that focuses on oxygen-sensitive proteins, an untapped set of therapeutic targets. MqnE is a member of the radical S-adenosyl-l-methionine (RS) superfamily, all of which rely on an oxygen-sensitive [4Fe-4S] cluster for catalytic activity. MqnE catalyzes the conversion of didehydrochorismate to aminofutalosine in the essential menaquinone biosynthetic pathway present in a limited set of species, including the gut pathogen Helicobacter pylori (Hp), making it an attractive target for narrow-spectrum antibiotic development. Indeed, we show that MqnE is inhibited by the mechanism-derived 2-fluoro analogue of didehydrochorismate (2F-DHC) due to accumulation of a radical intermediate under turnover conditions. Structures of MqnE in the apo and product-bound states afford insight into its catalytic mechanism, and electron paramagnetic resonance approaches provide direct spectroscopic evidence consistent with the predicted structure of the radical intermediate. In addition, we demonstrate the essentiality of the menaquinone biosynthetic pathway and unambiguously validate 2F-DHC as a selective inhibitor of Hp growth that exclusively targets MqnE. These data provide the foundation for designing effective Hp therapies and demonstrate proof of principle that radical SAM proteins can be effectively leveraged as therapeutic targets.

Introduction: Vitamin K (VK) is a co-factor in the post-translational gamma glutamic carboxylation of Gla-proteins. VK-dependent coagulation factors are carboxylated in the liver by VK1. Osteocalcin and Matrix-Gla protein (MGP) are carboxylated in extrahepatic tissues by VK2. A model of VK deficiency would be suitable for studying extrahepatic Gla-proteins provided that severe bleeding is prevented. Aim: The aim of this work was to adapt an established protocol of vascular calcification by warfarin-induced inactivation of MGP as a calcification inhibitor, in an attempt to create a broader state of subclinical VK deficiency and to verify its safety. Materials and methods: Two consecutive experiments, each lasting 4 weeks, were required to modify the dosing schedule of warfa­rin and VK1 and to adapt it to the Wistar rats used. The original high doses of warfarin used initially had to be halved and the protective dose of VK1 to be doubled, in order to avoid treatment-induced hemorrhagic deaths. The second experiment aimed to confirm the efficacy and safety of the modified doses. To verify the VK deficiency, blood vessels were examined histologically for calcium deposits and serum osteocalcin levels were mea­sured. Results: The original dosing schedule induced VK deficiency, manifested by arterial calcifications and dramatic changes in carboxyl­ated and uncarboxylated osteocalcin. The modified dosing regimen caused similar vascular calcification and no bleeding. Conclusion: The modified protocol of carefully balanced warfarin and VK1 doses is an effective and safe way to induce subclinical VK deficiency that can be implemented to investigate VK-dependent proteins like osteocalcin.

A novel Gram-stain-positive, strictly aerobic, non-motile, rod-shaped bacterium, designated strain R14T was isolated from steep grove soil and taxonomically characterized using a polyphasic approach. Cells showed oxidase-negative and catalase-positive activities and grew at 25–37 °C (optimum, 30 °C), pH 5.0–8.0 (optimum, pH 6.5), and in the presence of 0–0.5% (w/v) NaCl (optimum, 0%). Phylogenetic trees based on 16S rRNA gene sequences revealed that strain R14T formed a phylogenetic lineage with Flavihumibacter genus members within the family Chitinophagaceae. Comparison of 16S rRNA gene sequences showed that strain R14T shared highest similarities with Flavihumibacter solisilvae 3-3T (97.5%), Flavihumibacter petaseus NBRC 106054T (96.7%), and Flavihumibacter stibioxidans YS-17T (96.1%). The G+C content of strain R14T calculated from its whole genome sequence was 44.6 mol%. Strain R14T contained menaquinone-7 and iso-C15:0, iso-C17:0 3-OH, C16:0, C15:1 ω6c, and iso-C15:0-G as the sole respiratory isoprenoid quinone and major cellular fatty acids, respectively. Major polar lipids consisted of phosphatidylethanolamine, two unidentified aminolipids, and four unidentified lipids. Based on phylogenetic, phenotypic, and chemotaxonomic characteristics of strain R14T, it could be concluded that strain R14T represents a novel species of the genus Flavihumibacter, for which the name Flavihumibacter soli sp. nov. is proposed. The type strain is R14T (=KACC 21229T = JCM 33473T).

Objectives Obesity is an important risk factor for morbidity and mortality. Vitamin K2 is involved in the production of bone and matrix amino acid g-carboxy-glutamic acid (Gla) proteins (vitamin K-dependent proteins [VKDPs]), regulating bone and vascular calcification (VC). Bone Gla protein (BGP) is involved both in bone mineralization and VCs. We assessed the relationships between vitamin K levels and body mass index (BMI) according to the hypothesis that the impact of BMI on mortality is partly driven by low vitamin K levels. Methods The Vitamin K Italian (VIKI) study included 387 hemodialysis patients from 18 dialysis centers in Italy. We determined plasma levels of bone markers: vitamin K levels, VKDPs, vitamin 25(OH)D, alkaline phosphatase (ALP), parathyroid hormone (PTH), calcium (Ca), phosphorus (P) and routine biochemistry. BMI was classified into the following categories: underweight (BMI 2), normal weight (18.5 ≤ BMI 2), overweight (25 ≤ BMI 2) and obese (BMI ≥ 30 kg/m2). Results 45.2% of patients were overweight or obese. Stratification by BMI demonstrated lower median menaquinone-7 (MK7)/triglycerides levels in obese patients (0.42 ng/mg [0.19, 0.87], p = 0.005). BGP levels were lower in overweight and obese patients (152 mcg/L [83.2, 251] and 104 mcg/L [62.7, 230], p = Conclusions These data are the first to report an inverse relationship between Vitamin K2 levels and BMI in hemodialysis patients. Further studies are needed to confirm these findings and to determine if lower levels of Vitamin K are related to greater morbidity and mortality in this at-risk population.

Vitamin menaquinone-7 (MK-7) supplementation improves bone health and reduces the incidence of osteoporosis. Despite the recent developments in MK-7 fermentation using Bacillus subtilis natto, low fermentation yields, as well as complicated downstream processing steps, are still the main reasons for the expensive final product. To overcome these issues, developing a fermented dairy-based product rich in MK-7 by avoiding costly downstream steps and optimising the fermentation operating conditions to enhance the MK-7 concentration would be an alternative approach. The present study, therefore, aims to evaluate the role of agitation and aeration as the key operating conditions on MK-7 production by Bacillus subtilis natto using a milk media. The agitation and aeration rates of 525 RPM and 5 VVM were found to be the optimum levels leading to the production of 3.54 mg/L of MK-7. Further, the sensory evaluation was performed to compare the sensory properties of the freeze-dried fermented samples with non-fermented milk samples. The results illustrated that the fermented samples had a significant saltiness with intense aroma resulting in the less acceptability of them by the panellists.

The autosomal dominant disorder Schnyder corneal dystrophy (SCD) is caused by mutations in UbiA prenyltransferase domain-containing protein-1 (UBIAD1), which uses geranylgeranyl pyrophosphate (GGpp) to synthesize the vitamin K(2) subtype menaquinone-4 (MK-4). SCD is characterized by opacification of the cornea, owing to aberrant build-up of cholesterol in the tissue. We previously discovered that sterols stimulate association of UBIAD1 with ER-localized HMG-CoA reductase, which catalyzes a rate-limiting step in the synthesis of cholesterol and nonsterol isoprenoids, including GGpp. Binding to UBIAD1 inhibits sterol-accelerated ER-associated degradation (ERAD) of reductase and permits continued synthesis of GGpp in cholesterol-replete cells. GGpp disrupts UBIAD1-reductase binding and thereby allows for maximal ERAD of reductase as well as ER-to-Golgi translocation of UBIAD1. SCD-associated UBIAD1 is refractory to GGpp-mediated dissociation from reductase and remains sequestered in the ER to inhibit ERAD. Here, we report development of a biochemical assay for UBIAD1-mediated synthesis of MK-4 in isolated membranes and intact cells. Using this assay, we compared enzymatic activity of WT UBIAD1 with that of SCD-associated variants. Our studies revealed that SCD-associated UBIAD1 exhibited reduced MK-4 synthetic activity, which may result from its reduced affinity for GGpp. Sequestration in the ER protects SCD-associated UBIAD1 from autophagy and allows intracellular accumulation of the mutant protein, which amplifies the inhibitory effect on reductase ERAD. These findings have important implications not only for the understanding of SCD etiology but also for the efficacy of cholesterol-lowering statin therapy, which becomes limited, in part, because of UBIAD1-mediated inhibition of reductase ERAD.

An aerobic, oligotrophic, Gram-positive, non-sporulating, motile, rod-shaped, palladium-leaching bacterial strain, Deinococcus sp. KR-1, was previously isolated from pond water collected in Japan. This strain grew at 10 °C to 40 °C (optimum 30 °C), at pH 4.5 to 11.5 (optimum pH 8.0), and in the presence of 2.0% NaCl. Its major cellular fatty acids were C15: 1ω6 and C16 : 1ω7c. The quinone system was menaquinone 8. Multilocus sequence analysis based on partial sequences of four housekeeping genes (atpD, dnaA, gyrB and rpoB) showed that branching of Deinococcus sp. KR-1 was distant to those of Deinococcus type strains. The genome average nucleotide identity value between strain KR-1 and its closest related Deinococcus type strain was less than 95.69%. Based on its phenotypic, chemotaxonomic and phylogenetic data, strain KR-1 (= HUT-8138T = KCTC 33977T) can be considered a novel species within the genus Deinococcus with the proposed name Deinococcus kurensis sp. nov.

A novel Streptomyces strain, designated TRM43335T, was isolated from the Taklimakan desert in Alar City, Xinjiang, north-west China. The strain was found to exhibit an inhibitory effect on biofilm formation by Candida albicans and Staphylococcus epidermidis. A polyphasic approach was used to determine its taxonomic status. The strain was observed to form abundant aerial mycelium, occasionally twisted and which differentiated into spiral spore chains. Spores of TRM43335T were observed to be oval-shaped, with a smooth surface. Strain TRM43335T was found to grow optimally at 37 °C, pH 8 and in the presence of 1% (w/v) NaCl. The major sugars were identified as ribose, xylose, glucose, mannose and galactose, and the principal phospholipids were found to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol mannoside and phosphatidylinositol. The diagnostic cell wall amino acid was identified as LL-diaminopimelic acid. The predominant menaquinone was found to be MK-9(H6). The major cellular fatty acids were identified as iso-C16:1 H, anteiso-C15:0, iso-C16:0, anteiso-C17:0, anteiso-C17:1 w9c and iso-C15:0. Analysis of the 16S rRNA sequence showed that strain TRM43335T exhibits high sequence similarity to Streptomyces desertarenae SYSU D8023T 98.69%. A multilocus sequence analysis of five house-keeping genes (atpD, gyrB, rpoB, recA and trpB) also illustrated that strain TRM43335T should be assigned to the genus Streptomyces. The DNA G + C content of the strain was determined to be 72.8 mol%. The average nucleotide identity relatedness between strain TRM43335T and the phylogenetically related strain S. desertarenae SYSU D8023T was found to be 89.23%, and the in silico DNA-DNA hybridization value to be 36.70%. Therefore, it is concluded that strain TRM43335T represents a novel species of the genus Streptomyces, for which the name Streptomyces taklimakanensis sp. nov is proposed. The type strain is TRM43335T (CCTCC AA 2018052 T = KCTC 49254 T).

Shewanella oneidensis MR-1 is a potent hydrogen producer in the deficiency of exogenous electron acceptors. The electron transfer pathway for hydrogen production remains unclear, although enzymes for hydrogen production have been identified in S. oneidensis MR-1. In this study, we investigated the electron transfer pathway from formate to hydrogen, given that formate is commonly a key chemical for bacterial hydrogen production. We revealed that two formate dehydrogenases FdhA1B1C1 and FdhA2B2C2, rather than FdnGHI, played a dominant role in formate-driven hydrogen production. Menaquinone was indispensable for the electron transfer from formate to hydrogen, which excluded the presence of formate hydrogen-lyase in S. oneidensis MR-1. A previously proposed formate dehydrogenase subunit HydC was identified as a menaquinone-binding subunit of [FeFe] hydrogenase HydAB, and the hydABC operon is conserved in bacteria living in diverse environments. A formate exporter FocA and transcriptional regulator FhlA were identified for their effect on formate metabolism and hydrogen production. FhlA positively affected the metabolism of formate and hydrogen by regulating the expression of fdhA2B2C2, fdnGHI, focA, and dld-II. Overall, the electron transfer pathway deciphered in this work will facilitate the improvement of biohydrogen production by S. oneidensis MR-1.Key Points• The electron transfer pathway from formate to hydrogen in MR-1 is deciphered.• Menaquinone is indispensable for hydrogen production.• A cytochrome b subunit transfers electrons from menaquinone to [FeFe] hydrogenase.