Sunxiuqinia dokdonensis sp. nov., isolated from deep sub-seafloor sediment

A novel facultatively anaerobic strain DH1^T was isolated from deep sub-seafloor sediment at a depth of 900 m below the seafloor off Seo-do (the west part of Dokdo Island) in the East Sea of the Republic of Korea. The new strain was characterized using polyphasic approaches. The isolate was Gram-stain-negative, motile by gliding, non-spore-forming rods, oxidase-negative, and catalase-positive; and formed colonies of orange-red color. The NaCl range for growth was 0.5–7.0% (w/v) and no growth was observed in the absence of NaCl. The isolate grew optimally at 30°C, with 2% (w/v) NaCl and at pH 7. The cell-wall hydrolysates contained ribose as a major sugar. The DNA G+C content was 40.8 mol%. The closest related strains are Sunxiuqinia faeciviva JAM-BA0302^T and Sunxiuqinia elliptica DQHS-4^T (97.9 and 96.3% sequence similarity, respectively). The level of DNA-DNA relatedness between strain DH1^T and S. faeciviva JAM-BA0302^T was around 41% (but only 6% between DH1T and S. elliptica DQHS-4^T). The major cellular fatty acids of the isolate were contained iso-C_15:0 (25.9%), anteiso-C_15:0 (16.7%), and summed feature 9 (comprising C_16:0 3-OH and/or unknown fatty acid of dimethylacetal ECL 17.157; 13.2%). The predominant menaquinone was MK-7. On the basis of polyphasic evidence from this study, the isolate was considered to represent a novel species of the genus Sunxiuqinia, for which the name Sunxiuqinia dokdonensis sp. nov. is proposed; the type strain is DH1^T (=KCTC 32503^T =CGMCC 1.12676^T =JCM 19380^T).     

Minding the gaps: metabolomics mends functional genomics

Two recent studies in PNAS and Nat Chem Biol highlight the power of modern mass-spectrometry techniques for enzyme discovery applied to microbiology. In so doing, they have uncovered new potential targets for the treatment of tuberculosis.Proc Natl Acad Sci USA (2013) 110 28, 11320–11325 doi: 10.1073/pnas.1221597110Nat Chem Biol (2013). doi:10.1038/nchembio.1355. Advance online publication 29 September 2013Many have come to regard metabolism as a well-understood housekeeping activity of all cells, functionally compartmentalized away from other biological processes. However, growing reports of unexpected links between a diverse range of disease states and specific metabolic enzymes or pathways have begun to challenge this view. In doing so, such discoveries have exposed more glaring, and neglected, deficiencies in our understanding of cellular metabolism, triggering a broad resurgence of interest in metabolism.“Metabolomics […] offers a global window into the biochemical state of a cell or organism…”Metabolomics is the newest of the systems-level disciplines and seeks to reveal the physiological state of a given cell or organism through the global and unbiased study of its small-molecule metabolites [1]. Metabolites are the final products of enzymes and enzyme networks, the substrates and products of which often cannot be deduced from genetic information and the levels of which reflect the integrated product of the genome, proteome and environment [2]. Metabolomics thus offers a global window into the biochemical state of a cell or organism, made experimentally possible by the unprecedented discriminatory power and sensitivity of modern mass-spectrometry-based technologies (Fig 1). Two recent reports from the Carvalho and Neyrolles groups, published recently in Proceedings of the National Academy of Science USA and Nature Chemical Biology [3,4], exemplify the rapidly growing impact of metabolomics-based approaches on tuberculosis research.Open in a separate windowFigure 1Modern mass spectrometry illuminates bacterial metabolism. A comparison of activity-based metabolomic profiling with classic metabolic tracing. See the text for details.Within the field of infectious diseases, the deficiencies in our understanding of microbial metabolism have emerged most prominently in the area of tuberculosis research. Despite the development of the first chemotherapies more than 50 years ago, tuberculosis remains the leading bacterial cause of death worldwide, due in part to a failure to keep pace with the emergence of drug resistance [5]. The causes of this shortfall are multifactorial. However, a key contributing factor is our incomplete understanding of the metabolic properties of Mycobacterium tuberculosis (Mtb), its aetiological agent. Unlike most bacterial pathogens, Mtb infects humans as its only known host and reservoir, within whom it resides largely isolated from other microbes. Mtb has thus evolved its metabolism to serve interdependent physiological and pathogenic roles. Yet, more than a century after Koch''s initial discovery of Mtb and 15 years after the first publication of its genome sequence, knowledge of Mtb''s metabolic network remains surprisingly incomplete [6,7,8].“…tuberculosis remains the leading bacterial cause of death worldwide…”As for almost all sequenced microbial genomes, homology-based in silico approaches have failed to suggest a function for nearly 40% of Mtb genes that, presumably, include a significant number of orphan enzyme activities for which no gene has been ascribed [8]. Such approaches have further neglected the impact of evolutionary selection and its ability to dissociate sequence conservation from biochemical activity and physiological function, in order to help optimize the fitness of a given organism within its specific niche. For Mtb, such genes and enzymes represent an especially promising and biologically selective, but untapped, source of potential drug targets.In the study from the Carvalho group, successful application of a recently developed metabolomics assay—known as activity-based metabolomic profiling (ABMP)—allowed the authors to reassign a putatively annotated nucleotide phosphatase (Rv1692) as a D,L-glycerol 3-phosphate phosphatase [3,9]. ABMP was specifically developed to identify enzymatic activities for genes of unknown function by leveraging the analytical discriminatory power of liquid-chromatography-coupled high-resolution mass spectrometry (LC-MS) to analyse the impact of a recombinant enzyme and potential co-factors on a highly concentrated, small-molecule extract derived from the homologous organism (Fig 1). By monitoring for the matched time and enzyme-dependent depletion and accumulation of putative substrates and products, this assay enables the discovery of catalytic activities—rather than simple binding—by using the cellular metabolome as arguably the most physiological chemical library of potential substrates that can be tested, in a label and synthesis-free manner. Moreover, candidate activities assigned by this method can be confirmed by using independent biochemical approaches—such as reconstitution with purified components—and genetic techniques—such as wild-type and genetic knockout, knockdown or overexpression strains. In reassigning Rv1692 as a glycerol phosphate phosphatase, rather than a nucleotide phosphatase, Carvalho and colleagues demonstrate the potential of ABMP to overcome the biochemical challenge of assigning substrate specificity to a member of a large enzyme superfamily—in this case, the haloacid dehydrogenase superfamily. But, perhaps more significantly, they also direct new biological attention to the largely neglected area of Mtb membrane homeostasis, in which Rv1692 might play an important role in glycerophospholipid recycling and catabolism.“…knowledge of Mtb''s metabolic network remains surprisingly incomplete”Neyrolles and colleagues make use of the same metabolomics platform to perform metabolite-tracing studies by using stable-isotope-labelled precursors, which led them to reassign a putatively annotated asparagine transporter (AnsP1) as an aspartate transporter. AnsP1 bears 55% sequence identity and 70% similarity to an orthologue in Salmonella that belongs to the amino acid transporter family 2.A.3.1, whereas aspartate transporters are typically members of the dicarboxylate amino acid:cation symporter family 2.A.23 [4]. This study demonstrates the ability of metabolomic platforms to not only characterize the activity of a given protein within its natural physiological milieu, but also revive classical experimental methods by using modern technologies. The availability of stable (non-radioactive) isotopically labelled precursors has now made it possible to resolve their specific metabolic fates. In this case, such an approach revealed that Mtb can use aspartate as both a carbon and nitrogen source, after its uptake through AnsP1. Looking beyond the specific biochemical assignment of AnsP1 as an aspartate—rather than asparagine—transporter, this study illustrates the potential impact of such discoveries on downstream paths of investigation. In this case, the remarkable application of high-resolution dynamic secondary ion mass spectroscopy to provide the first direct biochemical images of the nutritional environment of the Mtb-infected phagosome.New technologies are often developed in the context of specific needs. However, their impact is usually not realized until extended beyond such contexts, sometimes resulting in major paradigm shifts. The above examples highlight just two emerging possibilities of how metabolomics technologies can be extended beyond the context of global comparisons and provide unique biological insights. To the extent that the analytical power of these platforms can be adapted to other functional approaches, metabolomics promises to pay handsome biochemical and physiological dividends.     

Anti-apoptotic mechanism of silkworm hemolymph in HeLa cell apoptosis

Silkworm hemolymph (SH) was found to exhibit anti-apoptotic activities in mammalian and insect cell systems. An anti-apoptotic mechanism of SH was investigated in a staurosporine-induced HeLa cell using flow cytometry, caspase assay, Immunoblot, and Immunochemistry. The addition of 5% SH to the medium resulted in lower intracellular activities of caspase-3 and caspase-9 after 0.6 μM of staurosporine treatment; however, SH did not directly inhibit the activities of those enzymes. This suggests SH inhibits the event upstream of these caspase activation steps, such as mitochondrial level events. We found from Immunoblot and Immunochemistry that cytochrome c release from the mitochondria was blocked by SH. SH also inhibited Bax translocation to the mitochondria. On the contrary, SH did not block the apoptosis when Bax is not involved in promoting apoptosis. With these results, we propose that SH protects mitochondria from apoptosis signal via blocking Bax translocation, and the subsequent apoptotic events are then inhibited. The inhibition of apoptosis using SH and its components may lead to new approaches for the minimization of cell death during commercial animal cell cultures.     

Prevalence of and Factors Associated with Albuminuria in the Korean Adult Population: The 2011 Korea National Health and Nutrition Examination Survey

Background

Microalbuminuria is associated with increased risk of renal disease and cardiovascular diseases even in non-diabetic subjects. High incidence rates of microalbuminuria have been found in a number of population-based studies. However, the prevalence and risk factors associated with microalbuminuria in the general population in Korea are unclear.

Objectives

The present study was performed to estimate the prevalence of microalbuminuria and investigate the associated risk factors in the general adult population using the Fifth Korea National Health and Nutrition Examination Survey (KNHANES V-2) data from 2011.

Methods

A total of 5,202 participants (mean age, 45.6 years; men, 2,337; women, 2,865) were included in the analysis. Microalbuminuria was evaluated in participants of KNHANES V-2 based on the urine albumin–creatinine ratio. Estimated glomerular filtration rate was calculated using the Modification of Diet in Renal Disease study equation.

Results

The weighted prevalence of microalbuminuria was 5.2% (95% CI, 4.4–6.1) in the general population. The prevalence of albuminuria is increased with age. After adjustment for age and sex, the presence of albuminuria was associated with increased waist circumference, systolic and diastolic blood pressure, aspartate aminotransferase, triglyceride, fasting plasma glucose, and the presence of hypertension and diabetes. In logistic regression analyses, older age, female sex, diabetes, hypertension, and serum aspartate aminotransferase were independently associated with the presence of albuminuria.

Conclusion

The prevalence of microalbuminuria was found to be 5.2%, and conventional risk factors for cardiovascular diseases are closely related to the presence of microalbuminuria in Korea. Microalbuminuria may be a useful marker to identify individuals with increased risk of cardiovascular disease.     

Glucose Phosphorylation Is Required for Mycobacterium tuberculosis Persistence in Mice

Mycobacterium tuberculosis (Mtb) is thought to preferentially rely on fatty acid metabolism to both establish and maintain chronic infections. Its metabolic network, however, allows efficient co-catabolism of multiple carbon substrates. To gain insight into the importance of carbohydrate substrates for Mtb pathogenesis we evaluated the role of glucose phosphorylation, the first reaction in glycolysis. We discovered that Mtb expresses two functional glucokinases. Mtb required the polyphosphate glucokinase PPGK for normal growth on glucose, while its second glucokinase GLKA was dispensable. ¹³C-based metabolomic profiling revealed that both enzymes are capable of incorporating glucose into Mtb''s central carbon metabolism, with PPGK serving as dominant glucokinase in wild type (wt) Mtb. When both glucokinase genes, ppgK and glkA, were deleted from its genome, Mtb was unable to use external glucose as substrate for growth or metabolism. Characterization of the glucokinase mutants in mouse infections demonstrated that glucose phosphorylation is dispensable for establishing infection in mice. Surprisingly, however, the glucokinase double mutant failed to persist normally in lungs, which suggests that Mtb has access to glucose in vivo and relies on glucose phosphorylation to survive during chronic mouse infections.     

Soluble Guanylate Cyclase α1–Deficient Mice: A Novel Murine Model for Primary Open Angle Glaucoma

Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide. The molecular signaling involved in the pathogenesis of POAG remains unknown. Here, we report that mice lacking the α₁ subunit of the nitric oxide receptor soluble guanylate cyclase represent a novel and translatable animal model of POAG, characterized by thinning of the retinal nerve fiber layer and loss of optic nerve axons in the context of an open iridocorneal angle. The optic neuropathy associated with soluble guanylate cyclase α₁–deficiency was accompanied by modestly increased intraocular pressure and retinal vascular dysfunction. Moreover, data from a candidate gene association study suggests that a variant in the locus containing the genes encoding for the α₁ and β₁ subunits of soluble guanylate cyclase is associated with POAG in patients presenting with initial paracentral vision loss, a disease subtype thought to be associated with vascular dysregulation. These findings provide new insights into the pathogenesis and genetics of POAG and suggest new therapeutic strategies for POAG.     

Microbial diversity and prevalence of foodborne pathogens in cheap and junk foods consumed by primary schoolchildren

Aerobic plate counts (APC), coliforms, Bacillus cereus, Escherichia coli and eight foodborne pathogens were tested in 1008 cheap and junk foods, including candies, dried cakes, chewing gum, chocolate, dried and seasoned seafood, ice cream, and sugary foods. APCs were positive for 342 samples (33·9%), and the majority of the counts were 2–3 log CFU g^?1 or ml^?1 (average: 1·10 log CFU g^?1 or ml^?1). Most samples (97·3%) contained no coliforms (average: 0·07 log CFU g^?1 or ml^?1). Bacillus cereus was detected in 68 samples (average: 0·14 log CFU g^?1 or ml^?1). Escherichia coli and Listeria monocytogenes were detected in 6 and 1 samples, respectively, whereas other foodborne pathogens were not isolated. The highest bacterial counts were associated with dried and seasoned seafood products and dried cakes, suggesting that appropriate regulations of these food types should be considered. Cheap and junk foods were produced mainly in developing countries, but there were no significant differences in the bacterial counts among different countries of origin. The presence of foodborne pathogens may pose a risk for children. These results suggest that there is cause for deeper concern about the safety of these foods and that effective countermeasures should be established to improve their microbiological safety.

Significance and Impact of the Study

Food safety is especially important for children, but only limited information is available about the microbiological quality of cheap and junk foods that are consumed frequently by primary schoolchildren (e.g. dried cakes, candies and chocolates). The present study investigated the microbial quality of cheap and junk foods, and our results indicate that these foods are a potential health risk for children, therefore, deeper concern about the safety of these foods and effective countermeasures should be established to improve their microbiological safety. The present study may contribute to the development of an appropriate child food safety management system.