Hydrogen metabolism in Shewanella oneidensis MR-1

Shewanella oneidensis MR-1 is a facultative sediment microorganism which uses diverse compounds, such as oxygen and fumarate, as well as insoluble Fe(III) and Mn(IV) as electron acceptors. The electron donor spectrum is more limited and includes metabolic end products of primary fermenting bacteria, such as lactate, formate, and hydrogen. While the utilization of hydrogen as an electron donor has been described previously, we report here the formation of hydrogen from pyruvate under anaerobic, stationary-phase conditions in the absence of an external electron acceptor. Genes for the two S. oneidensis MR-1 hydrogenases, hydA, encoding a periplasmic [Fe-Fe] hydrogenase, and hyaB, encoding a periplasmic [Ni-Fe] hydrogenase, were found to be expressed only under anaerobic conditions during early exponential growth and into stationary-phase growth. Analyses of DeltahydA, DeltahyaB, and DeltahydA DeltahyaB in-frame-deletion mutants indicated that HydA functions primarily as a hydrogen-forming hydrogenase while HyaB has a bifunctional role and represents the dominant hydrogenase activity under the experimental conditions tested. Based on results from physiological and genetic experiments, we propose that hydrogen is formed from pyruvate by multiple parallel pathways, one pathway involving formate as an intermediate, pyruvate-formate lyase, and formate-hydrogen lyase, comprised of HydA hydrogenase and formate dehydrogenase, and a formate-independent pathway involving pyruvate dehydrogenase. A reverse electron transport chain is potentially involved in a formate-hydrogen lyase-independent pathway. While pyruvate does not support a fermentative mode of growth in this microorganism, pyruvate, in the absence of an electron acceptor, increased cell viability in anaerobic, stationary-phase cultures, suggesting a role in the survival of S. oneidensis MR-1 under stationary-phase conditions.     

Importance of rare taxa for bacterial diversity in the rhizosphere of Bt- and conventional maize varieties

Ribosomal 16S rRNA gene pyrosequencing was used to explore whether the genetically modified (GM) Bt-maize hybrid MON 89034 × MON 88017, expressing three insecticidal recombinant Cry proteins of Bacillus thuringiensis, would alter the rhizosphere bacterial community. Fine roots of field cultivated Bt-maize and three conventional maize varieties were analyzed together with coarse roots of the Bt-maize. A total of 547 000 sequences were obtained. Library coverage was 100% at the phylum and 99.8% at the genus rank. Although cluster analyses based on relative abundances indicated no differences at higher taxonomic ranks, genera abundances pointed to variety specific differences. Genera-based clustering depended solely on the 49 most dominant genera while the remaining 461 rare genera followed a different selection. A total of 91 genera responded significantly to the different root environments. As a benefit of pyrosequencing, 79 responsive genera were identified that might have been overlooked with conventional cloning sequencing approaches owing to their rareness. There was no indication of bacterial alterations in the rhizosphere of the Bt-maize beyond differences found between conventional varieties. B. thuringiensis-like phylotypes were present at low abundance (0.1% of Bacteria) suggesting possible occurrence of natural Cry proteins in the rhizospheres. Although some genera indicated potential phytopathogenic bacteria in the rhizosphere, their abundances were not significantly different between conventional varieties and Bt-maize. With an unprecedented sensitivity this study indicates that the rhizosphere bacterial community of a GM maize did not respond abnormally to the presence of three insecticidal proteins in the root tissue.     

Effects of Modified Handling on the Physiological Stress of Trawled-and-Discarded Yellowfin Bream (Acanthopagrus australis)

Modified handling is often claimed to reduce (sub-)lethal impacts among organisms caught-and-released in fisheries. Improving welfare of discarded fish warrants investigation, when their survival is of both economic and ecological importance. In this study, juvenile yellowfin bream (Acanthopagrus australis) were trawled in an Australian penaeid fishery and then discarded after on-board sorting in either dry or water-filled (modified) trays and with delays in starting sorting of either 2 or 15 mins. Blood plasma cortisol, glucose and potassium were sampled immediately from some yellowfin bream, while others were placed into cages (with controls) and sampled after five days. Irrespective of their on-board handling, all trawled fish incurred a relatively high acute stress response (i.e. an increase in Mean ± SE cortisol from a baseline of <4 to 122.0 ± 14.9 ng/mL) that was mostly attributed to the trawling process, and exacerbated by variation in key parameters (low salinity, changes in water temperature and the presence of jellyfish Catostylus mosaicus in catches). When C. mosaicus was present, the potassium concentrations of fish sampled immediately after sorting were significantly elevated, possibly due to nematocyst contact and subsequent inhibition of ion pumps or cytolysis. Stress also increased during handling in response to warmer air temperatures and longer exposure. While most fish had substantially recovered by 120 hours after discarding, deploying selective trawls (to reduce jellyfish) for short periods and then quickly sorting catches in water would benefit discard welfare.     

CSPP Is a Ciliary Protein Interacting with Nephrocystin 8 and Required for Cilia Formation

We described previously the cell cycle- and microtubule-related functions of two splice isoforms of the centrosome spindle pole-associated protein (CSPP and CSPP-L). Here, we show that endogenous CSPP isoforms not only localize to centrosomes and the midbody in cycling cells but also extend to the cilia axoneme in postmitotic resting cells. They are required for ciliogenesis in hTERT-RPE1 cells in vitro and are expressed in ciliated renal, retinal, and respiratory cells in vivo. We report that CSPP isoforms require their common C-terminal domain to interact with Nephrocystin 8 (NPHP8/RPGRIP1L) and to form a ternary complex with NPHP8 and NPHP4. We find CSPP-L to be required for the efficient localization of NPHP8 but not NPHP4 to the basal body. The ciliogenesis defect in hTERT-RPE1 cells is, however, not mediated through loss of NPHP8. Similar to the effects of ectopical expression of CSPP-L, cilia length increased in NPHP8-depleted cells. Our results thus suggest that CSPP proteins may be involved in further cytoskeletal organization of the basal body and its primary cilium. To conclude, we have identified a novel, nonmitotic function of CSPP proteins placing them into a ciliary protein network crucial for normal renal and retinal tissue architecture and physiology.     

The Function of the Na+-Driven Flagellum of Vibrio cholerae Is Determined by Osmolality and pH

Vibrio cholerae is motile by its polar flagellum, which is driven by a Na⁺-conducting motor. The stators of the motor, composed of four PomA and two PomB subunits, provide access for Na⁺ to the torque-generating unit of the motor. To characterize the Na⁺ pathway formed by the PomAB complex, we studied the influence of chloride salts (chaotropic, Na⁺, and K⁺) and pH on the motility of V. cholerae. Motility decreased at elevated pH but increased if a chaotropic chloride salt was added, which rules out a direct Na⁺ and H⁺ competition in the process of binding to the conserved PomB D23 residue. Cells expressing the PomB S26A/T or D42N variants lost motility at low Na⁺ concentrations but regained motility in the presence of 170 mM chloride. Both PomA and PomB were modified by N,N′-dicyclohexylcarbodiimide (DCCD), indicating the presence of protonated carboxyl groups in the hydrophobic regions of the two proteins. Na⁺ did not protect PomA and PomB from this modification. Our study shows that both osmolality and pH have an influence on the function of the flagellum from V. cholerae. We propose that D23, S26, and D42 of PomB are part of an ion-conducting pathway formed by the PomAB stator complex.     

Patterns of Frailty in Older Adults: Comparing Results from Higher and Lower Income Countries Using the Survey of Health,Ageing and Retirement in Europe (SHARE) and the Study on Global AGEing and Adult Health (SAGE)

We use the method of deficit accumulation to describe prevalent and incident levels of frailty in community-dwelling older persons and compare prevalence rates in higher income countries in Europe, to prevalence rates in six lower income countries. Two multi-country data collection efforts, SHARE and SAGE, provide nationally representative samples of adults aged 50 years and older. Forty items were used to construct the frailty index in each data set. Our study shows that the level of frailty was distributed along the socioeconomic gradient in both higher and lower income countries such that those individuals with less education and income were more likely to be frail. Frailty increased with age and women were more likely to be frail in most countries. Across samples we find that the level of frailty was higher in the higher income countries than in the lower income countries.     

Comparison of the somatic TADs and lampbrush chromomere-loop complexes in transcriptionally active prophase I oocytes

Chromosoma - In diplotene oocyte nuclei of all vertebrate species, except mammals, chromosomes lack interchromosomal contacts and chromatin is linearly compartmentalized into distinct...     

Observation of correlated X-ray scattering at atomic resolution

Tools to study disordered systems with local structural order, such as proteins in solution, remain limited. Such understanding is essential for e.g. rational drug design. Correlated X-ray scattering (CXS) has recently attracted new interest as a way to leverage next-generation light sources to study such disordered matter. The CXS experiment measures angular correlations of the intensity caused by the scattering of X-rays from an ensemble of identical particles, with disordered orientation and position. Averaging over 15 496 snapshot images obtained by exposing a sample of silver nanoparticles in solution to a micro-focused synchrotron radiation beam, we report on experimental efforts to obtain CXS signal from an ensemble in three dimensions. A correlation function was measured at wide angles corresponding to atomic resolution that matches theoretical predictions. These preliminary results suggest that other CXS experiments on disordered ensembles—such as proteins in solution—may be feasible in the future.