High Rates of Photobiological H2 Production by a Cyanobacteriium Under Aerobic Conditions.

Among the emerging renewable and green energy sources, biohydrogen stands out as an appealing choice. Hydrogen can be produced by certain groups of microorganisms that possess functional nitrogenase and/or bidirectional hydrogenases. In particular, the potential of photobiological hydrogen production by oxygenic photosynthetic microbes has attracted significant interest. However, nitrogenase and hydrogenase are generally oxygen sensitive, and require protective mechanisms to function in an aerobic extracellular environment. Here, we describeCyanothece sp. ATCC 51142, a unicellular, diazotrophic cyanobacterium with the capacity to generate high levels of hydrogen under aerobic conditions. Wild-type Cyanothece 51142 can produce hydrogen at rates as high as 465 μmol per mg of chlorophyll per hour in the presence of glycerol. Hydrogen production in this strain is mediated by an efficient nitrogenase system, which can be manipulated to convert solar energy into hydrogen at rates that are several fold higher, compared with any previously described wild-type hydrogen-producing photosynthetic microbe

Novel Metabolic Attributes of Cyanothece, a Group of Unicellular Nitrogen Fixing Cyanobacteria.

The genus Cyanothece comprises unicellular cyanobacteria that are morphologically diverse and ecologically versatile. Studies over the last decade have established members of this genus to be important components of the marine ecosystem, contributing significantly to the nitrogen and carbon cycle. System-level studies of Cyanothece sp. ATCC 51142, a prototypic member of this group, revealed many interesting metabolic attributes. To identify the metabolic traits that define this class of cyanobacteria, five additional Cyanothece strains were sequenced to completion. The presence of a large, contiguous nitrogenase gene cluster and the ability to carry out aerobic nitrogen fixation distinguishCyanothece as a genus of unicellular, aerobic nitrogen-fixing cyanobacteria.Cyanothece cells can create an anoxic intracellular environment at night, allowing oxygen-sensitive processes to take place in these oxygenic organisms. Large carbohydrate reserves accumulate in the cells during the day, ensuring sufficient energy for the processes that require the anoxic phase of the cells. Our study indicates that this genus maintains a plastic genome, incorporating new metabolic capabilities while simultaneously retaining archaic metabolic traits, a unique combination which provides the flexibility to adapt to various ecological and environmental conditions. Rearrangement of the nitrogenase cluster inCyanothece sp. strain 7425 and the concomitant loss of its aerobic nitrogen-fixing ability suggest that a similar mechanism might have been at play in cyanobacterial strains that eventually lost their nitrogen-fixing ability. IMPORTANCE The unicellular cyanobacterial genus Cyanothece has significant roles in the nitrogen cycle in aquatic and terrestrial environments. Cyanothece sp. ATCC 51142 was extensively studied over the last decade and has emerged as an important model photosynthetic microbe for bioenergy production. To expand our understanding of the distinctive metabolic capabilities of this cyanobacterial group, we analyzed the genome sequences of five additional Cyanothece strains from different geographical habitats, exhibiting diverse morphological and physiological attributes. These strains exhibit high rates of N2 fixation and H2production under aerobic conditions. They can generate copious amounts of carbohydrates that are stored in large starch-like granules and facilitate energy-intensive processes during the dark, anoxic phase of the cells. The genomes of some Cyanothece strains are quite unique in that there are linear elements in addition to a large circular chromosome. Our study provides novel insights into the metabolism of this class of unicellular nitrogen-fixing cyanobacteria

Cellular efflux of auxin catalyzed by the Arabidopsis MDR/PGP transporter AtPGP1

Directional transport of the phytohormone auxin is required for the establishment and maintenance of plant polarity, but the underlying molecular mechanisms have not been fully elucidated. Plant homologs of human multiple drug resistance/P-glycoproteins (MDR/PGPs) have been implicated in auxin transport, as defects in MDR1 (AtPGP19) and AtPGP1 result in reductions of growth and auxin transport in Arabidopsis (atpgp1, atpgp19), maize (brachytic2) and sorghum (dwarf3). Here we examine the localization, activity, substrate specificity and inhibitor sensitivity of AtPGP1. AtPGP1 exhibits non-polar plasma membrane localization at the shoot and root apices, as well as polar localization above the root apex. Protoplasts from Arabidopsis pgp1 leaf mesophyll cells exhibit reduced efflux of natural and synthetic auxins with reduced sensitivity to auxin efflux inhibitors. Expression of AtPGP1 in yeast and in the standard mammalian expression system used to analyze human MDR-type proteins results in enhanced efflux of indole-3-acetic acid (IAA) and the synthetic auxin 1-naphthalene acetic acid (1-NAA), but not the inactive auxin 2-NAA. AtPGP1-mediated efflux is sensitive to auxin efflux and ABC transporter inhibitors. As is seen in planta, AtPGP1 also appears to mediate some efflux of IAA oxidative breakdown products associated with apical sites of high auxin accumulation. However, unlike what is seen in planta, some additional transport of the benzoic acid is observed in yeast and mammalian cells expressing AtPGP1, suggesting that other factors present in plant tissues confer enhanced auxin specificity to PGP-mediated transport. © 2005 Blackwell Publishing Ltd

Role of Arabidopsis p-glycoproteins and the membrane associated aminopeptidase APM1 in regulating cellular auxin transport

The purpose of the present study was to investigate the functions of the Arabidopsis p-glycoproteins and the membrane associated aminopeptidase APM1 in regulation of cellular auxin transport. Polar transport of the plant hormone auxin is essential for the establishment and maintenance of plant polarity. Regulation of polar auxin transport involves intricate interactions between multiple components of membrane transport and cellular trafficking complexes. The auxin efflux inhibitor 1-naphthylphthalamic acid (NPA) acts on regulatory sites in these complexes and affects auxin transport and vesicular trafficking. In Arabidopsis, p-glycoprotein (PGP) ABC transporters have been shown to exhibit higher affinity NPA binding while an M1 membrane aminopeptidase APM1 was shown to exhibit low affinity binding. PGPs and members of the PIN (from pinformed inflorescence) subfamily of ion-coupled major facilitator proteins have been shown to transport auxin independently. Flavonoids, the endogenous regulators of auxin transport, inhibit transport primarily at the root and shoot tip. PIN localization is altered in flavonoid deficient mutants and appears to be modulated by developmental cues. PGPs are likely to be the principal targets of flavonoid regulation at the plasma membrane. Although PINS and PGPs can transport auxin independently they interact in planta to confer specificity, inhibitor sensitivity and transport directionality. PIN mislocalization in pgp19 mutants suggests that PGPs are involved in stabilizing PINs on the plasma membrane. PGP19 and PIN1 membrane localization overlaps in specific tissues and co-immunoprecipitation and yeast two hybrid studies indicate direct interaction between the two. APM1 is a component of the vesicular trafficking pathway and it appears to mediate regulation of PIN protein trafficking. It plays an essential role in Arabidopsis root development. The root defects observed in apm1 mutants can be traced back to the late globular stage of embryogenesis. Aminopeptidase inhibitors that disrupt cellular trafficking phenocopy apm1 mutants. High concentrations of NPA also phenocopy these defects. APM1 is auxin responsive and responds to changes in endogenous auxin levels in a tissue specific manner. Like mammalian dual function M1 aminopeptidases, APM1 appears to function in both processing and trafficking of membrane proteins

Application of design space methodology for optimum sizing of wind-battery systems

A methodology for optimum sizing of different components (i.e., rotor diameter, electrical generator rating, and battery capacity) of a standalone wind-battery system is proposed in this paper. On the basis of time series simulation of the system performance along with different design constraints, the entire set of feasible design options, also known as the design space, has been identified on a rotor diameter vs. rated power diagram. The design space of a standalone wind-battery system identifies the entire envelope within which a feasible system may be designed. The optimum configuration of the standalone system is identified on the basis of minimum cost of energy (US$/kWh). It is observed that the cost of energy is sensitive to the magnitude of average demand and the wind regime. Sensitivity of the capital cost on the minimum cost of energy is also studied.System sizing Wind-battery systems Isolated power system design Design space

Relationship of vertical jump test with anthropomethric parameters and body composition in university students – a gender variation

Vertical jump test (VJT) is one of the important determinants of physical fitness. VJT score in school going children of West Bengal, India has been reported. However, pertinent data in young sedentary Indian males and females are unavailable. Moreover, the relationship of VJT with anthropometric parameters and different components of body composition has not yet been explored in Indian context. Debatable findings have been reported regarding the impact of body composition on VJT score. The present study was aimed to evaluate the VJT score in young sedentary Indian university students and its relationship with anthropometric parameters and different components of body composition with special reference to gender variation. Healthy sedentary university students (males n=40 and females n=40) with similar socio-economic background and age group of 21–25 years were randomly sampled for the study from the post-graduate section of the University of Calcutta, Kolkata, India. VJT was evaluated by Sargent Jump Test, and body composition was determined by skinfold measurements. Body height, body mass, %Fat, Total Fat (TF), LBM and VJT score depicted significant (p<0.001) difference between male and female groups. The VJT scores obtained in the male and female groups were in the range of below average and poor, respectively. Physical parameters did not influence the VJT score in both genders. In the present study the VJT score exhibited significant (p<0.001) negative correlation with %fat, individual skinfold, sum of skinfolds, and TF. Hence, body fat content posed as a hindrance to achieve higher jumping height, especially in females, where the lean mass helped to achieve greater VJT score in males

Relationship of Vertical Jump Test with Anthropometric Parameters and Body Composition in University Students- A Gender Variation

Vertical jump test (VJT) is one of the important determinants of physical fitness. VJT score in school going children of West Bengal, India has been reported. However, pertinent data in young sedentary Indian males and females are unavailable. Moreover, the relationship of VJT with anthropometric parameters and different components of body composition has not yet been explored in Indian context. Debatable findings have been reported regarding the impact of body composition on VJT score. The present study was aimed to evaluate the VJT score in young sedentary Indian university students and its relationship with anthropometric parameters and different components of body composition with special reference to gender variation. Healthy sedentary university students (males n=40 and females n=40) with similar socio-economic background and age group of 21&ndash;25 years were randomly sampled for the study from the post-graduate section of the University of Calcutta, Kolkata, India. VJT was evaluated by Sargent Jump Test, and body composition was determined by skinfold measurements. Body height, body mass, %Fat, Total Fat (TF), LBM and VJT score depicted significant (p&amp;lt;0.001) difference between male and female groups. The VJT scores obtained in the male and female groups were in the range of below average and poor, respectively. Physical parameters did not influence the VJT score in both genders. In the present study the VJT score exhibited significant (p&amp;lt;0.001) negative correlation with %fat, individual skinfold, sum of skinfolds, and TF. Hence, body fat content posed as a hindrance to achieve higher jumping height, especially in females, where the lean mass helped to achieve greater VJT score in males