Phosphorous content and rhythmic growth

Phosphorous content and rhythmic growt

Energy limitation of cyanophage development : implications for marine carbon cycling

RJP was in receipt of a Natural Environment Research Council (NERC) PhD studentship and a Warwick University IAS Fellowship. This work was also supported in part by NERC grant NE/N003241/1 and Leverhulme Trust grant RPG-2014-354 to A.D.M., D.J.E., and D.J.S.Marine cyanobacteria are responsible for ~25% of the fixed carbon that enters the ocean biosphere. It is thought that abundant co-occurring viruses play an important role in regulating population dynamics of cyanobacteria and thus the cycling of carbon in the oceans. Despite this, little is known about how viral infections ‘play-out’ in the environment, particularly whether infections are resource or energy limited. Photoautotrophic organisms represent an ideal model to test this since available energy is modulated by the incoming light intensity through photophosphorylation. Therefore, we exploited phototrophy of the environmentally relevant marine cyanobacterium Synechococcus and monitored growth of a cyanobacterial virus (cyanophage). We found that light intensity has a marked effect on cyanophage infection dynamics, but that this is not manifest by a change in DNA synthesis. Instead, cyanophage development appears energy limited for the synthesis of proteins required during late infection. We posit that acquisition of auxiliary metabolic genes (AMGs) involved in light-dependent photosynthetic reactions acts to overcome this limitation. We show that cyanophages actively modulate expression of these AMGs in response to light intensity and provide evidence that such regulation may be facilitated by a novel mechanism involving light-dependent splicing of a group I intron in a photosynthetic AMG. Altogether, our data offers a mechanistic link between diurnal changes in irradiance and observed community level responses in metabolism, i.e., through an irradiance-dependent, viral-induced release of dissolved organic matter (DOM).Publisher PDFPeer reviewe

<i>Exormotheca bulbigena</i> sp. nov. (Hepaticae, Marchantiales) and its relation to <i>E. holstii</i> in southern Africa

A new species Exormotheca bulbigena is described from southern Africa and its relation to E. holstii Steph. is discussed. Morphologically these species arc very similar and can be distinguished only when fertile. The chromosome numbers, however, n = 32 for E. bulbigena and n = 18 for E. holstii, distinguish sterile living plants

Studies in the genus <i>Riccia</i> (Marchantiales) from southern Africa. 10. Two new white-scaled species of the group ‘Squamatae’: <i>R. argenteolimbata</i> and <i>R. albomata</i>

Two new white-scaled species,  R. argenteolimbata and  R. albomata  have been isolated by one of us (Volk). R. argenteolimbata has a compact thallus with stiff, regular scales and apolar spores, whereas R. albomata has a somewhat more spongy structure of the thallus, large, frilly, hyaline scales and polar spores

Die Literaturrundschau

Die Literaturrundschau dieser Ausgabe von Communicatio Socialis.Materialien zur Entstehungsgeschichte von „Publik

Die Literaturrundschau

Die Literaturrundschau dieser Ausgabe von Communicatio Socialis.Materialien zur Entstehungsgeschichte von „Publik

The development of temperature fields and powder flow during laser direct metal deposition wall growth

The additive manufacturing technique of laser direct metal deposition (DMD) has had an impact in rapid prototyping, tooling and small-volume manufacturing applications. Components are built from metallic materials that are deposited by the continuous injection of powder into a moving melt pool, created by a defocused laser beam. The size of the melt pool, the temperature distributions around it and the powder flux are critical in determining process characteristics such as deposition rate. In this paper, the effects that changes in the distance between the laser deposition head and the melt pool have on these factors as a part is built using a coaxial powder feeding system are considered Via a two-part analytical model. A heat flow model considers three-dimensional temperature distributions due to a moving Gaussian heat source in a finite volume and a simple mass-flow model considers changes in powder concentration with distance from the deposition head. The model demonstrates the effect of adjusting the melt pool standoff in different ways on melt pool and powder flow characteristics as a DMD structure is built, and hence allows the effect on build rate to be predicted. Its validity is verified by comparison with a series of 316L stainless steel walls, built using different standoff adjustment methods. The model is found to be able to explain the dimensional characteristics found