222 research outputs found

    Salt Adaptation of the Cyanobacterium Synechococcus

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    Space-Efficient Uniform Deployment of Mobile Agents in Asynchronous Unidirectional Rings

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    In this paper, we consider the uniform deployment problem of mobile agents in asynchronous unidirectional ring networks. This problem requires agents to spread uniformly in the network. In this paper, we focus on the memory space per agent required to solve the problem. We consider two problem settings. The first setting assumes that agents have no multiplicity detection, that is, agents cannot detect whether another agent is staying at the same node or not. In this case, we show that each agent requires Ω(log n) memory space to solve the problem, where n is the number of nodes. In addition, we propose an algorithm to solve the problem with O(k+log n) memory space per agent, where k is the number of agents. The second setting assumes that each agent is equipped with the weak multiplicity detection, that is, agents can detect another agent staying at the same node, but cannot learn the exact number. Then, we show that the memory space per agent can be reduced to O(log k+log log n) . To the best of our knowledge, this is the first research considering the effect of the multiplicity detection on memory space required to solve problems.25th International Colloquium (SIROCCO 2018), June 18-21, 2018, Ma\u27ale HaHamisha, Israe

    Evolution of alternative biosynthetic pathways for vitamin C following plastid acquisition in photosynthetic eukaryotes.

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    Ascorbic acid (vitamin C) is an enzyme co-factor in eukaryotes that also plays a critical role in protecting photosynthetic eukaryotes against damaging reactive oxygen species derived from the chloroplast. Many animal lineages, including primates, have become ascorbate auxotrophs due to the loss of the terminal enzyme in their biosynthetic pathway, L-gulonolactone oxidase (GULO). The alternative pathways found in land plants and Euglena use a different terminal enzyme, L-galactonolactone dehydrogenase (GLDH). The evolutionary processes leading to these differing pathways and their contribution to the cellular roles of ascorbate remain unclear. Here we present molecular and biochemical evidence demonstrating that GULO was functionally replaced with GLDH in photosynthetic eukaryote lineages following plastid acquisition. GULO has therefore been lost repeatedly throughout eukaryote evolution. The formation of the alternative biosynthetic pathways in photosynthetic eukaryotes uncoupled ascorbate synthesis from hydrogen peroxide production and likely contributed to the rise of ascorbate as a major photoprotective antioxidant
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