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Algae frequently get a bad press. Pond slime is a problem in garden pools, algal blooms can produce toxins that incapacitate or kill animals and humans and even the term seaweed is pejorative - a weed being a plant growing in what humans consider to be the wrong place. Positive aspects of algae are generally less newsworthy - they are the basis of marine food webs, supporting fisheries and charismatic marine megafauna from albatrosses to whales, as well as consuming carbon dioxide and producing oxygen. Here we consider what algae are, their diversity in terms of evolutionary origin, size, shape and life cycles, and their role in the natural environment and in human affairs., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Microcell parasites have independently evolved in several eukaryotic lineages and are increasingly recognized as important and emerging pathogens of diverse hosts, including species of economic importance subject to international legislation concerning the trading of aquatic animals [1-3]. The microcell Mikrocytos mackini causes Denman Island disease of oysters and represents one of the most genetically divergent eukaryotes known. Mikrocytos has remained an isolated lineage with a limited distribution. We investigated two emerging diseases of juvenile crabs and oysters from the UK using massively parallel sequencing and targeted primer approaches to reveal that their causative agents are highly divergent lineages related to M. mackini (Paramikrocytos canceri n. gen. et n. sp. and M. mimicus sp. nov., respectively). We demonstrate a major new globally distributed parasite radiation (Mikrocytida ord. nov.) with phylogenetic affinities to the commercially important haplosporidian parasites of invertebrates. Mikrocytids have eluded detection because of their small size, intracellular habit, and extreme sequence divergence. P. canceri was frequently detected in a range of shoreline invertebrates, demonstrating that these newly recognized parasites are in fact common, diverse, and widespread and should be considered when assessing the risks of aquaculture activities, invasive species spread, and movements of ballast water and sediments with associated invertebrates., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)

DNA-based methods continue to unveil the diversity and evolutionary origins of life on Earth. 'Next generation' methods have just solved a long-standing puzzle by uncovering previously unseen yet globally distributed diversity within a lineage of amitochondriate parasites affecting commercially exploited aquatic hosts. This discovery will impact both pure and applied research fields., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Rhizaria are a major branch of eukaryote evolution with an extensive microfossil record, but only scarce molecular data are available. The rhizarian species Reticulomyxa filosa, belonging to the Foraminifera, is free-living in freshwater environments. In culture, it thrives only as a plasmodium with thousands of haploid nuclei in one cell. The R. filosa genome is the first foraminiferal genome to be deciphered., Results: The genome is extremely repetitive, and the large amounts of identical sequences hint at frequent amplifications and homologous recombination events. Presumably, these mechanisms are employed to provide more gene copies for higher transcriptional activity and to build up a reservoir of gene diversification in certain gene families, such as the kinesin family. The gene repertoire indicates that it is able to switch to a single-celled, flagellated sexual state never observed in culture. Comparison to another rhizarian, the chlorarachniophyte alga Bigelowiella natans, reveals that proteins involved in signaling were likely drivers in establishing the Rhizaria lineage. Compared to some other protists, horizontal gene transfer is limited, but we found evidence of bacterial-to-eukaryote and eukaryote-to-eukaryote transfer events., Conclusions: The R. filosa genome exhibits a unique architecture with extensive repeat homogenization and gene amplification, which highlights its potential for diverse life-cycle stages. The ability of R. filosa to rapidly transport matter from the pseudopodia to the cell body may be supported by the high diversification of actin and kinesin gene family members., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Mikrocytos mackini is an intracellular protistan parasite of oysters whose position in the phylogenetic tree of eukaryotes has been a mystery for many years [1,2]. M. mackini is difficult to isolate, has not been cultured, and has no defining morphological feature. Furthermore, its only phylogenetic marker that has been successfully sequenced to date (the small subunit ribosomal RNA) is highly divergent and has failed to resolve its evolutionary position [2]. M. mackini is also one of the few eukaryotes that lacks mitochondria [1], making both its phylogenetic position and comparative analysis of mitochondrial function particularly important. Here, we have obtained transcriptomic data for M. mackini from enriched isolates and constructed a 119-gene phylogenomic data set. M. mackini proved to be among the fastest-evolving eukaryote lineages known to date, but, nevertheless, our analysis robustly placed it within Rhizaria. Searching the transcriptome for genetic evidence of a mitochondrion-related organelle (MRO) revealed only four mitochondrion-derived genes: IscS, IscU, mtHsp70, and FdxR. Interestingly, all four genes are involved in iron-sulfur cluster formation, a biochemical pathway common to other highly reduced "mitosomes" in unrelated MRO-containing lineages [7]. This is the first evidence of MRO in Rhizaria, and it suggests the parallel evolution of mitochondria to mitosomes in this supergroup., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Mitochondria play import roles in the overall metabolism of eukaryotes. Traditionally, they have played a secondary role to the nucleus in the origin of eukaryotes. However, their relative positions in this crucial event for eukaryotic evolution might be reversed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Multicellular forms of life have evolved many times, independently giving rise to a diversity of organisms such as animals, plants, and fungi that together comprise the visible biosphere. Yet multicellular life is far more widespread among eukaryotes than just these three lineages. A particularly common form of multicellularity is a social aggregative fruiting lifestyle whereby individual cells associate to form a "fungus-like" sorocarp. This complex developmental process that requires the interaction of thousands of cells working in concert was made famous by the "cellular slime mold"Dictyostelium discoideum, which became an important model organism. Although sorocarpic protistan lineages have been identified in five of the major eukaryote groups, the ubiquitous and globally distributed species Guttulinopsis vulgaris has eluded proper classification. Here we demonstrate, by phylogenomic analyses of a 159-protein data set, that G. vulgaris is a member of Rhizaria and is thus the first member of this eukaryote supergroup known to be capable of aggregative multicellularity., (Copyright © 2012 Elsevier Ltd. All rights reserved.)