Bacterial influence on alkenones in live microalgae

The microalga Emiliania huxleyi produces alkenone lipids that are important proxies for estimating past sea surface temperatures. Field calibrations of this proxy are robust but highly variable results are obtained in culture. Here, we present results suggesting that algal‐bacterial interactions may be responsible for some of this variability. Co‐cultures of E. huxleyi and the bacterium Phaeobacter inhibens resulted in a 2.5‐fold decrease in algal alkenone‐containing lipid bodies. In addition levels of unsaturated alkenones increase in co‐cultures. These changes result in an increase in the reconstructed growth temperature of up to 2°C relative to axenic algal cultures.     

贺兰山东麓荒漠藻结皮微生物群落结构及其演替研究

以宁夏贺兰山东麓荒漠藻结皮为研究对象,对处于不同发育阶段的藻结皮中微生物群落结构及其演替进行了研究。结皮样品高通量测序结果分别得到521个16S rDNA序列操作分类单元(OTU)和64个18S rDNA序列OTU,表明藻结皮中原核微生物多样性远高于真核微生物;贺兰山东麓藻结皮中原核微生物分布于26个纲,Cyanobacteria在各个发育阶段中都是优势微生物类群,Actinobacteria、Chloroplast、Alphaproteobacteria和Bacilli在藻结皮发育的各个阶段相对丰度也较高;从属水平上分析,Bacillus、Leptolyngbya、Microcoleus、Microvirga、Chroococcidiopsis、Rubellimicrobium、Phormidium、Mastigocladopsis、Skermanella、Nostoc、Scytonema共11个属在各个发育阶段的藻结皮中都存在,只是出现了丰度的差异。Bacillus在藻结皮形成期、发育初期和发育中期相对丰度较大,成熟期丰度显著下降,而成熟期Microvirga丰度较前3个时期显著增加,表现出明显的细菌菌群演替现象。藻结皮样品中主要真核微生物分布于13个纲,其中Dothideomycetes和Pezizomycetes在各个发育阶段样品中丰度都很高,Agaricomycetes在形成期样品中相对丰度高达32.6%,但在藻结皮发育过程中其相对丰度迅速下降;原生生物的相对丰度在藻结皮发育过程中逐渐增加;4个发育阶段藻结皮样品中均未检测到真核微藻序列。4个发育阶段的藻结皮样品中有明确分类学信息的真核微生物共13个属,其中4个发育阶段中共有的为Coniothyrium、Dendryphion、Friedmanniomyces、Phloeopeccania、Sarocladium共5个属,其余8个属只在个别发育阶段样品中检出,表明在藻结皮发育过程中真核微生物的群落结构也发生着变化。藻结皮厚度、全氮含量及有机质含量是影响结皮层微生物群落组成的主要因素。     

The role of dissolved organic matter (DOM) quality in the growth enhancement of Alexandrium fundyense (Dinophyceae) in laboratory culture1

Several algal species responsible for harmful algal blooms (HABs), such as Alexandrium fundyense, are mixotrophic under certain environmental conditions. The ability to switch between photosynthetic and heterotrophic modes of growth may play a role in the development of HABs in coastal regions. We examined the influence of humic dissolved organic matter (HDOM) derived from terrestrial (plant/soil) and microbial sources on the growth of A. fundyense. We found that a terrestrially derived HDOM, Suwannee River humic acid (SRHA), did enhance A. fundyense growth; however, a microbially derived HDOM, Pony Lake fulvic acid (PLFA) did not enhance growth. A. fundyense grows in association with bacteria in culture and we observed that bacterial cell densities were much lower in A. fundyense cultures than in bacteria‐only cultures, consistent with bacterial grazing by A. fundyense in culture. In bacteria‐only cultures with added algal exudates (EX), the addition of PLFA and SRHA resulted in a slight increase in bacterial cell density compared to cultures without HDOM added. Changes over time in the chemical quality of the HDOM in the A. fundyense cultures reflected contributions of microbially derived material with similar characteristics as the PLFA. Overall, these results suggest that the chemical differences between SRHA and PLFA are responsible for the greater effect of SRHA on A. fundyense growth, and that the differential effect is not a result of an effect on the growth of associated bacteria.     

Complete mitochondrial genomes of prasinophyte algae Pyramimonas parkeae and Cymbomonas tetramitiformis

Mitochondria are archetypal eukaryotic organelles that were acquired by endosymbiosis of an ancient species of alpha‐proteobacteria by the last eukaryotic common ancestor. The genetic information contained within the mitochondrial genome has been an important source of information for resolving relationships among eukaryotic taxa. In this study, we utilized mitochondrial and chloroplast genomes to explore relationships among prasinophytes. Prasinophytes are represented by diverse early‐diverging green algae whose physical structures and genomes have the potential to elucidate the traits of the last common ancestor of the Viridiplantae (or Chloroplastida). We constructed de novo mitochondrial genomes for two prasinophyte algal species, Pyramimonas parkeae and Cymbomonas tetramitiformis, representing the prasinophyte clade. Comparisons of genome structure and gene order between these species and to those of other prasinophytes revealed that the mitochondrial genomes of P. parkeae and C. tetramitiformis are more similar to each other than to other prasinophytes, consistent with other molecular inferences of the close relationship between these two species. Phylogenetic analyses using the inferred amino acid sequences of mitochondrial and chloroplast protein‐coding genes resolved a clade consisting of P. parkeae and C. tetramitiformis; and this group (representing the prasinophyte clade I) branched with the clade II, consistent with previous studies based on the use of nuclear gene markers.     

A metagenome for lacustrine Cladophora (Cladophorales) reveals remarkable diversity of eukaryotic epibionts and genes relevant to materials cycling

Periphyton dominated by the cellulose‐rich filamentous green alga Cladophora forms conspicuous growths along rocky marine and freshwater shorelines worldwide, providing habitat for diverse epibionts. Bacterial epibionts have been inferred to display diverse functions of biogeochemical significance: N‐fixation and other redox reactions, phosphorus accumulation, and organic degradation. Here, we report taxonomic diversity of eukaryotic and prokaryotic epibionts and diversity of genes associated with materials cycling in a Cladophora metagenome sampled from Lake Mendota, Dane Co., WI, USA, during the growing season of 2012. A total of 1,060 distinct 16S, 173 18S, and 351 28S rRNA operational taxonomic units, from which >220 genera or species of bacteria (~60), protists (~80), fungi (6), and microscopic metazoa (~80), were distinguished with the use of reference databases. We inferred the presence of several algal taxa generally associated with marine systems and detected Jaoa, a freshwater periphytic ulvophyte previously thought endemic to China. We identified six distinct nifH gene sequences marking nitrogen fixation, >25 bacterial and eukaryotic cellulases relevant to sedimentary C‐cycling and technological applications, and genes encoding enzymes in aerobic and anaerobic pathways for vitamin B₁₂ biosynthesis. These results emphasize the importance of Cladophora in providing habitat for microscopic metazoa, fungi, protists, and bacteria that are often inconspicuous, yet play important roles in ecosystem biogeochemistry.     

Probiotic consortia are not uniformly effective against different amphibian chytrid pathogen isolates

Symbiotic bacterial communities can protect their hosts from infection by pathogens. Treatment of wild individuals with protective bacteria (probiotics) isolated from hosts can combat the spread of emerging infectious diseases. However, it is unclear whether candidate probiotic bacteria can offer consistent protection across multiple isolates of globally distributed pathogens. Here, we use the lethal amphibian fungal pathogen Batrachochytrium dendrobatidis to investigate whether probiotic richness (number of bacteria) or genetic distance among consortia members influences broad‐scale in vitro inhibitory capabilities of probiotics across multiple isolates of the pathogen. We show that inhibition of multiple pathogen isolates by individual bacteria is rare, with no systematic pattern among bacterial genera in ability to inhibit multiple B. dendrobatidis isolates. Bacterial consortia can offer stronger protection against B. dendrobatidis compared to single strains, and this tended to be more pronounced for consortia containing multiple genera compared with those consisting of bacteria from a single genus (i.e., with lower genetic distance), but critically, this effect was not uniform across all B. dendrobatidis isolates. These novel insights have important implications for the effective design of bacterial probiotics to mitigate emerging infectious diseases.     

Identification of Intracellular Bacteria in the Ciliate Balantidium ctenopharyngodoni (Ciliophora,Litostomatea)

The ciliate Balantidium ctenopharyngodoni is the most prominent protist in the guts of grass carp, where it mainly inhabits the creamy luminal contents of the hindgut. Ciliates are generally colonized by microorganisms via phagotrophic feeding. In order to study the intracellular bacteria in this ciliate, we have successfully established it in in vitro culture. Herein, we investigated and compared the bacterial community structures of cultured and freshly collected B. ctenopharyngodoni. The results showed that these two groups exhibited different bacterial communities. The most abundant bacterial family in freshly collected samples was Enterobacteriaceae, while in cultured samples it was Fusobacteriaceae. In addition, a key intracellular bacterium, Cetobacterium somerae, was identified in the cytoplasm of cultured ciliates using fluorescence in situ hybridization (FISH). This study shows that ciliates can retain the intracellular bacteria acquired in the natural habitat for quite a long time, but the bacterial community structure of ciliates eventually changes after a long period of cultivation.     

Shotgun metagenomics and microscopy indicate diverse cyanophytes,other bacteria,and microeukaryotes in the epimicrobiota of a northern Chilean wetland Nostoc (Cyanobacteria)

Prokaryotic Nostoc, one of the world's most conspicuous and widespread algal genera (similar to eukaryotic algae, plants, and animals) is known to support a microbiome that influences host ecological roles. Past taxonomic characterizations of surface microbiota (epimicrobiota) of free‐living Nostoc sampled from freshwater systems employed 16S rRNA genes, typically amplicons. We compared taxa identified from 16S, 18S, 23S, and 28S rRNA gene sequences filtered from shotgun metagenomic sequence and used microscopy to illuminate epimicrobiota diversity for Nostoc sampled from a wetland in the northern Chilean Altiplano. Phylogenetic analysis and rRNA gene sequence abundance estimates indicated that the host was related to Nostoc punctiforme PCC 73102. Epimicrobiota were inferred to include 18 epicyanobacterial genera or uncultured taxa, six epieukaryotic algal genera, and 66 anoxygenic bacterial genera, all having average genomic coverage ≥90X. The epicyanobacteria Geitlerinemia, Oscillatoria, Phormidium, and an uncultured taxon were detected only by 16S rRNA gene; Gloeobacter and Pseudanabaena were detected using 16S and 23S; and Phormididesmis, Neosynechococcus, Symphothece, Aphanizomenon, Nodularia, Spirulina, Nodosilinea, Synechococcus, Cyanobium, and Anabaena (the latter corroborated by microscopy), plus two uncultured cyanobacterial taxa (JSC12, O77) were detected only by 23S rRNA gene sequences. Three chlamydomonad and two heterotrophic stramenopiles genera were inferred from 18S; the streptophyte green alga Chaetosphaeridium globosum was detected by microscopy and 28S rRNA genes, but not 18S rRNA genes. Overall, >60% of epimicrobial taxa were detected by markers other than 16S rRNA genes. Some algal taxa observed microscopically were not detected from sequence data. Results indicate that multiple taxonomic markers derived from metagenomic sequence data and microscopy increase epimicrobiota detection.     

Patterns of environmental variability influence coral‐associated bacterial and algal communities on the Mesoamerican Barrier Reef

A coral's capacity to alter its microbial symbionts may enhance its fitness in the face of climate change. Recent work predicts exposure to high environmental variability may increase coral resilience and adaptability to future climate conditions. However, how this heightened environmental variability impacts coral‐associated microbial communities remains largely unexplored. Here, we examined the bacterial and algal symbionts associated with two coral species of the genus Siderastrea with distinct life history strategies from three reef sites on the Belize Mesoamerican Barrier Reef System with low or high environmental variability. Our results reveal bacterial community structure, as well as alpha‐ and beta‐diversity patterns, vary by host species. Differences in bacterial communities between host species were partially explained by high abundance of Deltaproteobacteria and Rhodospirillales and high bacterial diversity in Siderastrea radians. Our findings also suggest Siderastrea spp. have dynamic core bacterial communities that likely drive differences observed in the entire bacterial community, which may play a critical role in rapid acclimatization to environmental change. Unlike the bacterial community, Symbiodiniaceae composition was only distinct between host species at high thermal variability sites, suggesting that different factors shape bacterial versus algal communities within the coral holobiont. Our findings shed light on how domain‐specific shifts in dynamic microbiomes may allow for unique methods of enhanced host fitness.     

Arctic marine phytobenthos of northern Baffin Island

Global climate change is expected to alter the polar bioregions faster than any other marine environment. This study assesses the biodiversity of seaweeds and associated eukaryotic pathogens of an established study site in northern Baffin Island (72° N), providing a baseline inventory for future work assessing impacts of the currently ongoing changes in the Arctic marine environment. A total of 33 Phaeophyceae, 24 Rhodophyceae, 2 Chlorophyceae, 12 Ulvophyceae, 1 Trebouxiophyceae, and 1 Dinophyceae are reported, based on collections of an expedition to the area in 2009, complemented by unpublished records of Robert T. Wilce and the first‐ever photographic documentation of the phytobenthos of the American Arctic. Molecular barcoding of isolates raised from incubated substratum samples revealed the presence of 20 species of brown seaweeds, including gametophytes of kelp and of a previously unsequenced Desmarestia closely related to D. viridis, two species of Pylaiella, the kelp endophyte Laminariocolax aecidioides and 11 previously unsequenced species of the Ectocarpales, highlighting the necessity to include molecular techniques for fully unraveling cryptic algal diversity. This study also includes the first records of Eurychasma dicksonii, a eukaryotic pathogen affecting seaweeds, from the American Arctic. Overall, this study provides both the most accurate inventory of seaweed diversity of the northern Baffin Island region to date and can be used as an important basis to understand diversity changes with climate change.     

Immunotherapy using algal‐produced Ara h 1 core domain suppresses peanut allergy in mice

Peanut allergy is an IgE‐mediated adverse reaction to a subset of proteins found in peanuts. Immunotherapy aims to desensitize allergic patients through repeated and escalating exposures for several months to years using extracts or flours. The complex mix of proteins and variability between preparations complicates immunotherapy studies. Moreover, peanut immunotherapy is associated with frequent negative side effects and patients are often at risk of allergic reactions once immunotherapy is discontinued. Allergen‐specific approaches using recombinant proteins are an attractive alternative because they allow more precise dosing and the opportunity to engineer proteins with improved safety profiles. We tested whether Ara h 1 and Ara h 2, two major peanut allergens, could be produced using chloroplast of the unicellular eukaryotic alga, Chlamydomonas reinhardtii. C. reinhardtii is novel host for producing allergens that is genetically tractable, inexpensive and easy to grow, and is able to produce more complex proteins than bacterial hosts. Compared to the native proteins, algal‐produced Ara h 1 core domain and Ara h 2 have a reduced affinity for IgE from peanut‐allergic patients. We further found that immunotherapy using algal‐produced Ara h 1 core domain confers protection from peanut‐induced anaphylaxis in a murine model of peanut allergy.     

Latent virus‐like infections are present in a diverse range of Symbiodinium spp. (Dinophyta)

Coral reefs are increasingly threatened by disease outbreaks, which affect the coral animal and/or its algal symbionts (Symbiodinium spp.) and can cause mass mortalities. Currently around half of the recognized coral diseases have unknown causative agents. While many of the diseases are thought to be bacterial in origin, there is growing evidence that viruses may play a role. In particular, it appears that viruses may infect the algal symbionts, causing breakdown of the coral‐algal mutualism. In this study, we screened a wide range of Symbiodinium cultures in vitro for the presence of latent viral infections. Using flow cytometry and electron microscopy, we found that many types of Symbiodinium apparently harbor such infections, and that the type of putative virus varied within and among host types. Furthermore, the putative viral infections could be induced via abiotic stress and cause host cell lysis and population decline. If similar processes occur in Symbiodinium cells in hospite, they may provide an explanation for some of the diseases affecting corals and other organisms forming symbioses with these algae.     

Synthesis of bacteriophage lytic proteins against Streptococcus pneumoniae in the chloroplast of Chlamydomonas reinhardtii

There is a pressing need to develop novel antibacterial agents given the widespread antibiotic resistance among pathogenic bacteria and the low specificity of the drugs available. Endolysins are antibacterial proteins that are produced by bacteriophage‐infected cells to digest the bacterial cell wall for phage progeny release at the end of the lytic cycle. These highly efficient enzymes show a considerable degree of specificity for the target bacterium of the phage. Furthermore, the emergence of resistance against endolysins appears to be rare as the enzymes have evolved to target molecules in the cell wall that are essential for bacterial viability. Taken together, these factors make recombinant endolysins promising novel antibacterial agents. The chloroplast of the green unicellular alga Chlamydomonas reinhardtii represents an attractive platform for production of therapeutic proteins in general, not least due to the availability of established techniques for foreign gene expression, a lack of endotoxins or potentially infectious agents in the algal host, and low cost of cultivation. The chloroplast is particularly well suited to the production of endolysins as it mimics the native bacterial expression environment of these proteins while being devoid of their cell wall target. In this study, the endolysins Cpl‐1 and Pal, specific to the major human pathogen Streptococcus pneumoniae, were produced in the C. reinhardtii chloroplast. The antibacterial activity of cell lysates and the isolated endolysins was demonstrated against different serotypes of S. pneumoniae, including clinical isolates and total recombinant protein yield was quantified at ~1.3 mg/g algal dry weight.     

An association network analysis among microeukaryotes and bacterioplankton reveals algal bloom dynamics

Algal blooms are a worldwide phenomenon and the biological interactions that underlie their regulation are only just beginning to be understood. It is established that algal microorganisms associate with many other ubiquitous, oceanic organisms, but the interactions that lead to the dynamics of bloom formation are currently unknown. To address this gap, we used network approaches to investigate the association patterns among microeukaryotes and bacterioplankton in response to a natural Scrippsiella trochoidea bloom. This is the first study to apply network approaches to bloom dynamics. To this end, terminal restriction fragment (T‐RF) length polymorphism analysis showed dramatic changes in community compositions of microeukaryotes and bacterioplankton over the blooming period. A variance ratio test revealed significant positive overall associations both within and between microeukaryotic and bacterioplankton communities. An association network generated from significant correlations between T‐RFs revealed that S. trochoidea had few connections to other microeukaryotes and bacterioplankton and was placed on the edge. This lack of connectivity allowed for the S. trochoidea sub‐network to break off from the overall network. These results allowed us to propose a conceptual model for explaining how changes in microbial associations regulate the dynamics of an algal bloom. In addition, key T‐RFs were screened by principal components analysis, correlation coefficients, and network analysis. Dominant T‐RFs were then identified through 18S and 16S rRNA gene clone libraries. Results showed that microeukaryotes clustered predominantly with Dinophyceae and Perkinsea while the majority of bacterioplankton identified were Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. The ecologi‐cal roles of both were discussed in the context of these findings.     

“Ectrogella” Parasitoids of the Diatom Licmophora sp. are Polyphyletic

The diatom genera Licmophora and Fragilaria are frequent epiphytes on marine macroalgae and can be infected by intracellular parasitoids traditionally assigned to the oomycete genus Ectrogella. Much debate and uncertainty remains about the taxonomy of these oomycetes, not least due to their morphological and developmental plasticity. Here, we used single‐cell techniques to obtain partial sequences of the parasitoids 18S and cox2 genes. The former falls into two recently identified clades of Pseudo‐nitzschia parasites temporarily named OOM_1_2 and OOM_2, closely related to the genera of brown and red algal pathogens Anisolpidium and Olpidiopsis. A third group of sequences falls at the base of the red algal parasites assigned to Olpidiopsis. In one instance, two oomycete parasitoids seemed to co‐exist in a single diatom cell; this co‐occurrence of distinct parasitoid taxa not only within a population of diatom epiphytes, but also within the same host cell, possibly explains the ongoing confusion in the taxonomy of these parasitoids. We demonstrate the polyphyly of Licmophora parasitoids previously assigned to Ectrogella (sensu Sparrow, 1960) and show that parasites of red algae assigned to the genus Olpidiopsis are most likely not monophyletic. We conclude that combining single‐cell microscopy and molecular methods is necessary for their full characterisation.     

Bacterial Uptake by the Marine Sponge <Emphasis Type="Italic">Aplysina aerophoba</Emphasis>

Sponges (Porifera) are filter feeders that take up microorganisms from seawater and digest them by phagocytosis. At the same time, many sponges are known to harbor massive consortia of symbiotic microorganisms, which are phylogenetically distinct from those in seawater, within the mesohyl matrix. In the present study, feeding experiments were performed to investigate whether phylogenetically different bacterial isolates, hereafter termed “food bacteria,” microbial seawater consortia, and sponge symbiont consortia are taken up and processed differently by the host sponge. Aplysina aerophoba retained high numbers of bacterial isolates and microbial seawater consortia with rates of up to 2.76 × 10⁶ bacteria (g sponge wet weight)^–1 h^–1, whereas the retention of sponge symbionts was lower by nearly two orders of magnitude [5.37 × 10⁴ bacteria (g sponge wet weight)⁻¹ h^–1]. In order to visualize the processing of a food bacterium within sponge tissues, the green fluorescent protein-labeled Vibrio strain MMW1, which had originally been isolated from A. aerophoba, was constructed. Incubation of this strain with A. aerophoba and subsequent visualization in tissue cryosections showed its presence in the choanocytes and/or endopinacocytes lining the canals but, unlike latex beads, not in deeper regions of the mesohyl, which suggests digestion of the bacteria upon contact with the host. Denaturing gradient gel electrophoresis (DGGE) was performed on the incubation seawater to monitor the changes in phylogenetic composition after incubation of the sponge with either seawater or sponge symbiont consortia. However, the DGGE experiment provided no evidence for selective processing of individual lineages by the host sponge. In conclusion, this study extends early studies by Wilkinson et al. (Proc R Soc London B 220:519–528, 1984) that sponges, here A. aerophoba, are able to differentiate between food bacteria and their own bacterial symbionts.     

Abundance and diversity of eukaryotic rather than bacterial community relate closely to the trophic level of urban lakes

Scientific understanding of biotic effects on the water trophic level is lacking for urban lakes during algal bloom development stage. Based on the Illumina MiSeq sequencing, quantitative polymerase chain reaction (PCR), and multiple statistical analyses, we estimated distribution patterns and ecological roles of planktonic bacteria and eukaryotes in urban lakes during algal bloom development stage (i.e., April, May, and June). Cyanobacteria and Chlorophyta mainly dominated algal blooms. Bacteria exhibited significantly higher absolute abundance and community diversity than eukaryotes, whereas abundance and diversity of eukaryotic rather than bacterial community relate closely to the water trophic level. Multinutrient cycling (MNC) index was significantly correlated with eukaryotic diversity rather than bacterial diversity. Stronger species replacement, broader environmental breadth, and stronger phylogenetic signal were found for eukaryotic community than for bacterial community. In contrast, bacterial community displayed stronger community stability and environmental constraint than eukaryotic community. Stochastic and differentiating processes contributed more to community assemblies of bacteria and eukaryotes. Our results emphasized that a strong linkage between planktonic diversity and MNC ensured a close relationship between planktonic diversity and the water trophic level of urban lakes. Our findings could be useful to guide the formulation and implementation of environmental lake protection measures.     

HSP33 in eukaryotes – an evolutionary tale of a chaperone adapted to photosynthetic organisms

HSP33 was originally identified in bacteria as a redox‐sensitive chaperone that protects unfolded proteins from aggregation. Here, we describe a eukaryote ortholog of HSP33 from the green algae Chlamydomonas reinhardtii, which appears to play a protective role under light‐induced oxidizing conditions. The algal HSP33 exhibits chaperone activity, as shown by citrate synthase aggregation assays. Studies from the Jakob laboratory established that activation of the bacterial HSP33 upon its oxidation initiates by the release of pre‐bound Zn from the well conserved Zn‐binding motif Cys–X–Cys–X_n–Cys–X–X–Cys, and is followed by significant structural changes (Reichmann et al., 2012 ). Unlike the bacterial protein, the HSP33 from C. reinhardtii had lost the first cysteine residue of its center, diminishing Zn‐binding activity under all conditions. As a result, the algal protein can be easily activated by minor structural changes in response to oxidation and/or excess heat. An attempt to restore the missing first cysteine did not have a major effect on Zn‐binding and on the mode of activation. Replacement of all remaining cysteines abolished completely any residual Zn binding, although the chaperone activation was maintained. A phylogenetic analysis of the algal HSP33 showed that it clusters with the cyanobacterial protein, in line with its biochemical localization to the chloroplast. Indeed, expression of the algal HSP33 increases in response to light‐induced oxidative stress, which is experienced routinely by photosynthetic organisms. Despite the fact that no ortholog could be found in higher eukaryotes, its abundance in all algal species examined could have a biotechnological relevance.     

Comparative Metabolism of Free‐living Bodo saltans and Parasitic Trypanosomatids

Comparison of the genomes of free‐living Bodo saltans and those of parasitic trypanosomatids reveals that the transition from a free‐living to a parasitic life style has resulted in the loss of approximately 50% of protein‐coding genes. Despite this dramatic reduction in genome size, B. saltans and trypanosomatids still share a significant number of common metabolic traits: glycosomes; a unique set of the pyrimidine biosynthetic pathway genes; an ATP‐PFK which is homologous to the bacterial PP_i‐PFKs rather than to the canonical eukaryotic ATP‐PFKs; an alternative oxidase; three phosphoglycerate kinases and two GAPDH isoenzymes; a pyruvate kinase regulated by fructose‐2,6‐bisphosphate; trypanothione as a substitute for glutathione; synthesis of fatty acids via a unique set of elongase enzymes; and a mitochondrial acetate:succinate coenzyme A transferase. B. saltans has lost the capacity to synthesize ubiquinone. Among genes that are present in B. saltans and lost in all trypanosomatids are those involved in the degradation of mureine, tryptophan and lysine. Novel acquisitions of trypanosomatids are components of pentose sugar metabolism, pteridine reductase and bromodomain‐factor proteins. In addition, only the subfamily Leishmaniinae has acquired a gene for catalase and the capacity to convert diaminopimelic acid to lysine.