Ocean currents promote rare species diversity in protists

Oceans host communities of plankton composed of relatively few abundant species and many rare species. The number of rare protist species in these communities, as estimated in metagenomic studies, decays as a steep power law of their abundance. The ecological factors at the origin of this pattern remain elusive. We propose that chaotic advection by oceanic currents affects biodiversity patterns of rare species. To test this hypothesis, we introduce a spatially explicit coalescence model that reconstructs the species diversity of a sample of water. Our model predicts, in the presence of chaotic advection, a steeper power law decay of the species abundance distribution and a steeper increase of the number of observed species with sample size. A comparison of metagenomic studies of planktonic protist communities in oceans and in lakes quantitatively confirms our prediction. Our results support that oceanic currents positively affect the diversity of rare aquatic microbes

Unmapped RNA Virus Diversity in Termites and Their Symbionts

Despite their ecological importance, nothing is known about the diversity and abundance of RNA viruses in termites (Termitoidae). We used a metatranscriptomics approach to determine the RNA virome structure of 50 diverse species of termite that differ in both phylogenetic position and colony composition. From these samples, we identified 67 novel RNA viruses, characterized their genomes, quantified their abundance and inferred their evolutionary history. These viruses were found within or similar to those from the Togaviridae, Iflaviridae, Polycipiviridae, Flaviviridae, Leviviridae, Narnaviridae, Mitoviridae, Lispivirdae, Phasmaviridae, Picobirnaviridae and Partitiviridae. However, all viruses identified were novel and divergent, exhibiting only 20% to 45% amino acid identity to previously identified viruses. Our analysis suggested that 17 of the viruses identified were termite-infecting, with the remainder likely associated with the termite microbiome or diet. Unclassified sobemo-like and bunya-like viruses dominated termite viromes, while most of the phylogenetic diversity was provided by the picobirna- and mitovirus-like viruses. Of note was the identification of a novel flavi-like virus most closely related to those found in marine vertebrates and invertebrates. Notably, the sampling procedure had the strongest association with virome composition, with greater RNA virome diversity in libraries prepared from whole termite bodies than those that only sampled heads

Neoisoptera repeatedly colonised Madagascar after the Middle Miocene climatic optimum

Madagascar is home to many endemic plant and animal species owing to its ancient isolation from other landmasses. This unique fauna includes several lineages of termites, a group of insects known for their key role in organic matter decomposition in many terrestrial ecosystems. How and when termites colonised Madagascar remains unknown. In this study, we used 601 mitochondrial genomes, 93 of which were generated from Malagasy samples, to infer the global historical biogeography of Neoisoptera, a lineage containing more than 80% of described termite species. Our results indicate that Neoisoptera colonised Madagascar between 7 and 10 times independently during the Miocene, between 8.4 and 16.6 Ma (95% HPD: 6.1–19.9 Ma). This timing matches that of the colonization of Australia by Neoisoptera. Furthermore, the taxonomic composition of the Neoisopteran fauna of Madagascar and Australia are strikingly similar, with Madagascar harbouring an additional two lineages absent from Australia. Therefore, akin to Australia, Neoisoptera colonised Madagascar during the global expansion of grasslands, possibly helped by the ecological opportunities arising from the spread of this new biome.journal articl

Identification and characterization of fatty acid desaturases from Candida parapsilosis

Department of BiochemistryKatedra biochemieFaculty of SciencePřírodovědecká fakult

Study of evolution of insect pheromone biosynthetic fatty acyl desaturases

Insects account for more than one million of described species with an ecological and economic impact disproportional to their minute body size. Among the factors which have contributed to their evolutionary success, insect secondary metabolites such as defensive compounds and chemical signals are regarded to play a major role. This thesis aims at uncovering the molecular mechanisms underlying evolution of ubiquitous insect secondary metabolites - sex pheromones (SPs), i.e. chemical signals mediating mate finding and mating between individuals of the same species. The thesis focuses on a class of oxidoreductase enzymes, membrane fatty acid desaturases (mFADs), which introduce double bonds into hydrocarbon chains of fatty acyls and thus produce precursors of unsaturated fatty acid- derived SPs. mFADs are involved in SP biosynthesis in e.g. moths (Lepidoptera), flies (Diptera), cockroaches and termites (Blattodea), wasps and bees (Hymenoptera) - some of the most species-rich insect orders. Since SPs are principal to species reproductive isolation, uncovering the molecular basis of insect SP biosynthesis holds promises to contribute to answering fundamental questions concerning the insect ecology and evolution. The insect mFADs with diverse enzymatic specificities also represent a naturally available..

Desaturases of pathogenic yeasts

Katedra biochemieDepartment of BiochemistryFaculty of SciencePřírodovědecká fakult

Identification and characterization of fatty acid desaturases from Candida parapsilosis

Department of BiochemistryKatedra biochemieFaculty of SciencePřírodovědecká fakult

Studium evoluce desaturas mastných kyselin zapojených v biosyntéze hmyzích feromonů

Hmyz čitající více než jeden milion popsaných druhů představuje skupinu organismů s ekologickým a ekonomickým významem disproporčně větším než je jejich často zanedbatelná tělesná velikost. Mezi faktory, které zásadní měrou přispěly k evoluční úspěšnosti hmyzu, je počítána schopnost produkovat řadu sekundárních metabolitů, jako jsou obranné látky a chemické signály. Tato disertační práce se věnuje studiu molekulárních mechanismů evoluce jedné široce zastoupené skupiny hmyzích chemických signálů - pohlavních feromonů - tedy látek, které zprostředkovávají vyhledávání pohlavních partnerů a páření jedinců téhož druhu. Téma práce je zaměřeno na membránové desaturasy mastných kyselin (dále jen desaturasy), oxidoreduktasy, které zavádí dvojné vazby do uhlovodíkových řetězců mastných kyselin a tak produkují nenasycené prekurzory pohlavních feromonů odvozených od mastných kyselin. Desaturasy jsou zapojeny v biosyntéze pohlavních feromonů například u můr (Lepidoptera), dvoukřídlých (Diptera), blanokřídlých (Hymenoptera), švábů a termitů (Blattodea) - tedy jedněch z druhově nejbohatších hmyzích řádů. Jelikož pohlavní feromony slouží jako reprodukční bariéry u mnohých blízce příbuzných druhů či subpopulací, odhalení molekulárních základů biosyntézy feromonů může pomoci zodpovědět klíčové otázky týkající se...Insects account for more than one million of described species with an ecological and economic impact disproportional to their minute body size. Among the factors which have contributed to their evolutionary success, insect secondary metabolites such as defensive compounds and chemical signals are regarded to play a major role. This thesis aims at uncovering the molecular mechanisms underlying evolution of ubiquitous insect secondary metabolites - sex pheromones (SPs), i.e. chemical signals mediating mate finding and mating between individuals of the same species. The thesis focuses on a class of oxidoreductase enzymes, membrane fatty acid desaturases (mFADs), which introduce double bonds into hydrocarbon chains of fatty acyls and thus produce precursors of unsaturated fatty acid- derived SPs. mFADs are involved in SP biosynthesis in e.g. moths (Lepidoptera), flies (Diptera), cockroaches and termites (Blattodea), wasps and bees (Hymenoptera) - some of the most species-rich insect orders. Since SPs are principal to species reproductive isolation, uncovering the molecular basis of insect SP biosynthesis holds promises to contribute to answering fundamental questions concerning the insect ecology and evolution. The insect mFADs with diverse enzymatic specificities also represent a naturally available...Katedra biochemieDepartment of BiochemistryFaculty of SciencePřírodovědecká fakult