Behavioural differences underlie toxicity and predation variation in blooms of Prymnesium parvum

Much of the evolutionary ecology of toxic algal blooms (TABs) remains unclear, including the role of algal toxins in the adaptive ‘strategies’ of TAB-forming species. Most eukaryotic TABs are caused by mixotrophs that augment autotrophy with organic nutrient sources, including competing algae (intraguild predation). We leverage the standing diversity of TABs formed by the toxic, invasive mixotroph Prymnesium parvum to identify cell-level behaviours involved in toxin-assisted predation using direct observations as well as comparisons between genetically distinct low- and high-toxicity isolates. Our results suggest that P. parvum toxins are primarily delivered at close range and promote subsequent prey capture/consumption. Surprisingly, we find opposite chemotactic preferences for organic (prey-derived) and inorganic nutrients between differentially toxic isolates, respectively, suggesting behavioural integration of toxicity and phagotrophy. Variation in toxicity may, therefore, reflect broader phenotypic integration of key traits that ultimately contribute to the remarkable flexibility, diversity, and success of invasive populations.     

DNA polymerase activity in embryos of Allium cepa seed

A low level of DNA polymerase (deoxyribonucleosidetriphosphate: deoxynucleotidyltransferase; E.C. 2.7.7.7) activity can be detected by autoradiography after incubating frozen sections of unimbibed onion seed embryos in an aqueous solution of tritium labelled deoxynucleoside triphosphate. The enzyme is sensitive to sulfhydryl reagents, and incorporation was reduced by high levels of deoxyribonuclease, but inclusion of cycloheximide, ribonuclease, or nucleoside triphosphate did not change activity. On germination, activity remained relatively constant and at a low level until 30 hr after imbibition when it began to increase significantly.     

Microbially influenced corrosion and rust tubercle formation on sheet piles in freshwater systems

The extent of how complex natural microbial communities contribute to metal corrosion is still not fully resolved, especially not for freshwater environments. In order to elucidate the key processes, we investigated rust tubercles forming massively on sheet piles along the river Havel (Germany) applying a complementary set of techniques. In-situ microsensor profiling revealed steep gradients of O₂, redox potential and pH within the tubercle. Micro-computed tomography and scanning electron microscopy showed a multi-layered inner structure with chambers and channels and various organisms embedded in the mineral matrix. Using Mössbauer spectroscopy we identified typical corrosion products including electrically conductive iron (Fe) minerals. Determination of bacterial gene copy numbers and sequencing of 16S rRNA and 18S rRNA amplicons supported a densely populated tubercle matrix with a phylogenetically and metabolically diverse microbial community. Based on our results and previous models of physic(electro)chemical reactions, we propose here a comprehensive concept of tubercle formation highlighting the crucial reactions and microorganisms involved (such as phototrophs, fermenting bacteria, dissimilatory sulphate and Fe(III) reducers) in metal corrosion in freshwaters.     

ALLELOPATHY AS AN EMERGENT,EXPLOITABLE PUBLIC GOOD IN THE BLOOM‐FORMING MICROALGA PRYMNESIUM PARVUM

Many microbes cooperatively secrete extracellular products that favorably modify their environment. Consistent with social evolution theory, structured habitats play a role in maintaining these traits in microbial model systems, by localizing the benefits and separating strains that invest in these products from ‘cheater’ strains that benefit without paying the cost. It is thus surprising that many unicellular, well‐mixed microalgal populations invest in extracellular toxins that confer ecological benefits upon the entire population, for example, by eliminating nutrient competitors (allelopathy). Here we test the hypotheses that microalgal exotoxins are (1) exploitable public goods that benefit all cells, regardless of investment, or (2) nonexploitable private goods involved in cell‐level functions. We test these hypotheses with high‐toxicity (TOX+) and low‐toxicity (TOX?) strains of the damaging, mixotrophic microalga Prymnesium parvum and two common competitors: green algae and diatoms. TOX+ actually benefits from dense populations of competing green algae, which can also be prey for P. parvum, yielding a relative fitness advantage over coexisting TOX?. However, with nonprey competitors (diatoms), TOX? increases in frequency over TOX+, despite benefiting from the exclusion of diatoms by TOX+. An evolutionary unstable, ecologically devastating public good may emerge from traits selected at lower levels expressed in novel environments.     

Lightweight genome viewer: portable software for browsing genomics data in its chromosomal context

Background  

Lightweight genome viewer (lwgv) is a web-based tool for visualization of sequence annotations in their chromosomal context. It performs most of the functions of larger genome browsers, while relying on standard flat-file formats and bypassing the database needs of most visualization tools. Visualization as an aide to discovery requires display of novel data in conjunction with static annotations in their chromosomal context. With database-based systems, displaying dynamic results requires temporary tables that need to be tracked for removal.     

Seventh-Day Adventist Adolescents—Life-style Patterns and Cardiovascular Risk Factors

The life-style of adolescents attending a Seventh-Day Adventist boarding school was evaluated as it related to cardiovascular risk factors. The diet contained 34% calories as fat, with 11% derived from saturated fat. Total serum cholesterol levels were low (mean, standard deviation=138±15 mg per dl), and apolipoprotein B level was low as well (46±9 mg per dl). The high-density lipoprotein cholesterol level was within the usual range (52.4±13.3 mg per dl). Mean blood pressures were also low (systolic, 104.1±9.6 mm of mercury; diastolic, 65.7±9.7 mm of mercury). There was no self-reported use of cigarettes. If this life-style were to continue through adulthood, the incidence of premature atherosclerotic disease, particularly coronary artery disease, for this group might well be reduced, compared with other North Americans, as suggested by findings from previous studies of adult Seventh-Day Adventists.     

Tagging of biomolecules with deuterated water (D2O) in commercially important microalgae

To understand the effect of any biomolecules in specific metabolic pathways in humans, bioavailability and for other basic understanding, stable isotopically-labelled biomolecules (preferably deuterated) is the fundamental pre-requisite. Production of deuterated biomolecules such as, astaxanthin, β-carotene, lutein, chlorophyll-a, and eicosapentaenoic acid (EPA, 20:5n-3) by metabolic tagging have been shown in commercially important microalgae, Haematococcus pluvialis and Phaeodactylum tricornutum. These microalgae were grown in appropriate optimized medium supplemented with 25 % (v/v) deuterated water. LC–MS analysis showed a maximum of 20, 25, 23, 24, and 27 % replacement of hydrogen by deuterium atoms respectively in astaxanthin, β-carotene, lutein, chlorophyll-a, and EPA. To our knowledge, this is the first report on the production of deuterated astaxanthin, chlorophyll-a and EPA by these microalgae.