Fatty acids of microalgae: diversity and applications

Reviews in Environmental Science and Bio/Technology - The possibility of obtaining commercially valuable products from microalgae stimulates scientific research in this direction. The ability of...     

Addition of new neurons and the emergence of a local neural circuit for precise timing

During development, neurons arrive at local brain areas in an extended period of time, but how they form local neural circuits is unknown. Here we computationally model the emergence of a network for precise timing in the premotor nucleus HVC in songbird. We show that new projection neurons, added to HVC post hatch at early stages of song development, are recruited to the end of a growing feedforward network. High spontaneous activity of the new neurons makes them the prime targets for recruitment in a self-organized process via synaptic plasticity. Once recruited, the new neurons fire readily at precise times, and they become mature. Neurons that are not recruited become silent and replaced by new immature neurons. Our model incorporates realistic HVC features such as interneurons, spatial distributions of neurons, and distributed axonal delays. The model predicts that the birth order of the projection neurons correlates with their burst timing during the song.     

Simultaneous increase in cellular content and volumetric concentration of lipids in <Emphasis Type="Italic">Bracteacoccus bullatus</Emphasis> cultivated at reduced nitrogen and phosphorus concentrations

Manipulation of the nutrient concentration is an inexpensive and efficient method for increasing lipid and TAG accumulation in algal cells. However, high volumetric production requires finding a proper balance between the decrease of biomass production and the increase in the total lipid content. We isolated a strain of green microalga Bracteacoccus bullatus and increased its lipid content from 17 to 59% of biomass dry weight by manipulating of nitrogen and phosphorus content in the medium. The 10-fold reduction of the nitrogen and phosphorus concentration in the medium was the most efficient method of the lipid induction compared to nutrient deplete and high nutrient conditions. The oleic (48–64% mass of total fatty acids) and linoleic (14–24% mass of total fatty acids) acids dominated in the fatty acid profile, thus making this strain a suitable candidate for biodiesel production.     

Transmembrane Signaling in the Maltose ABC Transporter MalFGK2-E: PERIPLASMIC MalF-P2 LOOP COMMUNICATES SUBSTRATE AVAILABILITY TO THE ATP-BOUND MalK DIMER*

ABC transporters are ubiquitous membrane proteins that translocate solutes across biological membranes at the expense of ATP. In prokaryotic ABC importers, the extracytoplasmic anchoring of the substrate-binding protein (receptor) is emerging as a key determinant for the structural rearrangements in the cytoplasmically exposed ATP-binding cassette domains and in the transmembrane gates during the nucleotide cycle. Here the molecular mechanism of such signaling events was addressed by electron paramagnetic resonance spectroscopy of spin-labeled ATP-binding cassette maltose transporter variants (MalFGK₂-E). A series of doubly spin-labeled mutants in the MalF-P2 domain involving positions 92, 205, 239, 252, and 273 and one triple mutant labeled at positions 205/252 in P2 and 83 in the Q-loop of MalK were assayed. The EPR data revealed that the substrate-binding protein MalE is bound to the transporter throughout the transport cycle. Concomitantly with the three conformations of the ATP-binding cassette MalK₂, three functionally relevant conformations are found also in the periplasmic MalF-P2 loop, strictly dependent on cytoplasmic nucleotide binding and periplasmic docking of liganded MalE to MalFG. The reciprocal communication across the membrane unveiled here gives first insights into the stimulatory effect of MalE on the ATPase activity, and it is suggested to be an important mechanistic feature of receptor-coupled ABC transporters.     

The IronChip evaluation package: a package of perl modules for robust analysis of custom microarrays

Background  

Gene expression studies greatly contribute to our understanding of complex relationships in gene regulatory networks. However, the complexity of array design, production and manipulations are limiting factors, affecting data quality. The use of customized DNA microarrays improves overall data quality in many situations, however, only if for these specifically designed microarrays analysis tools are available.     

Parasites on parasites: hyper-, epi-, and autoparasitism among flowering plants

All organisms engage in parasitic relations, as either parasites or hosts. Some species may even play both roles simultaneously. Among flowering plants, the most widespread form of parasitism is characterized by the development of an intrusive organ called the haustorium, which absorbs water and nutrients from the host. Despite this functionally unifying feature of parasitic plants, haustoria are not homologous structures; they have evolved 12 times independently. These plants represent ca. 1% of all extant flowering species and show a wide diversity of life histories. A great variety of plants may also serve as hosts, including other parasitic plants. This phenomenon of parasitic exploitation of another parasite, broadly known as hyper- or epiparasitism, is well described among bacteria, fungi, and animals, but remains poorly understood among plants. Here, we review empirical evidence of plant hyperparasitism, including variations of self-parasitism, discuss the diversity and ecological importance of these interactions, and suggest possible evolutionary mechanisms. Hyperparasitism may provide benefits in terms of improved nutrition and enhanced host–parasite compatibility if partners are related. Different forms of self-parasitism may facilitate nutrient sharing among and within parasitic plant individuals, while also offering potential for the evolution of hyperparasitism. Cases of hyperparasitic interactions between parasitic plants may affect the ecology of individual species and modulate their ecosystem impacts. Parasitic plant phenology and disperser feeding behavior are considered to play a major role in the occurrence of hyperparasitism, especially among mistletoes. There is also potential for hyperparasites to act as biological control agents of invasive primary parasitic host species.     

Transforming growth factor beta-1 enhances cytotoxic effect of doxorubicin in human lung adenocarcinoma cells of A549 line

Transforming growth factor beta-1 (TGFbeta-1) is a regulator of cell proliferation, differentiation and apoptosis. Doxorubicin (adriamycin), an anthracycline drug causing double-strand DNA breaks, is widely used in anticancer chemotherapy. Here we demonstrated that TGFbeta-1 enhanced cytotoxic (proapoptotic) action of doxorubicin towards cultured human lung carcinoma A549 cells. Western-blot analysis and immunocytochemistry were used to show that doxorubicin induced PARP degradation in A549 cells, and TGFbeta-1 enhanced that action of the drug. The obtained results suggest a possibility of biomodulating effect of TGFbeta-1 on tumor cell treatment with doxorubicin.     

Differential effect of sanguinarine, chelerythrine and chelidonine on DNA damage and cell viability in primary mouse spleen cells and mouse leukemic cells

Sanguinarine, chelerythrine and chelidonine are isoquinoline alkaloids derived from the greater celandine. They possess a broad spectrum of pharmacological activities. It has been shown that their anti-tumor activity is mediated via different mechanisms, which can be promising targets for anti-cancer therapy. We focused our study on the differential effects of these alkaloids upon cell viability, DNA damage effect and nucleus integrity in mouse primary spleen cells and mouse lymphocytic leukemic cells, L1210. Sanguinarine and chelerythrine produce a dose-dependent increase in DNA damage and cytotoxicity in both primary mouse spleen cells and L1210 cells. Chelidonine did not show a significant cytotoxicity or damage DNA in both cell types, but completely arrested growth of L1210 cells. Examination of nuclear morphology revealed more cells with apoptotic features upon treatment with chelerythrine and sanguinarine, but not chelidonine. In contrast to primary mouse spleen cells, L1210 cells showed slightly higher sensitivity to sanguinarine and chelerythrine treatment. This suggests that cytotoxic and DNA damaging effects of chelerythrine and sanguinarine are more selective against mouse leukemic cells and primary mouse spleen cells, whereas chelidonine blocks proliferation of L1210 cells. The action of chelidonine on normal and tumor cells requires further investigation.     

Using exclusion rate to unify niche and neutral perspectives on coexistence

The competitive exclusion principle is one of the most influential concepts in ecology. The classical formulation suggests a correlation between competitor species similarity and competition severity, leading to rapid competitive exclusion where species are very similar; yet neutral models show that identical species can persist in competition for long periods. Here, we resolve the conflict by examining two components of similarity – niche overlap and competitive similarity – and modeling the effects of each on exclusion rate (defined as the inverse of time to exclusion). Studying exclusion rate, rather than the traditional focus on binary outcomes (coexistence versus exclusion), allows us to examine classical niche and neutral perspectives using the same currency. High niche overlap speeds exclusion, but high similarity in competitive ability slows it. These predictions are confirmed by a well‐known model of two species competing for two resources. Under ecologically plausible scenarios of correlation between these two factors, the strongest exclusion rates may be among moderately similar species, while very similar and highly dissimilar competitors have very low exclusion rates. Adding even small amounts of demographic stochasticity to the model blurs the line between deterministic and probabilistic coexistence still further. Thus, focusing on exclusion rate, instead of on the binary outcome of coexistence versus exclusion, allows a variety of outcomes to result from competitive interactions. This approach may help explain species coexistence in diverse competitive communities and raises novel issues for future work.