Effects of oil spill response technologies on marine microorganisms in the high Arctic.

We studied how exposure to oil spill response technologies affect marine microorganisms during Arctic winter and spring. Microorganisms were exposed to chemically dispersed oil (DISP), in situ burnt oil (ISB), and natural attenuated oil (NATT) in mesocosms from February to May. We subsampled the mesocosms and studied the effects of oil in laboratory incubations as changes in biomass of the major functional groups: bacteria, heterotrophic-nanoflagellates, dinoflagellates, ciliates, pico- and nanophytoplankton, and diatoms over two 14-day periods. In winter, the majority of polycyclic aromatic hydrocarbons (PAHs) remained encapsulated in the ice, and the low concentrations of PAHs in water led to minute changes in biomass of the investigated groups. In spring, however, when the PAHs were partially released from the melting ice, the biomass of many functional groups in DISP and NATT decreased significantly, while the changes in ISB were less pronounced. The overall biomass reduction, as observed in this study, could lead to a disrupted transfer of energy from the primary producers to the higher trophic levels in oil affected areas.

Publisher Correction: Engineered bidirectional promoters enable rapid multi-gene co-expression optimization.

The original version of this Article was updated after publication to add the ORCID ID of the author Thomas Vogl, which was inadvertently omitted, and to include a corrected version of the 'Description of Additional Supplementary Files' which originally lacked legends for each file.

Engineered bidirectional promoters enable rapid multi-gene co-expression optimization.

Numerous synthetic biology endeavors require well-tuned co-expression of functional components for success. Classically, monodirectional promoters (MDPs) have been used for such applications, but MDPs are limited in terms of multi-gene co-expression capabilities. Consequently, there is a pressing need for new tools with improved flexibility in terms of genetic circuit design, metabolic pathway assembly, and optimization. Here, motivated by nature's use of bidirectional promoters (BDPs) as a solution for efficient gene co-expression, we generate a library of 168 synthetic BDPs in the yeast Komagataella phaffii (syn. Pichia pastoris), leveraging naturally occurring BDPs as a parts repository. This library of synthetic BDPs allows for rapid screening of diverse expression profiles and ratios to optimize gene co-expression, including for metabolic pathways (taxadiene, ß-carotene). The modular design strategies applied for creating the BDP library could be relevant in other eukaryotic hosts, enabling a myriad of metabolic engineering and synthetic biology applications.

Synapse clusters are preferentially formed by synapses with large recycling pool sizes.

Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1-43 from electrically stimulated synapses in rat hippocampal tissue cultures, a strong positive correlation between the number of neighbouring synapses and recycling vesicle pool sizes was observed. Accordingly, vesicle-rich synapses were found to preferentially reside next to neighbours with large recycling pool sizes. Although these synapses with large recycling pool sizes were rare, they were densely arranged and thus exhibited a high amount of release per volume. To consolidate these findings, functional terminals were marked by live-cell antibody staining with anti-synaptotagmin-1-cypHer or overexpression of synaptopHluorin. Analysis of synapse distributions in these systems confirmed the results obtained with FM 1-43. Our findings support the idea that clustering of synapses with large recycling pool sizes is a distinct developmental feature of newly formed neural networks and may contribute to functional plasticity.

Beta-catenin degradation mediated by the CID domain of APC provides a model for the selection of APC mutations in colorectal, desmoid and duodenal tumours.

Biallelic mutation of the ADENOMATOUS POLYPOSIS COLI (APC) gene is a hallmark of sporadic colorectal cancer and colorectal, duodenal and desmoid tumours that develop in familial adenomatous polyposis (FAP) patients. The mutations affecting both APC alleles are interdependent, the position of the first APC mutation determining where the second hit will occur. This results in a complex pattern of mutation distribution in the APC sequence that translates into the stabilization of beta-catenin that in turn feeds the affected cells with a permanent mitogenic signal. We describe here a new APC domain, the beta-catenin inhibitory domain (CID) of APC located between the second and third 20 amino acid repeats and therefore present in many truncated APC products found in human tumours. In truncated APC, the CID is absolutely necessary to down-regulate the transcriptional activity and the level of beta-catenin, even when an axin/conductin binding site is present. The activity of the CID is dramatically reduced in several colon cancer cell lines and can be inhibited by shorter truncated APC lacking the CID. The CID is a direct target of the selective pressure acting on APC during tumourigenesis. It explains the interdependence of both APC mutations, not only in colorectal but also in duodenal and desmoid tumours.

Functional definition of the mutation cluster region of adenomatous polyposis coli in colorectal tumours.

The mutation cluster region (MCR) of adenomatous polyposis coli (APC) is located within the central part of the open reading frame, overlapping with the region encoding the 20 amino acid repeats (20R) that are beta-catenin-binding sites. Each mutation in the MCR leads to the synthesis of a truncated APC product expressed in a colorectal tumour. The MCR extends from the 3' border of the first 20R coding region to approximately the middle of the third 20R coding region, reflecting both positive and negative selections of the N- and C-terminal halves of the APC protein in colon cancer cells, respectively. In contrast, the second 20R escapes selection and can be either included or excluded from the truncated APC products found in colon cancer cells. To specify the functional outcome of the selection of the mutations, we investigated the beta-catenin binding capacity of the first three 20R in N-terminal APC fragments. We found in co-immunoprecipitation and intracellular co-localization experiments that the second 20R is lacking any beta-catenin binding activity. Similarly, we also show that the tumour-associated truncations abolish the interaction of beta-catenin with the third 20R. Thus, our data provide a functional definition of the MCR: the APC fragments typical of colon cancer are selected for the presence of a single functional 20R, the first one, and are therefore equivalent relative to beta-catenin binding.