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Rare earth elements (RE) are indispensable metallic resources in the production of advanced materials, hence, a cost- and energy-effective recovery process is required to meet the rapidly increasing RE demand. Here, we propose an artificial RE recovery approach that uses a functional silk displaying a RE-recognizing peptide. Using the piggyBac system, we constructed a transgenic silkworm in which one or two copies of the gene coding for the RE-recognizing peptide (Lamp1) was fused with that of the fibroin L (FibL) protein. The purified FibL-Lamp1 fusion protein from the transgenic silkworm was able to recognize dysprosium (Dy3+), a RE, under physiological conditions. This method can also be used with silk from which sericin has been removed. Furthermore, the Dy-recovery ability of this silk was significantly improved by crushing the silk. Our simple approach is expected to facilitate the direct recovery of RE from an actual mixed solution of metal ions, such as seawater and industrial wastewater, under mild conditions without additional energy input.

We developed a metabolically engineered yeast which produces lactic acid efficiently. In this recombinant strain, the coding region for pyruvate decarboxylase 1 (PDC1) on chromosome XII is substituted for that of thel-lactate dehydrogenase gene (LDH) through homologous recombination. The expression of mRNA for the genome-integratedLDHis regulated under the control of the nativePDC1promoter, whilePDC1is completely disrupted. Using this method, we constructed a diploid yeast transformant, with each haploid genome having a single insertion of bovineLDH. Yeast cells expressingLDHwere observed to convert glucose to both lactate (55.6 g/liter) and ethanol (16.9 g/liter), with up to 62.2% of the glucose being transformed into lactic acid under neutralizing conditions. This transgenic strain, which expresses bovineLDHunder the control of thePDC1promoter, also showed high lactic acid production (50.2 g/liter) under nonneutralizing conditions. The differences in lactic acid production were compared among four different recombinants expressing a heterologousLDHgene (i.e., either the bovineLDHgene or theBifidobacterium longum LDHgene): two transgenic strains with 2μm plasmid-based vectors and two genome-integrated strains.

UDP-galactose reaches the Golgi lumen through the UDP-galactose transporter (UGT) and is used for the galactosylation of proteins and lipids. Ceramides and diglycerides are galactosylated within the endoplasmic reticulum by the UDP-galactose:ceramide galactosyltransferase. It is not known how UDP-galactose is transported from the cytosol into the endoplasmic reticulum. We transfected ceramide galactosyltransferase cDNA into CHOlec8 cells, which have a defective UGT and no endogenous ceramide galactosyltransferase. Cotransfection with the human UGT1 greatly stimulated synthesis of lactosylceramide in the Golgi and of galactosylceramide in the endoplasmic reticulum. UDP-galactose was directly imported into the endoplasmic reticulum because transfection with UGT significantly enhanced synthesis of galactosylceramide in endoplasmic reticulum membranes. Subcellular fractionation and double label immunofluorescence microscopy showed that a sizeable fraction of ectopically expressed UGT and ceramide galactosyltransferase resided in the endoplasmic reticulum of CHOlec8 cells. The same was observed when UGT was expressed in human intestinal cells that have an endogenous ceramide galactosyltransferase. In contrast, in CHOlec8 singly transfected with UGT 1, the transporter localized exclusively to the Golgi complex. UGT and ceramide galactosyltransferase were entirely detergent soluble and form a complex because they could be coimmunoprecipitated. We conclude that the ceramide galactosyltransferase ensures a supply of UDP-galactose in the endoplasmic reticulum lumen by retaining UGT in a molecular complex.

For intracellular pathogens, residence in a vacuole provides a shelter against cytosolic host defense to the cost of limited access to nutrients. The human pathogen Chlamydia trachomatis grows in a glycogen-rich vacuole. How this large polymer accumulates there is unknown. We reveal that host glycogen stores shift to the vacuole through two pathways: bulk uptake from the cytoplasmic pool, and de novo synthesis. We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion. Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase. Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens. DOI: http://dx.doi.org/10.7554/eLife.12552.001, eLife digest Chlamydia trachomatis is the most common sexually transmitted bacteria that causes disease. Infections often do not produce any obvious symptoms, but can lead to infertility or other severe problems if left untreated. This microbe is also the leading cause of blindness by an infectious agent.The bacteria grow in the human body by infecting host cells. Inside these cells, the bacteria are found inside compartments known as inclusions, which protect them from the host’s defense responses and enable them to create a comfortable environment for themselves. However, this comes at a cost because the bacteria lose immediate access to the nutrients in the rest of the host cell. Thus, C.trachomatis has developed ways to import these nutrients into inclusions, and, more generally, to take the control of its interactions with the host cell. The inclusions built up by C. trachomatis contain a high amount of glycogen, a carbohydrate that generally acts as an energy storage molecule. Although this observation was made many decades ago, the molecular mechanism by which such a large molecule accumulates in the inclusion has not been clarified. Gehre et al. have now used a variety of cell biology techniques to address this question. The experiments show that there are two different pathways through which glycogen accumulates within the inclusion. Some glycogen is transported in bulk from the interior of the host cell into the inclusion. However, the bacteria also make new glycogen in the inclusion from a building block molecule called UDP-glucose. To do this, the bacteria recruit a host transport molecule to the membrane that surrounds the inclusion. This transport molecule brings UDP-glucose into the inclusion, where an enzyme called glycogen synthase – which is released by the bacteria – uses the UDP-glucose to make glycogen. The C. trachomatis glycogen synthase is unusual because most other bacteria can only make glycogen from another type of glucose. By using both pathways, C. trachomatis is able to trap most of the glycogen stores of the infected cell within the inclusion so that they are inaccessible to the host but ready for the bacteria to use. Previous work has shown that C. trachomatis is much better at accumulating glycogen than other Chlamydia bacteria are. Therefore, a future challenge will be to find out exactly how this helps C. trachomatis survive inside human cells. DOI: http://dx.doi.org/10.7554/eLife.12552.002