In oleaginous yeast, nitrogen limitation is a critical parameter for lipid synthesis. GATA-family transcriptional factor GAT1, a member of the target of rapamycin (TOR) pathway and nitrogen catabolite repression (NCR), regulates nitrogen uptake and utilization. Therefore, it is significant to study the SpGAT1 regulatory mechanism of lipid metabolism for conversion of biomass to microbial oil in [Formula: see text] zwy-2-3.Compared with WT, [Formula: see text], and OE::gat1, the lipid yield of OE::gat1 increased markedly in the low carbon and nitrogen ratio (C/N ratio) mediums, while the lipid yield and residual sugar of [Formula: see text] decreased in the high C/N ratio medium. According to yeast two-hybrid assays, SpGAT1 interacted with SpMIG1, and its deletion drastically lowered SpMIG1 expression on the high C/N ratio medium. MIG1 deletion has been found in earlier research to affect glucose metabolic capacity, resulting in a prolonged lag period. Therefore, we speculated that SpGAT1 influenced glucose consumption rate across SpMIG1. Based on yeast one-hybrid assays and qRT-PCR analyses, SpGAT1 regulated the glyoxylate cycle genes ICL1, ICL2, and pyruvate bypass pathway gene ACS, irrespective of the C/N ratio. SpGAT1 also could bind to the ACAT2 promoter in the low C/N medium and induce sterol ester (SE) accumulation.Our findings indicated that SpGAT1 positively regulated lipid metabolism in S.podzolica zwy-2-3, but that its regulatory patterns varied depending on the C/N ratio. When the C/N ratio was high, SpGAT1 interacted with SpMIG1 to affect carbon absorption and utilization. SpGAT1 also stimulated lipid accumulation by regulating essential lipid anabolism genes. Our insights might spur more research into how nitrogen and carbon metabolism interact to regulate lipid metabolism.
Endophytic fungi are a rich source of novel organic compounds with interesting biological activities and a high level of biodiversity. A total of 76 endophytic fungus strains were isolated from 13 species of plants. Through a preliminary screening and fermentation assay, a fungi named ML-GEN.1 isolated from Strobilanthes cusia was found and the lipid content reached 59%. This is the first report of oleaginous microorganism which is isolated from S. cusia. ML-GEN.1 was identified as Fusarium sp.ML-GEN.1 through morphological and molecular methods. Similar to vegetable oils, the fatty acid composition of lipid from Fusarium sp. ML-GEN.1 contained oleic acid (41.66%), palmitic acid (23.26%), linoleic acid (19.18%), and the unsaturated fatty acids amounted to about 61%. In waste molasses fermentation, Fusarium sp. ML-GEN.1 accumulated lipid to 29% of biomass when various sugars in waste molasses were utilized as the carbon source. The biomass was 22.8 g/L, which was much higher than the original value (12.7 g/L). Key words: Oleaginous endophytic fungi, biodiesel, waste molasses.
Phytases play a very important role in increasing phytate digestion and reducing phosphorus pollution in the environment, and phytate-degrading bacteria have a ubiquitous distribution in the environment. Due to its extremely harsh environment, the Tibetan Plateau breeds possibly abundant, extreme microorganisms. In this research, 67 phytate-degrading bacteria were isolated from different habitats in the Tibetan Plateau. Among all isolates, 40.3% were screened from farmland, 25.3% from wetland, 4.5% from saline-alkaline soil, 7.5% from hot springs, and 22.4% from lawns, which showed that the distribution of the phytate-degrading bacteria varied with habitats. By the PCR-RFLP method, 16 different species were identified and named, 4 of which are reported for the first time as phytate-degrading bacteria, that is, Uncultured Enterococcus sp. GYPB01, Bacillaceae bacterium strain GYPB05, Endophytic bacterium strain GYPB16, and Shigella dysenteria strain GYPB22. Through the assay of phytase activity of 16 strains, Klebsiella sp. strain GYPB15 displayed the highest capability of phytase production. Through analysis of the optimum pH, the optimum temperature, and the thermal stability of enzyme from 16 strains, some especial phytate-degrading bacteria were obtained. Our findings clearly indicate a good relation between the composition of the soils from the different environments in the Tibetan Plateau and populations of cultivable phytate-degrading bacteria. Moreover, extreme harsh soils are logically the best soils in which to find some strains of phytate-degrading bacteria for exploiting in the fields of biotechnology and industry.
Abstract Background ： Dunaliella salina can produce a large amount of glycerol under salt stress, which can quickly adapt to the change of external salt concentration, and glycerol is one of the ideal energy sources. In recent years, it has been reported that Mitogen-activated protein kinase cascade pathway plays an important role in regulating salt stress, and in Dunaliella tertiolecta DtMAPK can regulate glycerol synthesis under salt stress. Therefore, it is urgent to study the relationship between MAPK cascade pathway and salt stress in D. salina , and help it to increase the content of glycerol. Results ： In our study, we identified and analyzed the alternative splicing of DsMEK1 (DsMEK1-X1, DsMEK1-X2) from the unicellular green alga D. salina . DsMEK1-X1, DsMEK1-X2 both localized in the cytoplasm. The qRT-PCR assays showed that DsMEK1-X2 induced by salt stress. Overexpression of DsMEK1-X2 revealed a higher increase rate of glycerol compared to the control and DsMEK1-X1-oe under salt stress. The expression of DsGPDH2/3/5/6 increased in DsMEK1-X2-oe strains compared to the control under salt stress. It means that DsMEK1-X2 is involved in the regulation of DsGPDHs expression and glycerol overexpression under salt stress. Overexpression of DsMEK1-X1 increasing the proline content and reducing the MDA content under salt stress, and DsMEK1-X1 can regulate oxidative stress, thus we speculate that DsMEK1-X1 can reduce the damage of oxidative under salt stress. Yeast two-hybrid analysis showed that DsMEK1-X2 can interact with DsMAPKKK1/2/3/9/10/17 and DsMAPK1, however, DsMEK1-X1 interacted with neither upstream MAPKKK nor downstream MAPK. DsMEK1-X2-oe transgenic lines increased the expression of DsMAPKKK1/3/10/17 and DsMAPK1, and DsMEK1-X2-RNAi lines decreased the expression of DsMAPKKK2/10/17. DsMEK1-X1-oe transgenic lines do not increased genes expression, except for DsMAPKKK9. Conclusion ： Our findings demonstrate that DsMEK1-X1 and DsMEK1-X2 can response to salt stress in two different pathways, DsMEK1-X1 response to salt stress by reducing oxidative damage, however, DsMAPKKK1/2/3/9/10/17- DsMEK1-X2-DsMAPK1 cascade is involved in the regulated of DsGPDH expression and thus glycerol synthesis under salt stress.
Abstract Algae provide a solar powered pathway to capture and sequester carbon by injecting stable fucan made from carbon dioxide into the ocean 1–4 . Stability of the pathway is at odds with the presence of marine bacteria with genes of enzymes that can digest fucan and release the carbon dioxide 5 . Biochemical explanations for stable fucan remain hypothetical 6 . We assembled a biological carbon cycle model and found phosphate limitation enhanced fucan synthesis by algae, stopped digestion by bacteria and thereby stabilized the fucan carbon sequestration pathway. Marine microalgae Glossomastix sp. PLY432 increased synthesis of fucan, a part of its extracellular matrix, under nutrient-growth limiting conditions. Rate and extent of fucan digestion by a marine, isolated bacterium of the Akkermansiaceae family decreased with decreasing phosphate concentration. Phosphate starvation restricted bacterial growth rate, biomass yield and in turn increased the amount of stable fucan. Phosphate is universally required for growth but rare relative to glycan carbon in photosynthesis-derived ecosystems. The fact that phosphate is required for replication, transcription and translation explains why bacteria can digest gigatons of laminarin with a few enzymes, but not fucan during nutrient limited algal blooms. We conclude phosphate starvation constrains the ability of bacteria to digest fucan, which evolves to maintain stability around algal cells and consequentially also to keep carbon dioxide in the ocean.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)