Project description:In this study, we screened morphological mutants in the filamentous fungus N. crassa. Of the 90 morphological mutants screened, 14 mutants exhibited considerably higher viscosity compared with that of the wild type strain, and only 2 mutants showed low-viscosity morphologies in submerged culture. We observed that disruption of gul-1 (NCU01197), which encodes an mRNA binding protein involved in cell wall remodeling, caused pellet formation as the fermentation progressed, and resulted in the most significant decrease in viscosity of culture broth. Moreover, over-expression of gul-1 caused dramatically increased viscosity, suggesting that the gul-1 had an important function in mycelial morphology during submerged cultivation. Additionally, the deletion of gul-1 caused increased protein secretion, probably due to a defect in cell wall integrity, suggesting this as an alternative strategy of strain improvement for enzyme production. To confirm practical application, deleting gul-1 in the hyper-cellulase producing strain (∆ncw-1∆Ncap3m) significantly reduced the viscosity of culture broth.
Project description:BackgroundThe cellulolytic fungus Neurospora crassa is considered a potential host for enzyme and bioethanol production. However, large scale applications are hindered by its filamentous growth. Although previous investigations have shown that mycelial morphology in submerged culture can be controlled by altering physical factors, there is little knowledge available about the potential for morphology control by genetic modification.ResultsIn this study, we screened morphological mutants in the filamentous fungus N. crassa. Of the 90 morphological mutants screened, 14 mutants exhibited considerably higher viscosity compared with that of the wild type strain, and only two mutants showed low-viscosity morphologies in submerged culture. We observed that disruption of gul-1 (NCU01197), which encodes an mRNA binding protein involved in cell wall remodeling, caused pellet formation as the fermentation progressed, and resulted in the most significant decrease in viscosity of culture broth. Moreover, over-expression of gul-1 caused dramatically increased viscosity, suggesting that the gul-1 had an important function in mycelial morphology during submerged cultivation. Transcriptional profiling showed that expression of genes encoding eight GPI-anchored cell wall proteins was lowered in Δgul-1 while expression of genes associated with two non-anchored cell wall proteins was elevated. Meanwhile, the expression levels of two hydrophobin genes were also significantly altered. These results suggested that GUL-1 affected the transcription of cell wall-related genes, thereby influencing cell wall structure and mycelial morphology. Additionally, the deletion of gul-1 caused increased protein secretion, probably due to a defect in cell wall integrity, suggesting this as an alternative strategy of strain improvement for enzyme production. To confirm practical applications, deletion of gul-1 in the hyper-cellulase producing strain (∆ncw-1∆Ncap3m) significantly reduced the viscosity of culture broth.ConclusionsUsing the model filamentous fungus N. crassa, genes that affect mycelial morphology in submerged culture were explored through systematic screening of morphological mutants. Disrupting several candidate genes altered viscosities in submerged culture. This work provides an example for controlling fungal morphology in submerged fermentation by genetic engineering, and will be beneficial for industrial fungal strain improvement.
Project description:Wild-type diploid cells were shifted from yeast-form growth in SHAD liquid (plentiful glucose and ammonium) to filamentous-form growth on SLAD agar (low ammonium). Samples of filamentous-form cells were collected hourly for 10 hours. Filamentous-form and yeast-form exponential-phase targets were co-hybridized. Keywords: time-course
Project description:<p>Adaptive laboratory evolution has proven highly effective for obtaining microorganisms with enhanced capabilities. Yet, this method is inherently restricted to the traits that are positively linked to cell fitness, such as nutrient utilization. Here, we introduce coevolution of obligatory mutualistic communities for improving secretion of fitness-costly metabolites through natural selection. In this strategy, metabolic cross-feeding connects secretion of the target metabolite, despite its cost to the secretor, to the survival and proliferation of the entire community. We thus co-evolved wild-type lactic acid bacteria and engineered auxotrophic <em>Saccharomyces cerevisiae</em> in a synthetic growth medium leading to bacterial isolates with enhanced secretion of two B-group vitamins, viz., riboflavin and folate. The increased production was specific to the targeted vitamin, and evident also in milk, a more complex nutrient environment that naturally contains vitamins. Genomic, proteomic and metabolomic analyses of the evolved lactic acid bacteria, in combination with flux balance analysis, showed altered metabolic regulation towards increased supply of the vitamin precursors. Together, our findings demonstrate how microbial metabolism adapts to mutualistic lifestyle through enhanced metabolite exchange.</p>
Project description:Bariatric surgeries remain the most effective treatments for sustained weight loss and remission of type 2 diabetes. In addition to decreased body weight and improved glucose regulation, these procedures also dramatically increase secretion of several gut hormones including GLP-1. Despite these benefits, there are deleterious side effects to these procedures that include an increased incidence of iron-deficiency related anemias. The transcription factor HIF2a is heavily expressed in the duodenum and regulates the molecular machinery of iron absorption from the lumen. Lower iron levels after both gastric bypass and sleeve gastrectomy procedures occur despite dramatic upregulation of HIF2a signaling in the duodenum and are likely the result of increased hepcidin levels. Low iron diets also stimulate increased HIF2a signaling in the duodenum and produce effects similar to bariatric surgery that include reduced body weight/fat, improved glucose regulation and increased secretion of the GLP-1. Gut-specific deletion of VHL results in a constitutive upregulation of HIF2a signaling in the small intestine and produces a dramatic phenotype that includes reduced body weight/fat, improved glucose tolerance and increased GLP-1 secretion from the intestine. These data demonstrate an important role of HIF2a signaling in the duodenum to regulate multiple aspects of systemic metabolism and gut hormone secretion pointing towards critical cross-talk between the systems that regulate iron and other aspects of systemic physiology important to prevalent metabolic diseases.
Project description:Bariatric surgeries remain the most effective treatments for sustained weight loss and remission of type 2 diabetes. In addition to decreased body weight and improved glucose regulation, these procedures also dramatically increase secretion of several gut hormones including GLP-1. Despite these benefits, there are deleterious side effects to these procedures that include an increased incidence of iron-deficiency related anemias. The transcription factor HIF2a is heavily expressed in the duodenum and regulates the molecular machinery of iron absorption from the lumen. Lower iron levels after both gastric bypass and sleeve gastrectomy procedures occur despite dramatic upregulation of HIF2a signaling in the duodenum and are likely the result of increased hepcidin levels. Low iron diets also stimulate increased HIF2a signaling in the duodenum and produce effects similar to bariatric surgery that include reduced body weight/fat, improved glucose regulation and increased secretion of the GLP-1. Gut-specific deletion of VHL results in a constitutive upregulation of HIF2a signaling in the small intestine and produces a dramatic phenotype that includes reduced body weight/fat, improved glucose tolerance and increased GLP-1 secretion from the intestine. These data demonstrate an important role of HIF2a signaling in the duodenum to regulate multiple aspects of systemic metabolism and gut hormone secretion pointing towards critical cross-talk between the systems that regulate iron and other aspects of systemic physiology important to prevalent metabolic diseases.