Mutant strains of Escherichia coli lacking global regulators, arcA and fis, demonstrate better growth fitness by pathway reprogramming under acetate metabolism

Global regulatory transcription factors play a significant role in controlling microbial metabolism under genetic and environmental perturbations. A systems-level effect of carbon sources such as acetate on microbial metabolism under disrupted global regulators has not been well established. Acetate is one of the substrates available in a range of nutrient niches such as the mammalian gut and high-fat diet. Therefore, investigating the study on acetate metabolism is highly significant. It is well known that the global regulators arcA and fis regulate acetate uptake genes in E. coli under glucose condition. In this study, we deciphered the growth and flux distribution of E.coli transcription regulatory knockout mutants ΔarcA, Δfis and double deletion mutant, ΔarcAfis under acetate using 13C-Metabolic Flux Analysis which has not been investigated before. We observed that the mutants exhibited an expeditious growth rate (~1.2-1.6 fold) with a proportionate increase in acetate uptake rates compared to the wild-type. 13C-MFA displayed the distinct metabolic reprogramming of intracellular fluxes, which conferred an advantage of faster growth with better carbon usage in all the mutants. Under acetate metabolism, the mutants exhibited higher fluxes in the TCA cycle (~18-90%) and lower gluconeogenesis flux (~15-35%) with the proportional increase in growth rate. This study reveals a novel insight by stating the sub-optimality of the wild-type strain grown under acetate substrate aerobically. These mutant strains efficiently oxidize acetate to acetyl-CoA and therefore are potential candidates that can serve as a precursor for the biosynthesis of isoprenoids, biofuels, vitamins and various pharmaceutical products.

Visualizing reactive astrogliosis extends survival in glioblastoma patients

ABSTRACTGlioblastoma is a devastating brain tumor with dismal prognosis of only 15-month survival regardless of surgical resection with few alternatives. Here, we report a reactive astrogliosis-targeted neuroimaging technique using the fusion of 11C-acetate PET and MRI (AcePET) extended the overall survival of patients by 5.25 months compared to conventional MRI-guided surgery. Targeted biopsy of 11C-acetate uptake-increased regions showed the signs of reactive astrogliosis with cancer stem cells at the boundary of high-grade gliomas. The appearance of marginal reactive astrogliosis and MCT1-dependent 11C-acetate uptake was recapitulated in U87MG-orthotophic models. U87MG-derived excessive glutamate caused reactive astrogliosis and aberrant astrocytic GABA-release, which subsequently reduced neuronal glucose uptake through glucose transporter-3 (GLUT3). We propose AcePET-guided surgery, visualizing reactive astrogliosis, as an advanced surgical strategy to improve glioblastoma patient survival.One-Sentence SummaryAcePET-guided surgery extends patient survival by visualizing reactive astrogliosis at the tumor margin

Acetate uptake by PHA-accumulating and non-PHA-accumulating organisms in activated sludge from an aerobic sequencing batch reactor fed with acetate

The present study was conducted to evaluate the specific acetate uptake rates of microorganisms with and without polyhydroxyalkanoates (PHA) accumulation. Activated sludge was aerobically incubated with 75 mgC L−1 radiolabeled or non-labeled acetate, and acetate consumption and PHA accumulation were monitored. Microorganisms were quantified as follows: all microbial cells by DAPI staining, whole acetate utilizing organisms by microautoradiography, and PHA-accumulating organisms by staining with Nile blue A. The abundance of acetate-utilizing organisms without PHA accumulation was also calculated from the outcomes. The estimate of acetate utilized by PHAAOs included both the acetate converted to PHA and that used to supply reducing power and ATP. Acetate utilized by PHAAOs and non-PHAAOs were divided by their respective abundances to obtain their respective specific acetate uptake rates: PHAAOs ranged between 5.3 and 8.0 × 10−10 mgC cell−1 h−1, and non-PHAAOs ranged between 2.8 and 4.2 × 10−10 mgC cell−1 h−1.

Acetate uptake efficiency of polyphosphate-accumulating organisms under exposure to surfactants

We investigated the influence of surfactants such as linear alkylbenzene sulfonates (LAS) and alcohol ethoxylates (AE) on acetate uptake by polyphosphate-accumulating organisms (PAOs) under anaerobic conditions, using the phosphate requirement for acetate uptake (+ΔP/−ΔAc ratio). In order to estimate the +ΔP/−ΔAc ratio, anaerobic batch tests were conducted using activated sludge collected from an anaerobic/oxic sequencing batch reactor used to treat municipal wastewater continuously supplemented with a detergent containing LAS and AE. We demonstrated that LAS and AE have both positive and negative impacts on acetate uptake by PAOs. The disadvantage is that long-term exposure to the detergent inhibits acetate uptake by PAOs, thus deteriorating the efficiency, even if the surfactants are no longer present during the tests. Furthermore, the existence of LAS and/or AE with acetate further diminishes the efficiency. The advantage is that LAS and AE are potential sources of polyhydroxyalkanoate for PAOs, because acetate is produced from the surfactants under anaerobic conditions.