Acceleration of cell lysis (Fig. 6). These changes are consistent with those caused by eliminating Cu2+ from the medium (Fig. 5). Therefore, wesuggest that a prolonged stationary phase and rapid pH rebound are caused by increases in PHB. emPAI semiquantitative (Additional file 1: Table S3) comparative analysis and qRT-PCR results showed upregulation of EF-G, KAS II, and ALDH in the medium to which Cu2+ had been added (Table 2; Fig. 3). EF-G is a translation elongation factor that catalyzes the GTPdependent ribosomal translocation step during translation elongation [25]. Crystal Celecoxib proteins are proteins produced ribosomally, whose expressions require translation elongation factors. Thus, upregulation of EF-G indicates increased active translation promoting crystal protein production. We suggest that the extra energy required for translation comes from utilization of more PHB deposits. KAS II takes part in fatty acid synthesis. It catalyzes the condensation reaction of fatty acid synthesis by addition of two carbons from malonyl-ACP to an acyl acceptorLiu et al. Microb Cell Fact (2015) 14:Page 11 ofand has a preference for short chain acid substrates [26, 27]. ALDH acts on the aldehyde or oxo group of donors with NAD or NADP as an acceptor. It eliminates aldehydes produced by over-oxidation of substances in vivo (such as unsaturated fatty acids) and thus performs an important function in detoxification [28?0]. During alcohol detoxification, ALDH further oxidizes acetaldehyde to acetic acid, which is used in the TCA cycle [31]. Upregulation of KAS II and ALDH support the hypothesis that Cu2+ promotes changes in metabolism in B. thuringiensis X022.Conclusions In summary, B. thuringiensis X022 mainly expresses Cry1Ca, Cry1Ac, and Cry1Da. Cu2+ increases the expression of Cry1Da and Cry1Ca, and also enhances the toxicity of fermentation broth to S. exigua and H. armigera. In this work, mass spectrometry-based proteomics techniques, with qRT-PCR, were used to explore the molecular mechanisms of the effects caused by Cu2+ for the first time. Results showed that Cu2+ addition causes downregulation of environmental information-processing proteins, glycan biosynthesis and metabolism proteins, and also causes upregulation of PhaR, BDH, EF-G, KAS II, and ALDH. It is suggested that Cu2+ increased the expression of PhaR and consequently changed the carbon carbon-energy flow. Thereby reducing extracellular polysaccharide production and accelerating cell lysis. More carbon sources can be used to synthesize intracellular PHB. Increases in PHB as a storage material induces a prolonged stationary phase, rapid pH rebound, and releasing more energy for protein translation, ultimately raising ICP production (Fig. 9). Methods16S rRNA gene sequencing and analysisFig. 9 Metabolic changes caused by Cu2+ in B. thuringiensis X022. indicates promoting; indicates promoting speculated; indicates inhibiting. Cu2+ upregulates the expression of PhaR and consequently changes the carbon flow in B. thuringiensis X022. Cu2+ addition causes downregulation of environmental information-processing proteins, glycan biosynthesis and metabolism proteins, and, therefore, reduces extracellular polysaccharide PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/17139194 production, resulting in accelerated cell lysis. More carbon sources can be used to synthesize intracellular PHB. Increases in PHB as a storage material induces a prolonged stationary phase, rapid pH rebound, and releasing more energy for protein translation, ultimately increasin.
