Proteomic Responses To Inoculum Sizes Of Streptomyces Lydicus Under Fermentation

Streptomyces lydicus has been reported to produce an antibiotic of streptolydigin,which inhibits bacterial RNA polymerase by inhibiting initiation, elongation, andpyrophosphorolysis. To improve the antibiotic activety and streptolydigin productionand to understand the physiological characteristics of S. lydicus, the strain S. lydicusE9was applied to explore the changes in cellular growth, intracellular proteins andmetabolites at different pitching ratios in this work. The main results were displayedas follow:Firstly, there are significant differences of growth of S. lydicus E9at differentpitching ratios (1%,10%,30%, v/v). The high inoculation size (30%) significantlyshortened the cellular lag phase and enhanced the levels of streptolydigin products inS. lydicus.Secondly, a total of242differentially expressed spots corresponding to195proteins were identified by MALDI-TOF MS and MALDI-TOF MS/MS afterqualitative and quantitative analyses. These proteins were involved in severalmetabolic pathways and bioprocesses. Among them, the levels of beta-glucosidaseand UTP-glucose-1-phosphate uridylyltransferase, involved in the glucose andmaltose biosynthesis pathways from starch, were significantly increased at the highpitching ratio. The expression levels of PfkA2, PfkA3, Zwf2, SucD, GalE1, GatB,TktA1and ThcA, associated with glycolysis, pentose phosphate pathway, TCA cycleand amino acid metabolism, were dramatically elevated at high pitching ratio.However, the levels of glutamine synthetase (GlnA, GlnII, GltD) were decreased withthe increases of pitching ratio, revealing that pitching ratio altered the glutaminesynthetase levels and consequently regulated the streptolydigin production of S.lydicus E9. In addition, the expression levels of proteins involved in secondarymetabolism and cell redox homeostasis were significantly changed at differentpitching ratios.Finnally, metabolomics analysis revealed that the levels of metabolites weredramatically impacted by pitching ratios. A total of32differential expressionmetabolites were detected with GC-TOF MS,14of which were amino acids. Theirlevels were declined with the increase of pitching ratios. PCA analysis revealed that8 metabolites, including glucopyranoside、maltose、CAMP、glycine、proline、lysine、isoleucine and valine, were taken as potential biomarker.Taken together, these findings provide new insights into S. lydicus E9inresponses to pitching ratios in view of proteomics and metabolomics and potentialstrategies to improve streptolydigin production of S. lydicus E9.