Enhanced synthesis of poly gamma glutamic acid by increasing the intracellular reactive oxygen species in the Bacillus licheniformis Δ1-pyrroline-5-carboxylate dehydrogenase gene ycgN-deficient strain

Abstract

Poly gamma glutamic acid (γ-PGA) is an anionic polyamide with numerous applications. Previous studies revealed that L-proline metabolism is implicated in a wide range of cellular processes by increasing intercellular reactive oxygen species (ROS) generation. However, the relationship between L-proline metabolism and γ-PGA synthesis has not yet been analyzed. In this study, our results confirmed that deletion of Δ1-pyrroline-5-carboxylate dehydrogenase gene ycgN in Bacillus licheniformis WX-02 increased γ-PGA yield to 13.91 g L, 85.22% higher than that of the wild type (7.51 g L). However, deletion of proline dehydrogenase gene ycgM had no effect on γ-PGA synthesis. Furthermore, a 2.92-fold higher P5C content (19.24 μmol gDCW) was detected in the ycgN deficient strain WXΔycgN, while the P5C levels of WXΔycgM and the double mutant strain WXΔycgMN showed no difference, compared to WX-02. Moreover, the ROS level of WXΔycgN was increased by 1.18-fold, and addition of n-acetylcysteine (antioxidant) decreased its ROS level, which further reduced γ-PGA synthesis capability of WXΔycgN. Collectively, our results demonstrated that proline catabolism played an important role in maintaining ROS homeostasis, and deletion of ycgN-enhanced P5C accumulation, which induced a transient ROS signal to promote γ-PGA synthesis in B. licheniformis.

Investigation of Glutamate Dependence Mechanism for Poly-γ-glutamic Acid Production in Bacillus subtilis on the Basis of Transcriptome Analysis

“…revealed that the overexpression of the gene ycgM (encoding proline dehydrogenase) and ycgN (encoding Δ 1 -pyrroline-5-carboxylate dehydrogenase) decreases the production of γ-PGA by B. licheniformis WX-02 by disturbing the intrinsic reactive oxygen species level . In contrast to B.…”

“…Real-time reverse transcription (qRT-PCR) was applied to confirm the RNA-Seq results. The procedure of qRT-PCR was performed as described before . The specific primers used for qRT-PCR are presented in Table S2.…”

Celastrol Combats Methicillin‐Resistant Staphylococcus aureus by Targeting Δ1‐Pyrroline‐5‐Carboxylate Dehydrogenase

“…Proline metabolism is of vital importance for bacterial growth. Li et al [11] reported that the lag phase of deletion of the ycgN gene (the gene for P5CDH in B. licheniformis) in B. licheniformis was prolonged by 4-8 h compared to the WT. Accordingly, a similar situation was also observed in S. aureus.…”

“…PRODH and P5CDH are the two enzymes in this reaction, but P5CDH could affect electron transfer and the TCA cycle. Importantly, Halsey [10] and Li et al [11] reported that P5CDH-deficient strains of MRSA had significant growth yield defects whereas PRODH-deficient strains did not. Therefore, P5CDH was speculated to be a target of celastrol (Figure 4D).…”

“…Importantly, a mutant of P5CDH could influence the growth of bacteria. [ 10 , 11 ] Therefore, we speculate that P5CDH is a promising target for the development of antibacterial drugs.…”