System-wide analysis of manganese starvation-induced metabolism in key elements of Lactobacillus plantarum

To analyze the response mechanisms of Lactobacillus plantarum against manganese starvation stress, different metabolisms from physiology, proteomics and transporters aspects in L. plantarum CCFM 436 were systematically investigated. The kinetics of cell growth (mu(max)) decreased from 0.310 to 0.256 h(-1), while thinner cell morphology was observed by transmission electron microscopy under Mn-starvation conditions. Gas chromatography-mass spectrometry analysis indicated that membrane mobility and compactness increased, with a higher proportion of unsaturated fatty acids and cyclopropane fatty acids. High-performance liquid chromatography analysis showed that intracellular Asp, Glu, and Arg contents, closely related to energy metabolism, were significantly increased. Fourier transform infrared spectroscopy proved that some functional groups (N-H and O=C-OH) were significantly affected by Mn starvation. Comparative two-dimensional proteomic analysis identified 73 proteins that differed significantly under Mn starvation conditions. These differentially expressed proteins involved in carbohydrate, amino acid and transcription/translation metabolisms and stress response were categorized as crucial components required to resist manganese starvation stress. Moreover, qRT-PCR analysis proved that MntH 1-5, negatively regulated by MntR, acted as potential Mn importers under Mn starvation conditions. The proposed coordinated mechanism model provides a reference for, and insight into, the intracellular metabolism of LAB strains.