Short-Term Temporal Metabolic Behavior in Halophilic Cyanobacterium Synechococcus sp. Strain PCC 7002 after Salt Shock
Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
Engineering Biology Research Center, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan
Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan
Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
Biomass Engineering Program, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan
Author to whom correspondence should be addressed.
Present address: Biological Resource and Post-Harvest Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
Metabolites 2019, 9(12), 297; https://doi.org/10.3390/metabo9120297
Received: 31 October 2019 / Revised: 2 December 2019 / Accepted: 4 December 2019 / Published: 5 December 2019
(This article belongs to the Special Issue Metabolomics-Driven Biotechnology)
In response to salt stress, cyanobacteria increases the gene expression of Na+/H+ antiporter and K+ uptake system proteins and subsequently accumulate compatible solutes. However, alterations in the concentrations of metabolic intermediates functionally related to the early stage of the salt stress response have not been investigated. The halophilic cyanobacterium Synechococcus sp. PCC 7002 was subjected to salt shock with 0.5 and 1 M NaCl, then we performed metabolomics analysis by capillary electrophoresis/mass spectrometry (CE/MS) and gas chromatography/mass spectrometry (GC/MS) after cultivation for 1, 3, 10, and 24 h. Gene expression profiling using a microarray after 1 h of salt shock was also conducted. We observed suppression of the Calvin cycle and activation of glycolysis at both NaCl concentrations. However, there were several differences in the metabolic changes after salt shock following exposure to 0.5 M and 1 M NaCl: (i): the main compatible solute, glucosylglycerol, accumulated quickly at 0.5 M NaCl after 1 h but increased gradually for 10 h at 1 M NaCl; (ii) the oxidative pentose phosphate pathway and the tricarboxylic acid cycle were activated at 0.5 M NaCl; and (iii) the multi-functional compound spermidine greatly accumulated at 1 M NaCl. Our results show that Synechococcus sp. PCC 7002 acclimated to different levels of salt through a salt stress response involving the activation of different metabolic pathways.