Abstract
Shewanella algae, which produces tetrodotoxin and exists in various seafoods, can cause human diseases, such as spondylodiscitis and bloody diarrhea. In the present study, we focused on the temporal, dynamic process in salt-stressed S. algae by monitoring the gene transcript levels at different time points after high salt exposure. Transcript changes in amino acid metabolism, carbohydrate metabolism, energy metabolism, membrane transport, regulatory functions, and cellular signaling were found to be important for the high salt response in S. algae. The most common strategies used by bacteria to survive and grow in high salt environments, such as Na+ efflux, K+ uptake, glutamate transport and biosynthesis, and the accumulation of compatible solutes, were also observed in S. algae. In particular, genes involved in peptidoglycan biosynthesis and DNA repair were highly and steadily up-regulated, accompanied by rapid and instantaneous enhancement of the transcription of large- and small-ribosome subunits, which suggested that the structural changes in the cell wall and some stressful responses occurred in S. algae. Furthermore, the transcription of genes involved in the tricarboxylic acid (TCA) cycle and the glycolytic pathway was decreased, whereas the transcription of genes involved in anaerobic respiration was increased. These results, demonstrating the multi-pathway reactions of S. algae in response to salt stress, increase our understanding of the microbial stress response mechanisms.
Highlights
Shewanella belongs to the order Alteromonadales and the family Alteromonadceae, the latter of which is a member of the gamma subdivision of Proteobacteria [1]
To investigate the concentrations of salt that could sustain the growth of S. algae, strain 2736 was cultivated in triplicate in LB broth containing different concentrations of NaCl, ranging from 0.5% to 9%
Under conditions of 8% NaCl, the bacterial growth slowed at the beginning but did reach the stationary phase, similar to growth in lower NaCl concentrations (Fig. 1); this concentration was regarded as the turning point of the NaCl concentration for the growth of S. algae 2736
Summary
Shewanella belongs to the order Alteromonadales and the family Alteromonadceae, the latter of which is a member of the gamma subdivision of Proteobacteria [1]. We explored the responses and the possible adaptive mechanisms of S. algae strain to elevated salt stress by analyzing the transcriptome profiles of high salt cultures at different time points. We harvested S. algae strain 2736 cells exposed to salt stress, and the gene transcript levels were serially monitored at 0, 1, 4, and 14 h.
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