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New insight into the mechanism by which antifreeze peptides regulate the physiological function of Streptococcus thermophilus subjected to freezing stress
Journal of Advanced Research  (IF12.822),  Pub Date : 2022-05-10, DOI: 10.1016/j.jare.2022.05.002
Xu Chen, Jinhong Wu, Fujia Yang, Mi Zhou, Ruibin Wang, Jianlian Huang, Yuzhi Rong, Jianhua Liu, Shaoyun Wang

Introduction

Antifreeze peptides regulate the physiological functions of frozen cells and even their apoptosis; however, the mechanisms by which antifreeze peptides regulate these processes remain unclear, although the interactions between cell membranes and ice are well known to be important in this process.

Objectives

Our study aims to investigate how antifreeze peptides regulate cell physiological functions during the freezing process.

Methods

We investigated the cryoprotective effect of rsfAFP on the physiological functions of S. thermophilus under freezing stress by measuring cellular metabolism activity, intracellular enzyme activity, cell membrane characterization, and cell apoptosis. The mechanism by which rsfAFP impacts S. thermophilus physiological functions under freezing stress was investigated using multispectral techniques and cryo-TEM.

Results

We show that a recombinant antifreeze peptide (rsfAFP) interacts with the extracellular capsular polysaccharides and peptidoglycan of Streptococcus thermophilus and ice to cover the outer layer of the membrane, forming a dense protective layer that regulates the molecular structure of extracellular ice crystals, which results in reduced extracellular membrane damage, depressed apoptosis and increased intracellular metabolic activity. This interaction mechanism was indicated by the fact that S. thermophilus better maintained its permeability barrier, membrane fluidity, membrane structural integrity, and cytoplasmic membrane potential during freezing stress with rsfAFP treatment.

Conclusion

These results provide new insights into the mechanism by which rsfAFP regulates frozen cell physiological functions and apoptosis under freezing stress.