title: Listeria monocytogenes varies among strains to maintain intracellular pH homeostasis under stresses by different acids as analyzed by a high-throughput microplate-based fluorometry.
abstract: Listeria monocytogenes, a food-borne pathogen, has the capacity to maintain intracellular pH (pHi) homeostasis in acidic environments, but the underlying mechanisms remain elusive. Here, we report a simple microplate-based fluorescent method to determine pHi of listerial cells that were prelabeled with the fluorescent dye carboxyfluorescein diacetate N-succinimidyl ester and subjected to acid stress. We found that L. monocytogenes responds differently among strains toward organic and inorganic acids to maintain pHi homeostasis. The capacity of L. monocytogenes to maintain pHi at extracellular pH 4.5 (pHex) was compromised in the presence of acetic acid and lactic acid, but not by hydrochloric acid and citric acid. Organic acids exhibited more inhibitory effects than hydrochloric acid at certain pH conditions. Furthermore, the virulent stains L. monocytogenes EGDe, 850658 and 10403S was more resistant to acidic stress than the avirulent M7 which showed a defect in maintaining pHi homeostasis. Deletion of sigB, a stress-responsive alternative sigma factor from 10403S, markedly altered intracellular pHi homeostasis, and showed a significant growth and survival defect under acidic conditions. Thus, this work provides new insights into bacterial survival mechanism to acidic stresses.
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Changyong
authors: C
authors: Cheng
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Yongchun
authors: Y
authors: Yang
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Zhimei
authors: Z
authors: Dong
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Xiaowen
authors: X
authors: Wang
authors: Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Zhejiang University Institute of Preventive Veterinary Medicine Hangzhou, China.
authors: Chun
authors: C
authors: Fang
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Menghua
authors: M
authors: Yang
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Jing
authors: J
authors: Sun
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Liya
authors: L
authors: Xiao
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China ; Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Zhejiang University Institute of Preventive Veterinary Medicine Hangzhou, China.
authors: Weihuan
authors: W
authors: Fang
authors: College of Animal Science and Technology, Zhejiang A&F University Lin'an, China.
authors: Houhui
authors: H
authors: Song
keywords: Listeria monocytogenes; SigB; acid tolerance; intracellular pH; pH homeostasis