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Proteomic analysis of Lactobacillus casei GCRL163 cell-free extracts reveals a SecB homolog and other biomarkers of prolonged heat stress

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posted on 2023-05-19, 22:08 authored by Adu, KT, Richard WilsonRichard Wilson, David NicholsDavid Nichols, Baker, AL, John BowmanJohn Bowman, Margaret BritzMargaret Britz
Prolonged heat stress is one of the harsh conditions Lactobacillus casei strains encounter as non-starter lactic acid bacteria in dairy product manufacture. To understand the physiological and molecular mechanisms through which Lb. casei GCRL163 adapts to persistent elevated temperature, label-free quantitative proteomics of cell-free extracts was used to characterize the global responses of the strain cultured anaerobically in bioreactors at 30 to 45°C, pH 6.5, together with GC-MS for fatty acid methyl ester analysis at different growth phases. At higher growth temperatures, repression of energy-consuming metabolic pathways, such as fatty acid, nucleotide and amino acid biosynthesis, was observed, while PTS- and ABC-type transporter systems associated with uptake of nitrogen and carbon sources were up-regulated. Alkaline shock protein Asp23_2 was only detected at 45°C, expressed at high abundance, and presumptive α-L-fucosidase only at 40 and 45°C, with highly increased abundance (log2-fold change of 7) at 45°C. We identified a novel SecB homolog as a protein export chaperone putatively involved in posttranslational translocation systems, which was down-regulated as growth temperature increased and where the modelled 3D-structure shared architectural similarities with the Escherichia coli SecB protein. Membrane lipid analyses revealed temporal changes in fatty acid composition, cyclization of oleic acid to cyclopropane and novel cyclopentenyl moieties, and reduced synthesis of vaccenic acid, at higher temperatures. An 18kDa α-crystallin domain, Hsp20 family heat shock protein was more highly up-regulated in response to heat stress compared to other molecular chaperones, suggesting this protein could be a useful biomarker of prolonged heat stress in Lb. casei GCRL163.

History

Publication title

PLoS One

Volume

13

Issue

10

Article number

e0206317

Number

e0206317

Pagination

1-28

ISSN

1932-6203

Department/School

Tasmanian Institute of Agriculture (TIA)

Publisher

Public Library of Science

Place of publication

United States

Rights statement

Copyright 2018 Adu et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

Repository Status

  • Open

Socio-economic Objectives

Dairy products not elsewhere classified; Expanding knowledge in the biological sciences