Quantifying the effect of sorbic acid, heat and combination of both on germination and outgrowth of Bacillus subtilis spores at single cell resolution.
Bacillus subtilis spores are a problem for the food industry as they are able to survive preservation processes. The spores often reside in food products, where their inherent protection against various stress treatments causes food spoilage. Sorbic acid is widely used as a weak acid preservative in the food industry. Its effect on spore germination and outgrowth in a combined, 'hurdle', preservation setting has gained limited attention. Therefore, the effects of mild sorbic acid (3 mM), heat-treatment (85 °C for 10 min) and a combination of both mild stresses on germination and outgrowth of B. subtilis 1A700 spores were analysed at single spore level. The heat-treatment of the spore population resulted in a germination efficiency of 46.8% and an outgrowth efficiency of 32.9%. In the presence of sorbic acid (3 mM), the germination and outgrowth efficiency was 93.3% and 80.4% respectively whereas the combined heat and sorbic acid stress led to germination and outgrowth efficiencies of 52.7% and 27.0% respectively. The heat treatment clearly primarily affected the germination process, while sorbic acid affected the outgrowth and generation time. In addition a new 'burst' time-point was defined as the time-point at which the spore coat visibly breaks and/or is shed. The combined stresses had a synergistic effect on the time of the end of germination to the burst time-point, increasing both the mean and its variation more than either of the single stresses did.
Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands; Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: r.pandey@uva.nl.
Rachna
R
Pandey
Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: gerardhpieper@gmail.com.
Gerard H
GH
Pieper
Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: Alexander.TerBeek@gmail.com.
Alexander
A
Ter Beek
Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: vischer@science.uva.nl.
Norbert O E
NO
Vischer
Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: J.P.P.M.Smelt@uva.nl.
Jan P P M
JP
Smelt
Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: E.M.M.Manders@uva.nl.
Erik M M
EM
Manders
Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: S.Brul@uva.nl.
Stanley
S
Brul
D001412:Bacillus subtilis / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D005516:Food Microbiology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D013011:Sorbic Acid / Q000494:pharmacology*; D013171:Spores, Bacterial / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects
D013011:Sorbic Acid
Bacillus subtilis; Heat-treatment; Live cell imaging; Sorbic acid; Spore germination and outgrowth; SporeTracker