Stability of active prophages in industrial Lactococcus lactis strains in the presence of heat, acid, osmotic, oxidative and antibiotic stressors

Ho, Chun-Hoong, Stanton-Cook, Mitchell, Beatson, Scott A., Bansal, Nidhi and Turner, Mark S. (2016) Stability of active prophages in industrial Lactococcus lactis strains in the presence of heat, acid, osmotic, oxidative and antibiotic stressors. International Journal of Food Microbiology, 220 26-32. doi:10.1016/j.ijfoodmicro.2015.12.012

Attached Files (Some files may be inaccessible until you login with your UQ eSpace credentials)
Name Description MIMEType Size Downloads
UQ377258_OA.pdf application/pdf 462.09KB 0

Author Ho, Chun-Hoong
Stanton-Cook, Mitchell
Beatson, Scott A.
Bansal, Nidhi
Turner, Mark S.
Title Stability of active prophages in industrial Lactococcus lactis strains in the presence of heat, acid, osmotic, oxidative and antibiotic stressors
Formatted title
Stability of active prophages in industrial Lactococcus lactis strains in the presence of heat, acid, osmotic, oxidative and antibiotic stressors
Journal name International Journal of Food Microbiology   Check publisher's open access policy
ISSN 1879-3460
0168-1605
Publication date 2016-03-02
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.ijfoodmicro.2015.12.012
Open Access Status File (Author Post-print)
Volume 220
Start page 26
End page 32
Total pages 7
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Subject 1106 Food Science
2404 Microbiology
Abstract Lactococcus lactis is a starter bacterium commonly used in cheese making where it has an important role in acid-mediated curd formation as well as the development of flavour compounds. Industrial L. lactis strains can harbour one or more inducible prophages which when induced can affect cell growth and possibly lead to cell lysis. This is undesirable during growth and fermentation, but can beneficially lead to faster release of enzymes during cheese ripening. Lactococci can encounter multiple stress inducing conditions during the production of cheese, such as low and high temperatures, low pH, high osmotic pressure and long-term incubation. In this study, we tested the effect of these industrial stressors on prophage induction in two cheese making L. lactis subsp. cremoris strains (ASCC890049 and ASCC890310) as well as the laboratory strain L. lactis MG1363. Firstly, in order to identify inducible prophages in these strains we exposed them to the prophage inducing chemical mitomycin C (MMC) for 1 and 2. h and then subjected the total genomic DNA to next-generation Illumina sequencing. Mapping of sequence reads back to the genome sequences revealed regions which contained a much higher fold coverage indicating DNA replication. These regions were amplified by up to 332-fold per cell (relative to the control tufA gene) and were identified as having similarities to different subgroups of P335 phages including MG-5, TP901-1, ul36.k1, bIL286, TP712 and BK5-T. Next, quantitative PCR was used to confirm the strong induction of prophages by MMC and then determine the copy number of the inducible prophages following exposure to various growth inhibitory levels of HCl, lactic acid, high temperature, NaCl, hydrogen peroxide and bacitracin. With the exception of a slight induction (2 to 4-fold) with hydrogen peroxide and long-term incubation after 21. days in one industrial strain, none of the other stressors induced prophage DNA replication. These findings show that the repression system that maintains prophages in the dormant state in cheese making lactococcal strains is very tight and that several stressors encountered singularly are not predicted to be major inducers of prophage activation.
Formatted abstract
Lactococcus lactis is a starter bacterium commonly used in cheese making where it has an important role in acid-mediated curd formation as well as the development of flavour compounds. Industrial L. lactis strains can harbour one or more inducible prophages which when induced can affect cell growth and possibly lead to cell lysis. This is undesirable during growth and fermentation, but can beneficially lead to faster release of enzymes during cheese ripening. Lactococci can encounter multiple stress inducing conditions during the production of cheese, such as low and high temperatures, low pH, high osmotic pressure and long-term incubation. In this study, we tested the effect of these industrial stressors on prophage induction in two cheese making L. lactis subsp. cremoris strains (ASCC890049 and ASCC890310) as well as the laboratory strain L. lactis MG1363. Firstly, in order to identify inducible prophages in these strains we exposed them to the prophage inducing chemical mitomycin C (MMC) for 1 and 2 h and then subjected the total genomic DNA to next-generation Illumina sequencing. Mapping of sequence reads back to the genome sequences revealed regions which contained a much higher fold coverage indicating DNA replication. These regions were amplified by up to 332-fold per cell (relative to the control tufA gene) and were identified as having similarities to different subgroups of P335 phages including MG-5, TP901-1, ul36.k1, bIL286, TP712 and BK5-T. Next, quantitative PCR was used to confirm the strong induction of prophages by MMC and then determine the copy number of the inducible prophages following exposure to various growth inhibitory levels of HCl, lactic acid, high temperature, NaCl, hydrogen peroxide and bacitracin. With the exception of a slight induction (2 to 4-fold) with hydrogen peroxide and long-term incubation after 21 days in one industrial strain, none of the other stressors induced prophage DNA replication. These findings show that the repression system that maintains prophages in the dormant state in cheese making lactococcal strains is very tight and that several stressors encountered singularly are not predicted to be major inducers of prophage activation.
Keyword Lactococcus lactis
Next-generation sequencing
Prophage
qPCR
Stress
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID LP120100282
Institutional Status UQ
Additional Notes Published online 30 December 2015

 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 4 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 4 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Tue, 19 Jan 2016, 10:13:28 EST by System User on behalf of Learning and Research Services (UQ Library)