New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>

ABSTRACT The formation of viable but nonculturable (VBNC) Escherichia coli O157:H7 induced by high-pressure CO2 (HPCD) was investigated using RNA sequencing (RNA-Seq) transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) proteomic methods. The analyses revealed that 97 gene...

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Autores principales:	Feng Zhao, Yongtao Wang, Haoran An, Yanling Hao, Xiaosong Hu, Xiaojun Liao
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2016
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/69eda2fb457d4ab5a99ed35bab7236f9
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spelling	oai:doaj.org-article:69eda2fb457d4ab5a99ed35bab7236f92021-11-15T15:50:19ZNew Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>10.1128/mBio.00961-162150-7511https://doaj.org/article/69eda2fb457d4ab5a99ed35bab7236f92016-09-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00961-16https://doaj.org/toc/2150-7511ABSTRACT The formation of viable but nonculturable (VBNC) Escherichia coli O157:H7 induced by high-pressure CO2 (HPCD) was investigated using RNA sequencing (RNA-Seq) transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) proteomic methods. The analyses revealed that 97 genes and 56 proteins were significantly changed upon VBNC state entry. Genes and proteins related to membrane transport, central metabolisms, DNA replication, and cell division were mainly downregulated in the VBNC cells. This caused low metabolic activity concurrently with a division arrest in cells, which may be related to VBNC state formation. Cell division repression and outer membrane overexpression were confirmed to be involved in VBNC state formation by homologous expression of z2046 coding for transcriptional repressor and ompF encoding outer membrane protein F. Upon VBNC state entry, pyruvate catabolism in the cells shifted from the tricarboxylic acid (TCA) cycle toward the fermentative route; this led to a low level of ATP. Combating the low energy supply, ATP production in the VBNC cells was compensated by the degradation of l-serine and l-threonine, the increased AMP generation, and the enhanced electron transfer. Furthermore, tolerance of the cells with respect to HPCD-induced acid, oxidation, and high CO2 stresses was enhanced by promoting the production of ammonia and NADPH and by reducing CO2 production during VBNC state formation. Most genes and proteins related to pathogenicity were downregulated in the VBNC cells. This would decrease the cell pathogenicity, which was confirmed by adhesion assays. In conclusion, the decreased metabolic activity, repressed cell division, and enhanced survival ability in E. coli O157:H7 might cause HPCD-induced VBNC state formation. IMPORTANCE Escherichia coli O157:H7 has been implicated in large foodborne outbreaks worldwide. It has been reported that the presence of as few as 10 cells in food could cause illness. However, the presence of only 0.73 to 1.5 culturable E. coli O157:H7 cells in salted salmon roe caused infection in Japan. Investigators found that E. coli O157:H7 in the viable but nonculturable (VBNC) state was the source of the outbreak. So far, formation mechanisms of VBNC state are not well known. In a previous study, we demonstrated that high-pressure CO2 (HPCD) could induce the transition of E. coli O157:H7 into the VBNC state. In this study, we used RNA-Seq transcriptomic analysis combined with the iTRAQ proteomic method to investigate the formation of VBNC E. coli O157:H7 induced by HPCD treatment. Finally, we proposed a putative formation mechanism of the VBNC cells induced by HPCD, which may provide a theoretical foundation for controlling the VBNC state entry induced by HPCD treatment.Feng ZhaoYongtao WangHaoran AnYanling HaoXiaosong HuXiaojun LiaoAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 7, Iss 4 (2016)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Feng Zhao Yongtao Wang Haoran An Yanling Hao Xiaosong Hu Xiaojun Liao New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
description	ABSTRACT The formation of viable but nonculturable (VBNC) Escherichia coli O157:H7 induced by high-pressure CO2 (HPCD) was investigated using RNA sequencing (RNA-Seq) transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) proteomic methods. The analyses revealed that 97 genes and 56 proteins were significantly changed upon VBNC state entry. Genes and proteins related to membrane transport, central metabolisms, DNA replication, and cell division were mainly downregulated in the VBNC cells. This caused low metabolic activity concurrently with a division arrest in cells, which may be related to VBNC state formation. Cell division repression and outer membrane overexpression were confirmed to be involved in VBNC state formation by homologous expression of z2046 coding for transcriptional repressor and ompF encoding outer membrane protein F. Upon VBNC state entry, pyruvate catabolism in the cells shifted from the tricarboxylic acid (TCA) cycle toward the fermentative route; this led to a low level of ATP. Combating the low energy supply, ATP production in the VBNC cells was compensated by the degradation of l-serine and l-threonine, the increased AMP generation, and the enhanced electron transfer. Furthermore, tolerance of the cells with respect to HPCD-induced acid, oxidation, and high CO2 stresses was enhanced by promoting the production of ammonia and NADPH and by reducing CO2 production during VBNC state formation. Most genes and proteins related to pathogenicity were downregulated in the VBNC cells. This would decrease the cell pathogenicity, which was confirmed by adhesion assays. In conclusion, the decreased metabolic activity, repressed cell division, and enhanced survival ability in E. coli O157:H7 might cause HPCD-induced VBNC state formation. IMPORTANCE Escherichia coli O157:H7 has been implicated in large foodborne outbreaks worldwide. It has been reported that the presence of as few as 10 cells in food could cause illness. However, the presence of only 0.73 to 1.5 culturable E. coli O157:H7 cells in salted salmon roe caused infection in Japan. Investigators found that E. coli O157:H7 in the viable but nonculturable (VBNC) state was the source of the outbreak. So far, formation mechanisms of VBNC state are not well known. In a previous study, we demonstrated that high-pressure CO2 (HPCD) could induce the transition of E. coli O157:H7 into the VBNC state. In this study, we used RNA-Seq transcriptomic analysis combined with the iTRAQ proteomic method to investigate the formation of VBNC E. coli O157:H7 induced by HPCD treatment. Finally, we proposed a putative formation mechanism of the VBNC cells induced by HPCD, which may provide a theoretical foundation for controlling the VBNC state entry induced by HPCD treatment.
format	article
author	Feng Zhao Yongtao Wang Haoran An Yanling Hao Xiaosong Hu Xiaojun Liao
author_facet	Feng Zhao Yongtao Wang Haoran An Yanling Hao Xiaosong Hu Xiaojun Liao
author_sort	Feng Zhao
title	New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
title_short	New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
title_full	New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
title_fullStr	New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
title_full_unstemmed	New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>
title_sort	new insights into the formation of viable but nonculturable <named-content content-type="genus-species">escherichia coli</named-content> o157:h7 induced by high-pressure co<sub>2</sub>
publisher	American Society for Microbiology
publishDate	2016
url	https://doaj.org/article/69eda2fb457d4ab5a99ed35bab7236f9
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New Insights into the Formation of Viable but Nonculturable <named-content content-type="genus-species">Escherichia coli</named-content> O157:H7 Induced by High-Pressure CO<sub>2</sub>

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