The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates

ABSTRACT The initiation of Escherichia coli chromosomal DNA replication starts with the oligomerization of the DnaA protein at repeat sequences within the origin (ori) region. The amount of ori DNA per cell directly correlates with the growth rate. During fast growth, the cell generation time is sho...

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Autores principales:	Llorenç Fernández-Coll, Monika Maciag-Dorszynska, Krishma Tailor, Stephen Vadia, Petra Anne Levin, Agnieszka Szalewska-Palasz, Michael Cashel
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	chromosome initiation DNA replication Escherichia coli growth rate ppGpp Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/c70362e54d2e42d18cd060baed7d9443
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spelling	oai:doaj.org-article:c70362e54d2e42d18cd060baed7d94432021-11-15T15:57:03ZThe Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates10.1128/mBio.03223-192150-7511https://doaj.org/article/c70362e54d2e42d18cd060baed7d94432020-04-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.03223-19https://doaj.org/toc/2150-7511ABSTRACT The initiation of Escherichia coli chromosomal DNA replication starts with the oligomerization of the DnaA protein at repeat sequences within the origin (ori) region. The amount of ori DNA per cell directly correlates with the growth rate. During fast growth, the cell generation time is shorter than the time required for complete DNA replication; therefore, overlapping rounds of chromosome replication are required. Under these circumstances, the ori region DNA abundance exceeds the DNA abundance in the termination (ter) region. Here, high ori/ter ratios are found to persist in (p)ppGpp-deficient [(p)ppGpp0] cells over a wide range of balanced exponential growth rates determined by medium composition. Evidently, (p)ppGpp is necessary to maintain the usual correlation of slow DNA replication initiation with a low growth rate. Conversely, ori/ter ratios are lowered when cell growth is slowed by incrementally increasing even low constitutive basal levels of (p)ppGpp without stress, as if (p)ppGpp alone is sufficient for this response. There are several previous reports of (p)ppGpp inhibition of chromosomal DNA synthesis initiation that occurs with very high levels of (p)ppGpp that stop growth, as during the stringent starvation response or during serine hydroxamate treatment. This work suggests that low physiological levels of (p)ppGpp have significant functions in growing cells without stress through a mechanism involving negative supercoiling, which is likely mediated by (p)ppGpp regulation of DNA gyrase. IMPORTANCE Bacterial cells regulate their own chromosomal DNA synthesis and cell division depending on the growth conditions, producing more DNA when growing in nutritionally rich media than in poor media (i.e., human gut versus water reservoir). The accumulation of the nucleotide analog (p)ppGpp is usually viewed as serving to warn cells of impending peril due to otherwise lethal sources of stress, which stops growth and inhibits DNA, RNA, and protein synthesis. This work importantly finds that small physiological changes in (p)ppGpp basal levels associated with slow balanced exponential growth incrementally inhibit the intricate process of initiation of chromosomal DNA synthesis. Without (p)ppGpp, initiations mimic the high rates present during fast growth. Here, we report that the effect of (p)ppGpp may be due to the regulation of the expression of gyrase, an important enzyme for the replication of DNA that is a current target of several antibiotics.Llorenç Fernández-CollMonika Maciag-DorszynskaKrishma TailorStephen VadiaPetra Anne LevinAgnieszka Szalewska-PalaszMichael CashelAmerican Society for Microbiologyarticlechromosome initiationDNA replicationEscherichia coligrowth rateppGppMicrobiologyQR1-502ENmBio, Vol 11, Iss 2 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	chromosome initiation DNA replication Escherichia coli growth rate ppGpp Microbiology QR1-502
spellingShingle	chromosome initiation DNA replication Escherichia coli growth rate ppGpp Microbiology QR1-502 Llorenç Fernández-Coll Monika Maciag-Dorszynska Krishma Tailor Stephen Vadia Petra Anne Levin Agnieszka Szalewska-Palasz Michael Cashel The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
description	ABSTRACT The initiation of Escherichia coli chromosomal DNA replication starts with the oligomerization of the DnaA protein at repeat sequences within the origin (ori) region. The amount of ori DNA per cell directly correlates with the growth rate. During fast growth, the cell generation time is shorter than the time required for complete DNA replication; therefore, overlapping rounds of chromosome replication are required. Under these circumstances, the ori region DNA abundance exceeds the DNA abundance in the termination (ter) region. Here, high ori/ter ratios are found to persist in (p)ppGpp-deficient [(p)ppGpp0] cells over a wide range of balanced exponential growth rates determined by medium composition. Evidently, (p)ppGpp is necessary to maintain the usual correlation of slow DNA replication initiation with a low growth rate. Conversely, ori/ter ratios are lowered when cell growth is slowed by incrementally increasing even low constitutive basal levels of (p)ppGpp without stress, as if (p)ppGpp alone is sufficient for this response. There are several previous reports of (p)ppGpp inhibition of chromosomal DNA synthesis initiation that occurs with very high levels of (p)ppGpp that stop growth, as during the stringent starvation response or during serine hydroxamate treatment. This work suggests that low physiological levels of (p)ppGpp have significant functions in growing cells without stress through a mechanism involving negative supercoiling, which is likely mediated by (p)ppGpp regulation of DNA gyrase. IMPORTANCE Bacterial cells regulate their own chromosomal DNA synthesis and cell division depending on the growth conditions, producing more DNA when growing in nutritionally rich media than in poor media (i.e., human gut versus water reservoir). The accumulation of the nucleotide analog (p)ppGpp is usually viewed as serving to warn cells of impending peril due to otherwise lethal sources of stress, which stops growth and inhibits DNA, RNA, and protein synthesis. This work importantly finds that small physiological changes in (p)ppGpp basal levels associated with slow balanced exponential growth incrementally inhibit the intricate process of initiation of chromosomal DNA synthesis. Without (p)ppGpp, initiations mimic the high rates present during fast growth. Here, we report that the effect of (p)ppGpp may be due to the regulation of the expression of gyrase, an important enzyme for the replication of DNA that is a current target of several antibiotics.
format	article
author	Llorenç Fernández-Coll Monika Maciag-Dorszynska Krishma Tailor Stephen Vadia Petra Anne Levin Agnieszka Szalewska-Palasz Michael Cashel
author_facet	Llorenç Fernández-Coll Monika Maciag-Dorszynska Krishma Tailor Stephen Vadia Petra Anne Levin Agnieszka Szalewska-Palasz Michael Cashel
author_sort	Llorenç Fernández-Coll
title	The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
title_short	The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
title_full	The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
title_fullStr	The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
title_full_unstemmed	The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates
title_sort	absence of (p)ppgpp renders initiation of <named-content content-type="genus-species">escherichia coli</named-content> chromosomal dna synthesis independent of growth rates
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/c70362e54d2e42d18cd060baed7d9443
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The Absence of (p)ppGpp Renders Initiation of <named-content content-type="genus-species">Escherichia coli</named-content> Chromosomal DNA Synthesis Independent of Growth Rates

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