TY - JOUR
T1 - Genomewide transcriptional responses of iron-starved chlamydia trachomatis reveal prioritization of metabolic precursor synthesis over protein translation
AU - Brinkworth, Amanda J.
AU - Wildung, Mark R.
AU - Carabeo, Rey A.
N1 - Funding Information:
This work was funded by startup funds for R.A.C. from the School of Molecular Biosciences, College of Veterinary Medicine, Washington State University; by NIH grant 2R01AI065545-06A1 awarded to R.A.C.; and by NIH training grant for A.J.B.
Publisher Copyright:
Copyright © 2018 Brinkworth et al.
PY - 2018/2
Y1 - 2018/2
N2 - Iron is essential for growth and development of Chlamydia. Its longterm starvation in cultured mammalian cells leads to production of aberrant noninfectious chlamydial forms, also known as persistence. Immediate transcriptional responses to iron limitation have not been characterized, leaving a knowledge gap of how Chlamydia regulates its response to changes in iron availability. We used the fast-chelating agent 2,2'-bipyridyl (BPDL) to homogeneously starve Chlamydia trachomatis serovar L2 of iron, starting at 6 or 12 h postinfection. Immediate transcriptional responses were monitored after only 3 or 6 h of BPDL treatment, well before formation of aberrant Chlamydia. The first genomewide transcriptional response of C. trachomatis to iron starvation was subsequently determined utilizing RNA sequencing. Only 7% and 8% of the genome were differentially expressed in response to iron starvation at the early and middle stages of development, respectively. Biological pathway analysis revealed an overarching theme. Synthesis of macromolecular precursors (deoxynucleotides, amino acids, charged tRNAs, and acetyl coenzyme A [acetyl-CoA]) was upregulated, while energy-expensive processes (ABC transport and translation) were downregulated. A large fraction of differentially downregulated genes are involved in translation, including those encoding ribosome assembly and initiation and termination factors, which could be analogous to the translation downregulation triggered by stress in other prokaryotes during stringent responses. Additionally, transcriptional upregulation of DNA repair, oxidative stress, and tryptophan salvage genes reveals a possible coordination of responses to multiple antimicrobial and immunological insults. These responses of replicative-phase Chlamydia to iron starvation indicate a prioritization of survival over replication, enabling the pathogen to "stock the pantry"with ingredients needed for rapid growth once optimal iron levels are restored.
AB - Iron is essential for growth and development of Chlamydia. Its longterm starvation in cultured mammalian cells leads to production of aberrant noninfectious chlamydial forms, also known as persistence. Immediate transcriptional responses to iron limitation have not been characterized, leaving a knowledge gap of how Chlamydia regulates its response to changes in iron availability. We used the fast-chelating agent 2,2'-bipyridyl (BPDL) to homogeneously starve Chlamydia trachomatis serovar L2 of iron, starting at 6 or 12 h postinfection. Immediate transcriptional responses were monitored after only 3 or 6 h of BPDL treatment, well before formation of aberrant Chlamydia. The first genomewide transcriptional response of C. trachomatis to iron starvation was subsequently determined utilizing RNA sequencing. Only 7% and 8% of the genome were differentially expressed in response to iron starvation at the early and middle stages of development, respectively. Biological pathway analysis revealed an overarching theme. Synthesis of macromolecular precursors (deoxynucleotides, amino acids, charged tRNAs, and acetyl coenzyme A [acetyl-CoA]) was upregulated, while energy-expensive processes (ABC transport and translation) were downregulated. A large fraction of differentially downregulated genes are involved in translation, including those encoding ribosome assembly and initiation and termination factors, which could be analogous to the translation downregulation triggered by stress in other prokaryotes during stringent responses. Additionally, transcriptional upregulation of DNA repair, oxidative stress, and tryptophan salvage genes reveals a possible coordination of responses to multiple antimicrobial and immunological insults. These responses of replicative-phase Chlamydia to iron starvation indicate a prioritization of survival over replication, enabling the pathogen to "stock the pantry"with ingredients needed for rapid growth once optimal iron levels are restored.
KW - Chlamydia
KW - Global regulatory networks
KW - Intracellular bacteria
KW - Iron reduction
KW - Microbiology
KW - Stress response
KW - Stringent response
KW - Systems
KW - Transcriptional regulation
KW - Translational control
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U2 - 10.1128/MSYSTEMS.00184-17
DO - 10.1128/MSYSTEMS.00184-17
M3 - Article
AN - SCOPUS:85079032655
SN - 2379-5077
VL - 3
JO - mSystems
JF - mSystems
IS - 1
M1 - e00184
ER -