title: Delineating the effect of host environmental signals on a fully virulent strain of Bacillus anthracis using an integrated transcriptomics and proteomics approach.
abstract: Pathogenic bacteria sense the host environment and regulate expression of virulence-related genes. Environmental signals like temperature, bicarbonate/CO2 and glucose induce toxin production in Bacillus anthracis, but the mechanisms by which these signals contribute to virulence and overall physiological adaptation remains elusive. An integrated, systems level investigation using transcriptomics and iTRAQ-based proteomics was done to assess the effect of temperature, bicarbonate/CO2 and glucose on B. anthracis. Significant changes observed in amino acid, carbohydrate, energy and nucleotide metabolism indicates events of metabolic readjustments by environmental factors. Directed induction of genes involved in polyamine biosynthesis and iron metabolism revealed the redirection of cellular metabolite pool towards iron uptake. Protein levels of glycolytic enzymes, ptsH and Ldh along with transcripts involved in immune evasion (mprF, bNOS, Phospholipases and asnA), cell surface remodeling (rfbABCD, antABCD, and cls) and utilization of lactate (lutABC) and inositol showed constant repression under environmental perturbations. Discrepancies observed in mRNA/protein level of genes involved in glycolysis, protein synthesis, stress response and nucleotide metabolism hinted at the existence of additional regulatory layers and illustrated the utility of an integrated approach. The above findings might assist in the identification of novel adaptive strategies of B. anthracis during host associated survival and pathogenesis.
  
  
  CONCLUSIONS
  In this study, the changes observed at both transcript and protein level were quantified and integrated to understand the effect of host environmental factors (host temperature, bicarbonate and glucose) in shaping the physiology and adaptive strategies of a fully virulent strain of B. anthracis for efficient survival and virulence in its host. Perturbations affecting toxin production were found to concordantly affect vital metabolic pathways and several known as well as novel virulence factors. These changes act as a valuable asset for generating testable hypotheses that can be further verified by detailed molecular and mutant studies to identify novel adaptive strategies of B. anthracis during infection. Adaptation of an integrated transcriptomics and proteomics approach also led to the identification of discrepancies between mRNA/protein levels among genes across major functional categories. Few of these discrepancies have been previously reported in literature for model organisms. However their existence in B. anthracis and that too as a result of growth perturbations have not been reported till date. These findings demonstrate a substantial role of regulatory processes post mRNA synthesis via post transcriptional, translational or protein degradation mechanisms. This article is part of a Special Issue entitled: Proteomics of non-model organisms.
authors.affiliation: Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
authors.forename: Gurudutta
authors.initials: G
authors.lastname: Panda
authors.affiliation: Genomics and Molecular Medicine Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, 110020, India; Academy of Scientific & Innovative Research, Delhi, India.
authors.forename: Trayambak
authors.initials: T
authors.lastname: Basak
authors.affiliation: Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India.
authors.forename: Pooja
authors.initials: P
authors.lastname: Tanwer
authors.affiliation: Genomics and Molecular Medicine Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, 110020, India; Academy of Scientific & Innovative Research, Delhi, India.
authors.forename: Shantanu
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Systems and Synthetic Biology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, The Netherlands; LifeGlimmer GmbH, Markelstrasse 38, Berlin 12163, Germany.
authors.forename: Vítor A P Martins
authors.initials: VA
authors.lastname: dos Santos
authors.affiliation: Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India. Electronic address: rakeshbhatnagar@jnu.ac.in.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Bhatnagar
mesh_terms: D001408:Bacillus anthracis / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods; D020543:Proteome / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D015398:Signal Transduction / Q000502:physiology*; D059467:Transcriptome / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D020543:Proteome
keywords: Bacillus anthracis; Environmental perturbation; Host associated lifestyle; Microarrays; SCX-LC-MS/MS; iTRAQ; mRNA-protein correlation