title: Developmental transcriptome of resting cell formation in Mycobacterium smegmatis.
abstract: Mycobacteria, along with exospore forming Streptomyces, belong to the phylum actinobacteria. Mycobacteria are generally believed to be non-differentiating. Recently however, we showed that the mycobacterial model organism M. smegmatis is capable of forming different types of morphologically distinct resting cells. When subjected to starvation conditions, cells of M. smegmatis exit from the canonical cell division cycle, segregate and compact their chromosomes, and become septated and multi-nucleoided. Under zero nutrient conditions the differentiation process terminates at this stage with the formation of Large Resting Cells (LARCs). In the presence of traces of carbon sources this multi-nucleoided cell stage completes cell division and separates into Small Resting Cells (SMRCs). Here, we carried out RNA-seq profiling of SMRC and LARC development to characterize the transcriptional program underlying these starvation-induced differentiation processes.
  
  
  
  Changes among the top modulated genes demonstrated that SMRCs and LARCs undergo similar transcriptional changes. The formation of multi-nucleoided cells (i.e. LARCs and the LARC-like intermediates observed during SMRC formation) was accompanied by upregulation of septum formation functions FtsZ, FtsW, and PbpB, as well as the DNA translocase FtsK. The observed compaction of chromosomes was accompanied by an increase of the transcript level of the DNA binding protein Hlp, an orthologue of the Streptomyces spore-specific chromosome condensation protein HupS. Both SMRC and LARC development were accompanied by similar temporal expression patterns of candidate regulators, including the transcription factors WhiB2, WhiB3, and WhiB4, which are orthologues of the Streptomyces sporulation regulators WhiB, WhiD and WblA, respectively.
  
  
  
  Transcriptional analyses of the development of mycobacterial resting cell types suggest that these bacteria harbor a novel differentiation program and identify a series of potential regulators. This provides the basis for the genetic dissection of this actinobacterial differentiation process.
authors: Antibacterial Drug Discovery Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors: Mu-Lu
authors: ML
authors: Wu
authors: Tuberculosis Research Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors: Martin
authors: M
authors: Gengenbacher
authors: Department of Medicine, Division of Infectious Diseases, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.
authors: Jade C S
authors: JC
authors: Chung
authors: Department of Medicine, Division of Infectious Diseases, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.|Infectious Diseases Group, Genome Institute of Singapore, Singapore, Singapore.
authors: Swaine Lin
authors: SL
authors: Chen
authors: Core Facility Microarray / Genomics, Max Planck Institute for Infection Biology, Berlin, Germany.
authors: Hans-Joachim
authors: HJ
authors: Mollenkopf
authors: Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany.
authors: Stefan H E
authors: SH
authors: Kaufmann
authors: Antibacterial Drug Discovery Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. thomas_dick@nuhs.edu.sg.
authors: Thomas
authors: 0000-0002-9604-9452
authors: T
authors: Dick
mesh_terms: D002453:Cell Cycle / Q000235:genetics*; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D059014:High-Throughput Nucleotide Sequencing; D020102:Mycobacterium smegmatis / Q000235:genetics*; D059467:Transcriptome
keywords: Actinobacteria; Evolution; LARC; SMRC; Sporulation