Developmental transcriptome of resting cell formation in Mycobacterium smegmatis. (December 2016)

• Record Type: Journal Article
• Authors: Wu, Mu-Lu; Gengenbacher, Martin; Chung, Jade; Chen, Swaine; Mollenkopf, Hans-Joachim; Kaufmann, Stefan; Dick, Thomas
• Is Part Of: BMC genomics. Volume 17:Number 1(2016)
• Page Start: 1
• Page End: 9
• Publication Date: 2016-12
• Subjects: SMRC -- LARC -- Actinobacteria -- Sporulation -- Evolution; Genomes -- Periodicals; Gene mapping -- Periodicals; Genomics -- Periodicals; Base Sequence -- Periodicals; Chromosome Mapping -- Periodicals; Genetic Techniques -- Periodicals; Sequence Analysis, DNA -- Periodicals; 572.8605
• DOI: 10.1186/s12864-016-3190-4
• Languages: English
• ISSNs: 1471-2164

Abstract

Abstract Background Mycobacteria, along with exospore formingStreptomyces, belong to the phylum actinobacteria. Mycobacteria are generally believed to be non-differentiating. Recently however, we showed that the mycobacterial model organismM. smegmatis is capable of forming different types of morphologically distinct resting cells. When subjected to starvation conditions, cells ofM. 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. Results 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 theStreptomyces 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 theStreptomyces sporulation regulators WhiB, WhiD and WblA, respectively. Conclusions 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.