Abstract
The bacterium Myxococcus xanthus exhibits a complex multicellular life cycle. In the presence of nutrients, cells prey cooperatively. Upon starvation, they enter a developmental cycle wherein cells aggregate to produce macroscopic fruiting bodies filled with resistant myxospores. We used RNA-Seq technology to examine the transcriptome of the 96 hr developmental program. These data revealed that 1415 genes were sequentially expressed in 10 discrete modules, with expression peaking during aggregation, in the transition from aggregation to sporulation, or during sporulation. Analysis of genes expressed at each specific time point provided insights as to how starving cells obtain energy and precursors necessary for assembly of fruiting bodies and into developmental production of secondary metabolites. This study offers the first global view of developmental transcriptional profiles and provides important tools and resources for future studies.
Highlights
Myxococcus xanthus is a soil-dwelling d-proteobacterium that exhibits a complex multicellular life cycle with two phases: growth and starvation-induced development (Munoz-Dorado et al, 2016)
To form fruiting bodies, starving cells glide on solid surfaces by using two motility systems, known as A- and S- motility, which allow individual cell movement or group movement that requires cell-cell contact, respectively (Mauriello et al, 2010; Nan et al, 2014; Islam and Mignot, 2015; Chang et al, 2016; Schumacher and SøgaardAndersen, 2017)
After completion of aggregation (24 hr post-starvation), cells differentiate into environmentally resistant myxospores, which are embedded in a complex extracellular matrix (Figure 1)
Summary
Myxococcus xanthus is a soil-dwelling d-proteobacterium that exhibits a complex multicellular life cycle with two phases: growth and starvation-induced development (Munoz-Dorado et al, 2016). Cells in the swarm enter a developmental program, during which they migrate into aggregation centers and climb on top of each other to build macroscopic structures termed fruiting bodies. The first cue is starvation, which triggers accumulation of cyclic-diGMP and, via the stringent response, guanosine penta- and tetraphosphate [(p)ppGpp] inside the cells These global signals somehow activate four master cascade modules (Nla, Mrp, FruA, and bacterial enhancer-binding proteins [bEBPs]), which interconnect to control the correct timing of gene expression (Kroos, 2017). We found that at least 19.6% of M. xanthus genes (1415/7229) had statistically significant changes in transcript abundance during development These data and analyses provide, for the first time, a comprehensive view of the transcriptional regulatory patterns that drive the multicellular developmental program of this myxobacterium, offering an essential scaffold for future investigations
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