Single-cell measurement of the levels and distributions of the phosphorelay components in a population of sporulating Bacillus subtilis cells.
Upon nutrient starvation, the Gram-positive bacterium Bacillus subtilis switches from growth to sporulation by activating a multicomponent phosphorelay consisting of a major sensor histidine kinase (KinA), two phosphotransferases (Spo0F and Spo0B) and a response regulator (Spo0A). Although the primary sporulation signal(s) produced under starvation conditions is not known, it is believed that the reception of a signal(s) on the sensor kinase results in the activation of autophosphorylation of the enzyme. The phosphorylated kinase transfers the phosphate group to Spo0A via the phosphorelay and thus triggers sporulation. With a combination of quantitative immunoblot analysis, microscopy imaging and computational analysis, here we found that each of the phosphorelay components tested increased gradually over the period of sporulation, and that Spo0F was expressed in a more heterogeneous pattern than KinA and Spo0B in a sporulating cell population. We determined molecule numbers and concentrations of each phosphorelay component under physiological sporulation conditions at the single-cell level. Based on these results, we suggest that successful entry into the sporulation state is manifested by a certain critical level of each phosphorelay component, and thus that only a subpopulation achieves a sufficient intracellular quorum of the phosphorelay components to activate Spo0A and proceed successfully to the entry into sporulation.
Eswaramoorthy
Prahathees
P
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
Dinh
Jeffrey
J
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
Duan
Daniel
D
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
Igoshin
Oleg A
OA
Department of Bioengineering, Rice University, Houston, TX 77251-1892, USA.
Fujita
Masaya
M
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D010770:Phosphotransferases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D013171:Spores, Bacterial / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; C080950:Spo0A protein, Bacillus subtilis; C080951:Spo0F protein, Bacillus subtilis; D014157:Transcription Factors; C075521:kinA protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; D010770:Phosphotransferases; D011494:Protein Kinases