Regulated Control of the Assembly and Diversity of LPS by Noncoding sRNAs

Figure 5

Schematic depiction of various LPS glycoforms observed in E. coli K-12. Glycoform I is the major LPS glycoform under nonstress condition, that is, in the absence of RpoE induction and other two-component systems (a). Induction of RpoE leads to the accumulation of glycoforms IV, V, and VII due to RybB- and MicA-mediated translational suppression of WaaR and induction of waaZ and waaS transcription that may also involve Hfq. In this process, RybB plays the central role. Glycoforms IV, V, and VII contain a third Kdo and rhamnose with a concomitant truncation in the outer core (b, c, and d). Glycoform IV accumulates when MgrR repression of eptB is predominant. The translation of the eptB mRNA is repressed by base-paring with MgrR under PhoP/Q-inducing conditions and also by ArcZ sRNA (b). When the RpoE induction is maximal, RpoE-driven transcription overrides MgrR-mediated repression of the EptB synthesis due to the hyperinduction of RpoE-regulated transcription of the eptB gene. Under such conditions, RybB at the same time represses translationally the WaaR synthesis (c). The glycoform VII is the major glycoform when RpoE-dependent eptB and rybB expression is induced with simultaneous induction of the waaH gene transcription leading to the GlcUA incorporation (d).

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