The absence of CsdA in Escherichia coli increases DNA replication and cell size but decreases growth rate at low temperature

Abstract

The CsdA protein is a highly conserved, DEAD-box RNA helicase and assists RNA structural remodeling at low temperature. We show that the fast-growing wild-type (WT) cells contain higher number of replication origins per cell with bigger cell size and the slowly growing cells possess less number of replication origins per cell with smaller cell size. The absence of CsdA leads to production of larger cells with higher number of origins per cell but slower growth at low temperature in an independent-manner of growth media. The phenotypes in ΔcsdA mutant are reversed by ectopic expression of CsdA or RNase R. A global transcription analysis shows that the absence of CsdA leads to significant decreases in transcription of about 200 genes at low temperature. These genes are associated with essential metabolic pathways, flagger assembly and cell division (minDE). It is likely that the slow growth of ΔcsdA cell results from the decreased transcription of essential metabolic genes, and the larger ΔcsdA cell could be a result of decreased transcription of minDE. The increased transcription of the nrdHIEF genes in ΔcsdA mutant is a likely reason that promotes DNA replication. We conclude that CsdA coordinates the cell cycle to growth by stabilizing mRNA of essential metabolic and cell division genes and degrading mRNA for nucleotide metabolic genes at low temperature.

Keywords: Cell growth; Cell size; CsdA; DNA replication; Escherichia coli.