Gene expression of Escherichia coli in continuous culture during adaptation to artificial sunlight

Abstract

Escherichia coli growing in continuous culture under continuous UVA irradiation exhibits growth inhibition with a subsequent adaptation to the stress. Transcriptome analysis was performed during transient growth inhibition and in the UVA light-adapted growth state. The results indicate that UVA light induces stringent response and an additional response that includes the upregulation of the synthesis of valine, isoleucine, leucine, phenylalanine, histidine and glutamate. The induction of several SOS response-genes strongly points to DNA damage as a result of UVA exposure. The involvement of oxidative stress was observed with the induction of ahpCF. Taken together it supports the hypothesis of the production of reactive oxygen species by UVA light. In the UVA-adapted cell population strong repression of the acid tolerance response was found. We identified the enzyme chorismate mutase as a possible chromophore for UVA light-inactivation and found strong repression of the pyrBI operon and the gene mgtA encoding for an ATP-dependent Mg2+ transporter. Furthermore, our results indicate that the role of RpoS may not be as important in the adaptation of E. coli to UVA light as it was implicated by previous results with starved cells, but that RpoS might be of crucial importance for the resistance under transient light exposure.

Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure

“…Additionally, the ranges of relative expression ratios determined here (minimum, R ϭ 0.5; maximum, R ϭ 4.4) are similar to expression levels in previous studies of E. faecalis in oligotrophic seawater systems (6, 7), which found maximum changes in expression of ϳ3-fold by microarray. In contrast, some previous studies have observed larger expression changes in E. coli after sunlight exposure, but we expect this may be due to either the use of growth medium during sunlight exposure (9) or the use of a different method (i.e., transcriptome sequencing [RNA-seq]) to detect gene expression changes (26). Despite the fact that large changes in expression were not detected here, the approximately stable expression levels across samples in both systems suggest that cells remain transcriptionally active, even after the majority of cells are not culturable.…”

“…A number of studies have therefore investigated bacterial photoinactivation in the context of environmental water quality (1)(2)(3)(4)(5)(6)(7), with further studies also focusing on photoinactivation in drinking water treatment (8)(9)(10)(11), photodynamic therapy (12)(13)(14)(15), and wastewater treatment (16)(17)(18)(19)(20). Bacteria can be inactivated by sunlight by direct and indirect mechanisms.…”

Mechanisms for Photoinactivation of Enterococcus faecalis in Seawater

“…Researchers have found that growth rates and conditions are important determinants of how E. coli bacteria respond to stress (4,5,29). The E. faecalis bacteria used to seed the experiments presented here were grown to late stationary phase and then stored in filtered seawater at 4°C for 12 h before the start of the experiment.…”

yneA mRNA instability is involved in temporary inhibition of cell division during the SOS response of Bacillus megaterium

“…The SOS regulon of Escherichia coli comprises 31 experimentally proven damage-inducible (din) genes (Fernández de Henestrosa et al, 2000). Microarray analyses identified upregulation of 163 genes when E. coli cells were exposed to UV light (Berney et al, 2006). The SOS regulon of the Gram-positive model organism Bacillus subtilis consists of 63 (hitherto known) genes organized in 23 operons (Friedberg et al, 1995;Goranov et al, 2006).…”