Transcriptional Response ofEscherichia colito TPEN

Abstract

DNA microarrays were used to probe the transcriptional response of Escherichia coli to N, N, N, N-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN). Fifty-five transcripts were significantly up-regulated, including all of the genes that are regulated by Zur and many that are regulated by Fur. In the same TPEN-treated cells, 46 transcripts were significantly down-regulated.The transcriptional response of Escherichia coli to elevated levels of metal ions such as Zn(II), Cd(II), Co(II), Ni(II), and Fe(II) has been probed in an effort to understand the mechanisms by which the homeostatic levels of these metal ions are maintained (10,15,51,95,96). In contrast, very few studies have probed the global response of E. coli to low levels of metal ions, presumably due to the difficulty of sufficiently depleting the growth medium of metal ions. In this study, cDNA microarrays were used to probe the transcriptional response of E. coli to stress by N, N, NЈ, NЈ-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN). TPEN (58, 81), a cell-permeative, divalent metal chelator, is often called "Zn(II) specific" (17,33,38,48,59,64,71,79,80,83,88). Our data show significant changes in the transcription of several genes in cells stressed with TPEN.To identify genes that are differentially expressed in response to TPEN, E. coli BL21(DE3) cells were grown in minimal medium (76) until the cultures reached mid-log phase. TPEN was introduced, and the cells were cultured for 5 h; this time was chosen so that the results would correspond to previous transcriptional response studies with excess Zn(II) (51). The cultures containing 5 M TPEN were analyzed with DNA microarrays (E. coli K12 V2 array slides from MWG-BIOTECH), and the results were compared to those from E. coli cells grown in minimal medium containing no TPEN. A minimum of six slides was used for each experiment (three slides with one combination of Cy3 and Cy5 dyes and three slides with swapped dyes). Fifty-five transcripts were significantly up-regulated (twofold) ( Table 1). Four genes (ykgM, znuA, znuC, and yodA) that are regulated by Zur, the Zn(II) uptake regulator (30), exhibited significant increases in expression. The remaining Zur-regulated transcript, znuB, was also up-regulated; however, this transcript did not meet our filtering criteria: (i) P values of Յ0.5, (ii) Ն2-fold changes in expression, and (iii) consistent data in all six slides. The expression of zntA, which is regulated by ZntR and encodes the high-affinity Zn(II) exporter in E. coli (7,14,78), was unchanged in E. coli cultures stressed with TPEN (see the complete set of DNA array data).Twenty-nine of the up-regulated genes from TPEN-supplemented cultures are transcriptionally regulated by Fur, the iron uptake regulator (Table 1), and several are involved in Fe transport. The genes (entB, entA, entD, entE, and fes) which encode proteins involved with enterobactin synthesis and uptake (26, 29, 54) and the fec genes (fecR and fecI), which encode proteins involved in Fe import (23), were significantly up-regulated. S...

Characterization of the Response to Zinc Deficiency in the Cyanobacterium Anabaena sp. Strain PCC 7120

“…Anabaena, TPEN seems to induce a general divalent metal deficiency, which is consistent with the observations in E. coli (56).…”

“…Although TPEN is often referred to as a zinc-specific chelator, it has been reported to bind other metals (6), and in E. coli it has been shown to alter the expression of genes responding not only to zinc but also to a variety of other divalent metals (56). In our experiments, TPEN altered the expression of the isiA and the petE genes of Anabaena that respond to iron and copper, respectively (see Fig.…”

Zinc Uptake Contributes to Motility and Provides a Competitive Advantage to Proteus mirabilis during Experimental Urinary Tract Infection

“…Perhaps zinc homeostasis (as opposed to exclusively uptake or efflux) plays a role in motility. Indeed, in E. coli, the transcription of genes involved in flagellar biosynthesis is downregulated in response to treatment with TPEN (63), while the transcription of some motility-related genes is increased in E. coli treated with zinc (37).…”

Acinetobacter baumannii Response to Host-Mediated Zinc Limitation Requires the Transcriptional Regulator Zur

“…Some of the genes found to be Zur regulated in A. baumannii have homologs shown to be Zur or Zn regulated in other bacteria, largely those genes involved in metal homeostasis (36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51). These include znuA, znuB, znuC, znuD1, znuD2, rpmE2, czcD, and a gene encoding a putative siderophore receptor, A1S_0092.…”