Microbial responses to xenobiotic compounds. Identification of genes that allow Pseudomonas putida KT2440 to cope with 2,4,6‐trinitrotoluene

Abstract

SummaryPseudomonas putida KT2440 grows in M9 minimal medium with glucose in the presence of 2,4,6‐trinitrotoluene (TNT) at a similar rate than in the absence of TNT, although global transcriptional analysis using DNA microarrays revealed that TNT exerts some stress. Response to TNT stress is regulated at the transcriptional level, as significant changes in the level of expression of 65 genes were observed. Of these genes, 39 appeared upregulated, and 26 were downregulated. The identity of upregulated genes suggests that P. putida uses two kinds of strategies to overcome TNT toxicity: (i) induction of genes encoding nitroreductases and detoxification‐related enzymes (pnrA, xenD, acpD) and (ii) induction of multidrug efflux pump genes (mexEF/oprN) to reduce intracellular TNT concentrations. Mutants of 13 up‐ and 7 downregulated genes were analysed with regards to TNT toxicity revealing the role of the MexE/MexF/OprN pump and a putative isoquinoline 1‐oxidoreductase in tolerance to TNT. The ORF PP1232 whose transcriptional level did not change in response to TNT affected growth in the presence of nitroaromatic compounds and it was found in a screening of 4000 randomly generated mutants.

Enhanced Tolerance to Naphthalene and Enhanced Rhizoremediation Performance for Pseudomonas putida KT2440 via the NAH7 Catabolic Plasmid

“…This result could be explained by functional redundancy between the two transporters, similar to what has been reported previously in Pseudomonas (20,25,43).…”

Mechanisms of Resistance to Chloramphenicol in Pseudomonas putida KT2440

“…whose products are important for a particular process but which do not exhibit changes in transcriptional levels is not revealed by DNA microarray assays (21,54). To overcome this limitation, the whole mutant library was screened on plates containing 25 g/ml chloramphenicol and clones with impaired growth in the presence of the antibiotic were isolated.…”

“…Genome annotation of several natural chloramphenicol-resistant P. putida strains failed to show any specific chloramphenicol-modifying enzymes (36,41,45,67); however, Godoy and colleagues (23) showed that P. putida mutants in the multidrug TtgABC pump exhibited compromised growth in the presence of chloramphenicol (21). Further studies in P. putida DOT-T1E confirmed the role of the TtgABC efflux pump in tolerance to chloramphenicol and other toxic compounds while unveiling the molecular mechanisms involved in the regulation of the expression of this pump in this strain (14,18,58).…”

Expression of the Streptomyces coelicolor SoxR Regulon Is Intimately Linked with Actinorhodin Production

“…The P. putida SoxR regulon has not been elucidated empirically, but in silico analysis of the genome shows SoxR binding sites upstream of an RND transporter (encoded by PP2063-PP2065), an oxidoreductase (encoded by PP2507), and a GGDEF-containing protein (encoded by PP2505) (data not shown). Recently, it was demonstrated that the genes encoding these proteins (among other genes) are induced upon exposure to 2,4,6-trinitrotoluene, a nitroaromatic compound that causes toxicity by increasing cellular levels of reactive oxygen species and hydroxylamine compounds (18).…”