Dipartimento di Biotecnologie Agrarie, Sezione di Microbiologia and Laboratorio Genexpress, Università degli Studi di Firenze, Piazzale delle Cascine, 24, I-50144 Florence, Italy.
Res Microbiol. 2011 Oct;162(8):747-55. doi: 10.1016/j.resmic.2011.06.014. Epub 2011 Jul 20.
Bacteria are known to adopt complex metabolic strategies in an effort to counteract the impact of numerous toxic compounds. In this study, a Cr(VI)-sensitive mutant of the Cr(VI)-hyperresistant bacterium Pseudomonas corrugata 28, obtained by insertional mutagenesis using the EZ-Tn5™ <R6Kγori/KAN-2>Tnp, was employed to gain a greater understanding of Cr(VI) resistance in bacteria. The insertion of the transposon, which occurred 16 bp upstream from the start codon of an ORF encoding a soluble pyridine nucleotide transhydrogenase (STH), negatively affected expression of the sth gene. The compromised expression of the sth gene in the mutant had two main effects on the pyridine nucleotide pools: (i) a decrease in NADPH and NADH fractions with a consequent shift in the redox state toward oxidation; and (ii) a decrease in the total concentration of the pyridine nucleotides. In the absence of a suitable pool of NADPH, the mutant failed to sustain an effective defense against the oxidative stress induced by Cr(VI).
细菌已知会采取复杂的代谢策略，以抵消许多有毒化合物的影响。在这项研究中，使用 EZ-Tn5™ <R6Kγori/KAN-2>Tnp 插入诱变获得了 Cr(VI)超耐受菌假单胞菌皱皮 28 的 Cr(VI)敏感突变体，以更好地了解细菌中的 Cr(VI)抗性。转座子的插入发生在编码可溶性吡啶核苷酸转氢酶 (STH) 的 ORF 的起始密码子上游 16 个碱基对处，这对 sth 基因的表达产生了负面影响。突变体中 sth 基因表达的受损对吡啶核苷酸池有两个主要影响：(i) NADPH 和 NADH 分数减少，导致氧化还原状态向氧化方向转移；和 (ii) 吡啶核苷酸的总浓度降低。在没有合适的 NADPH 池的情况下，突变体无法对 Cr(VI)诱导的氧化应激产生有效的防御。
