Division of Biological Science, Nara Institute of Science & Technology, Ikoma, Nara, Japan
J Bacteriol. 2019 Mar 26;201(8). doi: 10.1128/JB.00712-18. Print 2019 Apr 15.
forms biofilms in response to internal and external stimuli. I previously showed that the deletion mutant was defective in biofilm formation, but the reason for this remains unidentified. CysL is a transcriptional activator of the operon, which encodes sulfite reductase, an enzyme involved in cysteine biosynthesis. Decreased production of sulfite reductase led to biofilm formation defects in the Δ mutant. The Δ mutation was suppressed by disrupting operon genes, whose products function upstream of sulfite reductase in the cysteine biosynthesis pathway, indicating that defects in cysteine biosynthesis were not a direct cause for the defective biofilm formation observed in the Δ mutant. The gene encodes phosphoadenosine phosphosulfate reductase, which requires a reduced form of thioredoxin (TrxA) as an electron donor. High expression of inhibited biofilm formation in the Δ mutant but not in the wild-type strain. Northern blot analysis showed that transcription was induced in the Δ mutant in a disulfide stress-induced regulator Spx-dependent manner. On the basis of these results, I propose that the Δ mutation causes phosphoadenosine phosphosulfate reductase to consume large amounts of reduced thioredoxin, inducing disulfide stress and activating Spx. The mutation restored biofilm formation to the Δ mutant. The Δ mutation reduced expression of the operon, which is required for exopolysaccharide production. Moreover, overexpression of the operon restored biofilm formation to the Δ mutant. Taken together, these results suggest that the Δ mutation activates Spx, which then inhibits biofilm formation through repression of the operon. has been studied as a model organism for biofilm formation. In this study, I explored why the deletion mutant was defective in biofilm formation. I demonstrated that the Δ mutation activated the disulfide stress response regulator Spx, which inhibits biofilm formation by repressing biofilm matrix genes. Homologs of Spx are highly conserved among Gram-positive bacteria with low G+C contents. In some pathogens, Spx is also reported to inhibit biofilm formation by repressing biofilm matrix genes, even though these genes and their regulation are quite different from those of Thus, the negative regulation of biofilm formation by Spx is likely to be well conserved across species and may be an appropriate target for control of biofilm formation.
它会对内外刺激作出生物膜反应。我之前曾表明，缺失突变体在生物膜形成方面有缺陷，但原因尚不清楚。CysL 是操纵子的转录激活因子，该操纵子编码亚硫酸盐还原酶，这是一种参与半胱氨酸生物合成的酶。亚硫酸盐还原酶产量下降导致Δ突变体生物膜形成缺陷。Δ突变被破坏操纵子基因的突变所抑制，其产物在半胱氨酸生物合成途径中位于亚硫酸盐还原酶的上游起作用，这表明半胱氨酸生物合成缺陷不是导致观察到的Δ突变体生物膜形成缺陷的直接原因。基因编码磷酸腺苷磷酸硫酸还原酶，它需要还原型硫氧还蛋白 (TrxA) 作为电子供体。基因的高表达抑制了Δ突变体中的生物膜形成，但对野生型菌株没有影响。Northern blot 分析表明，在Δ突变体中，以二硫键应激诱导调节因子 Spx 依赖的方式诱导转录。基于这些结果，我提出Δ突变导致磷酸腺苷磷酸硫酸还原酶消耗大量还原型硫氧还蛋白，诱导二硫键应激并激活 Spx。突变恢复了Δ突变体的生物膜形成。Δ突变降低了操纵子的表达，该操纵子是产生胞外多糖所必需的。此外，操纵子的过表达恢复了Δ突变体的生物膜形成。综上所述，这些结果表明，Δ突变激活了 Spx，Spx 通过抑制操纵子的表达来抑制生物膜形成。已被研究为生物膜形成的模式生物。在这项研究中，我探讨了为什么缺失突变体在生物膜形成方面有缺陷。我证明了Δ突变激活了二硫键应激反应调节因子 Spx，Spx 通过抑制生物膜基质基因的表达来抑制生物膜形成。Spx 的同源物在低 GC 含量的革兰氏阳性菌中高度保守。在一些病原体中，Spx 也通过抑制生物膜基质基因的表达来抑制生物膜形成，尽管这些基因及其调控机制与截然不同。因此，Spx 对生物膜形成的负调控可能在物种间得到很好的保守，并且可能是控制生物膜形成的合适目标。
