a Department of Microbiology, Faculty of Science, Khon Kaen University, 123 Mittapap Road, Tambon Nai-Muang, Muang District, Khon Kaen, 40002 Thailand.
Can J Microbiol. 2014 Mar;60(3):121-31. doi: 10.1139/cjm-2013-0713. Epub 2014 Jan 3.
Cupriavidus taiwanensis KKU2500-3 is a cadmium (Cd)-tolerant bacterial strain that was previously isolated from rice fields contaminated with high levels of Cd. In 500 μmol/L CdCl2, the KKU2500-3 strain grew slower and with a more prolonged lag-phase than when grown in the absence of Cd. A proteomic approach was used to characterize the protein expression in the Cd-tolerant bacteria C. taiwanensis KKU2500-3 during growth under Cd stress. When compared with the untreated cells, a total of 982 differentially expressed protein spots were observed in the CdCl2-treated cells, and 59 and 10 spots exhibited >2- and >4-fold changes, respectively. The level of up- and downregulation varied from 2.01- to 11.26-fold and from 2.01- to 5.34-fold, respectively. Of the 33 differentially expressed protein spots analyzed by MALDI TOF MS/MS, 19 spots were successfully identified, many of which were involved in stress responses. The most highly upregulated protein (+7.95-fold) identified was the chaperone GroEL, which indicated that this factor likely contributed to the bacterial survival and growth in response to Cd toxicity. Detection of the downregulated protein flagellin (-3.52-fold) was consistent with the less effective ATP-mediated and flagella-driven motility. The flagella-losing cells were also observed in the Cd-treated bacteria when analyzed by scanning electron microscopy. Thus, the Cd-stressed cells may downregulate pathways involving ATP utilization in favor of other mechanisms in response to Cd toxicity. When the KKU2500-3 strain was grown in the presence of Cd, H2S was not detected, suggesting a possible role of the sulfur in precipitation with Cd. Apart from a general response, no specific process could be determined using the present proteomic approach. However, the potential role of protein folding-mediated GroEL, flagella-mediated motility and CdS biotransformation in Cd toxicity response observed in this study as well as the extent of Cd-tolerant mechanisms using other methods could facilitate the future application of this strain in addressing Cd environmental contamination.
台湾铜绿假单胞菌 KKU2500-3 是一株耐镉细菌，先前从受高浓度镉污染的稻田中分离得到。在 500μmol/L CdCl2 中，KKU2500-3 菌株的生长速度比在无镉条件下更慢，潜伏期更长。采用蛋白质组学方法研究了耐镉细菌 C. taiwanensis KKU2500-3 在镉胁迫下生长过程中的蛋白表达特征。与未经处理的细胞相比，在 CdCl2 处理的细胞中观察到总共 982 个差异表达的蛋白斑点，其中 59 个和 10 个斑点的变化分别超过 2 倍和 4 倍。上调和下调的水平分别为 2.01 倍至 11.26 倍和 2.01 倍至 5.34 倍。通过 MALDI TOF MS/MS 分析的 33 个差异表达蛋白斑点中，有 19 个斑点成功鉴定，其中许多与应激反应有关。鉴定出的上调最显著的蛋白（+7.95 倍）是伴侣蛋白 GroEL，这表明该因子可能有助于细菌在应对镉毒性时的存活和生长。鞭毛蛋白（-3.52 倍）的下调检测与 ATP 介导的和鞭毛驱动的运动效率降低一致。用扫描电子显微镜分析时，也观察到在镉处理的细菌中出现鞭毛缺失的细胞。因此，镉胁迫的细胞可能下调涉及 ATP 利用的途径，转而依赖于其他应对镉毒性的机制。当 KKU2500-3 菌株在镉存在下生长时，未检测到 H2S，这表明硫可能在与镉的沉淀中起作用。除了一般反应外，目前的蛋白质组学方法还不能确定特定的过程。然而，在本研究中观察到的蛋白折叠介导的 GroEL、鞭毛介导的运动和 CdS 生物转化在镉毒性反应中的潜在作用，以及使用其他方法确定的镉耐受机制的程度，都可能有助于该菌株在解决镉环境污染方面的未来应用。
