Hung Chia-Suei, Zingarelli Sandra, Nadeau Lloyd J, Biffinger Justin C, Drake Carrie A, Crouch Audra L, Barlow Daniel E, Russell John N, Crookes-Goodson Wendy J
Soft Matter Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, USA UES, Inc., Dayton, Ohio, USA.
Soft Matter Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, USA.
Appl Environ Microbiol. 2016 Sep 30;82(20):6080-6090. doi: 10.1128/AEM.01448-16. Print 2016 Oct 15.
Polyester polyurethane (PU) coatings are widely used to help protect underlying structural surfaces but are susceptible to biological degradation. PUs are susceptible to degradation by Pseudomonas species, due in part to the degradative activity of secreted hydrolytic enzymes. Microorganisms often respond to environmental cues by secreting enzymes or secondary metabolites to benefit their survival. This study investigated the impact of exposing several Pseudomonas strains to select carbon sources on the degradation of the colloidal polyester polyurethane Impranil DLN (Impranil). The prototypic Pseudomonas protegens strain Pf-5 exhibited Impranil-degrading activities when grown in sodium citrate but not in glucose-containing medium. Glucose also inhibited the induction of Impranil-degrading activity by citrate-fed Pf-5 in a dose-dependent manner. Biochemical and mutational analyses identified two extracellular lipases present in the Pf-5 culture supernatant (PueA and PueB) that were involved in degradation of Impranil. Deletion of the pueA gene reduced Impranil-clearing activities, while pueB deletion exhibited little effect. Removal of both genes was necessary to stop degradation of the polyurethane. Bioinformatic analysis showed that putative Cbr/Hfq/Crc-mediated regulatory elements were present in the intergenic sequences upstream of both pueA and pueB genes. Our results confirmed that both PueA and PueB extracellular enzymes act in concert to degrade Impranil. Furthermore, our data showed that carbon sources in the growth medium directly affected the levels of Impranil-degrading activity but that carbon source effects varied among Pseudomonas strains. This study uncovered an intricate and complicated regulation of P. protegens PU degradation activity controlled by carbon catabolite repression.
Polyurethane (PU) coatings are commonly used to protect metals from corrosion. Microbiologically induced PU degradation might pose a substantial problem for the integrity of these coatings. Microorganisms from diverse genera, including pseudomonads, possess the ability to degrade PUs via various means. This work identified two extracellular lipases, PueA and PueB, secreted by P. protegens strain Pf-5, to be responsible for the degradation of a colloidal polyester PU, Impranil. This study also revealed that the expression of the degradative activity by strain Pf-5 is controlled by glucose carbon catabolite repression. Furthermore, this study showed that the Impranil-degrading activity of many other Pseudomonas strains could be influenced by different carbon sources. This work shed light on the carbon source regulation of PU degradation activity among pseudomonads and identified the polyurethane lipases in P. protegens.
聚酯聚氨酯（PU）涂层被广泛用于帮助保护底层结构表面，但易受生物降解影响。聚氨酯易被假单胞菌属物种降解，部分原因是其分泌的水解酶具有降解活性。微生物通常通过分泌酶或次生代谢产物来响应环境线索，以利于其生存。本研究调查了将几种假单胞菌菌株暴露于特定碳源对胶体聚酯聚氨酯英普朗尼DLN（Impranil）降解的影响。典型的荧光假单胞菌菌株Pf-5在柠檬酸钠中生长时表现出英普朗尼降解活性，但在含葡萄糖的培养基中则没有。葡萄糖还以剂量依赖的方式抑制了由柠檬酸盐喂养的Pf-5诱导的英普朗尼降解活性。生化和突变分析确定了Pf-5培养上清液中存在的两种细胞外脂肪酶（PueA和PueB）与英普朗尼的降解有关。pueA基因的缺失降低了英普朗尼清除活性，而pueB基因的缺失影响不大。两个基因都去除才能停止聚氨酯的降解。生物信息学分析表明，在pueA和pueB基因上游的基因间序列中存在假定的Cbr/Hfq/Crc介导的调控元件。我们的结果证实，PueA和PueB两种细胞外酶共同作用降解英普朗尼。此外，我们的数据表明，生长培养基中的碳源直接影响英普朗尼降解活性的水平，但碳源的影响在不同假单胞菌菌株中有所不同。本研究揭示了荧光假单胞菌聚氨酯降解活性受碳分解代谢物阻遏控制的复杂调控机制。
聚氨酯（PU）涂层常用于保护金属免受腐蚀。微生物诱导的聚氨酯降解可能对这些涂层的完整性构成重大问题。包括假单胞菌在内的不同属的微生物具有通过各种方式降解聚氨酯的能力。这项工作确定了荧光假单胞菌菌株Pf-5分泌的两种细胞外脂肪酶PueA和PueB负责胶体聚酯聚氨酯英普朗尼的降解。本研究还表明，Pf-5菌株降解活性的表达受葡萄糖碳分解代谢物阻遏的控制。此外，这项研究表明，许多其他假单胞菌菌株的英普朗尼降解活性可能受到不同碳源的影响。这项工作揭示了假单胞菌中聚氨酯降解活性的碳源调控机制，并鉴定了荧光假单胞菌中的聚氨酯脂肪酶。
