Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA.
Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA
Appl Environ Microbiol. 2018 Nov 15;84(23). doi: 10.1128/AEM.02027-18. Print 2018 Dec 1.
The hydroxycinnamates (HCAs) ferulate and -coumarate are among the most abundant constituents of lignin, and their degradation by bacteria is an essential step in the remineralization of vascular plant material. Here, we investigate the catabolism of these two HCAs by the marine bacterium E-37, a member of the roseobacter lineage with lignolytic potential. Bacterial degradation of HCAs is often initiated by the activity of a hydroxycinnamoyl-coenzyme A (hydroxycinnamoyl-CoA) synthase. Genome analysis of revealed the presence of two feruloyl-CoA () synthase homologs, an unusual occurrence among characterized HCA degraders. In order to elucidate the role of these homologs in HCA catabolism, and were disrupted using insertional mutagenesis, yielding both single and double mutants. Growth on -coumarate was abolished in the double mutant, whereas maximum cell yield on ferulate was only 2% of that of the wild type. Interestingly, the single mutants demonstrated opposing phenotypes, where the mutant showed impaired growth (extended lag and ∼60% of wild-type rate) on -coumarate, and the mutant showed impaired growth (extended lag and ∼20% of wild-type rate) on ferulate, pointing to distinct but overlapping roles of the encoded homologs, with primarily dedicated to -coumarate utilization and playing a dominant role in ferulate utilization. Finally, a tripartite ATP-independent periplasmic (TRAP) family transporter was found to be required for growth on both HCAs. These findings provide evidence for functional redundancy in the degradation of HCAs in E-37 and offer important insight into the genetic complexity of aromatic compound degradation in bacteria. Hydroxycinnamates (HCAs) are essential components of lignin and are involved in various plant functions, including defense. In nature, microbial degradation of HCAs is influential to global carbon cycling. HCA degradation pathways are also of industrial relevance, as microbial transformation of the HCA, ferulate, can generate vanillin, a valuable flavoring compound. Yet, surprisingly little is known of the genetics underlying bacterial HCA degradation. Here, we make comparisons to previously characterized bacterial HCA degraders and use a genetic approach to characterize genes involved in catabolism and uptake of HCAs in the environmentally relevant marine bacterium We provide evidence of overlapping substrate specificity between HCA degradation pathways and uptake proteins. We conclude that is uniquely poised to utilize HCAs found in the complex mixtures of plant-derived compounds in nature. This strategy may be common among marine bacteria residing in lignin-rich coastal waters and has potential relevance to biotechnology sectors.
羟基肉桂酸(HCAs)阿魏酸和香豆酸是木质素中含量最丰富的成分之一,它们被细菌降解是维管束植物材料矿化的关键步骤。在这里,我们研究了海洋细菌 E-37 对这两种 HCA 的分解代谢,E-37 是具有木质素分解能力的玫瑰杆菌谱系的成员。HCA 的细菌降解通常是由羟基肉桂酰辅酶 A(羟基肉桂酰辅酶 A)合酶的活性启动的。对 的基因组分析表明,存在两种阿魏酰辅酶 A () 合酶同源物,这在已鉴定的 HCA 降解物中是不常见的。为了阐明这些同源物在 HCA 分解代谢中的作用,我们使用插入诱变破坏了 和 ,产生了单突变体和双突变体。-香豆酸盐的生长在 双突变体中被完全消除,而阿魏酸盐的最大细胞产量仅为野生型的 2%。有趣的是,单突变体表现出相反的表型,其中 突变体在 -香豆酸盐上的生长受到抑制(延长的潜伏期和野生型的 60%),而 突变体在阿魏酸盐上的生长受到抑制(延长的潜伏期和野生型的 20%),这表明编码的 同源物具有不同但重叠的作用,其中 主要专门用于 -香豆酸盐的利用,而 在阿魏酸盐的利用中起主导作用。最后,发现一种三部分非依赖于 ATP 的周质(TRAP)家族转运蛋白对于两种 HCA 的生长都是必需的。这些发现为 E-37 中 HCA 降解的功能冗余提供了证据,并为细菌中芳香化合物降解的遗传复杂性提供了重要的见解。羟基肉桂酸(HCAs)是木质素的重要组成部分,参与各种植物功能,包括防御。在自然界中,微生物对 HCAs 的降解对全球碳循环有重要影响。HCA 降解途径在工业上也很重要,因为微生物对 HCA、阿魏酸的转化可以生成香草醛,这是一种有价值的香料化合物。然而,令人惊讶的是,人们对细菌 HCA 降解的遗传基础知之甚少。在这里,我们将与以前描述的细菌 HCA 降解物进行比较,并使用遗传方法来描述在环境相关的海洋细菌 中参与 HCA 分解代谢和摄取的基因。我们提供了 HCA 降解途径和摄取蛋白之间具有重叠底物特异性的证据。我们得出的结论是, 特别适合利用自然界中植物衍生化合物复杂混合物中的 HCAs。这种策略可能在富含木质素的沿海水域的海洋细菌中很常见,并且对生物技术领域具有潜在的相关性。
Appl Environ Microbiol. 2018-11-15
Appl Environ Microbiol. 2013-4-5
Appl Environ Microbiol. 2004-5
J Bacteriol. 2014-12
Appl Environ Microbiol. 2018-10-30
Appl Environ Microbiol. 2023-10-31
Microbiol Spectr. 2022-12-21
Int J Syst Evol Microbiol. 2022-3
Biotechnol Rep (Amst). 2014-9-16
Front Bioeng Biotechnol. 2015-8-20
Plant Biotechnol J. 2014-11-21
J Bacteriol. 2014-12
Science. 2014-5-16