Williams Jane S, Thomas Marie, Clarke David J
Molecular Microbiology Laboratory, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
Microbiology (Reading). 2005 Aug;151(Pt 8):2543-2550. doi: 10.1099/mic.0.28136-0.
Photorhabdus is a genus of Gram-negative bacteria from the family Enterobacteriaceae. Members of Photorhabdus have a complex life cycle during which the bacterium has a pathogenic interaction with insect larvae whilst also maintaining a mutualistic relationship with nematodes from the family Heterorhabditidae. During growth in the insect, Photorhabdus bacteria produce a broad-spectrum antibiotic identified as 3,5-dihydroxy-4-isopropylstilbene (ST). The biochemical pathway responsible for the production of this antibiotic has not been characterized. In this report, a mutant strain of Photorhabdus luminescens subsp. laumondii TT01, BMM901, has been isolated, by transposon mutagenesis, that is unable to produce the ST antibiotic. Using in silico studies, feeding experiments and biochemical analyses, it is shown that the gene mutated in this strain, stlA, encodes phenylalanine ammonia-lyase (PAL). PAL catalyses the non-oxidative deamination of l-phenylalanine to trans-cinnamic acid and the enzyme is ubiquitous in plants, where it is involved in the production of phenylpropanoids such as lignin and phytoalexins. However, this is the first report of PAL activity in a member of the Proteobacteria.
发光杆菌属是肠杆菌科的革兰氏阴性菌属。发光杆菌属成员具有复杂的生命周期，在此期间，该细菌与昆虫幼虫存在致病相互作用，同时还与异小杆线虫科的线虫保持互利关系。在昆虫体内生长期间，发光杆菌属细菌会产生一种被鉴定为3,5 - 二羟基 - 4 - 异丙基芪（ST）的广谱抗生素。负责产生这种抗生素的生化途径尚未得到表征。在本报告中，通过转座子诱变分离出了一种不能产生ST抗生素的发光杆菌属劳氏亚种TT01的突变菌株BMM901。通过计算机研究、饲养实验和生化分析表明，该菌株中发生突变的基因stlA编码苯丙氨酸解氨酶（PAL）。PAL催化L - 苯丙氨酸非氧化脱氨生成反式肉桂酸，这种酶在植物中普遍存在，参与木质素和植物抗毒素等苯丙烷类化合物的生成。然而，这是首次报道变形菌门成员中存在PAL活性。
