Department of Microbiology, University of Washington, Seattle, Washington, USA.
Appl Environ Microbiol. 2013 Sep;79(18):5745-52. doi: 10.1128/AEM.01417-13. Epub 2013 Jul 12.
We are interested in the root microbiome of the fast-growing Eastern cottonwood tree, Populus deltoides. There is a large bank of bacterial isolates from P. deltoides, and there are 44 draft genomes of bacterial endophyte and rhizosphere isolates. As a first step in efforts to understand the roles of bacterial communication and plant-bacterial signaling in P. deltoides, we focused on the prevalence of acyl-homoserine lactone (AHL) quorum-sensing-signal production and reception in members of the P. deltoides microbiome. We screened 129 bacterial isolates for AHL production using a broad-spectrum bioassay that responds to many but not all AHLs, and we queried the available genome sequences of microbiome isolates for homologs of AHL synthase and receptor genes. AHL signal production was detected in 40% of 129 strains tested. Positive isolates included members of the Alpha-, Beta-, and Gammaproteobacteria. Members of the luxI family of AHL synthases were identified in 18 of 39 proteobacterial genomes, including genomes of some isolates that tested negative in the bioassay. Members of the luxR family of transcription factors, which includes AHL-responsive factors, were more abundant than luxI homologs. There were 72 in the 39 proteobacterial genomes. Some of the luxR homologs appear to be members of a subfamily of LuxRs that respond to as-yet-unknown plant signals rather than bacterial AHLs. Apparently, there is a substantial capacity for AHL cell-to-cell communication in proteobacteria of the P. deltoides microbiota, and there are also Proteobacteria with LuxR homologs of the type hypothesized to respond to plant signals or cues.
我们对快速生长的东方棉白杨（Populus deltoides）的根微生物群感兴趣。有大量来自 P. deltoides 的细菌分离株，还有 44 个细菌内生菌和根际分离株的草图基因组。作为了解细菌通讯和植物-细菌信号在 P. deltoides 中的作用的第一步，我们专注于酰基高丝氨酸内酯（AHL）群体感应信号产生和感知在 P. deltoides 微生物群成员中的普遍性。我们使用广谱生物测定法筛选了 129 个细菌分离株的 AHL 产生情况，该生物测定法可响应许多但不是所有 AHL，我们还查询了微生物群分离株的可用基因组序列，以寻找 AHL 合酶和受体基因的同源物。在测试的 129 个菌株中，有 40%检测到 AHL 信号产生。阳性分离株包括α-、β-和γ-变形菌纲的成员。在 39 个变形菌基因组中鉴定出了 AHL 合酶的 luxI 家族成员，包括在生物测定中测试为阴性的一些分离株的基因组。luxR 家族的转录因子成员，包括 AHL 反应性因子，比 luxI 同源物更丰富。在 39 个变形菌基因组中共有 72 个。一些 luxR 同源物似乎是响应未知植物信号而不是细菌 AHL 的 luxR 亚家族的成员。显然，P. deltoides 微生物群的变形菌中存在大量的 AHL 细胞间通讯能力，并且还有具有假定响应植物信号或线索的 luxR 同源物的变形菌。
