Genetic Analysis of the AdnA Regulon in Pseudomonas fluorescens: Nonessential Role of Flagella in Adhesion to Sand and Biofilm Formation
Genetic Analysis of the AdnA Regulon in Pseudomonas fluorescens: Nonessential Role of Flagella in Adhesion to Sand and Biofilm Formation
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DOI：
10.1128/jb.185.2.453-460.2003
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发表时间：
2003-01
影响因子：
3.2
通讯作者：
E. Robleto;I. López-Hernández;M. Silby;S. Levy
中科院分区：
文献类型：
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作者：
E. Robleto;I. López-Hernández;M. Silby;S. Levy
AdnA是荧光假单胞菌中的一种转录因子，影响鞭毛合成、生物膜形成和沙粒粘附。为了确定AdnA调节子，我们使用了一个启动子Tn 5-lacZ元件的插入突变体的存在和不存在的AdnA的表型研究。在12，000个插入中，我们鉴定了7个不同的推定开放阅读框架（ORF），其由AdnA激活（命名为阿坝，意为由AdnA激活）。aba 120和aba 177与铜绿假单胞菌鞭毛基体组分flgC和flgI具有同源性。另外两个插入，aba 18和aba 51，破坏了影响趋化性的基因。突变位点aba 160（可能影响脂多糖合成）和aba 175（未知功能）导致鞭毛丧失。突变体轴承aba 203成为运动时，补充adnA，但突变的基因没有显示出与已知基因的相似性。奇怪的是，aba 18、aba 51、aba 160和aba 203突变体即使在不存在AdnA的情况下也形成生物膜，抑制了adnA缺失突变体的表型。综合研究结果表明，鞭毛是不必要的沙子附着或生物膜的形成。序列和启动子分析表明，AdnA直接或通过极性效应影响至少23个ORF。这些结果支持AdnA调节除与鞭毛合成直接相关的细胞过程之外的细胞过程的概念，并且定义了荧光假单胞菌中比迄今为止在铜绿假单胞菌中对其同源物FleQ所描述的更广泛的基因干部。
ABSTRACT AdnA is a transcription factor in Pseudomonas fluorescens that affects flagellar synthesis, biofilm formation, and sand adhesion. To identify the AdnA regulon, we used a promoterless Tn5-lacZ element to study the phenotypes of insertion mutants in the presence and absence of AdnA. Of 12,000 insertions, we identified seven different putative open reading frames (ORFs) activated by AdnA (named aba for activated by AdnA). aba120 and aba177 showed homology to flgC and flgI, components of the basal body of the flagella in Pseudomonas aeruginosa. Two other insertions, aba18 and aba51, disrupted genes affecting chemotaxis. The mutant loci aba160 (possibly affecting lipopolysaccharide synthesis) and aba175 (unknown function) led to loss of flagella. The mutant bearing aba203 became motile when complemented with adnA, but the mutated gene showed no similarity to known genes. Curiously, aba18, aba51, aba160, and aba203 mutants formed biofilms even in the absence of AdnA, suppressing the phenotype of the adnA deletion mutant. The combined findings suggest that flagella are nonessential for sand attachment or biofilm formation. Sequence and promoter analyses indicate that AdnA affects at least 23 ORFs either directly or by polar effects. These results support the concept that AdnA regulates cell processes other than those directly related to flagellar synthesis and define a broader cadre of genes in P. fluorescens than that described so far for its homolog, FleQ, in P. aeruginosa.