RESUMO
Quorum sensing is a term used to describe cell-to-cell communication that allows cell-density-dependent gene expression. Many bacteria use acyl-homoserine lactone (acyl-HSL) synthases to generate fatty acyl-HSL quorum-sensing signals, which function with signal receptors to control expression of specific genes. The fatty acyl group is derived from fatty acid biosynthesis and provides signal specificity, but the variety of signals is limited. Here we show that the photosynthetic bacterium Rhodopseudomonas palustris uses an acyl-HSL synthase to produce p-coumaroyl-HSL by using environmental p-coumaric acid rather than fatty acids from cellular pools. The bacterium has a signal receptor with homology to fatty acyl-HSL receptors that responds to p-coumaroyl-HSL to regulate global gene expression. We also found that p-coumaroyl-HSL is made by other bacteria including Bradyrhizobium sp. and Silicibacter pomeroyi. This discovery extends the range of possibilities for acyl-HSL quorum sensing and raises fundamental questions about quorum sensing within the context of environmental signalling.
Assuntos
4-Butirolactona/análogos & derivados , Proteínas de Bactérias/metabolismo , Ácidos Cumáricos/metabolismo , Percepção de Quorum , Rodopseudomonas/crescimento & desenvolvimento , Rodopseudomonas/metabolismo , Transdução de Sinais , 4-Butirolactona/química , 4-Butirolactona/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Sequência de Bases , Bioensaio , Regulação Bacteriana da Expressão Gênica , Regulon , Rodopseudomonas/enzimologia , Rodopseudomonas/genética , Alinhamento de SequênciaRESUMO
The rate-limiting enzyme of anaerobic benzoate degradation by Rhodopseudomonas palustris, benzoyl coenzyme A (CoA) reductase, is highly sensitive to oxygen, and its synthesis is tightly regulated. We determined that a previously unknown gene in the benzoate gene cluster, badM, encodes a transcriptional repressor of benzoyl-CoA reductase gene expression. BadM controls gene expression from the benzoyl-CoA reductase promoter in concert with two previously described transcriptional activators.
Assuntos
Acil Coenzima A/metabolismo , Regulação Bacteriana da Expressão Gênica , Oxirredutases/genética , Proteínas Repressoras/metabolismo , Rodopseudomonas/metabolismo , Anaerobiose , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Benzoatos/metabolismo , Meios de Cultura , Oxirredutases/metabolismo , Regiões Promotoras Genéticas , Proteínas Repressoras/genética , Rodopseudomonas/enzimologia , Rodopseudomonas/genética , Rodopseudomonas/crescimento & desenvolvimento , Transcrição GênicaRESUMO
A pink-pigmented, aerobic, facultatively methylotrophic bacterium, strain BJ001T, was isolated from internal poplar tissues (Populus deltoidesxnigra DN34) and identified as a member of the genus Methylobacterium. Phylogenetic analyses showed that strain BJ001T is related to Methylobacterium thiocyanatum, Methylobacterium extorquens, Methylobacterium zatmanii and Methylobacterium rhodesianum. However, strain BJ001T differed from these species in its carbon-source utilization pattern, particularly its use of methane as the sole source of carbon and energy, an ability that is shared with only one other member of the genus, Methylobacterium organophilum. In addition, strain BJ001T is the only member of the genus Methylobacterium to be described as an endophyte of poplar trees. On the basis of its physiological, genotypic and ecological properties, the isolate is proposed as a member of a novel species of the genus Methylobacterium, Methylobacterium populi sp. nov. (type strain, BJ001T=ATCC BAA-705T=NCIMB 13946T).
