A new class of homoserine lactone quorum-sensing signals.

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.

BadM is a transcriptional repressor and one of three regulators that control benzoyl coenzyme A reductase gene expression in Rhodopseudomonas palustris.

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.

Methylobacterium populi sp. nov., a novel aerobic, pink-pigmented, facultatively methylotrophic, methane-utilizing bacterium isolated from poplar trees (Populus deltoides x nigra DN34).

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.