Identification of Quorum-Sensing Signal Molecules and a Biosynthetic Gene in Alicycliphilus sp. Isolated from Activated Sludge

Abstract

Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we isolated an AHL-producing bacteria from an activated sludge sample collected from an electronic component factory, which we named Alicycliphilus sp. B1. Clone library analysis revealed that Alicycliphilus was a subdominant genus in this sample. When we screened the activated sludge sample for AHL-producing strains, 12 of 14 the AHL-producing isolates were assigned to the genus Alicycliphilus. A putative AHL-synthase gene, ALISP_0667, was cloned from the genome of B1 and transformed into Escherichia coli DH5α. The AHLs were extracted from the culture supernatants of the B1 strain and E. coli DH5α cells harboring the ALISP_0667 gene and were identified by liquid chromatography-mass spectrometry as N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-hydroxydodecanoyl)-l-homoserine lactone. The results of comparative genomic analysis suggested that the quorum-sensing genes in the B1 strain might have been acquired by horizontal gene transfer within activated sludge.

Alicycliphilus : current knowledge and potential for bioremediation of xenobiotics

“…; Morohoshi et al . ). Further studies to identify AHLs target genes and how they are regulated will allow us to understand the AHLs role in the adaptations of Alicycliphilus sp.…”

“…B1 might have been acquired by horizontal gene transfer from other bacteria commonly found in activated sludges (Morohoshi et al . ).…”

“…An interesting feature that could be related to the Alicycliphilus biodegradative capacity was the finding that the strain B1 is able to produce two types of N-AHLs (Morohoshi et al 2016). AHLs are quorum-sensing (QS) signal molecules that, in proteobacteria from active sludge of wastewater treatment plants, are used to regulate the expression of genes encoding exoenzymes needed for degrading recalcitrant compounds (Chong et al 2012).…”

“…The AHL-synthase gene (ALISP_RS03145) from Alicycliphilus sp. B1 was cloned and expressed in Escherichia coli DH5a cells resulting in the production of the two types of AHLs (Okutsu et al 2015;Morohoshi et al 2016). Further studies to identify AHLs target genes and how they are regulated will allow us to understand the AHLs role in the adaptations of Alicycliphilus sp.…”

“…Cs1-4 genome, suggesting that the AHL-QS genes identified in Alicycliphilus sp. B1 might have been acquired by horizontal gene transfer from other bacteria commonly found in activated sludges (Morohoshi et al 2016).…”