Unravelling the genome of long chain N-acylhomoserine lactone-producing Acinetobacter sp. strain GG2 and identification of its quorum sensing synthase gene

Abstract

Myriad proteobacteria use N-acyl homoserine lactone (AHL) molecules as quorum sensing (QS) signals to regulate different physiological functions, including virulence, antibiotic production, and biofilm formation. Many of these proteobacteria possess LuxI/LuxR system as the QS mechanism. Recently, we reported the 3.89 Mb genome of Acinetobacter sp. strain GG2. In this work, the genome of this long chain AHL-producing bacterium was unravelled which led to the molecular characterization of luxI homologue, designated as aciI. This 552 bp gene was cloned and overexpressed in Escherichia coli BL21(DE3). The purified protein was ∼20.5 kDa and is highly similar to several autoinducer proteins of LuxI family among Acinetobacter species. To verify the AHL synthesis activity of this protein, high-resolution liquid chromatography–mass spectrometry analysis revealed the production of 3-oxo-dodecanoyl-homoserine lactone and 3-hydroxy-dodecanoyl-homoserine lactone from induced E. coli harboring the recombinant AciI. Our data show for the first time, the cloning and characterization of the luxI homologue from Acinetobacter sp. strain GG2, and confirmation of its AHLs production. These data are of great significance as the annotated genome of strain GG2 has provided a valuable insight in the study of autoinducer molecules and its roles in QS mechanism of the bacterium.

Multiple Quorum Quenching Enzymes Are Active in the Nosocomial Pathogen Acinetobacter baumannii ATCC17978

“…A. nosocomialis M2, formerly identified as A. baumannii (Carruthers et al, 2013 ), presents a typical LuxI/LuxR-type QS network, constituted by the AHL-synthase AbaI and the AHL-receptor and transcriptional activator AbaR (Niu et al, 2008 ; Bhargava et al, 2010 ). Genes homologous to abaI and abaR of A. nosocomialis M2 can be found in A. baumannii (Smith et al, 2007 ; Niu et al, 2008 ) and in the genomes of other Acinetobacter species (Kang and Park, 2010 ; Bitrian et al, 2012 ; How et al, 2015 ; Oh and Choi, 2015 ). Moreover, a number of studies have described the generation of AHL signals in members of the genus (Niu et al, 2008 ; Chan et al, 2011 , 2014 ; How et al, 2015 ).…”

Cloning and characterization of short‐chain N‐acyl homoserine lactone‐producing Enterobacter asburiae strain L1 from lettuce leaves

“…They are synthesized using S-adenosylmethionine (SAM) and acylated acyl carrier protein (Acyl-ACP) as the substrates (Schauder & Bassler, 2001;Swift et al, 1997). When the AHLs concentration has reached its threshold level, the AHLs bind to their cognate receptor (LuxR homolog), resulting in a complex that stimulates the expression of numerous downstream target genes and hence the physiological functions of the cells (How et al, 2015;Parsek & Greenberg, 2000). It was found that the biochemical mechanisms of AHLs synthesis and regulation are conserved in many bacterial species even though they show expression of different phenotypes (Dong, Gusti, Zhang, Xu, & Zhang, 2002).…”

N-Acyl Homoserine Lactone-Mediated Quorum Sensing in Aeromonas veronii biovar sobria Strain 159: Identification of LuxRI Homologs

“…Nitrogen gas was used as the collision gas in the collisionally-induced dissociation mode for the MS/MS analysis and the collision energy was set at 10 eV. The Agilent MassHunter software was used to analyse the MS data (Yin et al, 2012 ; How et al, 2015 ). Known amounts of synthetic AHLs (Sigma, St. Louis, MO) were injected as standards.…”