Quorum-sensing-directed protein expression in Serratia proteamaculans B5a

Abstract

N-Acyl-L-homoserine-lactone-producing Serratia species are frequently encountered in spoiling foods of vegetable and protein origin. The role of quorum sensing in the food spoiling properties of these bacteria is currently being investigated. A set of luxR luxI homologous genes encoding a putative quorum sensor was identified in the N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL)-producing Serratia proteamaculans strain B5a. The 3-oxo-C6-HSL synthase SprI showed 79 % similarity with EsaI from Pantoea stewartii and the putative regulatory protein SprR was 86 % similar to the SpnR of Serratia marcescens. Proteome analysis suggested that the presence of at least 39 intracellular proteins was affected by the 3-oxo-C6-HSL-based quorum sensing system. The lipB-encoded secretion system was identified as one target gene of the quorum sensing system. LipB was required for the production of extracellular lipolytic and proteolytic activities, thus rendering the production of food-deterioration-relevant exoenzymes indirectly under the control of quorum sensing. Strain B5a caused quorum-sensing-controlled spoilage of milk. Furthermore, chitinolytic activity was controlled by quorum sensing. This control appeared to be direct and not mediated via LipB. The data presented here demonstrate that quorum-sensing-controlled exoenzymic activities affect food quality. INTRODUCTIONThe bacterial phenomenon of quorum sensing enables bacteria to communicate and thereby coordinate the expression of specific target genes in response to the population density. In a minimum of 30 Gram-negative bacterial species, quorum sensing is mediated by small diffusible signal molecules, N-acylated derivatives of L-homoserine lactone, which may differ in the length and substitution of their respective acyl side chains. N-Acyl-Lhomoserine lactone (AHL) molecules with N-acyl side chains ranging from 4 to 14 carbons and with an oxo-, hydroxy-or no substituent at the C3 position have been identified [for recent reviews see Whitehead et al. (2001), Fuqua et al. (2001) and Miller & Bassler (2001)]. One of the best characterized quorum sensing systems is present in the marine bacterium Vibrio fischeri, in which LuxI synthesizes N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). It is believed that the signal molecule 3-oxo-C6-HSL at a certain threshold concentration binds to a regulatory protein, LuxR, and thereby renders it active. LuxR hereafter activates transcription of the luxICDABEG operon. As a consequence, the bacterial culture expresses a bioluminescent phenotype when it colonizes the light organs of certain fish and squids and a non-bioluminescent phenotype when the bacteria live in a planktonic state in sea water [(for reviews see Sitnikov et al. (1995) and Dunlap (1999)]. This is one of the few known examples of quorumsensing-regulated gene expression in relation to a symbiotic relationship. In most other cases, quorum sensing is related to pathogenicity traits such as conjugal transfer of the Ti plasmids from Agrobacterium tumefaciens ...

Characterization of <i>N</i>-acyl homoserine lactones (AHLs) producing bacteria isolated from vacuum-packaged refrigerated turbot (<i>Scophthalmus maximus</i>) and possible influence of exogenous AHLs on bacterial phenotype

“…The protease activity in these two bacterial strains was induced from the mid-logarithmic phase reaching a maximum at the stationary phase, Exoenzyme production has been reported to be regulated by a QS system in several Gram-negative bacteria. Christensen et al (2003) have described that the lipB gene required for the production of proteolytic and lipolytic activities in Serratia proteamaculans B5α was regulated by 3-oxo-C6-HSL. Jatt et al (2015) have indicated that exogenous AHLs enhance the production of alkalinephosphatase in Pantoea ananatis B9 isolated from marine snow; nevertheless, the addition of AHLs did not affect the exoenzyme activities of amylase, protease, and lipase.…”

A new repertoire of informations about the quorum sensing system in Salmonella enterica serovar Enteritidis PT4

“…Following homogenization, the culture was evenly spread over the plate surface and enclosed with a safeguard to prevent agar spillage. Upon solidification of the medium, the plates were incubated at 37°C for 16 to 24 h in a properly closed humidified plastic container (Ravn et al, 2001;Christensen et al, 2003). In this assay, the production of violacein by C. violaceum resulted in violet spots on the plates, which is considered a positive result for the presence of AHLs (Shaw et al, 1997).…”

Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria

“…Production of lipase, protease and chitinase [115] Aeromonas hydrophila AhyI/AhyR C4HSL (major), C6HSL, C7HSL Serine protease and metalloprotease production; biofilm maturation; Butanediol fermentation [117,119,122] Indian J Microbiol (Jan-Mar 2016) 56(1):1-18 9 …”

“…SmaI/SmaR, SwrI/SwrR, SpnI/SpnR and SplI/SplR are the four homologues of the luxIR system present across Serratia species that regulates phenotypes such as swarming and sliding motility, exo-enzymes, antibiotic production, biofilm formation, butanediol fermentation (Table 3) [114][115][116][117][118].…”