Introduction about the Role of Lux-s gene in Quorum sensing.

Hello all,

Today we are going to see the topic related to quorum sensing and the function of Lux-s genes in regulating cell multiplication and virulence. The world aquaculture industry is facing a lot of struggles in treating diseases. Increased antimicrobial resistance on one side and decreased recovery on another side. In this topic we will discuss the overview about Lux-s genes and its roles in quorum sensing.

We all know that, A. hydrophila is a prevalent and opportunistic pathogen of aquatic organisms, including fish, shrimp, and prawns. Furthermore, A. hydrophila also causes severe diseases in humans, including gastrointestinal illnesses, septicemia, and cellulitis. In several bacterial species, gene expression is controlled by the secretion, detection, and production of extracellular signaling molecules (AI-2) that accumulate in environments in proportion to cell densities of signal molecule-producing cells. This phenomenon is commonly referred to as ‘quorum sensing

Quorum sensing (QS) is a bacterial intercommunication system that controls the expression of multiple genes in response to population density. QS systems use small signal molecules called autoinducers (AIs). When the AIs accumulate to a threshold concentration, the system is activated and directly or indirectly controls the transcription of target genes.

Gram-negative bacteria normally use acylated homoserine lactones (AHLs) as AIs, while gram-positive bacteria use oligopeptide AIs, which act through two-component phosphorelay cascades.

Lux-s associated with the synthesis of AI-2. Lux-s genes are important to mediate the production of AI-2.

Vibrio harveyi can cause infections and diseases in a variety of marine vertebrates and invertebrates, which are harmful to the aquaculture industry. The LuxS quorum-sensing system regulates the expression of virulence factors in a wide variety of pathogenic bacteria.

LuxS/AI-2 is an important quorum sensing system which affects the growth, biofilm formation, virulence, and metabolism of bacteria. LuxS is encoded by the luxS gene, but how this gene is associated with a diverse array of physiological activities in Edwardsiella piscicida (E. piscicida) is not known.Here, an luxS gene mutant strain, the △luxS strain, to identify how LuxS/AI-2 affects pathogenicity. The results showed that LuxS was not found in the luxS gene mutant strain, and this gene deletion decreased E. piscicida growth compared to that of the wild-type strain. Meanwhile, the wild-type strain significantly increased penetration and motility in mucin compared to levels with the △luxS strain.

luxS is found in Gram-positive and Gram-negative bacteria, including A. hydrophila, and performs critical transcription functions in the regulation of genes associated with transport of nucleotides, metabolism, and the synthesis of cell walls or membranes Mutant strains of luxS fail to produce mature biofilms, although increased concentrations of salinity and increased incubation periods also reduce biofilm formation, motility, protease biogenesis, and quorum sensing. Moreover, mutation of the luxS AI-2 synthase gene decreases virulence towards hosts, although virulence can be recovered when AI-2 is added from exogenous sources. From several studies it is clear that Lux-s genes are responsible for inducing virulence in host organisms. On the other hand, several compounds are identified to reduce AI-2 inducers by inhibiting Lux-s gene. Lux-s and AI-2 are correlated in inducing pathogenicity.Studies in inhibiting quorum sensing are limited. 

In the next blog, we will discuss elaborately regarding virulence genes.

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References;

1.https://doi.org/10.1139/cjm-2021-0311

2.10.1128/IAI.74.1.488-496.2006

3.10.1128/IAI.00907-19

4.https://doi.org/10.3390/molecules23102627

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