Abstract
BackgroundAcute hepatopancreatic necrosis syndrome (AHPND) caused by Vibrio parahaemolyticus strain (VPAHPND) impacts the shrimp industry worldwide. With the increasing problem of antibiotic abuse, studies on quorum sensing (QS) system and anti-QS compounds bring potential breakthroughs for disease prevention and treatment.MethodsIn this study, the cell-free culture supernatant (CFCS) and its extract of V. alginolyticus BC25 were investigated for anti-QS activity against a reporter bacteria, Chromobacterium violaceum DMST46846. The effects of CFCS and/ or extract on motility, biofilm formation and extracellular polymeric substances (EPSs) of VPAHPND PSU5591 were evaluated. Moreover, the effects of V. alginolyticus BC25 on virulence of VPAHPND PSU5591 were investigated by shrimp challenge test. The potentially active anti-QS compounds presented in the extract and effect on gene expression of VPAHPND PSU5591 were identified.ResultsThe CFCS of V. alginolyticus BC25 and its extract showed a significant anti-QS activity against the reporter bacteria as well as swimming and swarming motilities, biofilms, and EPSs production by VPAHPND PSU5591. Transcriptome analysis revealed that V. alginolyticus BC25 extract significantly reduced the flagella genes involved in biofilm formation and iron-controlled virulence regulatory gene of VPAHPND PSU5591. Whereas, the LuxR family transcriptional regulator gene, c-factor, a cell-cell signaling gene, and capsular polysaccharide were up-regulated. The potentially active anti-QS compounds identified in extract were Cyclo-(L-Leu-L-Pro), and Cyclo-(L-Phe-L-Pro). Furthermore, V. alginolyticus BC25 enhanced disease resistance against VPAHPND PSU5591 in tested shrimp larvae.ConclusionThese findings suggest that V. alginolyticus BC25 could provide natural anti-QS and anti-biofilms compounds and has great ability to be used as biocontrol agent against VPAHPND infection in shrimp aquaculture.
Highlights
In recent years, the global shrimp aquaculture industry has suffered serious losses from acute hepatopancreatic necrotic disease (AHPND) outbreak caused by a unique Vibrio parahaemolyticus strain (VPAHPND)
It has been reported that VPAHPND from penaeid shrimp in Mexico demonstrated a high level of resistance to tetracycline (≥ 5 μg/mL) and carried the tetB gene coding for tetracycline resistance (Han et al, 2015)
Our results revealed that cell-free culture supernatant (CFCS) of V. alginolyticus and its extract showed anti-quorum sensing system (QS) activity
Summary
The global shrimp aquaculture industry has suffered serious losses from acute hepatopancreatic necrotic disease (AHPND) outbreak caused by a unique Vibrio parahaemolyticus strain (VPAHPND). Bacteria have a mechanism for cell to cell communication as a quorum sensing system (QS) through the use of small signaling molecule called autoinducer They use signaling molecule to coordinate their behavior such as bioluminescence, biofilm formation, spore formation, motility and developing antibiotic resistance (Ryan & Dow, 2008). The potentially active anti-QS compounds presented in the extract and effect on gene expression of VPAHPND PSU5591 were identified. The CFCS of V. alginolyticus BC25 and its extract showed a significant anti-QS activity against the reporter bacteria as well as swimming and swarming motilities, biofilms, and EPSs production by VPAHPND PSU5591. These findings suggest that V. alginolyticus BC25 could provide natural anti-QS and anti-biofilms compounds and has great ability to be used as biocontrol agent against VPAHPND infection in shrimp aquaculture
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