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Schwob G, Cabrol L, Saucède T, Gérard K, Poulin E, Orlando J. Unveiling the co-phylogeny signal between plunderfish Harpagifer spp. and their gut microbiomes across the Southern Ocean. Microbiol Spectr 2024; 12:e0383023. [PMID: 38441978 PMCID: PMC10986581 DOI: 10.1128/spectrum.03830-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 02/09/2024] [Indexed: 03/07/2024] Open
Abstract
Understanding the factors that sculpt fish gut microbiome is challenging, especially in natural populations characterized by high environmental and host genomic complexity. However, closely related hosts are valuable models for deciphering the contribution of host evolutionary history to microbiome assembly, through the underscoring of phylosymbiosis and co-phylogeny patterns. Here, we propose that the recent diversification of several Harpagifer species across the Southern Ocean would allow the detection of robust phylogenetic congruence between the host and its microbiome. We characterized the gut mucosa microbiome of 77 individuals from four field-collected species of the plunderfish Harpagifer (Teleostei, Notothenioidei), distributed across three biogeographic regions of the Southern Ocean. We found that seawater physicochemical properties, host phylogeny, and geography collectively explained 35% of the variation in bacterial community composition in Harpagifer gut mucosa. The core microbiome of Harpagifer spp. gut mucosa was characterized by a low diversity, mostly driven by selective processes, and dominated by a single Aliivibrio Operational Taxonomic Unit (OTU) detected in more than 80% of the individuals. Nearly half of the core microbiome taxa, including Aliivibrio, harbored co-phylogeny signal at microdiversity resolution with host phylogeny, indicating an intimate symbiotic relationship and a shared evolutionary history with Harpagifer. The clear phylosymbiosis and co-phylogeny signals underscore the relevance of the Harpagifer model in understanding the role of fish evolutionary history in shaping the gut microbiome assembly. We propose that the recent diversification of Harpagifer may have led to the diversification of Aliivibrio, exhibiting patterns that mirror the host phylogeny. IMPORTANCE Although challenging to detect in wild populations, phylogenetic congruence between marine fish and its microbiome is critical, as it highlights intimate associations between hosts and ecologically relevant microbial symbionts. Our study leverages a natural system of closely related fish species in the Southern Ocean to unveil new insights into the contribution of host evolutionary trajectory on gut microbiome assembly, an underappreciated driver of the global marine fish holobiont. Notably, we unveiled striking evidence of co-diversification between Harpagifer and its microbiome, demonstrating both phylosymbiosis of gut bacterial communities and co-phylogeny of some specific bacterial symbionts, mirroring the host diversification patterns. Given Harpagifer's significance as a trophic resource in coastal areas and its vulnerability to climatic and anthropic pressures, understanding the potential evolutionary interdependence between the hosts and its microbiome provides valuable microbial candidates for future monitoring, as they may play a pivotal role in host species acclimatization to a rapidly changing environment.
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Affiliation(s)
- Guillaume Schwob
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
- Department of Ecological Sciences, Faculty of Sciences, University of Chile, Santiago, Chile
- Institute of Ecology and Biodiversity, Santiago, Chile
| | - Léa Cabrol
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
- Institute of Ecology and Biodiversity, Santiago, Chile
- Aix Marseille University, Univ Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, Marseille, France, Marseille, France
| | - Thomas Saucède
- UMR 6282 Biogeosciences, University Bourgogne Franche-Comté, CNRS, EPHE, Dijon, France
| | - Karin Gérard
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
- Laboratory of Antarctic and Subantarctic Marine Ecosystems, Faculty of Sciences, University of Magallanes, Punta Arenas, Chile
- Cape Horn International Center, Puerto Williams, Chile
| | - Elie Poulin
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
- Department of Ecological Sciences, Faculty of Sciences, University of Chile, Santiago, Chile
- Institute of Ecology and Biodiversity, Santiago, Chile
| | - Julieta Orlando
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems (BASE), Santiago, Chile
- Department of Ecological Sciences, Faculty of Sciences, University of Chile, Santiago, Chile
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Yan C, Li X, Zhang G, Bi J, Hao H, Hou H. Quorum Sensing (QS)-regulated target predictions of Hafnia alvei H4 based on the joint application of genome and STRING database. Food Res Int 2022; 157:111356. [DOI: 10.1016/j.foodres.2022.111356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 05/03/2022] [Accepted: 05/10/2022] [Indexed: 11/25/2022]
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Maharajan AD, Hjerde E, Hansen H, Willassen NP. Quorum Sensing Controls the CRISPR and Type VI Secretion Systems in Aliivibrio wodanis 06/09/139. Front Vet Sci 2022; 9:799414. [PMID: 35211539 PMCID: PMC8861277 DOI: 10.3389/fvets.2022.799414] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 01/12/2022] [Indexed: 12/26/2022] Open
Abstract
For bacteria to thrive in an environment with competitors, phages and environmental cues, they use different strategies, including Type VI Secretion Systems (T6SSs) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) to compete for space. Bacteria often use quorum sensing (QS), to coordinate their behavior as the cell density increases. Like other aliivibrios, Aliivibrio wodanis 06/09/139 harbors two QS systems, the main LuxS/LuxPQ system and an N-acyl homoserine lactone (AHL)-mediated AinS/AinR system and a master QS regulator, LitR. To explore the QS and survival strategies, we performed genome analysis and gene expression profiling on A. wodanis and two QS mutants (ΔainS and ΔlitR) at two cell densities (OD600 2.0 and 6.0) and temperatures (6 and 12°C). Genome analysis of A. wodanis revealed two CRISPR systems, one without a cas loci (CRISPR system 1) and a type I-F CRISPR system (CRISPR system 2). Our analysis also identified three main T6SS clusters (T6SS1, T6SS2, and T6SS3) and four auxiliary clusters, as well about 80 potential Type VI secretion effectors (T6SEs). When comparing the wildtype transcriptome data at different cell densities and temperatures, 13–18% of the genes were differentially expressed. The CRISPR system 2 was cell density and temperature-independent, whereas the CRISPR system 1 was temperature-dependent and cell density-independent. The primary and auxiliary clusters of T6SSs were both cell density and temperature-dependent. In the ΔlitR and ΔainS mutants, several CRISPR and T6SS related genes were differentially expressed. Deletion of litR resulted in decreased expression of CRISPR system 1 and increased expression of CRISPR system 2. The T6SS1 and T6SS2 gene clusters were less expressed while the T6SS3 cluster was highly expressed in ΔlitR. Moreover, in ΔlitR, the hcp1 gene was strongly activated at 6°C compared to 12°C. AinS positively affected the csy genes in the CRISPR system 2 but did not affect the CRISPR arrays. Although AinS did not significantly affect the expression of T6SSs, the hallmark genes of T6SS (hcp and vgrG) were AinS-dependent. The work demonstrates that T6SSs and CRISPR systems in A. wodanis are QS dependent and may play an essential role in survival in its natural environment.
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Affiliation(s)
- Amudha Deepalakshmi Maharajan
- Norwegian Structural Biology Center and Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
- *Correspondence: Amudha Deepalakshmi Maharajan
| | - Erik Hjerde
- Norwegian Structural Biology Center and Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
- Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Hilde Hansen
- Norwegian Structural Biology Center and Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Nils Peder Willassen
- Norwegian Structural Biology Center and Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
- Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
- Nils Peder Willassen
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Maharajan AD, Hansen H, Khider M, Willassen NP. Quorum sensing in Aliivibrio wodanis 06/09/139 and its role in controlling various phenotypic traits. PeerJ 2021; 9:e11980. [PMID: 34513327 PMCID: PMC8395575 DOI: 10.7717/peerj.11980] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/25/2021] [Indexed: 11/20/2022] Open
Abstract
Background Quorum Sensing (QS) is a cell-to-cell communication system that bacteria utilize to adapt to the external environment by synthesizing and responding to signalling molecules called autoinducers. The psychrotrophic bacterium Aliivibrio wodanis 06/09/139, originally isolated from a winter ulcer of a reared Atlantic salmon, produces the autoinducer N-3-hydroxy-decanoyl-homoserine-lactone (3OHC10-HSL) and encodes the QS systems AinS/R and LuxS/PQ, and the master regulator LitR. However, the role of QS in this bacterium has not been investigated yet. Results In the present work we show that 3OHC10-HSL production is cell density and temperature-dependent in A. wodanis 06/09/139 with the highest production occurring at a low temperature (6 °C). Gene inactivation demonstrates that AinS is responsible for 3OHC10-HSL production and positively regulated by LitR. Inactivation of ainS and litR further show that QS is involved in the regulation of growth, motility, hemolysis, protease activity and siderophore production. Of these QS regulated activities, only the protease activity was found to be independent of LitR. Lastly, supernatants harvested from the wild type and the ΔainS and ΔlitR mutants at high cell densities show that inactivation of QS leads to a decreased cytopathogenic effect (CPE) in a cell culture assay, and strongest attenuation of the CPE was observed with supernatants harvested from the ΔlitR mutant. Conclusion A. wodanis 06/09/139 use QS to regulate a number of activities that may prove important for host colonization or interactions. The temperature of 6 °C that is in the temperature range at which winter ulcer occurs, plays a role in AHL production and development of CPE on a Chinook Salmon Embryo (CHSE) cell line.
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Affiliation(s)
- Amudha Deepalakshmi Maharajan
- Norwegian Structural Biology Center and The Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Hilde Hansen
- Norwegian Structural Biology Center and The Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Miriam Khider
- Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, NTNU-Norwegian University of Science and Technology, Trondheim, Norway
| | - Nils Peder Willassen
- Norwegian Structural Biology Center and The Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.,Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
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The fish pathogen Aliivibrio salmonicida LFI1238 can degrade and metabolize chitin despite major gene loss in the chitinolytic pathway. Appl Environ Microbiol 2021; 87:e0052921. [PMID: 34319813 DOI: 10.1128/aem.00529-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fish pathogen Aliivibrio (Vibrio) salmonicida LFI1238 is thought to be incapable of utilizing chitin as a nutrient source since approximately half of the genes representing the chitinolytic pathway are disrupted by insertion sequences. In the present study, we combined a broad set of analytical methods to investigate this hypothesis. Cultivation studies revealed that Al. salmonicida grew efficiently on N-acetylglucosamine (GlcNAc) and chitobiose ((GlcNAc)2), the primary soluble products resulting from enzymatic chitin hydrolysis. The bacterium was also able to grow on chitin particles, albeit at a lower rate compared to the soluble substrates. The genome of the bacterium contains five disrupted chitinase genes (pseudogenes) and three intact genes encoding a glycoside hydrolase family 18 (GH18) chitinase and two auxiliary activity family 10 (AA10) lytic polysaccharide monooxygenases (LPMOs). Biochemical characterization showed that the chitinase and LPMOs were able to depolymerize both α- and β-chitin to (GlcNAc)2 and oxidized chitooligosaccharides, respectively. Notably, the chitinase displayed up to 50-fold lower activity compared to other well-studied chitinases. Deletion of the genes encoding the intact chitinolytic enzymes showed that the chitinase was important for growth on β-chitin, whereas the LPMO gene-deletion variants only showed minor growth defects on this substrate. Finally, proteomic analysis of Al. salmonicida LFI1238 growth on β-chitin showed expression of all three chitinolytic enzymes, and intriguingly also three of the disrupted chitinases. In conclusion, our results show that Al. salmonicida LFI1238 can utilize chitin as a nutrient source and that the GH18 chitinase and the two LPMOs are needed for this ability. IMPORTANCE The ability to utilize chitin as a source of nutrients is important for the survival and spread of marine microbial pathogens in the environment. One such pathogen is Aliivibrio (Vibrio) salmonicida, the causative agent of cold water vibriosis. Due to extensive gene decay, many key enzymes in the chitinolytic pathway have been disrupted, putatively rendering this bacterium incapable of chitin degradation and utilization. In the present study we demonstrate that Al. salmonicida can degrade and metabolize chitin, the most abundant biopolymer in the ocean. Our findings shed new light on the environmental adaption of this fish pathogen.
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Yan C, Li X, Zhang G, Zhu Y, Bi J, Hao H, Hou H. Quorum Sensing-Mediated and Growth Phase-Dependent Regulation of Metabolic Pathways in Hafnia alvei H4. Front Microbiol 2021; 12:567942. [PMID: 33737914 PMCID: PMC7960787 DOI: 10.3389/fmicb.2021.567942] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 01/26/2021] [Indexed: 11/13/2022] Open
Abstract
Quorum sensing (QS) is a widespread regulatory mechanism in bacteria used to coordinate target gene expression with cell density. Thus far, little is known about the regulatory relationship between QS and cell density in terms of metabolic pathways in Hafnia alvei H4. In this study, transcriptomics analysis was performed under two conditions to address this question. The comparative transcriptome of H. alvei H4 wild-type at high cell density (OD600 = 1.7) relative to low cell density (OD600 = 0.3) was considered as growth phase-dependent manner (GPDM), and the transcriptome profile of luxI/R deletion mutant (ΔluxIR) compared to the wild-type was considered as QS-mediated regulation. In all, we identified 206 differentially expressed genes (DEGs) mainly presented in chemotaxis, TCA cycle, two-component system, ABC transporters and pyruvate metabolism, co-regulated by the both density-dependent regulation, and the results were validated by qPCR and swimming phenotypic assays. Aside from the co-regulated DEGs, we also found that 59 DEGs, mediated by density-independent QS, function in pentose phosphate and histidine metabolism and that 2084 cell-density-dependent DEGs involved in glycolysis/gluconeogenesis and phenylalanine metabolism were influenced only by GPDM from significantly enriched analysis of transcriptome data. The findings provided new information about the interplay between two density-dependent metabolic regulation, which could assist with the formulation of control strategies for this opportunistic pathogen, especially at high cell density.
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Affiliation(s)
- Congyang Yan
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Xue Li
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Gongliang Zhang
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Yaolei Zhu
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Jingran Bi
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Hongshun Hao
- Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
| | - Hongman Hou
- School of Food Science and Technology, Dalian Polytechnic University, Dalian, China.,Liaoning Key Lab for Aquatic Processing Quality and Safety, Dalian, China
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Su T, Qiu Y, Hua X, Ye B, Luo H, Liu D, Qu P, Qiu Z. Novel Opportunity to Reverse Antibiotic Resistance: To Explore Traditional Chinese Medicine With Potential Activity Against Antibiotics-Resistance Bacteria. Front Microbiol 2020; 11:610070. [PMID: 33414777 PMCID: PMC7782309 DOI: 10.3389/fmicb.2020.610070] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 12/07/2020] [Indexed: 12/13/2022] Open
Abstract
Antibiotic resistance is becoming significantly prominent and urgent in clinical practice with the increasing and wide application of antibacterial drugs. However, developing and synthesizing new antimicrobial drugs is costly and time-consuming. Recently, researchers shifted their sights to traditional Chinese medicine (TCM). Here, we summarized the inhibitory mechanism of TCM herbs and their active ingredients on bacteria, discussed the regulatory mechanism of TCM on antibiotic-resistant bacteria, and revealed preclinical results of TCM herbs and their active components against antibiotic-resistant bacteria in mouse models. Those data suggest that TCM herbs and their effective constituents exhibit potential blockage ability on antibiotic-resistant bacteria, providing novel therapeutic ideas for reversing antibiotic resistance.
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Affiliation(s)
- Ting Su
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
| | - Ye Qiu
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
| | - Xuesi Hua
- College of Literature, Science and Arts University of Michigan, Ann Arbor, MI, United States
| | - Bi Ye
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
| | - Haoming Luo
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
| | - Da Liu
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
| | - Peng Qu
- National Cancer Institute, Frederick, MD, United States
| | - Zhidong Qiu
- College of Pharmacy Changchun University of Chinese Medicine, Changchun, China
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Qian J, Zhang M, Dai C, Huo S, Ma H. Transcriptomic analysis of Listeria monocytogenes under pulsed magnetic field treatment. Food Res Int 2020; 133:109195. [DOI: 10.1016/j.foodres.2020.109195] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 02/06/2023]
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Li X, Zhang G, Zhu Y, Bi J, Hao H, Hou H. Effect of the luxI/R gene on AHL-signaling molecules and QS regulatory mechanism in Hafnia alvei H4. AMB Express 2019; 9:197. [PMID: 31807954 PMCID: PMC6895348 DOI: 10.1186/s13568-019-0917-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 11/22/2019] [Indexed: 01/03/2023] Open
Abstract
Hafnia alvei H4 is a bacterium subject to regulation by a N-acyl-l-homoserine lactone (AHL)-mediated quorum sensing system and is closely related to the corruption of instant sea cucumber. Studying the effect of Hafnia alvei H4 quorum sensing regulatory genes on AHLs is necessary for the quality and preservation of instant sea cucumber. In this study, the draft genome of H. alvei H4, which comprises a single chromosome of 4,687,151 bp, was sequenced and analyzed and the types of AHLs were analyzed employing thin-layer chromatography (TLC) and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS). Then the wild-type strain of H. alvei H4 and the luxI/R double mutant (ΔluxIR) were compared by transcriptome sequencing (RNA-seq). The results indicate that the incomplete genome sequence revealed the presence of one quorum-sensing (QS) gene set, designated as lasI/expR. Three major AHLs, N-hexanoyl-l-homoserine lactone (C6-HSL), N-butyryl-l-homoserine lactone (C4-HSL), and N-(3-oxo-octanoyl)-l-homoserine lactone (3-oxo-C8-HSL) were found, with C6-HSL being the most abundant. C6-HSL was not detected in the culture of the luxI mutant (ΔluxI) and higher levels of C4-HSL was found in the culture of the luxR mutant (ΔluxR), which suggested that the luxR gene may have a positive effect on C4-HSL production. It was also found that AHL and QS genes are closely related in the absence of luxIR double deletion. The results of this study can further elucidate at the genetic level that luxI and luxR genes are involved in the regulation of AHL.
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Wang W, Ma Y, He J, Qi H, Xiao F, He S. Gene regulation for the extreme resistance to ionizing radiation of Deinococcus radiodurans. Gene 2019; 715:144008. [DOI: 10.1016/j.gene.2019.144008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/24/2019] [Accepted: 07/24/2019] [Indexed: 01/05/2023]
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Khider M, Hansen H, Hjerde E, Johansen JA, Willassen NP. Exploring the transcriptome of luxI- and ΔainS mutants and the impact of N-3-oxo-hexanoyl-L- and N-3-hydroxy-decanoyl-L-homoserine lactones on biofilm formation in Aliivibrio salmonicida. PeerJ 2019; 7:e6845. [PMID: 31106062 PMCID: PMC6499059 DOI: 10.7717/peerj.6845] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/18/2019] [Indexed: 01/12/2023] Open
Abstract
Background Bacterial communication through quorum sensing (QS) systems has been reported to be important in coordinating several traits such as biofilm formation. In Aliivibrio salmonicida two QS systems the LuxI/R and AinS/R, have been shown to be responsible for the production of eight acyl-homoserine lactones (AHLs) in a cell density dependent manner. We have previously demonstrated that inactivation of LitR, the master regulator of the QS system resulted in biofilm formation, similar to the biofilm formed by the AHL deficient mutant ΔainSluxI−. In this study, we aimed to investigate the global gene expression patterns of luxI and ainS autoinducer synthases mutants using transcriptomic profiling. In addition, we examined the influence of the different AHLs on biofilm formation. Results The transcriptome profiling of ΔainS and luxI− mutants allowed us to identify genes and gene clusters regulated by QS in A. salmonicida. Relative to the wild type, the ΔainS and luxI− mutants revealed 29 and 500 differentially expressed genes (DEGs), respectively. The functional analysis demonstrated that the most pronounced DEGs were involved in bacterial motility and chemotaxis, exopolysaccharide production, and surface structures related to adhesion. Inactivation of luxI, but not ainS genes resulted in wrinkled colony morphology. While inactivation of both genes (ΔainSluxI−) resulted in strains able to form wrinkled colonies and mushroom structured biofilm. Moreover, when the ΔainSluxI− mutant was supplemented with N-3-oxo-hexanoyl-L-homoserine lactone (3OC6-HSL) or N-3-hydroxy-decanoyl-L-homoserine lactone (3OHC10-HSL), the biofilm did not develop. We also show that LuxI is needed for motility and for repression of EPS production, where repression of EPS is likely operated through the RpoQ-sigma factor. Conclusion These findings imply that the LuxI and AinS autoinducer synthases play a critical role in the regulation of biofilm formation, EPS production, and motility.
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Affiliation(s)
- Miriam Khider
- Norwegian Structural Biology Centre, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Hilde Hansen
- Norwegian Structural Biology Centre, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Erik Hjerde
- Norwegian Structural Biology Centre, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.,Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Jostein A Johansen
- Norwegian Structural Biology Centre, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Nils Peder Willassen
- Norwegian Structural Biology Centre, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.,Centre for Bioinformatics, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway
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