Editorial

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Open AccessEditorial

Editorial for the Special Issue, ‘Secondary Metabolites from Microorganisms or Microorganism–Host Interaction?’

by Fengli Zhang and Michel Denis

Biology 2023, 12(12), 1515; https://doi.org/10.3390/biology12121515 - 12 Dec 2023

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Abstract

In this Special Issue, there are 13 published papers from over 10 countries [...] Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

Research

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13 pages, 2580 KiB

Open AccessArticle

Adaptation of Commensal Escherichia coli in Tomato Fruits: Motility, Stress, Virulence

by Alberto Vassallo, Roberta Amoriello, Prandvera Guri, Lorenzo Casbarra, Matteo Ramazzotti, Marco Zaccaroni, Clara Ballerini, Duccio Cavalieri and Massimiliano Marvasi

Biology 2023, 12(4), 633; https://doi.org/10.3390/biology12040633 - 21 Apr 2023

Cited by 1 | Viewed by 1712

Abstract

Food contamination can be a serious concern for public health because it can be related to the severe spreading of pathogens. This is a main issue, especially in the case of fresh fruits and vegetables; indeed, they have often been associated with gastrointestinal [...] Read more.

Food contamination can be a serious concern for public health because it can be related to the severe spreading of pathogens. This is a main issue, especially in the case of fresh fruits and vegetables; indeed, they have often been associated with gastrointestinal outbreak events, due to contamination with pathogenic bacteria. However, little is known about the physiological adaptation and bacterial response to stresses encountered in the host plant. Thus, this work aimed to investigate the adaptation of a commensal E. coli strain while growing in tomato pericarp. Pre-adapted and non-adapted cells were compared and used to contaminate tomatoes, demonstrating that pre-adaptation boosted cell proliferation. DNA extracted from pre-adapted and non-adapted cells was sequenced, and their methylation profiles were compared. Hence, genes involved in cell adhesion and resistance against toxic compounds were identified as genes involved in adaptation, and their expression was compared in these two experimental conditions. Finally, pre-adapted and non-adapted E. coli were tested for their ability to resist the presence of toxic compounds, demonstrating that adaptation exerted a protective effect. In conclusion, this work provides new information about the physiological adaptation of bacteria colonizing the tomato fruit pericarp. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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15 pages, 4813 KiB

Open AccessArticle

Genome-Based Analysis of the Potential Bioactivity of the Terrestrial Streptomyces vinaceusdrappus Strain AC-40

by Abdelrahman M. Sedeek, Israa Salah, Hasnaa L. Kamel, Mohamed A. Soltan, Eman Nour, Abdulrahman Alshammari, Muhammad Shahid Riaz Rajoka and Tarek R. Elsayed

Biology 2023, 12(3), 345; https://doi.org/10.3390/biology12030345 - 21 Feb 2023

Cited by 3 | Viewed by 2493

Abstract

Streptomyces are factories of antimicrobial secondary metabolites. We isolated a Streptomyces species associated with the Pelargonium graveolens rhizosphere. Its total metabolic extract exhibited potent antibacterial and antifungal properties against all the tested pathogenic microbes. Whole genome sequencing and genome analyses were performed to [...] Read more.

Streptomyces are factories of antimicrobial secondary metabolites. We isolated a Streptomyces species associated with the Pelargonium graveolens rhizosphere. Its total metabolic extract exhibited potent antibacterial and antifungal properties against all the tested pathogenic microbes. Whole genome sequencing and genome analyses were performed to take a look at its main characteristics and to reconstruct the metabolic pathways that can be associated with biotechnologically useful traits. AntiSMASH was used to identify the secondary metabolite gene clusters. In addition, we searched for known genes associated with plant growth-promoting characteristics. Finally, a comparative and pan-genome analysis with three closely related genomes was conducted. It was identified as Streptomyces vinaceusdrappus strain AC-40. Genome mining indicated the presence of several secondary metabolite gene clusters. Some of them are identical or homologs to gene clusters of known metabolites with antimicrobial, antioxidant, and other bioactivities. It also showed the presence of several genes related to plant growth promotion traits. The comparative genome analysis indicated that at least five of these gene clusters are highly conserved through rochei group genomes. The genotypic and phenotypic characteristics of S. vinaceusdrappus strain AC-40 indicate that it is a promising source of beneficial secondary metabolites with pharmaceutical and biotechnological applications. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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14 pages, 4794 KiB

Open AccessArticle

Towards the Understanding of the Function of Lanthipeptide and TOMM-Related Genes in Haloferax mediterranei

by Thales Costa, Elena Cassin, Catarina Moreirinha, Sónia Mendo and Tânia Sousa Caetano

Biology 2023, 12(2), 236; https://doi.org/10.3390/biology12020236 - 02 Feb 2023

Cited by 1 | Viewed by 1399

Abstract

Research on secondary metabolites produced by Archaea such as ribosomally synthesized and post-translationally modified peptides (RiPPs) is limited. The genome of Haloferax mediterranei ATCC 33500 encodes lanthipeptide synthetases (medM1, medM2, and medM3) and a thiazole-forming cyclodehydratase (ycaO), [...] Read more.

Research on secondary metabolites produced by Archaea such as ribosomally synthesized and post-translationally modified peptides (RiPPs) is limited. The genome of Haloferax mediterranei ATCC 33500 encodes lanthipeptide synthetases (medM1, medM2, and medM3) and a thiazole-forming cyclodehydratase (ycaO), possibly involved in the biosynthesis of lanthipeptides and the TOMMs haloazolisins, respectively. Lanthipeptides and TOMMs often have antimicrobial activity, and H. mediterranei has antagonistic activity towards haloarchaea shown to be independent of medM genes. This study investigated (i) the transcription of ycaO and medM genes, (ii) the involvement of YcaO in bioactivity, and (iii) the impact of YcaO and MedM-encoding genes’ absence in the biomolecular profile of H. mediterranei. The assays were performed with biomass grown in agar and included RT-qPCR, the generation of knockout mutants, bioassays, and FTIR analysis. Results suggest that ycaO and medM genes are transcriptionally active, with the highest number of transcripts observed for medM2. The deletion of ycaO gene had no effect on H. mediterranei antihaloarchaea activity. FTIR analysis of medM and ycaO knockout mutants suggest that MedMs and YcaO activity might be directly or indirectly related t lipids, a novel perspective that deserves further investigation. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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19 pages, 3266 KiB

Open AccessArticle

Role of Alternative Elicitor Transporters in the Onset of Plant Host Colonization by Streptomyces scabiei 87-22

by Isolde M. Francis, Danica Bergin, Benoit Deflandre, Sagar Gupta, Joren J. C. Salazar, Richard Villagrana, Nudzejma Stulanovic, Silvia Ribeiro Monteiro, Frédéric Kerff, Rosemary Loria and Sébastien Rigali

Biology 2023, 12(2), 234; https://doi.org/10.3390/biology12020234 - 01 Feb 2023

Cited by 6 | Viewed by 2268

Abstract

Plant colonization by Streptomyces scabiei, the main cause of common scab disease on root and tuber crops, is triggered by cello-oligosaccharides, cellotriose being the most efficient elicitor. The import of cello-oligosaccharides via the ATP-binding cassette (ABC) transporter CebEFG-MsiK induces the production of [...] Read more.

Plant colonization by Streptomyces scabiei, the main cause of common scab disease on root and tuber crops, is triggered by cello-oligosaccharides, cellotriose being the most efficient elicitor. The import of cello-oligosaccharides via the ATP-binding cassette (ABC) transporter CebEFG-MsiK induces the production of thaxtomin phytotoxins, the central virulence determinants of this species, as well as many other metabolites that compose the ‘virulome’ of S. scabiei. Homology searches revealed paralogues of the CebEFG proteins, encoded by the cebEFG2 cluster, while another ABC-type transporter, PitEFG, is encoded on the pathogenicity island (PAI). We investigated the gene expression of these candidate alternative elicitor importers in S. scabiei 87-22 upon cello-oligosaccharide supply by transcriptomic analysis, which revealed that cebEFG2 expression is highly activated by both cellobiose and cellotriose, while pitEFG expression was barely induced. Accordingly, deletion of pitE had no impact on virulence and thaxtomin production under the conditions tested, while the deletion of cebEFG2 reduced virulence and thaxtomin production, though not as strong as the mutants of the main cello-oligosaccharide transporter cebEFG1. Our results thus suggest that both ceb clusters participate, at different levels, in importing the virulence elicitors, while PitEFG plays no role in this process under the conditions tested. Interestingly, under more complex culture conditions, the addition of cellobiose restored thaxtomin production when both ceb clusters were disabled, suggesting the existence of an additional mechanism that is involved in sensing or importing the elicitor of the onset of the pathogenic lifestyle of S. scabiei. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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15 pages, 4115 KiB

Open AccessArticle

Chemical Defence by Sterols in the Freshwater Ciliate Stentor polymorphus

by Federico Buonanno, Francesco Trenti, Gabriele Achille, Adriana Vallesi, Graziano Guella and Claudio Ortenzi

Biology 2022, 11(12), 1749; https://doi.org/10.3390/biology11121749 - 30 Nov 2022

Cited by 1 | Viewed by 1566

Abstract

Heterotrich ciliates typically retain toxic substances in specialized ejectable organelles, called extrusomes, which are used in predator-prey interactions. In this study, we analysed the chemical defence strategy of the freshwater heterotrich ciliate Stentor polymorphus against the predatory ciliate Coleps hirtus, and the [...] Read more.

Heterotrich ciliates typically retain toxic substances in specialized ejectable organelles, called extrusomes, which are used in predator-prey interactions. In this study, we analysed the chemical defence strategy of the freshwater heterotrich ciliate Stentor polymorphus against the predatory ciliate Coleps hirtus, and the microturbellarian flatworm Stenostomum sphagnetorum. The results showed that S. polymorphus is able to defend itself against these two predators by deploying a mix of bioactive sterols contained in its extrusomes. Sterols were isolated in vivo and characterized by liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR), as ergosterol, 7-dehydroporiferasterol, and their two peroxidized analogues. The assessment of the toxicity of ergosterol and ergosterol peroxide against various organisms, indicated that these sterols are essential for the effectiveness of the chemical defence in S. polymorphus. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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9 pages, 1430 KiB

Open AccessArticle

Bacillamide F, Extracted from Marine Bacillus atrophaeus C89, Preliminary Effects on Leukemia Cell Lines

by Shengnan Zhang, Giorgia Croppi, Heng Hu, Yingxin Li, Chunmiao Zhu, Fang Wu, Fengli Zhang and Zhiyong Li

Biology 2022, 11(12), 1712; https://doi.org/10.3390/biology11121712 - 25 Nov 2022

Cited by 2 | Viewed by 1384

Abstract

Developing new treatments for leukemia is essential since current therapies often suffer from drug resistance and toxicity. Bacillamides are very promising, naturally occurring compounds with various bioactivities. In the present study, we investigated the use of bacillamide analogues, a new thiazole alkaloid bacillamide [...] Read more.

Developing new treatments for leukemia is essential since current therapies often suffer from drug resistance and toxicity. Bacillamides are very promising, naturally occurring compounds with various bioactivities. In the present study, we investigated the use of bacillamide analogues, a new thiazole alkaloid bacillamide F that was isolated from marine Bacillus atrophaeus C89 associated with sponge Dysidea avara. The structure of the new compound bacillamide F with indolyl–thiazolyl–pyrrolidine ring was determined by high resolution mass spectrometry, secondary mass spectrometry, and nuclear magnetic resonance analyses. Intriguingly, bacillamide F is able to inhibit the proliferation of an acute myeloid leukemia cell line HL60 (IC50 (24 h) 21.82 µM), and an acute T-cell leukemia Jurkat (IC50 (24 h) 46.90 µM), rather than inhibit the proliferation of the acute histiocytic lymphoma U-937 cell line, human fetal lung fibroblast MRC-5 cell line, and some solid tumor cell lines (IC50 (24 h) > 100 µM). The study provides a new indication of the pharmacological activity of natural product bacillamides. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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15 pages, 3123 KiB

Open AccessArticle

Cycle-Inhibiting Factor Is Associated with Burkholderia pseudomallei Invasion in Human Neuronal Cells

by Amporn Rungruengkitkun, Niramol Jitprasutwit, Watcharamat Muangkaew, Chantira Suttikornchai, Sarunporn Tandhavanant, Nitaya Indrawattana, Sumate Ampawong, Passanesh Sukphopetch, Narisara Chantratita and Pornpan Pumirat

Biology 2022, 11(10), 1439; https://doi.org/10.3390/biology11101439 - 01 Oct 2022

Cited by 3 | Viewed by 1442

Abstract

Burkholderia pseudomallei is a pathogenic bacterium that causes human melioidosis, which is associated with a high mortality rate. However, the underlying mechanisms of B. pseudomallei pathogenesis are largely unknown. In this study, we examined the infection of human neuronal SH-Sy5y cells by several [...] Read more.

Burkholderia pseudomallei is a pathogenic bacterium that causes human melioidosis, which is associated with a high mortality rate. However, the underlying mechanisms of B. pseudomallei pathogenesis are largely unknown. In this study, we examined the infection of human neuronal SH-Sy5y cells by several clinically relevant B. pseudomallei strains. We found that all tested B. pseudomallei strains can invade SH-Sy5y cells, undergo intracellular replication, cause actin-tail formation, and form multinucleated giant cells. Additionally, a deletion mutant of B. pseudomallei cycle-inhibiting factor (cif) was constructed that exhibited reduced invasion in SH-Sy5y cells. Complementation of cif restored invasion of the B. pseudomallei cif-deleted mutant. Our findings enhance understanding of B. pseudomallei pathogenicity in terms of the virulence factor Cif and demonstrate the function of Cif in neurological melioidosis. This may eventually lead to the discovery of novel targets for treatment and a strategy to control the disease. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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22 pages, 6504 KiB

Open AccessArticle

Micrococcus lylae MW407006 Pigment: Production, Optimization, Nano-Pigment Synthesis, and Biological Activities

by Yahya H. Shahin, Bassma H. Elwakil, Doaa A. Ghareeb and Zakia A. Olama

Biology 2022, 11(8), 1171; https://doi.org/10.3390/biology11081171 - 04 Aug 2022

Cited by 9 | Viewed by 2372

Abstract

Bacterial pigments (e.g., melanin and carotenoids) are considered to be among the most important secondary metabolites due to their various pharmacological activities against cancer and microbial resistance. Different pigmented bacterial strains were isolated from soil samples from El Mahmoudiyah governance and screened for [...] Read more.

Bacterial pigments (e.g., melanin and carotenoids) are considered to be among the most important secondary metabolites due to their various pharmacological activities against cancer and microbial resistance. Different pigmented bacterial strains were isolated from soil samples from El Mahmoudiyah governance and screened for their antimicrobial activity. The most promising pigment producer was identified as Micrococcus lylae MW407006; furthermore, the produced pigment was identified as echinenone (β-carotene pigment). The pigment production was optimized through a central composite statistical design to maximize the biomass production, pigment concentration, and the antimicrobial activity. It was revealed that the most significant fermentation parameters were the glucose (as a carbon source) and asparagine (as a nitrogen source) concentrations. Nano-echinenone was synthesized using the ball milling technique, characterized, and finally assessed for potential antimicrobial, antioxidant, and antitumor activities. The data revealed that the synthesized nano-echinenone had higher antimicrobial activity than the crude pigment. The cytotoxic potency of echinenone and nano-echinenone was investigated in different cell lines (normal and cancer cells). The inhibition of cell proliferation and induction of cell death was observed in Caco-2 and Hep-G2 cells. The data proved that nano-echinenone is a suitable candidate for use as a safe antimicrobial and anti-hepatocellular-carcinoma agent. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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Review

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12 pages, 1267 KiB

Open AccessReview

Overview of Yersinia pestis Metallophores: Yersiniabactin and Yersinopine

by Taghrid Chaaban, Yehya Mohsen, Zeinab Ezzeddine and Ghassan Ghssein

Biology 2023, 12(4), 598; https://doi.org/10.3390/biology12040598 - 14 Apr 2023

Cited by 9 | Viewed by 2680

Abstract

The pathogenic anaerobic bacteria Yersinia pestis (Y. pestis), which is well known as the plague causative agent, has the ability to escape or inhibit innate immune system responses, which can result in host death even before the activation of adaptive responses. [...] Read more.

The pathogenic anaerobic bacteria Yersinia pestis (Y. pestis), which is well known as the plague causative agent, has the ability to escape or inhibit innate immune system responses, which can result in host death even before the activation of adaptive responses. Bites from infected fleas in nature transmit Y. pestis between mammalian hosts causing bubonic plague. It was recognized that a host’s ability to retain iron is essential in fighting invading pathogens. To proliferate during infection, Y. pestis, like most bacteria, has various iron transporters that enable it to acquire iron from its hosts. The siderophore-dependent iron transport system was found to be crucial for the pathogenesis of this bacterium. Siderophores are low-molecular-weight metabolites with a high affinity for Fe³⁺. These compounds are produced in the surrounding environment to chelate iron. The siderophore secreted by Y. pestis is yersiniabactin (Ybt). Another metallophore produced by this bacterium, yersinopine, is of the opine type and shows similarities with both staphylopine and pseudopaline produced by Staphylococcus aureus and Pseudomonas aeruginosa, respectively. This paper sheds light on the most important aspects of the two Y. pestis metallophores as well as aerobactin a siderophore no longer secreted by this bacterium due to frameshift mutation in its genome. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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18 pages, 3626 KiB

Open AccessReview

A Review of Pseudomonas aeruginosa Metallophores: Pyoverdine, Pyochelin and Pseudopaline

by Ghassan Ghssein and Zeinab Ezzeddine

Biology 2022, 11(12), 1711; https://doi.org/10.3390/biology11121711 - 25 Nov 2022

Cited by 33 | Viewed by 5719

Abstract

P. aeruginosa is a common Gram-negative bacterium found in nature that causes severe infections in humans. As a result of its natural resistance to antibiotics and the ability of biofilm formation, the infection with this pathogen can be therapeutic challenging. During infection, P. [...] Read more.

P. aeruginosa is a common Gram-negative bacterium found in nature that causes severe infections in humans. As a result of its natural resistance to antibiotics and the ability of biofilm formation, the infection with this pathogen can be therapeutic challenging. During infection, P. aeruginosa produces secondary metabolites such as metallophores that play an important role in their virulence. Metallophores are metal ions chelating molecules secreted by bacteria, thus allowing them to survive in the host under metal scarce conditions. Pyoverdine, pyochelin and pseudopaline are the three metallophores secreted by P. aeruginosa. Pyoverdines are the primary siderophores that acquire iron from the surrounding medium. These molecules scavenge and transport iron to the bacterium intracellular compartment. Pyochelin is another siderophore produced by this bacterium, but in lower quantities and its affinity for iron is less than that of pyoverdine. The third metallophore, pseudopaline, is an opine narrow spectrum ion chelator that enables P. aeruginosa to uptake zinc in particular but can transport nickel and cobalt as well. This review describes all the aspects related to these three metallophore, including their main features, biosynthesis process, secretion and uptake when loaded by metals, in addition to the genetic regulation responsible for their synthesis and secretion. Full article

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14 pages, 3565 KiB

Open AccessReview

Antibiotics from Insect-Associated Actinobacteria

by Anna A. Baranova, Yuliya V. Zakalyukina, Anna A. Ovcharenko, Vladimir A. Korshun and Anton P. Tyurin

Biology 2022, 11(11), 1676; https://doi.org/10.3390/biology11111676 - 18 Nov 2022

Cited by 9 | Viewed by 3288

Abstract

Actinobacteria are involved into multilateral relationships between insects, their food sources, infectious agents, etc. Antibiotics and related natural products play an essential role in such systems. The literature from the January 2016–August 2022 period devoted to insect-associated actinomycetes with antagonistic and/or enzyme-inhibiting activity [...] Read more.

Actinobacteria are involved into multilateral relationships between insects, their food sources, infectious agents, etc. Antibiotics and related natural products play an essential role in such systems. The literature from the January 2016–August 2022 period devoted to insect-associated actinomycetes with antagonistic and/or enzyme-inhibiting activity was selected. Recent progress in multidisciplinary studies of insect–actinobacterial interactions mediated by antibiotics is summarized and discussed. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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14 pages, 922 KiB

Open AccessReview

The Key Element Role of Metallophores in the Pathogenicity and Virulence of Staphylococcus aureus: A Review

by Ghassan Ghssein and Zeinab Ezzeddine

Biology 2022, 11(10), 1525; https://doi.org/10.3390/biology11101525 - 18 Oct 2022

Cited by 16 | Viewed by 2425

Abstract

The ubiquitous bacterium Staphylococcus aureus causes many diseases that sometimes can be fatal due to its high pathogenicity. The latter is caused by the ability of this pathogen to secrete secondary metabolites, enabling it to colonize inside the host causing infection through various [...] Read more.

The ubiquitous bacterium Staphylococcus aureus causes many diseases that sometimes can be fatal due to its high pathogenicity. The latter is caused by the ability of this pathogen to secrete secondary metabolites, enabling it to colonize inside the host causing infection through various processes. Metallophores are secondary metabolites that enable bacteria to sequester metal ions from the surrounding environment since the availability of metal ions is crucial for bacterial metabolism and virulence. The uptake of iron and other metal ions such as nickel and zinc is one of these essential mechanisms that gives this germ its virulence properties and allow it to overcome the host immune system. Additionally, extensive interactions occur between this pathogen and other bacteria as they compete for resources. Staphylococcus aureus has high-affinity metal import pathways including metal ions acquisition, recruitment and metal–chelate complex import. These characteristics give this bacterium the ability to intake metallophores synthesized by other bacteria, thus enabling it to compete with other microorganisms for the limited nutrients. In scarce host conditions, free metal ions are extremely low because they are confined to storage and metabolic molecules, so metal ions are sequestered by metallophores produced by this bacterium. Both siderophores (iron chelating molecules) and staphylopine (wide- spectrum metallophore) are secreted by Staphylococcus aureus giving it infectious properties. The genetic regulation of the synthesis and export together with the import of metal loaded metallophores are well established and are all covered in this review. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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10 pages, 1782 KiB

Open AccessBrief Report

Osmotic Gradient Is a Factor That Influences the Gill Microbiota Communities in Oryzias melastigma

by Keng Po Lai, Delbert Almerick T. Boncan, Lu Yang, Cherry Chi Tim Leung, Jeff Cheuk Hin Ho, Xiao Lin, Ting Fung Chan, Richard Yuen Chong Kong and William Ka Fai Tse

Biology 2022, 11(10), 1528; https://doi.org/10.3390/biology11101528 - 19 Oct 2022

Cited by 3 | Viewed by 1687

Abstract

The fish gill is the first tissue that is exposed to the external media and undergoes continuous osmotic challenges. Recently, our group published an article entitled “Integrated Omics Approaches Revealed the Osmotic Stress-Responsive Genes and Microbiota in Gill of Marine Medaka” in the [...] Read more.

The fish gill is the first tissue that is exposed to the external media and undergoes continuous osmotic challenges. Recently, our group published an article entitled “Integrated Omics Approaches Revealed the Osmotic Stress-Responsive Genes and Microbiota in Gill of Marine Medaka” in the journal mSystems (e0004722, 2022), and suggested the possible host-bacterium interaction in the fish gill during osmotic stress. The previous study was performed by the progressive fresh water transfer (i.e., seawater to fresh water transfer via 50% seawater (FW)). Our group hypothesized that osmotic gradient could be a factor that determines the microbiota communities in the gill. The current 16S rRNA metagenomic sequencing study found that the direct transfer (i.e., seawater to fresh water (FWd)) could result in different gill microbiota communities in the same fresh water endpoints. Pseduomonas was the dominant bacteria (more than 55%) in the FWd gill. The Kyoto Encyclopedia of Genes and Genomes and MetaCyc analysis further suggested that the FWd group had enhanced osmosensing pathways, such as the ATP-binding cassette transporters, taurine degradation, and energy-related tricarboxylic acid metabolism compared to the FW group. Full article

(This article belongs to the Special Issue Secondary Metabolites from Microorganisms, or Microorganism-Host Interaction?)

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