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Microorganisms May 2023A monitoring program to follow vibriosis incidents in the Greek marine aquaculture was implemented over the past 13 years. 273 isolates, from various cases originating...
A monitoring program to follow vibriosis incidents in the Greek marine aquaculture was implemented over the past 13 years. 273 isolates, from various cases originating from eight regions and nine hosts, were collected and characterized. The main aquaculture species of the survey were the European seabass () and the gilthead seabream (). Various species of were associated with vibriosis. had the highest prevalence and was isolated throughout the year from all hosts. During the warm months, prevailed with frequent co-isolations of subsp. and , while during spring, other species were more abundant, such as and Phylogenetic analysis using the gene and the metabolic fingerprint of the isolates showed great variability within the species of the collection. The severity of the disease and the frequency of outbreaks make vibriosis (that is, mainly attributed to ) an important concern for the regional aquaculture sector.
PubMed: 37317171
DOI: 10.3390/microorganisms11051197 -
Applied and Environmental Microbiology Jul 2023Coral reefs are among the most biodiverse ecosystems, providing habitats for various organisms. Studies on coral bleaching have been increasing recently, but little is...
Coral reefs are among the most biodiverse ecosystems, providing habitats for various organisms. Studies on coral bleaching have been increasing recently, but little is known about the distribution and community assembly of coral pathogenic bacteria (e.g., several species). We elucidated the distribution pattern and interaction relationships of total bacteria and spp. in sediments from the Xisha Islands, which are characterized by their high coverage and diversity of coral resources. spp. showed significantly higher relative abundance values in the Xisha Islands (1.00 × 10 copies/g) than in other areas (approximately 1 × 10 to 9.04 × 10 copies/g), indicating that the coral bleaching event of 2020 may have promoted the bloom of vibrios. A spatial shift in community composition was observed between the northern (Photobacterium rosenbergii and Vibrio ponticus) and southern (Vibrio ishigakensis and Vibrio natriegens) sites, accompanied by a clear distance-decay pattern. The spatial distance and coral species (e.g., and ) had much greater correlations with the community than did environmental factors. However, complex mechanisms may exist in the community assembly of spp. due to the large proportion of unexplained variation. Stochastic processes may play an important role, as shown by the neutral model. Vibrio harveyi had the highest relative abundance (77.56%) and niche breadth, compared to other species, and it was negatively correlated with Acroporidae, likely reflecting its strong competitive ability and adverse effects on specific corals. Our study provides insights into the bloom and underlying assembly mechanisms of sedimentary vibrios in the Xisha Islands, thereby contributing to identify the potential indicator of coral bleaching and provide inspiration for the environmental management of coral reef areas. Coral reefs exert important roles in maintaining the sustainability of marine ecosystems but decline worldwide due to various drivers, especially pathogenic microorganisms. Here, we investigated the distribution pattern and interactions of total bacteria and spp. in the sediments from Xisha Islands during the coral bleaching event of 2020. Our results showed that the abundances of (1.00 × 10 copies/g) were high across the whole sites, indicating the bloom of sedimentary spp. Coral pathogenic species were abundant in the sediments, likely reflecting adverse effects on several kinds of corals. The compositions of the spp. were separated by geographical location, which was mainly attributable to the spatial distance and coral species. Overall, this work contributes by providing evidence for the outbreak of coral pathogenic vibrios. The pathogenic mechanism of the dominant species (especially V. harveyi) should be comprehensively considered by laboratory infection experiments in the future.
Topics: Animals; Ecosystem; Coral Bleaching; Islands; Coral Reefs; Anthozoa; Vibrio
PubMed: 37314342
DOI: 10.1128/aem.00543-23 -
Microbiology Spectrum Aug 2023Scombrotoxin (histamine) fish poisoning is a common seafood-borne illness attributed to toxin production by histamine-producing bacteria (HPB) in fish tissues during...
Scombrotoxin (histamine) fish poisoning is a common seafood-borne illness attributed to toxin production by histamine-producing bacteria (HPB) in fish tissues during decomposition. In laboratory studies, growth of HPB and other bacterial species is affected by physical and chemical attributes, but natural communities of HPB are not well understood. To determine how environmental and water quality variables may affect density of HPB in the natural aquatic environment, we compared presence and abundance of HPB to ambient temperature, salinity, dissolved oxygen, fecal coliforms, male-specific coliphage, nutrient concentrations, carbon and nitrogen stable isotope ratios, and C:N in water samples collected from July 2017 to February 2018 along a natural salinity gradient in a tidal river on the coast of northern Gulf of Mexico. HPB in water samples were quantified using a real-time PCR, most probable number method. HPB species were identified via 16S rRNA gene sequences. Temperature and salinity were determined to be the main factors driving HPB presence and concentration. Canonical correspondence analysis revealed that different HPB were associated with different environmental conditions. Photobacterium damselae was found under warmer, higher-salinity conditions; Raoultella planticola was found at colder, lower-salinity conditions; Enterobacter aerogenes was found at warmer, lower-salinity conditions; and Morganella morganii was found at most sites, independent of environmental conditions. These results showed that naturally occurring HPB abundance and species composition can be affected by environmental conditions, which could manifest in various potentials for histamine formation and scombrotoxin fish poisoning risk based on environmental factors. This study determined the effects of environmental conditions on presence and abundance of naturally occurring histamine-producing bacteria in the northern Gulf of Mexico. Here, we show that HPB abundance and species composition are related to ambient temperature and salinity, with the magnitude of this effect dependent on the particular HPB species. This finding suggests that environmental conditions at fishing sites could affect the risk of human illness from scombrotoxin (histamine) fish poisoning.
Topics: Animals; Male; Humans; Histamine; Gulf of Mexico; RNA, Ribosomal, 16S; Water Quality; Bacteria; Foodborne Diseases
PubMed: 37310253
DOI: 10.1128/spectrum.04720-22 -
MSystems Jun 2023Facultative marine bacterial pathogens sense environmental signals so that the expression of virulence factors is upregulated on entry into hosts and downregulated...
Facultative marine bacterial pathogens sense environmental signals so that the expression of virulence factors is upregulated on entry into hosts and downregulated during the free-living lifestyle in the environment. In this study, we utilized transcriptome sequencing to compare the transcriptional profiles of subsp. , a generalist pathogen that causes disease in diverse marine animals and fatal infections in humans at NaCl concentrations that mimic the free-living lifestyle or host internal milieu, respectively. We here show that NaCl concentration constitutes a major regulatory signal that shapes the transcriptome and uncover 1,808 differentially expressed genes (888 upregulated and 920 downregulated in response to low-salt conditions). Growth at 3% NaCl, a salinity that mimics the free-living lifestyle, upregulated genes involved in energy production, nitrogen metabolism, transport of compatible solutes, utilization of trehalose and fructose, and carbohydrate and amino acid metabolism with strong upregulation of the arginine deiminase system (ADS). In addition, we observed a marked increase in resistance to antibiotics at 3% NaCl. On the contrary, the low salinity conditions (1% NaCl) that mimic those encountered in the host triggered a virulence gene expression profile that maximized the production of the type 2 secretion system (T2SS)-dependent cytotoxins damselysin, phobalysin P, and a putative PirAB-like toxin, observations that were corroborated by the analysis of the secretome. Low salinity also upregulated the expression of iron-acquisition systems, efflux pumps, and other functions related to stress response and virulence. The results of this study greatly expand our knowledge of the salinity-responsive adaptations of a generalist and versatile marine pathogen. IMPORTANCE Pathogenic species experience continuous shifts of NaCl concentration in their life cycles. However, the impact of salinity changes in gene regulation has been studied in a small number of species. In this study, we analyzed the transcriptional response of subsp. (), a generalist and facultative pathogen, to changes in salinity, and demonstrate that growth at 1% NaCl in comparison to 3% NaCl triggers a virulence program of gene expression, with a major impact in the T2SS-dependent secretome. The decrease in NaCl concentration encountered by bacteria on entry into a host is proposed to constitute a regulatory signal that upregulates a genetic program involved in host invasion and tissue damage, nutrient scavenging (notably iron), and stress responses. This study will surely inspire new research on pathobiology, as well as on other important pathogens of the family and related taxa whose salinity regulons still await investigation.
Topics: Humans; Animals; Virulence; Sodium Chloride; Salinity; Photobacterium; Iron
PubMed: 37288979
DOI: 10.1128/msystems.01253-22 -
International Journal of Food... Jul 2023The aim of this study was to investigate seasonal variations (September, December and April) in the initial microbial communities of skin and gills' external mucosal...
Photobacterium predominate the microbial communities of muscle of European plaice (Pleuronectes platessa) caught in the Norwegian sea independent of skin and gills microbiota, fishing season, and storage conditions.
The aim of this study was to investigate seasonal variations (September, December and April) in the initial microbial communities of skin and gills' external mucosal tissues (EMT) and muscle of European plaice (Pleuronectes platessa). Moreover, a potential relationship between EMT and fresh muscle microbiota was examined. The microbial community succession in plaice muscle as a function of fishing season and storage conditions was also investigated. The selected seasons for the storage experiment were September and April. Investigated storage conditions were; fillets packaged in either vacuum or modified atmosphere (70 % CO, 20 % N, 10 % O) and chilled/refrigerated conditions (4 °C). Whole fish stored on ice (0 °C) was selected as a commercial standard. Seasonal variations were detected in the initial microbial communities of EMT and plaice muscle. The highest microbial diversity was found in EMT and muscle of April-caught plaice, followed by December and September catch indicating the important role of environmental factors in shaping the initial EMT and muscle microbial communities. The EMT microbial communities were more diverse than fresh muscle samples. The low number of shared taxa between EMT and initial muscle microbial communities indicates that only a minor part of the muscle microbiota came from the EMT. Psychrobacter and Photobacterium were the predominant genera in the EMT microbial communities in all seasons. Photobacterium dominated the initial muscle microbial communities with a gradual seasonal reduction of its abundance from September to April. Storage time and storage conditions shaped a less diverse and distinct community compared to the fresh muscle. However, no clear separation was seen between the communities at the middle and end of storage time. Regardless of EMT microbiota, fishing season and storage conditions, Photobacterium dominated the microbial communities of stored muscle samples. The Photobacterium prevalence as the primary specific spoilage organism (SSO) could be attributed to its high relative abundance in the initial microbiota of muscle and its CO-tolerance. The findings of this study indicate the important contribution of Photobacterium to the microbial spoilage of plaice. Thus, the development of innovative preservation techniques addressing the rapid growth of Photobacterium could contribute to the production of high-quality and shelf-stable convenient retail plaice products.
Topics: Animals; Carbon Dioxide; Flounder; Food Microbiology; Food Packaging; Food Preservation; Gills; Microbiota; Muscles; Photobacterium; Seasons
PubMed: 37099863
DOI: 10.1016/j.ijfoodmicro.2023.110222 -
3 Biotech May 2023GDSL esterase is designated as a member of Family II of lipolytic enzymes known to catalyse the synthesis and hydrolysis of ester bonds. The enzyme possesses a highly...
GDSL esterase is designated as a member of Family II of lipolytic enzymes known to catalyse the synthesis and hydrolysis of ester bonds. The enzyme possesses a highly conserved motif Ser-Gly-Asn-His in the four conserved blocks I, II, III and V respectively. The enzyme characteristics, such as region-, chemo-, and enantioselectivity, help in resolving the racemic mixture of single-isomer chiral drugs. Recently, crystal structure of GDSL esterase from J15 has been reported (PDB ID: 5XTU) but not in complex with substrate. Therefore, GDSL in complex with substrate could provide insights into the binding mode of substrate towards inactive form of GDSL esterase (S12A) and identify the hot spot residues for the designing of a better binding pocket. Insight into molecular mechanisms is limited due to the lack of crystal structure of GDSL esterase-substrate complex. In this paper, the crystallization of mutant GDSL esterase (S12A) (PDB ID: 8HWO) and its complex with butyric acid (PDB ID: 8HWP) are reported. The optimized structure would be vital in determining hot spot residue for GDSL esterase. This preliminary study provides an understanding of the interactions between enzymes and hydrolysed -nitro-phenyl butyrate. The information could guide in the rational design of GDSL esterase in overcoming the medical limitations associated with racemic mixture.
PubMed: 37064003
DOI: 10.1007/s13205-023-03534-x -
Frontiers in Nutrition 2023Valorising waste from the processing of fishery and aquaculture products into functional additives, and subsequent use in aquafeed as supplements could be a novel...
Valorising waste from the processing of fishery and aquaculture products into functional additives, and subsequent use in aquafeed as supplements could be a novel approach to promoting sustainability in the aquaculture industry. The present study supplemented 10% of various fish protein hydrolysates (FPHs), obtained from the hydrolysis of kingfish (KH), carp (CH) and tuna (TH) waste, with 90% of poultry by-product meal (PBM) protein to replace fishmeal (FM) completely from the barramundi diet. At the end of the trial, intestinal mucosal barriers damage, quantified by villus area (VA), lamina propria area (LPA), LPA ratio, villus length (VL), villus width (VW), and neutral mucin (NM) in barramundi fed a PBM-based diet was repaired when PBM was supplemented with various FPHs ( < 0.05, 0.01, and 0.001). PBM-TH diet further improved these barrier functions in the intestine of fish ( < 0.05 and 0.001). Similarly, FPHs supplementation suppressed PBM-induced intestinal inflammation by controlling the expression of inflammatory cytokines ( and ; < 0.05 and 0.001) and a mucin-relevant production gene (; < 0.001). The 16S rRNA data showed that a PBM-based diet resulted in dysbiosis of intestinal bacteria, supported by a lower abundance of microbial diversity ( < 0.001) aligned with a prevalence of Photobacterium. PBM-FPHs restored intestine homeostasis by enhancing microbial diversity compared to those fed a PBM diet ( < 0.001). PBM-TH improved the diversity ( < 0.001) further by elevating the Firmicutes phylum and the , , and genera. Muscle atrophy, evaluated by fiber density, hyperplasia and hypertrophy and associated genes (, , and ), occurred in barramundi fed PBM diet but was repaired after supplementation of FPHs with the PBM ( < 0.05, 0.01, and 0.001). Similarly, creatine kinase, calcium, phosphorous, and haptoglobin were impacted by PBM-based diet ( < 0.05) but were restored in barramundi fed FPHs supplemented diets ( < 0.05 and 0.01). Hence, using circular economy principles, functional FPHs could be recovered from the fish waste applied in aquafeed formulations and could prevent PBM-induced intestinal dysbiosis and muscular atrophy. GRAPHICAL ABSTRACT.
PubMed: 37057066
DOI: 10.3389/fnut.2023.1145068 -
Microorganisms Mar 2023Alteration of respiratory components as a function of pressure is a common strategy developed in deep-sea microorganisms, presumably to adapt to high hydrostatic...
Alteration of respiratory components as a function of pressure is a common strategy developed in deep-sea microorganisms, presumably to adapt to high hydrostatic pressure (HHP). While the electron transport chain and terminal reductases have been extensively studied in deep-sea bacteria, little is known about their adaptations for ATP generation. In this study, we showed that the deep-sea bacterium SS9 exhibits a more pronounced piezophilic phenotype when grown in minimal medium supplemented with glucose (MG) than in the routinely used MB2216 complex medium. The intracellular ATP level varied with pressure, but with opposite trends in the two culture media. Between the two ATPase systems encoded in SS9, ATPase-I played a dominant role when cultivated in MB2216, whereas ATPase-II was more abundant in the MG medium, especially at elevated pressure when cells had the lowest ATP level among all conditions tested. Further analyses of the Δ, Δ1 and Δ2 mutants showed that disrupting ATPase-I induced expression of ATPase-II and that the two systems are functionally redundant in MB2216. Collectively, we provide the first examination of the differences and relationships between two ATPase systems in a piezophilic bacterium, and expanded our understanding of the involvement of energy metabolism in pressure adaptation.
PubMed: 36985211
DOI: 10.3390/microorganisms11030637 -
International Journal of Molecular... Mar 2023subsp. () is a Gram-negative fish pathogen with worldwide distribution and broad host specificity that causes heavy economic losses in aquaculture. Although was first...
subsp. () is a Gram-negative fish pathogen with worldwide distribution and broad host specificity that causes heavy economic losses in aquaculture. Although was first identified more than 50 years ago, its pathogenicity mechanisms are not completely understood. In this work, we report that secretes large amounts of outer membrane vesicles (OMVs) when cultured in vitro and during in vivo infection. These OMVs were morphologically characterized and the most abundant vesicle-associated proteins were identified. We also demonstrate that OMVs protect cells from the bactericidal activity of fish antimicrobial peptides, suggesting that secretion of OMVs is part of the strategy used by to evade host defense mechanisms. Importantly, the vaccination of sea bass () with adjuvant-free crude OMVs induced the production of anti- antibodies and resulted in partial protection against infection. These findings reveal new aspects of biology and may provide a basis for developing new vaccines against this pathogen.
Topics: Animals; Bass; Photobacterium; Virulence; Vaccines; Fish Diseases; Gram-Negative Bacterial Infections
PubMed: 36982212
DOI: 10.3390/ijms24065138 -
International Journal of Molecular... Mar 2023Lumazine protein from marine luminescent bacteria of species bind with very high affinity to the fluorescent chromophore 6,7-dimethyl-8-ribitylumazine. The light...
Lumazine protein from marine luminescent bacteria of species bind with very high affinity to the fluorescent chromophore 6,7-dimethyl-8-ribitylumazine. The light emission of bacterial luminescent systems is used as a sensitive, rapid, and safe assay for an ever-increasing number of biological systems. Plasmid pRFN4, containing the genes encoding riboflavin from the operon of , was designed for the overproduction of lumazine. To construct fluorescent bacteria for use as microbial sensors, novel recombinant plasmids (pRFN4-Pp N-P and pRFN4-Pp LP N-P) were constructed by amplifying the DNA encoding the N-P gene (L) from and the promoter region (LP) present upstream of the operon of the gene by PCR and ligating into the pRFN4-Pp N-P plasmid. A new recombinant plasmid, pRFN4-Pp LP-N-P, was constructed with the expectation that the fluorescence intensity would be further increased when transformed into . When this plasmid was transformed into 43R, the fluorescence intensity of transformants was 500 times greater than that of alone. As a result, the recombinant plasmid in which the gene encoding N-LumP and DNA containing the promoter exhibited expression that was so high as to show fluorescence in single cells. The fluorescent bacterial systems developed in the present study using and riboflavin genes can be utilized in the future as biosensors with high sensitivity and rapid analysis times.
Topics: Escherichia coli; Riboflavin; Plasmids; Promoter Regions, Genetic; Operon; Luminescent Measurements; Bacterial Proteins
PubMed: 36982169
DOI: 10.3390/ijms24065096