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The symbiosis between Vibrio fischeri and the Hawaiian bobtail squid, Euprymna scolopes, is a tractable and well-studied model of bacteria-animal mutualism. Here, we developed a method to transiently colonize E. scolopes using D-alanine (D-ala) auxotrophy of the symbiont, controlling the persistence of viable infection by supplying or withholding D-ala. We generated alanine racemase (alr) mutants of V. fischeri that lack avenues for mutational suppression of auxotrophy or reversion to prototrophy. Surprisingly, an alr mutant did not require D-ala to grow in a minimal medium, a phenomenon requiring metC, which encodes cystathionine ß-lyase. Likewise, overexpression of metC suppressed D-ala auxotrophy in a rich medium. To block potential mechanisms of suppression, we combined the alr mutation with deletions of metC and/or bsrF, which encodes a broad-spectrum racemase and investigated the suppression rates of four D-ala auxotrophic strains. We then focused on alr bsrF mutant MC13, which has a suppression rate of <10-9. When D-ala was removed from a growing culture of MC13, cells rounded and lysed within 40 minutes. Transient colonization of E. scolopes was achieved by inoculating squid in seawater containing MC13 and D-ala, and then transferring the squid into water lacking D-ala, which resulted in loss of viable symbionts within hours. Interestingly, the symbionts within crypt 3 persisted longer than those of crypt 1, suggesting a difference in bacterial growth rate in distinct crypt environments. Our study highlights a new approach for inducing transient colonization and provides insight into the biogeography of the E. scolopes light organ. IMPORTANCE The importance of this study is multi-faceted, providing a valuable methodological tool and insight into the biology of the symbiosis between Vibrio fischeri and Euprymna scolopes. First, the study sheds light on the critical role of D-ala for bacterial growth, and the underpinnings of D-ala synthesis. Our observations that metC obviates the need for D-ala supplementation of an alr mutant in minimal medium and that MetC-dependent growth correlates with D-ala in peptidoglycan, corroborate and extend previous findings in Escherichia coli regarding a role of MetC in D-ala production. Second, our isolation of robust D-ala auxotrophs led us to a novel method for studying the squid-Vibrio symbiosis, allowing for transient colonization without the use of antibiotics, and revealed intriguing differences in symbiont growth parameters in distinct light organ crypts. This work and the methodology developed will contribute to our understanding of the persistence and dynamics of V. fischeri within its host. [ABSTRACT FROM AUTHOR]

Ecofriendly organically modified bentonite based on curcumin-extracted compounds was applied as a catalytic carrier for green ZnO particulates (Zn@CU/BEN). The composite developed was evaluated as a cost-effective, highly efficient, and versatile photocatalyst for improving the oxidation of 5-fluorouracil (5-FU) residues in water resources. The ZnO@CU/BEN blend, with a dose of 0.5 g/L, exhibits notable catalytic characteristics, leading to the full oxidation of 5-FU at a concentration of 25 mg/L within 80 min. The kinetic assessment reflects the high fitness of the Firs order model with best rate constant value of 0.0156 and quantum yield (ɸ) value of 2.9 × 10–7. Nevertheless, the total reduction in organic carbon (TOC) was identified only after 160 min, indicating the existence of considerable byproducts of intermediates. The secondary compounds that were detected, alongside the establishment of hydroxyl radicals as the crucial oxidizing agent, revealed a degradation path consisting of two steps: hydroxylation and defluorination reactions. The toxicity characteristics of untreated pollutants and their resulting oxidized products were evaluated by measuring the inhibitory effects of the solutions on Vibrio fischeri at various time intervals. The sample that underwent partial oxidation during the first period exhibited a greater degree of toxicity compared to the unprocessed 5-FU. Nevertheless, the sample that underwent treatment for 200 min exhibited noteworthy characteristics of biosafety and non-toxicity. The synergistic effect of bentonite and organo-modified bentonite with curcumin extracts improves both the retention and oxidation activities of green ZnO. [ABSTRACT FROM AUTHOR]

A hydrogel formulation of 2-hydroxy ethyl methacrylate (HEMA) containing covalently linked magnetite nanoparticles was developed to actively facilitate the selective removal and photocatalytic degradation of antibiotics. To this purpose, the hybrid materials were molecularly imprinted with Lomefloxacin (Lome) or Ciprofloxacin (Cipro), achieving a selectivity of 60% and 45%, respectively, starting from a solution of XX concentration. After the adsorption, the embedded magnetite was used with the double function of (i) magnetically removing the material from water and (ii) triggering photo-Fenton (PF) reactions assisted by UVA light and H2O2 to oxidize the captured antibiotic. The success of the material design was confirmed by a comprehensive characterization of the system from chemical–physical and morphological perspectives. Adsorption and degradation tests demonstrated the material's ability to efficiently degrade Lome until its complete disappearance from the electrospray ionization (ESI) mass spectra. Regeneration tests showed the possibility of reusing the material for up to three cycles. Ecotoxicological tests using algae Rapidocelis subcapitata, crustaceans Daphnia magna, and bacteria Vibrio fischeri were performed to evaluate the ecosafety of our synthesized materials. [ABSTRACT FROM AUTHOR]

All novel materials should be analyzed for their potential environmental hazard. In this study, the toxicity of different silver–chitosan nanocomposites—potential candidates for wound dressings or antimicrobial surface coatings—was evaluated using environmentally relevant aquatic microcrustaceans Daphnia magna and Thamnocephalus platyurus and naturally luminescent bacteria Vibrio fischeri. Three silver-chitosan nanocomposites (nAgCSs) with different weight ratios of Ag to CS were studied. Citrate-coated silver nanoparticles (nAg-Cit), AgNO3 (ionic control) and low molecular weight chitosan (LMW CS) were evaluated in parallel. The primary size of nAgCSs was ~50 nm. The average hydrodynamic sizes in deionized water were ≤100 nm, and the zeta potential values were positive (16–26 mV). The nAgCSs proved very toxic to aquatic crustaceans: the 48-h EC50 value for D. magna was 0.065–0.232 mg/L, and the 24-h LC50 value for T. platyurus was 0.25–1.04 mg/L. The toxic effect correlated with the shedding of Ag ions (about 1%) from nAgCSs. Upon exposure of V. fischeri to nAgCSs for 30 min, bacterial luminescence was inhibited by 50% at 13–33 mg/L. However, the inhibitory effect (minimum bactericidal concentration, MBC) on bacterial growth upon 1 h exposure was observed at higher concentrations of nAgCSs, 40–65 mg/L. LMW CS inhibited bacterial luminescence upon 30-min exposure at 5.6 mg/L, but bacterial growth was inhibited at a much higher concentration (1 h MBC > 100 mg/L). The multi-trophic test battery, where D. magna was the most sensitive test organism, ranked the silver-chitosan nanocomposites from 'extremely toxic' [L(E)C50 ≤ 0.1 mg/L] to 'very toxic' [L(E)C50 > 0.1–1 mg/L]. Chitosan was toxic (EC(L)50) to crustaceans at ~12 mg/L, and ranked accordingly as 'harmful' [L(E)C50 > 10–100 mg/L]. Thus, silver-chitosan nanocomposites may pose a hazard to aquatic organisms and must be handled accordingly. [ABSTRACT FROM AUTHOR]

Hospital effluents are important sources for the release of pharmaceuticals into the environment. Metronidazole (MTZ) is one of the most popular antimicrobial agent, widely used in veterinary and human medicine. This study aims to determine the concentrations of MTZ in the effluent of hospitals and to evaluate ecotoxicological risk for aquatic organisms. Grab samples were taken from the effluents of 15 large hospitals in Isfahan City (Iran) and MTZ concentrations were analyzed using HPLC-UV. Average daily MTZ prescriptions for patients in each hospital was also determined. MTZ was detected in effluents of all 15 hospitals in the range of 0.3 to 9.5 µg/L (mean = 4.8 ± 6.4 µg/L). A significant correlation was observed between MTZ concentration in hospital effluent and MTZ prescription as well as the hospital beds. Ecological risk assessment showed MTZ contamination of hospital effluent from 7 of 15 hospitals had median risk (risk quotient of 0.1 to 1) for green algae (Chlorella sp.) while the effluent of all hospitals had minimal risk (risk quotient <0.1) for gram-negative bacteria (Vibrio fischeri) and aquatic crustaceans (Daphnia magna). It is necessary to develop efficient treatment methods for the removal of MTZ from the hospital effluents before discharging them into the municipal wastewater systems. [ABSTRACT FROM AUTHOR]

ABSTRACT As bacterial symbionts transition from a motile free-living state to a sessile biofilm state, they must coordinate behavior changes suitable to each lifestyle. Cyclic diguanylate (c-di-GMP) is an intracellular signaling molecule that can regulate this transition, and it is synthesized by diguanylate cyclase (DGC) enzymes and degraded by phosphodiesterase (PDE) enzymes. Generally, c-di-GMP inhibits motility and promotes biofilm formation. While c-di-GMP and the enzymes that contribute to its metabolism have been well studied in pathogens, considerably less focus has been placed on c-di-GMP regulation in beneficial symbionts. Vibrio fischeri is the sole beneficial symbiont of the Hawaiian bobtail squid (Euprymna scolopes) light organ, and the bacterium requires both motility and biofilm formation to efficiently colonize. c-di-GMP regulates swimming motility and cellulose exopolysaccharide production in V. fischeri. The genome encodes 50 DGCs and PDEs, and while a few of these proteins have been characterized, the majority have not undergone comprehensive characterization. In this study, we use protein overexpression to systematically characterize the functional potential of all 50 V. fischeri proteins. All 28 predicted DGCs and 10 of the 14 predicted PDEs displayed at least one phenotype consistent with their predicted function, and a majority of each displayed multiple phenotypes. Finally, active site mutant analysis of proteins with the potential for both DGC and PDE activities revealed potential activities for these proteins. This work presents a systems-level functional analysis of a family of signaling proteins in a tractable animal symbiont and will inform future efforts to characterize the roles of individual proteins during lifestyle transitions.IMPORTANCECyclic diguanylate (c-di-GMP) is a critical second messenger that mediates bacterial behaviors, and Vibrio fischeri colonization of its Hawaiian bobtail squid host presents a tractable model in which to interrogate the role of c-di-GMP during animal colonization. This work provides systems-level characterization of the 50 proteins predicted to modulate c-di-GMP levels. By combining multiple assays, we generated a rich understanding of which proteins have the capacity to influence c-di-GMP levels and behaviors. Our functional approach yielded insights into how proteins with domains to both synthesize and degrade c-di-GMP may impact bacterial behaviors. Finally, we integrated published data to provide a broader picture of each of the 50 proteins analyzed. This study will inform future work to define specific pathways by which c-di-GMP regulates symbiotic behaviors and transitions.

CRISPRi (Clustered Regularly Interspaced Palindromic Repeats interference) is a gene knockdown method that uses a deactivated Cas9 protein (dCas9) that binds a specific gene target locus dictated by an encoded guide RNA (sgRNA) to block transcription. Mobile-CRISPRi is a suite of modular vectors that enable CRISPRi knockdowns in diverse bacteria by integrating IPTG-inducible dcas9 and sgRNA genes into the genome using Tn7 transposition. Here, we show that the Mobile-CRISPRi system functions robustly and specifically in multiple Vibrio species: Vibrio cholerae, Vibrio fischeri, Vibrio vulnificus, Vibrio parahaemolyticus, and Vibrio campbellii. We demonstrate efficacy by targeting both essential and non-essential genes that function to produce defined, measurable phenotypes: bioluminescence, quorum sensing, cell division, and growth arrest. We anticipate that Mobile-CRISPRi will be used in Vibrio species to systematically probe gene function and essentiality in various behaviors and native environments. [ABSTRACT FROM AUTHOR]

Cells of Vibrio fischeri colonize the light organ of Euprymna scolopes, providing the squid bioluminescence in exchange for nutrients and protection. The bacteria encounter DNA-rich mucus throughout their transition to a symbiotic lifestyle, leading us to hypothesize a role for nuclease activity in the colonization process. In support of this, we detected abundant extracellular nuclease activity in growing cells of V. fischeri. To discover the gene(s) responsible for this activity, we screened a V. fischeri transposon mutant library for nuclease-deficient strains. Interestingly, only one strain, whose transposon insertion mapped to nuclease gene VF_1451, showed a complete loss of nuclease activity in our screens. A database search revealed that VF_1451 is homologous to the nuclease-encoding gene xds in Vibrio cholerae. However, V. fischeri strains lacking xds eventually revealed slight nuclease activity on plates upon prolonged incubation. This led us to hypothesize that a second secreted nuclease, ident ified through a database search as VF_0437, a homolog of V. cholerae dns, might be responsible for the residual nuclease activity. Here, we show that Xds and/or Dns are involved in essential aspects of V. fischeri biology, including natural transformation, aggregation, and phosphate scavenging. Furthermore, strains lacking either nuclease were outcompeted by the wild type for squid colonization. Understanding the specific role of nuclease activity in the squid colonization process represents an intriguing area of future research. [ABSTRACT FROM AUTHOR]

This study evaluates, for the first time, the effects of UV/PMS and UV/H2O2/PMS processes on the degradation of sunscreen agents in synthetic and natural water matrices and compares their effectiveness with the more conventional UV/H2O2. Investigations were conducted using a mixture of organic UV filters containing 4-methylbenzylidene camphor (4-MBC) and 2-ethylhexyl-4-methoxycinnamate. Among the investigated UV-driven AOPs, UV/PMS/H2O2 was the most effective in synthetic water, while in natural water, the highest degradation rate was observed during the degradation of EHMC by UV/PMS. The degradation of UV filters in the UV/PMS system was promoted by sulfate radical (68% of the degradation), with hydroxyl radical contributing approximately 32%, while both radical species contributed approximately equally to the degradation in the UV/H2O2/PMS system. The Vibrio fischeri assay showed an increase in inhibition (up to 70%) at specific stages of UV/H2O2 treatment when applied to natural water, which further decreased to 30%, along with an increase in UV fluence and progressive degradation. The Pseudomonas putida test recorded minor toxicity (<15%) after treatments. Magnetic biochar utilized in conjunction with UV-driven AOPs exhibited superior performance in eliminating residual contaminants, providing an efficient and sustainable approach to mitigate sunscreen agents in water treatment. [ABSTRACT FROM AUTHOR]

In the present investigation, an ecofriendly magnetic inorganic-protein hybrid system-based enzyme immobilization was developed using partially purified laccase from Trametes versicolor (TvLac), Fe3O4 nanoparticles, and manganese (Mn), and was successfully applied for synthetic dye decolorization in the presence of enzyme inhibitors. After the partial purification of crude TvLac, the specific enzyme activity reached 212 U∙mg total protein−1. The synthesized Fe3O4/Mn3(PO4)2-laccase (Fe3O4/Mn-TvLac) and Mn3(PO4)2-laccase (Mn-TvLac) nanoflowers (NFs) exhibited encapsulation yields of 85.5% and 90.3%, respectively, with relative activities of 245% and 260%, respectively, compared with those of free TvLac. One-pot synthesized Fe3O4/Mn-TvLac exhibited significant improvements in catalytic properties and stability compared to those of the free enzyme. Fe3O4/Mn-TvLac retained a significantly higher residual activity of 96.8% over that of Mn-TvLac (47.1%) after 10 reuse cycles. The NFs showed potential for the efficient decolorization of synthetic dyes in the presence of enzyme inhibitors. For up to five reuse cycles, Fe3O4/Mn-TvLac retained a decolorization potential of 81.1% and 86.3% for Coomassie Brilliant Blue R-250 and xylene cyanol, respectively. The synthesized Fe3O4/Mn-TvLac showed a lower acute toxicity towards Vibrio fischeri than pure Fe3O4 nanoparticles did. This is the first report of the one-pot synthesis of biofriendly magnetic protein-inorganic hybrids using partially purified TvLac and Mn. [ABSTRACT FROM AUTHOR]

Water and several chemicals, including dyestuffs, surfactants, acids, and salts, are required during textile dyeing processes. Surfactants are harmful to the aquatic environment and induce several negative biological effects in exposed biota. In this context, the present study aimed to assess acute effects of five surfactants, comprising anionic and nonionic classes, and other auxiliary products used in fiber dyeing processes to aquatic organisms Vibrio fischeri (bacteria) and Daphnia similis (cladocerans). The toxicities of binary surfactant mixtures containing the anionic surfactant dodecylbenzene sulfonate + nonionic fatty alcohol ethoxylate and dodecylbenzene sulfonate + nonionic alkylene oxide were also evaluated. Nonionic surfactants were more toxic than anionic compounds for both organisms. Acute nonionic toxicity ranged from 1.3 mg/L (fatty alcohol ethoxylate surfactant) to 2.6 mg/L (ethoxylate surfactant) for V. fischeri and from 1.9 mg/L (alkylene oxide surfactant) to 12.5 mg/L (alkyl aryl ethoxylated and aromatic sulfonate surfactant) for D. similis, while the anionic dodecylbenzene sulfonate EC50s were determined as 66.2 mg/L and 19.7 mg/L, respectively. Both mixtures were very toxic for the exposed organisms: the EC50 average in the anionic + fatty alcohol ethoxylate mixture was of 1.0 mg/L ± 0.11 for V. fischeri and 4.09 mg/L ± 0.69 for D. similis. While the anionic + alkylene oxide mixture, EC50 of 3.34 mg/L for D. similis and 3.60 mg/L for V. fischeri. These toxicity data suggested that the concentration addition was the best model to explain the action that is more likely to occur for mixture for the dodecylbenzene sulfonate and alkylene oxide mixtures in both organisms. Our findings also suggest that textile wastewater surfactants may interact and produce different responses in aquatic organisms, such as synergism and antagonism. Ecotoxicological assays provide relevant information concerning hazardous pollutants, which may then be adequately treated and suitably managed to reduce toxic loads, associated to suitable management plans. [ABSTRACT FROM AUTHOR]

NiO nanoparticles were synthesized and modified with Ni0 in the form of Ni/NiO blend and supported on a porous diatomite substrate, forming hybrid structures of NiO/D and Ni@NiO/D with enhanced photocatalytic performances. The obtained structures were applied for the effective oxidation of acephate pesticides under visible light. The obtained results demonstrated enhancement in the catalytic performance of Ni@NiO/D compared to NiO, Ni/NiO, and NiO/D structures. The full oxidation of AC (50 mg L−1) was determined after 40 min using Ni@NiO/D at doses of 0.5 g L−1. Moreover, the complete mineralization of AC molecules over Ni@NiO/D was detected after 70 min, considering the complete removal of TOC and the detection of essential inorganic anions (NO3− (7.6 × 10−5 mol L−1), SO42− (1.7 × 10−5 mol L−1), and PO43− (5.4 × 10−5 mol L−1)). The oxidation pathway was illustrated by considering the estimated intermediates and the detection of hydroxyl radicals as main oxidizing species. The toxicity of untreated AC solutions and degraded intermediates was analyzed by assessing their inhibitory effect on Vibrio fischeri. Samples that underwent partial oxidation during their initial examination exhibited a greater degree of toxicity (65.3% inhibition) compared to AC. Nevertheless, a sample subjected to an 80 minute treatment exhibited neglected toxicity (1.4% inhibition). The combination of the diatomite substrate and Ni0 doping enhanced the adsorption and photocatalytic properties of NiO. [ABSTRACT FROM AUTHOR]

Dasatinib (DAS), a potent anticancer drug, has been subjected to formulation enhancements due to challenges such as significant first-pass metabolism, poor absorption, and limited oral bioavailability. To improve its release profile, DAS was embedded in a matrix of the hydrophilic polymer polyvinylpyrrolidone (PVP). Drug amorphization was induced in a planetary ball mill by solvent-free co-grinding, facilitating mechanochemical activation. This process resulted in the formation of amorphous solid dispersions (ASDs). The ASD capsules exhibited a notable enhancement in the release rate of DAS compared to capsules containing the initial drug. Given that anticancer drugs often undergo limited metabolism in the body with unchanged excretion, the ecotoxicological effect of the native form of DAS was investigated as well, considering its potential accumulation in the environment. The highest ecotoxicological effect was observed on the bacteria Vibrio fischeri, while other test organisms (bacteria Pseudomonas putida, microalgae Chlorella sp., and duckweed Lemna minor) exhibited negligible effects. The enhanced drug release not only contributes to improved oral absorption but also has the potential to reduce the proportion of DAS that enters the environment through human excretion. This comprehensive approach highlights the significance of integrating advances in drug development while considering its environmental implications. [ABSTRACT FROM AUTHOR]

• Synergistic harmlessness and resource utilization of GMRs were guaranteed at 200 °C. • The high level of residual gentamicin in GMRs could be completely eliminated. • Gentamicin-associated resistance genes could be almost inactivated. • The antibacterial activity of GMRs was greatly reduced. • The contents of soluble organic matters and humic acid-like organics were improved. Gentamicin mycelium residues (GMRs) abundant in organic substances were generated during the production of gentamicin. Inappropriate handling techniques not only waste valuable resources, they could also result in residual gentamicin into the natural environment, leading to the generation of antibiotic resistance genes (ARGs), which would cause a significant threat to ecological system and human health. In the present work, the effects of thermal treatment on the removal of residual gentamicin in GMRs, as well as the changes of associated ARGs abundance, antimicrobial activity and bioresources properties were investigated. The results indicated that the hazards of GMRs was significantly reduced through thermal treatment. The degradation rate of residual gentamicin in GMRs reached 100 %, the total abundance of gentamicin resistance genes declined from 8.20 to 1.14 × 10-5 and the antibacterial activity of the decomposition products of GMRs on Vibrio fischeri was markedly reduced at 200 °C for 120 min. Additionally, the thermal treatment remarkably influenced the bioresource properties of GMRs-decomposition products. The release of soluble organic matters including soluble carbohydrates and soluble proteins have been enhanced in GMRs, while excessively high temperatures could lead to a reduction of nutrient substances. Generally, thermal treatment technology was a promising strategy for synergistic reducing hazards and utilizing bioresources of GMRs. [ABSTRACT FROM AUTHOR]

Freitas, A.S.; Pompermayer, L.L.O.; Santos, A.D.O.; Nascimento, M.T.L.; Félix, L.C.; Bila, D.M.; Neto, J.A.B., and Fonseca, E.M., 2024. Sediment toxicity assessment using marine organism bioassays from an urban coastal lagoon (Padre Lagoon, southeastern Brazil). Journal of Coastal Research, 40(2), 278–288. Charlotte (North Carolina), ISSN 0749-0208. This study aimed to evaluate the environmental quality of Padre Lagoon, an urban coastal lagoon, by using ecotoxicological fossil organisms (dinoflagellate cysts) for biomarker analysis associated with 14C radiocarbon dating. This is the first toxicity study in this anthropogenic coastal lagoon. A total of 15 surface sediment samples and a sediment core were analysed by radiocarbon dating, grain size, dinoflagellate cysts, and acute toxicity bioassays to assess the influence of land use changes in accelerated urban development in recent decades. Sediments varied between coarse sand and mud at different proportions. Radiocarbon dating placed the oldest age at 470–314 calibrated YBP in the sediment core base according to 14C radiocarbon dating. Artemia sp. showed high toxicity in both surface and core sediment samples. Vibrio fischeri showed a toxicity gradient in the sediment core and high toxicity in several surface samples. A major dinoflagellate cyst occurrence was observed in the sediment core; however, the highest accumulation was observed in the surface sediments. The data obtained in this study revealed high toxicity in the analysed sediment samples and the need for greater monitoring of this coastal lagoon. [ABSTRACT FROM AUTHOR]

Compounds displaying estrogenic potential can lead to serious negative aquatic ecosystem impacts, and exposure to mixtures of endocrine disruptors present in environmental matrices with very complex characteristics, including sediments, can cause serious risks to biota, animals, and humans. Within this perspective, the aim of the present study was to assess estrogenic activity and toxicity in sediments sampled from Guanabara Bay, the most important, although chronically polluted, estuary in southeastern Brazil. To this end, estrogenic activity determinations were performed by the yeast estrogen screen (YES) assay, and acute toxicity assays were carried out employing Vibrio fischeri. Estrogenic activity was quantified up for 8.7 ng g−1 in E2‐EQ, although high levels of cytotoxicity (up to 95%) were observed and might have hindered the determination of the real estrogenic potential in most samples. Acute toxicity to V. fischeri ranged from 0 to 45.21%. These results point to potential deleterious effects caused by micropollutants and underline the urgency of continuous monitoring of the degradation degree of the Guanabara Bay estuary. [ABSTRACT FROM AUTHOR]

Marine bioprospecting is a dynamic research field that explores the oceans and their biodiversity as noteworthy sources of new bioactive compounds. Anthozoans are marine animals belonging to the Cnidaria phylum characterized by highly specialized mechanosensory cells used both for defence against predators and prey capture. Here, high concentration of cnidocysts have been isolated from the Mediterranean zoanthid coral Parazoanthus axinellae (Schmidt, 1862) and their antimicrobial potential has been investigated. The cnidocyst extract exerted significant antibacterial activity against some human pathogens capable of developing resistance to conventional antibiotics such as Streptococcus agalactiae and Coccus sp., and against several Vibrio species, including some microbial strains for humans and farmed fish, such as Vibrio alginolyticus, Vibrio anguillarum, Vibrio fischeri, Vibrio harveyi, and Vibrio vulnificus. Results have been discussed in light of both the ecological aspects and biotechnological value of the cnidocyst extract in the nutritional, nutraceutical, and pharmaceutical fields. [ABSTRACT FROM AUTHOR]

Despite concerns about the potential risk associated with the environmental occurrence of pharmaceuticals and personal care products (PPCPs), few studies address the emissions of hospitals to aquatic compartments. We examined within a 3-month sampling period the occurrence and environmental risk of PPCPs in seven Tunisian hospital wastewaters. From personal care products, UV filters, main metabolites, and benzotriazoles were quantified, with benzophenone 3 (oxybenzone, BP3) and benzotriazole (BZT) the most frequently found (71%) at median concentrations in the range 2.43 ± 0.87 ngL−1–64.05 ± 6.82 ngL−1 for BP3 and 51.67 ± 1.67 ngL−1–254 ± 9.9 ngL−1 for BZT. High concentrations were also found for 4-hydroxybenzophenone (4HB) (221 ± 6.22 ngL−1), one of the main metabolites of BP3. The antibiotics ofloxacin and trimethoprim, the anti-inflammatory acetaminophen, the antiepileptic carbamazepine, and the stimulant caffeine were present in all the wastewaters. The highest median concentration corresponded to acetaminophen, with 1240 ± 94 mgL−1 in Tunis Hospital, followed by ofloxacin with 78850 ± 39 μgL−1 in Sousse Hospital. For ecotoxicity assessment, acute toxicity was observed for Daphnia magna and Vibrio fischeri. The toxicity data were used in a hazard quotient (HQ) approach to evaluate the risk posed by the target PPCPs to aquatic organisms. The calculated HQs revealed that marbofloxacin (234 for V. fischeri), enrofloxacin (121 for D. magna), and BZT (82.2 for D. magna and 83.7 for V. fischeri) posed the highest risk, concluding that potential risk exists toward aquatic microorganisms. This study constitutes the first monitoring of UV filters in Tunisian hospital effluents and provides occurrence and toxicity data of PPCPs for reference in further surveys in the country. [ABSTRACT FROM AUTHOR]

Wastewater ingredients present risks to the environment and can cause health problems. The aim of this study was to identify the toxicological effects of influent and effluent wastewater from Konya Urban Wastewater Treatment Plant (KU WWTP) and Konya Organized Industrial Zone Wastewater Treatment Plant (KOI WWTP). Three different trophic level toxicity tests were conducted to determine the possible harmful effects of wastewater on the environment. The base toxic unit values of the Lepidium sativum toxicity test for the inlet and outlet samples of KU WWTP were found to be 1.43 and 1.10, respectively. Both values classified the analyzed wastewater into the "toxic" category. Wastewater entering the KU wastewater treatment facility was classified as "toxic" for the presence of toxic substances according to the Vibrio fischeri toxicity testing. Influent samples from the KOI wastewater treatment plant were classified as "toxic" with the Vibrio fischeri toxicity test. In addition, based on the fish bioassay value (TDF), wastewater from the KOI treatment facility was also classified as "toxic". It was concluded that increased chemical oxygen demand and concentrations of total nitrogen and phosphorus and of certain heavy metals above the limits played a decisive role in classifying the samples as "toxic". The results of this study suggest that all three tests have the potential to assess wastewater toxicity and that changes in wastewater properties may result in differences in test sensitivity. [ABSTRACT FROM AUTHOR]

This study investigates the photo-Fenton process's efficacy in degrading three textile dyes: acid red 52 (AR52), reactive orange 16 (RO16), and direct red 28 (DR28). AR52 undergoes rapid, complete decolorization with an 82% reduction in Total Organic Carbon (TOC), indicating non-toxic byproduct formation. In contrast, DR28 shows limited decolorization (55%), minimal TOC reduction (1%), and increased toxicity post-treatment. RO16 excels with complete decolorization and a 93% TOC reduction, suggesting near-total mineralization. Despite initial toxicity differences, AR52 and RO16 exhibit reduced toxicity after 90 minutes, while DR28's toxicity slightly increases. Proposed degradation pathways elucidate varied dye responses, underscoring the photo-Fenton process's complexity in mitigating toxicity.

This study explores the environmental effects of five common veterinary antibiotics widely detected in the environment, (chlortetracycline,CTC; oxytetracycline,OTC; florfenicol,FF; neomycin, NMC; and sulfadiazine, SDZ) on four bioindicators: Daphnia magna, Vibrio fischeri, Eisenia fetida, and Allium cepa, representing aquatic and soil environments. Additionally, microbial communities characterized through 16 S rRNA gene sequencing from a river and natural soil were exposed to the antibiotics to assess changes in population growth and metabolic profiles using Biolog EcoPlates™. Tetracyclines are harmful to Vibrio fisheri (LC50 ranges of 15–25 µg/mL), and the other three antibiotics seem to only affect D. magna, especially, SDZ. None of the antibiotics produced mortality in E. fetida at concentrations below 1000 mg/kg. NMC and CTC had the highest phytotoxicities in A. cepa (LC50 = 97–174 µg/mL, respectively). Antibiotics significantly reduced bacterial metabolism at 0.1–10 µg/mL. From the highest to the lowest toxicity on aquatic communities: OTC > FF > SDZ ≈ CTC > NMC and on edaphic communities: CTC ≈ OTC > FF > SDZ > NMC. In river communities, OTC and FF caused substantial decreases in bacterial metabolism at low concentrations (0.1 µg/mL), impacting carbohydrates, amino acids (OTC), and polymers (FF). At 10 µg/mL and above, OTC, CTC, and FF significantly decreased metabolizing all tested metabolites. In soil communities, a more pronounced decrease in metabolizing ability, detectable at 0.1 µg/mL, particularly affected amines/amides and carboxylic and ketonic acids (p < 0.05). These new ecotoxicity findings underscore that the concentrations of these antibiotics in the environment can significantly impact both aquatic and terrestrial ecosystems.

This document is a correction for an article titled "Vibrio fischeri Possesses Xds and Dns Nucleases That Differentially Influence Phosphate Scavenging, Aggregation, Competence, and Symbiotic Colonization of Squid." The correction addresses specific experiments that were repeated and confirms the previous findings regarding the nuclease activity of the xds mutant strain. The timing of measurable Dns activity was found to vary slightly, but these results do not change the conclusions of the original publication. The corrected and republished paper is available for further reference. [Extracted from the article]

Abstract Background The symbiosis between the Hawaiian bobtail squid Euprymna scolopes and bacterium Vibrio fischeri serves as a model for investigating the molecular mechanisms that promote the initial formation of animal-bacterial symbioses. Research with this system frequently depends on freshly hatched E. scolopes, but the husbandry factors that promote hatchling production in a mariculture facility remain underreported. Here we report on the reproductive performance of E. scolopes in response to decreased mating frequency. Results One animal cohort was maintained in a mariculture facility for 107 days, with females assigned to either a control group (mating once every 14 days) or an experimental group (mating once every 21 days). No differences between the groups were observed in survival, the number of egg clutches laid, or hatchling counts. Each group featured multiple females that were hyper-reproductive, i.e., they generated more than 8 egg clutches while in captivity. Examination of the distributions for daily hatchling counts of individual egg clutches revealed significant variation in the hatching patterns among clutches that was independent of mating frequency. Finally, an assessment of hatchling production showed that 93.5% of total hatchlings produced by the cohort were derived from egg clutches laid within the first 70 days. Conclusions These results suggest a lower mating frequency does not impede hatchling production. Furthermore, the variation in hatchling production among egg clutches provides new insight into the reproductive performance of E. scolopes as a lab animal for microbiology research.

Atenolol (ATL) is a beta-blocker pharmaceutical product which is excreted mainly unchanged and may represent a long-term risk for organisms present in the sea and in fresh water. Due to its low biodegradation rate, electrochemical advanced oxidation processes (EAOPs) can be used to remove this compound. In this work, ATL ecotoxicity was analyzed in the presence of sodium sulfate (Na2SO4), which is widely used as supporting electrolyte in EAOPs. Ecotoxicity values were expressed as the pollutant concentration that leads to a 50% inhibition of the root elongation of Lactuca sativa seeds in relation to the control (EC50(5 days)). The obtained values for ATL showed an EC50(5 days) of 1377 mg L−1 towards Lactuca sativa. When Na2SO4 was added, the toxicity of the sample increased but no synergy was detected between both compounds. With 2 g L−1 Na2SO4, ATL showed an EC50(5 days) of 972 mg L−1; and with 4 g L−1 Na2SO4 and higher concentrations, EC50 value for ATL was 0 mg L−1. Statistical tools were used to obtain the zones of the [ATL]-[Na2SO4] plane which are toxic towards Lactuca sativa.Solutions containing ATL and Na2SO4 were treated by electrooxidation. Two anode materials (a boron-doped diamond electrode and a microporous Sb-doped SnO2 ceramic one); three operation currents (0.4, 0.6 and 1 A); and two reactor configurations (one-compartment reactor and two-compartment reactor separated by a cation exchange membrane) were used. Lactuca sativa seeds and Vibrio fischeri bacterium tests were employed to evaluate the toxicity of the solutions before and after applying the electrooxidation process. In all the tests, the ecotoxicity of the treated sample increased. This fact is owing to the persulfate presence in the solution due to the sulfate electrochemical oxidation. Nevertheless, none of the final samples were toxic towards Vibrio fischeri because ecotoxicity values were lower than 10 TU; and, in the case of the one-compartment reactor, practically all of them were also non-toxic towards Lactuca sativa. The toxicity of the treated samples increased when using the two-compartment reactor in the presence of the BDD anode, and when the operation current was increased. This is attributed to the highest formation of persulfates. Amongst all the tests performed in this work, the lowest toxicity value (i.e., 3 TU) together with the complete mineralization and degradation degrees was achieved with the two-compartment reactor using the BDD anode and operating at 0.6 A.

Perturbations to host–microbe interactions, such as environmental stress, can alter and disrupt homeostasis. In this study, we examined the effects of a stressor, simulated microgravity, on beneficial bacteria behaviours when colonising their host. We studied the bacterium Vibrio fischeri, which establishes a mutualistic association in a symbiosis‐specific organ within the bobtail squid, Euprymna scolopes. To elucidate how animal–microbe interactions are affected by the stress of microgravity, squid were inoculated with different bacterial strains exhibiting either a dominant‐ or sharing‐colonisation behaviour in High Aspect Ratio Vessels, which simulate the low‐shear environment of microgravity. The colonisation behaviours of the sharing and dominant strains under modelled microgravity conditions were determined by counting light‐organ homogenate of squids as well as confocal microscopy to assess the partitioning of different strains within the light organ. The results indicated that although the colonisation behaviours of the strains did not change, the population levels of the sharing strains were at lower relative abundance in single‐colonised animals exposed to modelled microgravity compared to unit gravity; in addition, there were shifts in the relative abundance of strains in co‐colonised squids. Together these results suggest that the initiation of beneficial interactions between microbes and animals can be altered by environmental stress, such as simulated microgravity. [ABSTRACT FROM AUTHOR]

Anti-sigma factor antagonists SpoIIAA and RsbV from Bacillus subtilis are the archetypes for singledomain STAS proteins in bacteria. The structures and mechanisms of these proteins along with their cognate anti-sigma factors have been well studied. SpoIIAA and RsbV utilize a partnerswitching mechanism to regulate gene expression through protein-protein interactions to control the activity of their downstream anti-sigma factor partners. The Vibrio fischeri STAS domain protein SypA is also proposed to employ a partner-switching mechanism with its partner SypE, a serine kinase/phosphatase that controls SypA's phosphorylation state. However, this regulation appears opposite to the canonical pathway, with SypA being the more downstream component rather than SypE. Here we explore the commonalities and differences between SypA and the canonical single-domain STAS proteins SpoIIAA and RsbV. We use a combination of AlphaFold 2 structure predictions and computational modeling to investigate the SypA-SypE binding interface. We then test a subset of our predictions in V.fischeri by generating and expressing SypA variants. Our findings suggest that, while SypA shares many sequence and structural traits with anti-sigma factor antagonist STAS domain proteins, there are significant differences that may account for SypA's distinct regulatory output. [ABSTRACT FROM AUTHOR]

Considering that ammonium ion (NH 4 +) was widely distributed in natural water and many sewage, it was of great practical significance to study NH 4 + enhanced potassium ferrate (Fe(VI)) to rapid removal of levofloxacin (LEV) from water. In this experiment, firstly, the reaction kinetic of NH 4 + enhanced Fe(VI) removal of LEV was studied, and the results showed that the enhanced removal reaction conformed to the second-order kinetic equation. When pH ≤ 9, the second-order rate constant k app was linearly related to NH 4 + dosage, but when pH= 10, the above linear relationship was broken, and the slope of the fitting line would change toward a smaller trend. Subsequently, tert-butanol (TBA) and Methyl phenyl sulfoxide (PMSO) were used as probes for·OH and high-valent iron-based intermediate (Fe(V)/Fe(IV)) respectively, which further revealed the reaction mechanism that NH 4 + enhanced Fe(VI) to remove LEV as follows: NH 4 + could promote Fe(VI) to produce a large amount of Fe(V)/Fe(IV), thus accelerating the degradation of LEV. In addition, 10 degradation intermediates of LEV were identified by quadrupole time-of-flight tandem ultra-performance liquid chromatography mass spectrometer (Q-TOF LC-MS), and then combined with density functional theory (DFT) calculation, two possible degradation pathways were inferred. Through the luminescence inhibition experiment of Vibrio fischeri and the toxicity evaluation of ECOSAR, it could be concluded that in the process of NH 4 + enhancing Fe(VI) to remove LEV, the toxicity of the solution showed a trend of increasing first and then decreasing, and its toxicity was effectively improved and reduced after full oxidation. Finally, the experiments in actual water showed that it was feasible to use NH 4 + in actual water to enhance Fe(VI) for rapid removal of LEV. [ABSTRACT FROM AUTHOR]

This study assessed different regression models to estimate the concentration that inhibits 50% of Allium cepa root growth after exposure to different concentrations (5 to 100%v/v) of hospital wastewater for 72 h. In addition, the mitotic index was also calculated. The results indicate alterations in the normal development of A. cepa owing to the possible presence of toxic substances, identifying a maximum root inhibition of 61.01% and a minimum mitotic index of 2.15%. The Gompertz model was better than other models for its adequate adjustment and low error with a half maximal inhibitory concentration of 57.5% (moderately toxic waters) and a difference of 23% with traditional models such as Probit (80%) or Log-Logistic (80%). Toxicity tests with bioluminescent bacteria (Vibrio fischeri) confirmed the results obtained from A. cepa bioassays. [ABSTRACT FROM AUTHOR]

Bacteriocins are a kind of antimicrobial peptides that kill or inhibit the growth of bacterial strains. The purpose of this study was to investigate the antibacterial effect of Serratia marcescens on several pathogenic bacterial strains. Bacteriocin produced by S. marcescens was purified by chromatography with Sephadex G-75 column, and its antibacterial effect on gram-negative bacteria, including Escherichia coli ATCC 700928, Pseudomonas aeruginosa PTCC 1707, S. marcescens PTCC 1621, Vibrio fischeri PTCC 1693, and Vibrio harveyi PTCC 1755, were evaluated by the disk diffusion method. The structure of bacteriocin was determined by nuclear magnetic resonance spectroscopy. The interaction of bacteriocin with the antigen 43 (Ag43) of E. coli was evaluated by the molecular docking method. Bacteriocin extracted from bacterial isolates had antibacterial activity on E. coli strains but not on other studied strains. Bioinformatics analysis also showed bacteriocin docking with Ag43 with an energy of -159.968 kJ/mol. Natural compounds, such as bacteriocin, can be an alternative to common chemical compounds and antibiotics. To reach a definite conclusion in this regard, there is a need for further research and understanding of their mechanism of action. [ABSTRACT FROM AUTHOR]

This work summarizes our research on synthesis, characterization and toxicity of selected UV-A filters and their antioxidant shield in commercial formulation - resveratrol. Benzophenone type of UV filters react under disinfection conditions with chlorine and form different mono- and dichlorinated products, while dibenzoylmethane derivatives, such as avobenzone, react with chlorine and form two main bridge chlorinated products followed by numerous chlorinated species at the advanced stages of the process. Resveratrol showed three main susceptible centers to chlorination, starting from the electrophilic addition to the double bond and continuing with the chlorination of the phenolic moieties. Several experiments conducted under different disinfection conditions (pool/sea water, addition of salts, irradiation) showed basically similar chlorination patterns with some variations in terms of product formation. The results of toxicity assessment using different test organisms (Vibrio fischeri, microalgae, daphnids) have shown different sensitivity of testing organisms to the parent UV filters in comparison with chlorinated products as well as different toxicity for specific UV filter in comparison to the others. As the closing loop of all experiments in the laboratory, an up-scaling to the real human skin is presented. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the water quality of the Extrema River spring in a Brazilian Cerrado area. Three collection sites (P1 − P3) were sampled in the dry and rainy seasons, which are close to industries from different sectors. In the physicochemical analysis, a decrease in dissolved oxygen levels (<5 mg/L) and pH (< 6) at P3 was detected. An increase in heterotrophic bacteria count was recorded at all sites (> 500 colonies/ml). In ecotoxicological analyses, P2 and P3 exhibited toxicity using Vibrio fischeri (> 20%). In evaluating toxicity, the reduction in seed germination was significant utilizing Lactuca sativa at all locations and with Allium cepa only at P2; rootlet length was decreased at P3 on L. sativa and at all sites with A. cepa. In contrast, loss of membrane integrity and mitochondrial function of meristems was adversely affected at all locations using both L. sativa and A. cepa assays. Principal components analysis (PCA) approach indicated that seasonality apparently did not markedly interfere with the obtained data, but it is important to include more collection locations to be evaluated with multiple bioindicators in the spring region. Our data indicate the urgent need for more rigorous programs to monitor the discharge of effluents into water springs. [ABSTRACT FROM AUTHOR]

Vibrio fischeri is a cosmopolitan marine bacterium that oftentimes displays different colony morphologies, switching from a smooth to a wrinkly phenotype in order to adapt to changes in the environment. This wrinkly phenotype has also been associated with increased biofilm formation, an essential characteristic for V. fischeri to adhere to substrates, to suspended debris, and within the light organs of sepiolid squids. Elevated levels of biofilm formation are correlated with increased microbial survival of exposure to environmental stressors and the ability to expand niche breadth. Since V. fischeri has a biphasic life history strategy between its free-living and symbiotic states, we were interested in whether the wrinkly morphotype demonstrated differences in its expression profile in comparison to the naturally occurring and more common smooth variant. We show that genes involved in major biochemical cascades, including those involved in protein sorting, oxidative stress, and membrane transport, play a role in the wrinkly phenotype. Interestingly, only a few unique genes are specifically involved in macromolecule biosynthesis in the wrinkly phenotype, which underlies the importance of other pathways utilized for adaptation under the conditions in which Vibrio bacteria are producing this change in phenotype. These results provide the first comprehensive analysis of the complex form of genetic activation that underlies the diversity in morphologies of V. fischeri when switching between two different colony morphotypes, each representing a unique biofilm ecotype.IMPORTANCE The wrinkly bacterial colony phenotype has been associated with increased squid host colonization in V. fischeri The significance of our research is in identifying the genetic mechanisms that are responsible for heightened biofilm formation in V. fischeri This report also advances our understanding of gene regulation in V. fischeri and brings to the forefront a number of previously overlooked genetic networks. Several loci that were identified in this study were not previously known to be associated with biofilm formation in V. fischeri.

This study investigated the efficiency of two advanced oxidation processes (AOPs), ozonation (O3), and electrochemical oxidation (EO), applied individually or in combination, in the removal of contaminants of emerging concern (CECs) contained in hospital wastewaters, focusing on pharmaceuticals. The optimisation of the single technologies was performed using synthetic wastewater composed of four refractory pharmaceuticals, (carbamazepine-CBZ, lorazepam-LZP, ketoprofen-KTP, 10,11-epoxicarbamazepine-E-CBZ), first alone and then in mixture, in an initial concentration of 1 mg L−1 each. Once the best operational conditions for EO and O3 were defined, their combination (both simultaneous and sequential) was evaluated for the mixture of the selected pharmaceuticals. The treatment solution that showed the best performance was the simultaneous combination of O3 and EO. This treatment was validated using real hospital wastewater previously treated through a moving bed biofilm reactor (MBBR), evaluating its viability by testing the toxicity of the final effluent via Vibrio fischeri inhibition tests. The obtained results showed that the simultaneous combination of O3 and EO as the polishing step after a biological treatment is a very promising solution for hospital wastewater treatment, allowing for obtaining a non-toxic effluent and full degradation of refractory compounds. The disinfection potential of the proposed AOP was also assessed by determining Escherichia coli inactivation potential. [ABSTRACT FROM AUTHOR]

Symbiotic associations have been studied extensively in recent years, focusing mainly on the potential benefits to the host. However, understanding the role played by microorganisms in the physiology and fitness of the host, an aspect of the subject that had been neglected for a long time, has now become an important goal of symbiotic studies. Among the interesting philosophical questions are the following: how should we study the impact of symbiosis on the fitness of symbiotic microorganisms? What framework should scientists use, and on what philosophical assumptions should such research be based? In other words, when does comparing fitness make sense? In this paper, I develop such a framework, and argue that these requirements comprise: (i) phenotypically similar individuals put in the same (ii) sub-environment and contrast it with another popular approach. Finally, I apply this to the symbiosis between the Euprymna scolopes squid and Vibrio fischeri bacteria to show how scientists should evaluate the fitness of symbiotic microorganisms. [ABSTRACT FROM AUTHOR]

Municipal stormwater is a common source of organic and inorganic pollutants. Rainwater pollution from the streets can be affected by traffic, that is, wear and tear of tyres, brake linings, engines and vehicle bodies. The main objective of the research was to determine the type of pollutants present in rainwater from the highway, and then the possibility of their removal in membrane processes. A number of analyses were performed to determine the concentration of organic and inorganic pollutants and toxicity tests and microbiological studies were performed. Rainwater contained heavy metals in the amount as follows: nickel 0.41 mg/dm³, zinc 5 mg/dm³, lead 0.52 mg/dm³. In rainwater, both typically industrial compounds (biphenyls, polycyclic saturated hydrocarbons, aromatic hydrocarbons, phenols and bisphenol A), naturally occurring compounds and components of plant protection products were determined. Rainwater toxicity was expressed as percentage inhibition of Vibrio fischeri luminescence after 5 and 15 min of incubation and based on the growth of the freshwater vascular plant Lemna minor. Water showed toxicity to V. fischeri at 27.52% (5 min) vs. L. minor at 33%. In the ultrafiltration process, the retention coefficient of organic compounds, that is, TOC and phenol, was respectively 9% and 79%, while in the case of heavy metals, the following values were obtained: Ni(II) 75%, Pb(II) 67%, Zn(II) 98%, and octadecane was reduced by more than 81%. In the nanofiltration process, the retention coefficient was higher and was at the TOC level 100%, phenol 90%, Ni(II) 82%, Pb(II) 67%, Zn(II) 98%, and the octadecane was reduced by more than 85%. [ABSTRACT FROM AUTHOR]

With the wide usage of organic compounds, the assessment of their acute toxicity has drawn great attention to reduce animal testing and human labor. The development of graph models provides new opportunities for acute toxicity prediction. In this study, five graph models (message-passing neural network, graph convolution network, graph attention network, path-augmented graph transformer network, and Attentive FP) were applied on four toxicity tasks (fish, Daphnia magna, Tetrahymena pyriformis, and Vibrio fischeri). With the lowest prediction error, Attentive FP was reported to have the best performance in all four tasks. Moreover, the attention weights of the Attentive FP model helped to construct atomic heatmaps and provide good explainability. [ABSTRACT FROM AUTHOR]

Vibrio fischeri bioluminescence inhibition assay (VFBIA) is known for bacterial contamination measurement in water and food. This system is a type of quorum sensing identification that is an intracellular cumulative active mechanism. This experiment aims to increase the light emission of bioluminescent bacteria (V. fischeri and Vibrio sp. Persian 1 strains) using magnetic nanoparticles (MNPs). To this end, different concentrations of magnetic nanoparticles were added to the artificial seawater medium (ASW). Standard strains (V. fischeri) and Iranian native strain (Vibrio sp. Persian 1) were cultured in magnetic nanoparticles containing media. In the following, nanoparticles' features, including concentration, size, and surface modification, were optimized for sufficient bacterial growth. Mostly, nanoparticles with surface modifications using arginine and lysine (MNPs@Arg, MNPs@Lys) were selected accordingly, and the growth and light emission of bioluminescent bacteria in the presence of various factors of nanoparticles were analyzed. The results showed that ASW with 200 μg/L MNP@Lys and 150 μg/L MNP@Arg were suitable for increasing the growth rate and light emission of V. fischeri and Vibrio sp. Persian 1, respectively. V. fischeri and Vibrio sp. Persian 1 in the presence of a particular concentration of nanoparticles (MNP@Lys and MNP@Arg) in a medium grow faster and emit more rapid light than in the absence of nanoparticles. Finally, the results show that the iron nanoparticles do not have any bactericidal features. Also, they have a complex of ingredients that could improve the bacteria's functions and growth. [ABSTRACT FROM AUTHOR]

Background: The symbiosis between the Hawaiian bobtail squid Euprymna scolopes and bacterium Vibrio fischeri serves as a model for investigating the molecular mechanisms that promote the initial formation of animal-bacterial symbioses. Research with this system frequently depends on freshly hatched E. scolopes, but the husbandry factors that promote hatchling production in a mariculture facility remain underreported. Here we report on the reproductive performance of E. scolopes in response to decreased mating frequency. Results: One animal cohort was maintained in a mariculture facility for 107 days, with females assigned to either a control group (mating once every 14 days) or an experimental group (mating once every 21 days). No differences between the groups were observed in survival, the number of egg clutches laid, or hatchling counts. Each group featured multiple females that were hyper-reproductive, i.e., they generated more than 8 egg clutches while in captivity. Examination of the distributions for daily hatchling counts of individual egg clutches revealed significant variation in the hatching patterns among clutches that was independent of mating frequency. Finally, an assessment of hatchling production showed that 93.5% of total hatchlings produced by the cohort were derived from egg clutches laid within the first 70 days. Conclusions: These results suggest a lower mating frequency does not impede hatchling production. Furthermore, the variation in hatchling production among egg clutches provides new insight into the reproductive performance of E. scolopes as a lab animal for microbiology research. [ABSTRACT FROM AUTHOR]

Most animals establish long-term symbiotic associations with bacteria that are critical for normal host physiology. The symbiosis that forms between the Hawaiian squid Euprymna scolopes and the bioluminescent bacterium Vibrio fischeri serves as an important model system for investigating the molecular mechanisms that promote animal-bacterial symbioses. E. scolopes hatch from their eggs uncolonized, which has led to the development of squid-colonization assays that are based on introducing culture-grown V. fischeri cells to freshly hatched juvenile squid. Recent studies have revealed that strains often exhibit large differences in how they establish symbiosis. Therefore, we sought to develop a simplified and reproducible protocol that permits researchers to determine appropriate inoculum levels and provides a platform to standardize the assay across different laboratories. In our protocol, we adapt a method commonly used for evaluating the infectivity of pathogens to quantify the symbiotic capacity of V. fischeri strains. The resulting metric, the symbiotic dose-50 (SD50), estimates the inoculum level that is necessary for a specific V. fischeri strain to establish a light-emitting symbiosis. Relative to other protocols, our method requires 2–5-fold fewer animals. Furthermore, the power analysis presented here suggests that the protocol can detect up to a 3-fold change in the SD50 between different strains. [ABSTRACT FROM AUTHOR]

For the first time, a global regression quantitative structure–toxicity/activity relationship (QSTR/QSAR) model was developed for the toxicity of a large data set including 1236 chemicals towards Vibrio fischeri, by using random forest (RF) regression algorithm. The optimal RF model with RF parameters of mtry = 3, ntree = 150 and nodesize = 5 was based on 13 molecular descriptors. It can achieve accurate prediction for the toxicity of 99.1% of 1236 chemicals, and yield coefficients of determination R2 of 0.893 for 930 log(Mw/IBC50) in the training set, 0.723 for 306 log(Mw/IBC50) in the test se, and 0.865 for 1236 toxicity log(Mw/IBC50) in the total set. The optimal RF global model proposed in this work is comparable to other published local QSTR models on small datasets of the toxicity to Vibrio fischeri. [ABSTRACT FROM AUTHOR]

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Abstract Background Many animals and plants acquire their coevolved symbiotic partners shortly post-embryonic development. Thus, during embryogenesis, cellular features must be developed that will promote both symbiont colonization of the appropriate tissues, as well as persistence at those sites. While variation in the degree of maturation occurs in newborn tissues, little is unknown about how this variation influences the establishment and persistence of host-microbe associations. Results The binary symbiosis model, the squid-vibrio (Euprymna scolopes-Vibrio fischeri) system, offers a way to study how an environmental gram-negative bacterium establishes a beneficial, persistent, extracellular colonization of an animal host. Here, we show that bacterial symbionts occupy six different colonization sites in the light-emitting organ of the host that have both distinct morphologies and responses to antibiotic treatment. Vibrio fischeri was most resilient to antibiotic disturbance when contained within the smallest and least mature colonization sites. We show that this variability in crypt development at the time of hatching allows the immature sites to act as a symbiont reservoir that has the potential to reseed the more mature sites in the host organ when they have been cleared by antibiotic treatment. This strategy may produce an ecologically significant resiliency to the association. Conclusions The data presented here provide evidence that the evolution of the squid-vibrio association has been selected for a nascent organ with a range of host tissue maturity at the onset of symbiosis. The resulting variation in physical and chemical environments results in a spectrum of host-symbiont interactions, notably, variation in susceptibility to environmental disturbance. This “insurance policy” provides resiliency to the symbiosis during the critical period of its early development. While differences in tissue maturity at birth have been documented in other animals, such as along the infant gut tract of mammals, the impact of this variation on host-microbiome interactions has not been studied. Because a wide variety of symbiosis characters are highly conserved over animal evolution, studies of the squid-vibrio association have the promise of providing insights into basic strategies that ensure successful bacterial passage between hosts in horizontally transmitted symbioses. Video Abstract

The fluoroquinolone-type antibiotic ofloxacin is regularly detected in wastewaters. In this work, its hydroxyl radical (•OH) induced degradation was studied at a concentration of 0.1 mmol dm−3 in three water matrices, pure water, tap water, and purified wastewater (collected from a wastewater treatment plant). •OH was produced by γ-irradiation under conditions when it had a high yield. The •OH dosage dependencies of chemical (COD) and biochemical (BOD) oxygen demands, total organic carbon (TOC) content, oxygen uptake rate (OUR), Microtox® toxicity, and antibacterial activity values were evaluated. •OH effectively oxidized and mineralized ofloxacin; both processes were observed even at the lowest •OH dosage, 0.14 mmol dm−3 (0.5 kGy absorbed dose). When 0.28 mmol dm−3 •OH was introduced into pure or tap water, the antibacterial activity vanished. In purified wastewater, a higher dosage (0.56 mmol dm−3) was required to achieve the same effect as in pure water, due to the organic molecules of the matrix that quenched the •OH radicals. The products did not have antibacterial activity and showed little toxicity toward the test organism Vibrio fischeri. •OH preferentially attacks the pharmacophore part, the 4-quinolone unit of ofloxacin. •OH-induced reactions can be safely applied to destroy the antimicrobial potency of fluoroquinolone-type antibiotics in purified wastewater matrices. [ABSTRACT FROM AUTHOR]

Quorum sensing is an intercellular signaling mechanism that enables bacterial cells to coordinate population‐level behaviors. How quorum sensing functions in natural habitats remains poorly understood. Vibrio fischeri is a bacterial symbiont of the Hawaiian bobtail squid Euprymna scolopes and depends on LuxI/LuxR quorum sensing to produce the symbiotic trait of bioluminescence. A previous study demonstrated that animals emit light when co‐colonized by a Δlux mutant, which lacks several genes within the lux operon that are necessary for bioluminescence production, and a LuxI− mutant, which cannot synthesize the quorum signaling molecule N‐3‐oxohexanoyl‐homoserine lactone. Here, we build upon that observation and show that populations of LuxI− feature elevated promoter activity for the lux operon. We find that population structures comprising of Δlux and LuxI− are attenuated within the squid, but a wild‐type strain enables the LuxI− strain type to be maintained in vivo. These experimental results support a model of interpopulation signaling, which provides basic insight into how quorum sensing functions within the natural habitats found within a host. [ABSTRACT FROM AUTHOR]

To colonize a host, bacteria depend on an ensemble of signaling systems to convert information about the various environments encountered within the host into specific cellular activities. How these signaling systems coordinate transitions between cellular states in vivo remains poorly understood. To address this knowledge gap, we investigated how the bacterial symbiont Vibrio fischeri initially colonizes the light organ of the Hawaiian bobtail squid Euprymna scolopes. Previous work has shown that the small RNA Qrr1, which is a regulatory component of the quorumsensing system in V. fischeri, promotes host colonization. Here, we report that transcriptional activation of Qrr1 is inhibited by the sensor kinase BinK, which suppresses cellular aggregation by V. fischeri prior to light organ entry. We show that Qrr1 expression depends on the alternative sigma factor σ54 and the transcription factors LuxO and SypG, which function similar to an OR logic gate, thereby ensuring Qrr1 is expressed during colonization. Finally, we provide evidence that this regulatory mechanism is widespread throughout the Vibrionaceae family. Together, our work reveals how coordination between the signaling pathways underlying aggregation and quorum-sensing promotes host colonization, which provides insight into how integration among signaling systems facilitates complex processes in bacteria. [ABSTRACT FROM AUTHOR]

The present study investigated the acute toxic effects caused by the main pollutants found in landfill leachates: total ammonia nitrogen (TAN), alkalinity, and humic substances (HS) for the test organisms Vibrio fischeri , Danio rerio , Daphnia similis , and Artemia sp. The leachates were obtained from two Brazilian landfills with different ages and operating modes. Air stripping and membrane filtration treatability experiments were performed to remove pollutants from the leachate. The results showed high toxicity of the raw leachate from both landfills for the studied organisms. In the individual treatments, air stripping achieved TAN and alkalinity removal efficiencies > 99%, and the membrane filtration treatment achieved HS removal efficiencies > 98%. Compared to the individual treatments, the combination of treatments resulted in the most significant reductions in leachate toxicity from both landfills for all test organisms studied. The principal component analysis showed a strong correlation between COD or HS parameters and the toxicity of V. fischeri and strong correlations between TAN and the toxicity of D. rerio, D. similis , and Artemia sp. Finally, this study highlights the application of a treatment route to remove acute toxicity from complex effluents, such as landfill leachate, to avoid potential environmental hazards to the aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Abstract Background The Hawaiian bobtail squid Euprymna scolopes hosts various marine bacterial symbionts, and these symbioses have served as models for the animal-microbe relationships that are important for host health. Within a light organ, E. scolopes harbors populations of the bacterium Vibrio fischeri, which produce low levels of bioluminescence that the squid uses for camouflage. The symbiosis is initially established after a juvenile squid hatches from its egg and acquires bacterial symbionts from the ambient marine environment. The relative ease with which a cohort of wild-caught E. scolopes can be maintained in a mariculture facility has facilitated over 3 decades of research involving juvenile squid. However, because E. scolopes is native to the Hawaiian archipelago, their transport from Hawaii to research facilities often represents a stress that has the potential to impact their physiology. Results Here, we describe animal survival and reproductive capacity associated with a cohort of squid assembled from two shipments with markedly different transit times. We found that the lower juvenile squid counts generated by animals with the longer transit time were not due to the discrepancy in shipment but instead to fewer female squid that produced egg clutches at an elevated rate, which we term hyper-reproductivity. We find that hyper-reproductive females were responsible for 58% of the egg clutches laid. Conclusions The significance of these findings for E. scolopes biology and husbandry is discussed, thereby providing a platform for future investigation and further development of this cephalopod as a valuable lab animal for microbiology research.

To colonize a host, bacteria depend on an ensemble of signaling systems to convert information about the various environments encountered within the host into specific cellular activities. How these signaling systems coordinate transitions between cellular states in vivo remains poorly understood. To address this knowledge gap, we investigated how the bacterial symbiont Vibrio fischeri initially colonizes the light organ of the Hawaiian bobtail squid Euprymna scolopes. Previous work has shown that the small RNA Qrr1, which is a regulatory component of the quorum-sensing system in V. fischeri, promotes host colonization. Here, we report that transcriptional activation of Qrr1 is inhibited by the sensor kinase BinK, which suppresses cellular aggregation by V. fischeri prior to light organ entry. We show that Qrr1 expression depends on the alternative sigma factor σ54 and the transcription factors LuxO and SypG, which function similar to an OR logic gate, thereby ensuring Qrr1 is expressed during colonization. Finally, we provide evidence that this regulatory mechanism is widespread throughout the Vibrionaceae family. Together, our work reveals how coordination between the signaling pathways underlying aggregation and quorum-sensing promotes host colonization, which provides insight into how integration among signaling systems facilitates complex processes in bacteria.