Acinetobacter pittii, an emerging new multi-drug resistant fish pathogen isolated from diseased blunt snout bream (Megalobrama amblycephala Yih) in China

Cobalt (II) porphyrin nanoaggregates as sacrificial templates to improve the peroxidase-like activity of light-controlled TiO2-based nanozymes for colorimetric determination of amikacin

Although porphyrin modification can improve the peroxidase-like activity of some inorganic nanozymes, it is hardly studied that metal porphyrin self-assembled nanoaggregates as sacrificial templates to turn on the peroxidase-like activity of inorganic nanozymes under light illumination. In this work, cobalt (II) 5,10,15,20-Tetrakis (4-carboxylpheyl)porphyrin (CoTCPP) self-assembled nanoaggregates are firstly used as soft templates to prepare TiO2-based nanozymes with the enhanced peroxidase-like activity. Interestingly, CoTCPP nanoaggregates can be changed into Co oxide nanoparticles dispersed into the nanosphere composites. Furthermore, the peroxidase-like activity of CoTCPP-TiO2 nanospheres can be controlled by light illumination. Comparatively, CoTCPP-TiO2 nanoshperes exhibit the highest peroxidase-like activity of three nanospheres (CoTCPP-TiO2, H2TCPP-TiO2 and TiO2) with similar morphology under the light illumination. Other than the existence of oxygen vacancy, the formation of heterostructure between TiO2 and a small amount of Co3O4 are ascribed to increase the catalytic activity of CoTCPP-TiO2 composites. Thus, a facile and convenient colorimetric sensing platform has been constructed and tuned by light illumination for determining H2O2 and amikacin in a good linear range of 20-100 and 50-100 μM with a limit of detection (LOD) of 3.04 μM and 1.88 μM, respectively. The CoTCPP-TiO2 based colorimetric sensing platform has been validated by measuring the amikacin residue in lake water.

Analysis of Acinetobacter P-type type IV secretion system-encoding plasmid diversity uncovers extensive secretion system conservation and diverse antibiotic resistance determinants

Acinetobacter baumannii is globally recognized as a multi-drug-resistant pathogen of critical concern due to its capacity for horizontal gene transfer and resistance to antibiotics. Phylogenetically diverse Acinetobacter species mediate human infection, including many considered as important emerging pathogens. While globally recognized as a pathogen of concern, pathogenesis mechanisms are poorly understood. P-type type IV secretion systems (T4SSs) represent important drivers of pathogen evolution, responsible for horizontal gene transfer and secretion of proteins that mediate host-pathogen interactions, contributing to pathogen survival, antibiotic resistance, virulence, and biofilm formation. Genes encoding a P-type T4SS were previously identified on plasmids harboring the carbapenemase gene blaNDM-1 in several clinically problematic Acinetobacter; however, their prevalence among the genus, geographical distribution, the conservation of T4SS proteins, and full capacity for resistance genes remain unclear. Using systematic analyses, we show that these plasmids belong to a group of 53 P-type T4SS-encoding plasmids in 20 established Acinetobacter species, the majority of clinical relevance, including diverse A. baumannii sequence types and one strain of Providencia rettgeri. The strains were globally distributed in 14 countries spanning five continents, and the conjugative operon's T4SS proteins were highly conserved in most plasmids. A high proportion of plasmids harbored resistance genes, with 17 different genes spanning seven drug classes. Collectively, this demonstrates that P-type T4SS-encoding plasmids are more widespread among the Acinetobacter genus than previously anticipated, including strains of both clinical and environmental importance. This research provides insight into the spread of resistance genes among Acinetobacter and highlights a group of plasmids of importance for future surveillance.

Integrative genome-centric metagenomics for surface water surveillance: Elucidating microbiomes, antimicrobial resistance, and their associations

Surface water ecosystems are intimately intertwined with anthropogenic activities and have significant public health implications as primary sources of irrigation water in agricultural production. Our extensive metagenomic analysis examined 404 surface water samples from four different geological regions in Chile and Brazil, spanning irrigation canals (n = 135), rivers (n = 121), creeks (n = 74), reservoirs (n = 66), and ponds (n = 8). Overall, 50.25 % of the surface water samples contained at least one of the pathogenic or contaminant bacterial genera (Salmonella: 29.21 %; Listeria: 6.19 %; Escherichia: 35.64 %). Furthermore, a total of 1,582 antimicrobial resistance (AMR) gene clusters encoding resistance to 25 antimicrobial classes were identified, with samples from Brazil exhibiting an elevated AMR burden. Samples from stagnant water sources were characterized by dominant Cyanobacteriota populations, resulting in significantly reduced biodiversity and more uniform community compositions. A significant association between taxonomic composition and the resistome was supported by a Procrustes analysis (p < 0.001). Notably, regional signatures were observed regarding the taxonomic and resistome profiles, as samples from the same region clustered together on both ordinates. Additionally, network analysis illuminated the intricate links between taxonomy and AMR at the contig level. Our deep sequencing efforts not only mapped the microbial landscape but also expanded the genomic catalog with newly characterized metagenome-assembled genomes (MAGs), boosting the classification of reads by 12.85 %. In conclusion, this study underscores the value of metagenomic approaches in surveillance of surface waters, enhancing our understanding of microbial and AMR dynamics with far-reaching public health and ecological ramifications.

Effects of antibacterial peptides from Brevibacillus texasporus on growth performance, meat quality and gut health of cultured largemouth bass (Micropterus salmoides)

The aim of this study was to investigate the effects of antibacterial peptides from Brevibacillus texasporus (BT) on the growth performance, meat quality and gut health of cultured largemouth bass (Micropterus salmoides). Largemouth bass (36.17 ± 1.52 g) were divided into 2 groups and each group was fed with diets supplemented with or without 200 ppm of BT peptides for 130 days. The results showed that BT peptides had no significant influences on growth performance and body indexes, but significantly enhanced total antioxidant capacity and lysozyme content in the serum. Moreover, digestive enzymes activities and intestinal villous height were also prominently increased. From meat quality aspect, no significant differences were found in nutritional components, amino acid composition, fatty acid composition and texture property, except the values of hardness, gumminess and γ-linolenic acid (C18:3n6) were remarkably increased after BT peptides intervention. Finally, the results of gut microbiota and short chain fatty acids revealed that BT peptides significantly decreased the relative abundances of harmful bacteria such as genus Acinetobacter and Pseudomonas, and increased the production of short chain fatty acids. In conclusion, this study confirmed that BT peptides could be used to improve the health of largemouth bass, which provided novel insights into the application of antimicrobial peptides in aquacultures.

Acinetobacter pittii: the emergence of a hospital-acquired pathogen analyzed from the genomic perspective

Acinetobacter pittii has increasingly been associated with several types of hospital-acquired severe infections. Genes implicated in carbapenem resistance, tigecycline resistance, or genes encoding extended spectrum cephalosporinases, such as blaADC, are commonly found in isolates implicated in these infections. A. pittii strains that are pandrug resistant have occasionally been identified. Food for human consumption, animals and plants are environmental sources of this pathogen. An alarming situation is that A. pitti has been identified as responsible for outbreaks in different regions worldwide. In this study, 384 genomes of A. pittii were analyzed, comprising sequences from clinical and non-clinical origins from 32 countries. The objective was to investigate if clinical strains possess genetic traits facilitating hospital adaptation. Results indicate significant genomic variability in terms of size and gene content among A. pittii isolates. The core genome represents a small portion (25-36%) of each isolate's genome, while genes associated with antibiotic resistance and virulence predominantly belong to the accessory genome. Notably, antibiotic resistance genes are encoded by a diverse array of plasmids. As the core genome between environmental and hospital isolates is the same, we can assume that hospital isolates acquired ARGs due to a high selective pressure in these settings. The strain's phylogeographic distribution indicates that there is no geographical bias in the isolate distribution; isolates from different geographic regions are dispersed throughout a core genome phylogenetic tree. A single clade may include isolates from extremely distant geographical areas. Furthermore, strains isolated from the environment or animal, or plant sources frequently share the same clade as hospital isolates. Our analysis showed that the clinical isolates do not already possess specific genes, other than antibiotic-resistant genes, to thrive in the hospital setting.

Lactobacillus spp. in the reproductive system of female moths and mating induced changes and possible transmission

BACKGROUND

The microbiome in the insect reproductive tract is poorly understood. Our previous study demonstrated the presence of Lactobacillus spp. in female moths, but their distribution and function remain unclear. Lactobacillus spp. are known as the 'healthy' vaginal microbiome in humans.

RESULTS

Here, we studied the microbiome in the reproductive system (RS) and gut of Spodoptera frugiperda using 16S rDNA sequences. The obtained 4315 bacterial OTUs were classified into 61 phyla and 642 genera, with Proteobacteria, Firmicutes and Bacteroidota being the top three dominant phyla and Enterococcus and Asaia being dominant genera in most samples. Mating dramatically increased the abundance of pathogens or pathogenic functions in the gut, while in the RS, the change range was trivial. Taxonomy assignment identified thirteen Lactobacillus spp. in S. frugiperda, with Lactobacillus crustorum and Lactobacillus murinus showing high abundance. Three species found in S. frugiperda, namely L. reuteri, L. plantarum and L. brevis, have also been identified as human 'healthy' vaginal bacterial species. Lactobacillus spp. showed higher abundance in the RS of virgin females and lower abundance in the RS of virgin males and the gut of virgin females. Mating reduced their abundance in the RS of females but increased their abundance in the RS of males, especially in males mated with multiple females. The RS of virgin females and of multiple mated males were very similar in terms of composition and abundance of Lactobacillus species, with Lactobacillus crustorum showing much higher abundance in both tissues, potentially due to sexual transmission.

CONCLUSIONS

Lactobacillus spp. showed high abundance and diversity in the RS of female moths. The higher abundance of Lactobacillus spp. in the RS of female moths and the similarity of Lactobacillus species in female moths with human 'healthy' vaginal Lactobacillus spp. suggest that these bacterial strains are also an important microbiome in the RS of female moths.

Integrated Transcriptome and 16S rDNA Analyses Reveal That Transport Stress Induces Oxidative Stress and Immune and Metabolic Disorders in the Intestine of Hybrid Yellow Catfish (Tachysurus fulvidraco♀ × Pseudobagrus vachellii♂)

Live fish are often transported in aquaculture. To explore the effects of transport stress, hybrid yellow catfish (Tachysurus fulvidraco♀ × Pseudobagrus vachellii♂) were subjected to simulated transport treatments (0–16 h) with 96 h of recovery after the 16-h transport treatment, and intestinal biochemical parameters, the transcriptome, and gut microbiota were analyzed. Transportation affected the number of mucus cells and led to oxidative stress in the intestine, which activated immune responses. Changes in lipid metabolism reflected metabolic adaptation to oxidative stress. Toll-like receptor signaling, peroxisome proliferator-activated receptor signaling, and steroid biosynthesis pathways were involved in the transport stress response. Gene expression analyses indicated that transport-induced local immune damage was reversible, whereas disordered metabolism recovered more slowly. A 16S rDNA analysis revealed that transport stress decreased the alpha diversity of the gut microbiota and disrupted its homeostasis. The dominant phyla (Fusobacteria, Bacteroidetes) and genera (Cetobacterium, Barnesiellaceae) were involved in the antioxidant, immune, and metabolic responses of the host to transportation stress. Correlation analyses suggested that gut microbes participate in the transport stress response and the host–microbiota interaction may trigger multiple events in antioxidant, immune, and metabolic pathways. Our results will be useful for optimizing transport processes.

Immunomodulation and skin microbiota perturbations during an episode of chronic stress in gilthead seabream

Fish stress is a major concern in the aquaculture industry. Many stressors coming from routine practices can predispose fish to compromised growth, immunity and overall health. This study focuses on the characterization of the skin microbiota using next generation sequencing (NGS) platform by targeting a genomic marker 16S and to determine growth performance and immune status of gilthead seabream (Sparus aurata) during an episode of chronic stress. Two groups were established: control group and chronically stressed group. Stressed fish were subjected to 1 min air exposure twice a week for 4 weeks. Results showed that stress negatively affected fish growth performance. Cellular and humoral systemic immunity remained unaffected while local immunity in skin was positively stimulated (total IgM and peroxidase). Skin mucus microbial composition showed significant differences especially after 14 days. Stressed fish showed a decrease in the abundance of the genera Acinetobacter, NS3a_marine_group and Pseudomonas, while Pseudoalteromonas and Marinagarivorans increased significantly. In conclusion, air exposure stress was associated with alterations in skin mucosal immunity and microbial composition that may have been beneficial to the host favoring adaptation to stress.

Characterization of a novel broad-spectrum endolysin PlyD4 encoded by a highly conserved prophage found in Aeromonas hydrophila ST251 strains

Aeromonas hydrophila is a zoonotic pathogen that exhibits high level resistance to classic antibiotics and is a heavy burden for aquaculture industry. Lytic enzymes encoded by phages or prophages have shown potential for use against pathogenic bacteria. In this study, an intact prophage (named phAhD4) was identified from A. hydrophila D4. phAhD4 is highly conserved in all 10 published A. hydrophila sequence type (ST) 251 strains and is unique to the ST251 strains. The unique endolysin PlyD4, encoded by phAhD4, was obtained by prokaryotic expression. PlyD4 showed bactericidal activity against a broad range of bacterial species in vitro, including A. hydrophila, Aeromonas veronii, Vibrio parahemolyticus, Pseudomonas aeruginosa, and so on. Synergistically with 5 mmol/L ethylene diamine tetraacetic acid (EDTA), the ratio of the optical density at 600 nm (OD₆₀₀) of PlyD4 treatment versus the OD₆₀₀ with no PlyD4 treatment for most tested strains decreased from 1 to 0.1-0.8 within 2 h. PlyD4 exhibited optimal activity at 28 °C and maintained high activity over a wide pH range (pH 6-10). Divalent metal ions conferred significant enhancement to PlyD4 lytic activity at low concentrations (0.1 mmol/L). In vivo, a 4.5 μg dose of PlyD4 protected 75.0% (15/20) of zebrafish in a bacteremia model of A. hydrophila D4 infection. These results indicated that PlyD4 was an effective therapeutic agent against multiple aquaculture-related pathogens. To the best of our knowledge, this study is the first to report on an A. hydrophila prophage endolysin that exerts antibacterial activity against a broad range of pathogens. KEY POINTS: • The prophage phAhD4 is highly conserved in 10 published A. hydrophila ST251 strains. • PlyD4 exerts antibacterial activity against multiple aquaculture-related pathogens. • PlyD4 conferred protection against A. hydrophila infection in a zebrafish model.

Early life stress causes persistent impacts on the microbiome of Atlantic salmon

Farmed fish are commonly exposed to stress in intensive aquaculture systems, often leading to immune impairment and increased susceptibility to disease. As microbial communities associated with the gut and skin are vital to host health and disease resilience, disruption of microbiome integrity could contribute to the adverse consequences of stress exposure. Little is known about how stress affects the fish microbiome, especially during sensitive early life stages when initial colonisation and proliferation of host-associated microbial communities take place. Therefore, we compared the effects of two aquaculture-relevant early-life stressors on the gut and skin microbiome of Atlantic salmon fry (four months post hatching) using 16S rRNA amplicon sequencing. Acute cold stress applied during late embryogenesis had a pronounced, lasting effect on the structure of the skin microbiome, as well as a less consistent effect on the gut microbiome. Follow-up targeted qPCR assays suggested that this is likely due to disruption of the egg shell microbial communities at the initial stages of microbiome colonisation, with persistent effects on community structure. In contrast, chronic post hatching stress altered the structure of the gut microbiome, but not that of the skin. Both types of stress promoted similar Gammaproteobacteria ASVs, particularly within the genera Acinetobacter and Aeromonas, which include several important opportunistic fish pathogens. Our results demonstrate the sensitivity of the salmon microbiome to environmental stressors during early life, with potential associated health impacts on the host. We also identified common signatures of stress in the salmon microbiome, which may represent useful microbial stress biomarkers.

Toxicological effects of microplastics and phenanthrene to zebrafish (Danio rerio)

The toxicology of microplastics in combination with other pollutants has attracted widespread attention. In this study, zebrafish were exposed to 3 mg/L polystyrene microplastic, 0.2 mg/L phenanthrene, and a combination of both. Zebrafish microplastic uptake, phenanthrene accumulation, antioxidant-associated enzyme activity and related gene expression, immune-associated gene expression, and the gut microflora were measured after 12 and 24 days of exposure. Phenanthrene and microplastic accumulation increased with exposure time and was also greater in the combined exposure group than in the single exposure group. Combined analysis of antioxidant enzyme activity and immune and antioxidant-related genes shows that exposure alone causes oxidative stress in zebrafish, ultimately increasing immunity and the expression of oxidative stress genes, while combined exposure exacerbates these changes. Fusobacteria decreased and Proteobacteria and Bacteroidetes increased in the three exposure groups of gut microorganisms. Overall, our study demonstrates that microplastics enhance the toxicity of phenanthrene and that the two have a synergistic effect.

Skin and stinger bacterial communities in two critically endangered rays from the South Atlantic in natural and aquarium settings

Bacterial communities of two critically endangered rays from the South Atlantic, the butterfly ray (Gymnura altavela) and the groovebelly ray (Dasyatis hypostigma), were described using 16S rRNA gene metabarcoding. The study characterized the bacterial communities associated with (i) G. altavela in natural (in situ) and aquarium (ex situ) settings, (ii) skin and stinger of G. altavela, and D. hypostigma in aquaria, and (iii) newborns and adults of D. hypostigma. The results revealed potentially antibiotic‐producing bacterial groups on the skin of rays from the natural environment, and some taxa with the potential to benefit ray health, mainly in rays from the natural environment, as well as possible pathogens to other animals, including fish and humans. Differences were observed between the G. altavela and D. hypostigma bacteria composition, as well as between the skin and stinger bacterial composition. The bacterial community associated with D. hypostigma changed with the age of the ray. The aquarium environment severely impacted the G. altavela bacteria composition, which changed from a complex bacterial community to one dominated almost exclusively by two taxa, Oceanimonas sp. and Sediminibacterium sp. on the skin and stinger, respectively.

Acinetobacter spp. in food and drinking water - A review

Acinetobacter spp. has emerged as a pathogen of major public health concern due to their increased resistance to antibiotics and their association with a wide range of nosocomial infections, community-acquired infections and war and natural disaster-related infections. It is recognized as a ubiquitous organism however, information about the prevalence of different pathogenic species of this genus in food sources and drinking water is scarce. Since the implementation of molecular techniques, the role of foods as a source of several species, including the Acinetobacter baumannii group, has been elucidated. Multidrug resistance was also detected among Acinetobacter spp. isolated from food products. This highlights the importance of foods as potential sources of dissemination of Acinetobacter spp. between the community and clinical environments and reinforces the need for further investigations on the potential health risks of Acinetobacter spp. as foodborne pathogens. The aim of this review was to summarize the published data on the occurrence of Acinetobacter spp. in different food sources and drinking water. This information should be taken into consideration by those responsible for infection control in hospitals and other healthcare facilities.

Chemical Defense Mechanisms and Ecological Implications of Indo-Pacific Holothurians

Sea cucumbers are slow-moving organisms that use morphological, but also a diverse combination of chemical defenses to improve their overall fitness and chances of survival. Since chemical defense compounds are also of great pharmaceutical interest, we pinpoint the importance of biological screenings that are a relatively fast, informative and inexpensive way to identify the most bioactive organisms prior to further costly and elaborate pharmacological screenings. In this study, we investigated the presence and absence of chemical defenses of 14 different sea cucumber species from three families (Holothuriidae, Stichopodidae and Synaptidae) against ecological factors such as predation and pathogenic attacks. We used the different sea cucumber crude extracts as well as purified fractions and pure saponin compounds in a portfolio of ecological activity tests including fish feeding assays, cytotoxicity tests and antimicrobial assays against environmental pathogenic and non-pathogenic bacteria. Furthermore, we quantified and correlated the concentrations of sea cucumber characteristic saponin compounds as effective chemical defensive compounds in all 14 crude extracts by using the vanillin-sulfuric acid test. The initial results revealed that among all tested sea cucumber species that were defended against at least one ecological threat (predation and/or bacterial attack), Bohadschiaargus, Stichopuscholoronotus and Holothuria fuscopunctata were the three most promising bioactive sea cucumber species. Therefore, following further fractionation and purification attempts, we also tested saponin-containing butanol fractions of the latter, as well as two purified saponin species from B. argus. We could demonstrate that both, the amount of saponin compounds and their structure likely play a significant role in the chemical defense strategy of the sea cucumbers. Our study concludes that the chemical and morphological defense mechanisms (and combinations thereof) differ among the ecological strategies of the investigated holothurian species in order to increase their general fitness and level of survival. Finally, our observations and experiments on the chemical ecology of marine organisms can not only lead to a better understanding of their ecology and environmental roles but also can help in the better selection of bioactive organisms/compounds for the discovery of novel, pharmacologically active secondary metabolites in the near future.

16S rRNA sequencing analysis of the correlation between the intestinal microbiota and body-mass of grass carp (Ctenopharyngodon idella)

There appears to be a close correlation between intestinal microbiotas and obesity. Still, our understanding of the relationship between the intestinal microbiota and body-mass in grass carp (Ctenopharyngodon idella) remains limited. Herein, we explored this association in the anterior, middle, and posterior intestine of cohabitating grass carp by using next-generation sequencing of the 16S rRNA gene. The results showed that alpha diversity indices of the low-weight-gain (LWG) groups were higher than that of the high-weight-gain (HWG) groups. HWG groups possessed the decreased ratio of Bacteroidetes to Firmicutes compared with that in the LWG groups. Principal coordinate analysis (PCoA) and analysis of similarities (ANOSIM) revealed that there were significant differences between the HWG and LWG groups. Furthermore, linear discriminant analysis (LDA) coupled with effect size (LEfSe) showed that the order Clostridiales were significantly abundant in the HWG groups. Phylogenetic molecular ecology networks (pMENs) showed a lower average path distance (GD), higher average clustering coefficient (avgCC), and higher average degree (avgK) in the HWG group. Our results suggested that there appeared to be a tight correlation between the intestinal microbiota and body-mass in grass carp. The study provides a referable resource for establishing the relationship between intestinal microbiotas and economic traits, which also lays a foundation for the progress of new fish probiotic in the future.

Comparative analysis of cutaneous bacterial communities of farmed Rana dybowskii after gentamycin bath

Introduction

Pathogenic bacteria limit the success of Rana dybowskii breeding. Gentamicin is used to treat R. dybowskii disease. To understand the effects of gentamicin on the composition and structure of the cutaneous bacterial community of R. dybowskii, three groups (control, gentamicin and recovery) were established in this study.

Materials & Methods

The V3-V4 hypervariable region of the 16S rRNA gene was analyzed in samples by high-throughput sequencing. Alpha diversity and beta diversity were evaluated to compare the cutaneous bacterial community diversity.

Results

A total of 1,159,668 valid sequences and 3,132 operational taxonomic units (OTUs) were obtained from these three experimental groups. The number of OTUs obtained in the control group, gentamicin group and recovery group were 2,194, 2,288, and 2,047, respectively, and the number of shared OTUs was 1,313. The alpha diversity of the cutaneous bacterial community was not significantly affected by gentamicin, while beta diversity was significantly affected.

Discussion & Conclusions

The effect of a gentamicin bath on relative species abundance was greater than the effect on the species composition. The changes in Proteobacteria, Acinetobacter, and Chryseobacterium were significant, and reductions were observed after the recovery period. Six potentially pathogenic genera were detected, including Aeromonas, Citrobacter, Chryseobacterium, Pseudomonas, Staphylococcus, and Streptococcus. Among them, Aeromonas and Chryseobacterium were significantly inhibited by the gentamicin bath. The results of this study provide a theoretical basis for the application of gentamicin in R. dybowskii breeding.

Isolation, identification and characterisation of an emerging fish pathogen, Acinetobacter pittii, from diseased loach (Misgurnus anguillicaudatus) in China

Although members of the genus Acinetobacter have emerged as important nosocomial pathogens causing severe human infections, there are few reports about their occurrence as fish pathogens. In this study, five bacterial strains were isolated from diseased loach (Misgurnus anguillicaudatus) cultured in a farm in China. The diseased loach displayed shedding of skin mucus and many petechial haemorrhages all over the body. Based on sequence analyses of 16S rRNA and rpoB genes, the isolates were identified as Acinetobacter pittii. An experimental infection assay confirmed their pathogenicity to loach. The results of artificial infection in zebrafish (Barchydanio rerio) and nematode (Caenorhabditis elegans) suggested that, as well as loach, these A. pittii isolates are pathogenic and highly virulent to these organisms. Multilocus sequence typing analysis revealed that all the isolates belong to sequence type (ST) 839, which may be the dominant clone causing fish disease and exhibits a close phylogenetic relationship with ST396 from human clinical samples in Korea or Taiwan China. This is the first report demonstrating that A. pittii is an emerging causal agent of mass mortality in loach and poses significant risks to fish culturing besides causing human clinical infection worldwide.

Isolation and characterization of Sphingomonadaceae from fouled membranes

Membrane filtration systems are widely applied for the production of clean drinking water. However, the accumulation of particles on synthetic membranes leads to fouling. Biological fouling (i.e., biofouling) of reverse osmosis and nanofiltration membranes is difficult to control by existing cleaning procedures. Improved strategies are therefore needed. The bacterial diversity on fouled membranes has been studied, especially to identify bacteria with specialized functions and to develop targeted approaches against these microbes. Previous studies have shown that Sphingomonadaceae are initial membrane colonizers that remain dominant while the biofilm develops. Here, we characterized 21 Sphingomonadaceae isolates, obtained from six different fouled membranes, to determine which physiological traits could contribute to colonization of membrane surfaces. Their growth conditions ranged from temperatures between 8 and 42 oC, salinity between 0.0 and 5.0% w/v NaCl, pH from 4 and 10, and all isolates were able to metabolize a wide range of substrates. The results presented here show that Sphingomonadaceae membrane isolates share many features that are uncommon for other members of the Sphingomonadaceae family: all membrane isolates are motile and their tolerance for different temperatures, salt concentrations, and pH is high. Although relative abundance is an indicator of fitness for a whole group, for the Sphingomonadaceae it does not reveal the specific physiological traits that are required for membrane colonization. This study, therefore, adds to more fundamental insights in membrane biofouling.

Complete Genome Sequence of Highly Virulent Aeromonas hydrophila Strain D4, Isolated from a Diseased Blunt-Snout Bream in China

Aeromonas hydrophila is the causative agent of motile aeromonad septicemia. Here, we present the complete genome sequence of highly virulent A. hydrophila strain D4, which was isolated from a diseased blunt-snout bream in China.

Aeromonas hydrophila is the causative agent of motile aeromonad septicemia. Here, we present the complete genome sequence of highly virulent A. hydrophila strain D4, which was isolated from a diseased blunt-snout bream in China. It comprises one circular chromosome and four previously unreported plasmids with a total length of 5,275,132 bp.

Sponge chemical defenses are a possible mechanism for increasing sponge abundance on reefs in Zanzibar

Coral reefs are experiencing increasing anthropogenic impacts that result in substantial declines of reef-building corals and a change of community structure towards other benthic invertebrates or macroalgae. Reefs around Zanzibar are exposed to untreated sewage and runoff from the main city Stonetown. At many of these sites, sponge cover has increased over the last years. Sponges are one of the top spatial competitors on reefs worldwide. Their success is, in part, dependent on their strong chemical defenses against predators, microbial attacks and other sessile benthic competitors. This is the first study that investigates the bioactive properties of sponge species in the Western Indian Ocean region. Crude extracts of the ten most dominant sponge species were assessed for their chemical defenses against 35 bacterial strains (nine known as marine pathogens) using disc diffusion assays and general cytotoxic activities were assessed with brine shrimp lethality assays. The three chemically most active sponge species were additionally tested for their allelopathic properties against the scleractinian coral competitor Porites sp.. The antimicrobial assays revealed that all tested sponge extracts had strong antimicrobial properties and that the majority (80%) of the tested sponges were equally defended against pathogenic and environmental bacterial strains. Additionally, seven out of ten sponge species exhibited cytotoxic activities in the brine shrimp assay. Moreover, we could also show that the three most bioactive sponge species were able to decrease the photosynthetic performance of the coral symbionts and thus were likely to impair the coral physiology.