- Targeted metabolomics to investigate antimicrobial activity of itaconic acid in marine molluscs. [Journal Article]
- MMetabolomics 2019 Jun 22; 15(7):97
- CONCLUSIONS: We reported on the production of ITA in different tissues of P. canaliculus mussels challenged with a marine pathogen which confirmed ITA as an antimicrobial metabolite. The findings revealed insights into the biosynthesis of ITA and suggests its role in antimicrobial and anti-inflammatory activities in the innate immune system. This study also provided insights into the innate immune system of bivalves and highlighted the potential use of ITA as a biomarker for shellfish health assessment in aquaculture.
- Bacterial nucleobases synergistically induce larval settlement and metamorphosis in the invasive mussel Mytilopsis sallei. [Journal Article]
- AEAppl Environ Microbiol 2019 Jun 21
- Marine bacterial biofilms have long been recognized as potential inducers of larval settlement and metamorphosis in marine invertebrates, but few chemical cues from bacteria have been identified. Her…
Marine bacterial biofilms have long been recognized as potential inducers of larval settlement and metamorphosis in marine invertebrates, but few chemical cues from bacteria have been identified. Here, we show that larval settlement and metamorphosis of an invasive fouling mussel Mytilopsis sallei could be induced by biofilms of bacteria isolated from its adult shells and other substrates from the natural environment. One of the strains isolated, Vibrio owensii MS-9 showed strong inducing activity which was attributed to the release of a mixture of nucleobases, including uracil, thymine, xanthine, hypoxanthine and guanine into seawater. In particular the synergistic effect of hypoxanthine and guanine was sufficient for the inducing activity of V. owensii MS-9. The presence of two or three other nucleobases could enhance to some extent, the activity of the mixture of hypoxanthine and guanine. Furthermore, we determined that bacteria producing higher concentrations of nucleobases were more likely to induce larval settlement and metamorphosis of M. sallei The present study demonstrates that bacterial nucleobases play an important role in larval settlement and metamorphosis of marine invertebrates. This provides new insights into our understanding of the role of environmental bacteria in the colonization and aggregation of invasive fouling organisms, and of the metabolites used as chemical mediators in cross-kingdom communication within aquatic systems.Importance Invasive species are an increasingly serious problem globally. In aquatic ecosystems, invasive dreissenid mussels are well-known ecological and economic pests because they appear to effortlessly invade new environments and foul submerged structures with high-density aggregations. To efficiently control the exotic mussel recruitment and colonization, the need to investigate the mechanisms of substrates selection for larval settlement and metamorphosis is apparent. Our work is one of very few to experimentally demonstrate that compounds produced by environmental bacteria play an important role in larval settlement and metamorphosis in marine invertebrates. Additionally, this study demonstrates that bacterial nucleobases can be used as chemical mediators in cross-kingdom communication within aquatic systems, which will enhance our understanding of how microbes induce larval settlement and metamorphosis of dreissenid mussels, and furthermore, may allow the development of new methods for application in antifouling.
- Marine Microbial Assemblages on Microplastics: Diversity, Adaptation, and Role in Degradation. [Journal Article]
- ARAnn Rev Mar Sci 2019 Jun 21
- We have known for more than 45 years that microplastics in the ocean are carriers of microbially dominated assemblages. However, only recently has the role of microbial interactions with microplastic…
We have known for more than 45 years that microplastics in the ocean are carriers of microbially dominated assemblages. However, only recently has the role of microbial interactions with microplastics in marine ecosystems been investigated in detail. Research in this field has focused on three main areas: (a) the establishment of plastic-specific biofilms (the so-called plastisphere); (b) enrichment of pathogenic bacteria, particularly members of the genus Vibrio, coupled to a vector function of microplastics; and (c) the microbial degradation of microplastics in the marine environment. Nevertheless, the relationships between marine microorganisms and microplastics remain unclear. In this review, we deduce from the current literature, new comparative analyses, and considerations of microbial adaptation concerning plastic degradation that interactions between microorganisms and microplastic particles should have rather limited effects on the ocean ecosystems. The majority of microorganisms growing on microplastics seem to belong to opportunistic colonists that do not distinguish between natural and artificial surfaces. Thus, microplastics do not pose a higher risk than natural particles to higher life forms by potentially harboring pathogenic bacteria. On the other hand, microplastics in the ocean represent recalcitrant substances for microorganisms that are insufficient to support prokaryotic metabolism and will probably not be microbially degraded in any period of time relevant to human society. Because we cannot remove microplastics from the ocean, proactive action regarding research on plastic alternatives and strategies to prevent plastic entering the environment should be taken promptly. Expected final online publication date for the Annual Review of Marine Science Volume 12 is January 3, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
- Species-specific mechanisms of cytotoxicity toward immune cells determine the successful outcome of Vibrio infections. [Journal Article]
- PNProc Natl Acad Sci U S A 2019 Jun 20
- Vibrio species cause infectious diseases in humans and animals, but they can also live as commensals within their host tissues. How Vibrio subverts the host defenses to mount a successful infection r…
Vibrio species cause infectious diseases in humans and animals, but they can also live as commensals within their host tissues. How Vibrio subverts the host defenses to mount a successful infection remains poorly understood, and this knowledge is critical for predicting and managing disease. Here, we have investigated the cellular and molecular mechanisms underpinning infection and colonization of 2 virulent Vibrio species in an ecologically relevant host model, oyster, to study interactions with marine Vibrio species. All Vibrio strains were recognized by the immune system, but only nonvirulent strains were controlled. We showed that virulent strains were cytotoxic to hemocytes, oyster immune cells. By analyzing host and bacterial transcriptional responses to infection, together with Vibrio gene knock-outs, we discovered that Vibrio crassostreae and Vibrio tasmaniensis use distinct mechanisms to cause hemocyte lysis. Whereas V. crassostreae cytotoxicity is dependent on a direct contact with hemocytes and requires an ancestral gene encoding a protein of unknown function, r5.7, V. tasmaniensis cytotoxicity is dependent on phagocytosis and requires intracellular secretion of T6SS effectors. We conclude that proliferation of commensal vibrios is controlled by the host immune system, preventing systemic infections in oysters, whereas the successful infection of virulent strains relies on Vibrio species-specific molecular determinants that converge to compromise host immune cell function, allowing evasion of the host immune system.
- Transformation pathway and toxicity assessment of malathion in aqueous solution during UV photolysis and photocatalysis. [Journal Article]
- CChemosphere 2019 Jun 12; 234:204-214
- In drinking water treatment, complete mineralization of organophosphorus pesticides (OPPs) by UV-based advanced oxidation processes (UV AOPs) is rarely achieved. The formation of intermediate oxidati…
In drinking water treatment, complete mineralization of organophosphorus pesticides (OPPs) by UV-based advanced oxidation processes (UV AOPs) is rarely achieved. The formation of intermediate oxidation byproducts would likely have some profound effects on toxicity of the reaction solutions. This study investigated the intermediate oxidation byproducts, transformation pathway and toxicity of malathion solutions during the treatment processes of UV alone, UV/H2O2, UV/TiO2 and UV/Fenton. The main intermediate oxidation byproducts were derived using ultra-performance liquid chromatography - electrospray - time-of-flight mass spectrometry. Thereby the transformation pathway for each of these treatment processes was proposed. The results indicate that in UV photolysis, the transformation pathway of malathion proceeded initially via cleavage of the phosphorus-sulfur bonds while in photocatalysis, the desulfurization from a PS bond to a PO bond was the primary degradation pathway. Interestingly, only in the UV/TiO2 process a small fraction of malathion was found decomposed via a demethylation reaction. At the same time, a toxicity assessment of the treated solutions was conducted by both luminescence inhibition of Vibrio fischeri and inhibition of acetylcholinesterase (AChE). It was found that after UV AOP treatment, the toxicity of the malathion aqueous solution increased sharply. In contrast, no increase in toxicity was observed for the malathion aqueous solution after UV alone treatment. This study demonstrates that the high removal efficiency achieved by OPPs does not imply that detoxification of the water solution has been achieved. On the contrary, the toxicity of the treated solutions by OPPs may be increased significantly depending on the selected treatment processes.
- Blowing epithelial cell bubbles with GumB: ShlA-family pore-forming toxins induce blebbing and rapid cellular death in corneal epithelial cells. [Journal Article]
- PPPLoS Pathog 2019; 15(6):e1007825
- Medical devices, such as contact lenses, bring bacteria in direct contact with human cells. Consequences of these host-pathogen interactions include the alteration of mammalian cell surface architect…
Medical devices, such as contact lenses, bring bacteria in direct contact with human cells. Consequences of these host-pathogen interactions include the alteration of mammalian cell surface architecture and induction of cellular death that renders tissues more susceptible to infection. Gram-negative bacteria known to induce cellular blebbing by mammalian cells, Pseudomonas and Vibrio species, do so through a type III secretion system-dependent mechanism. This study demonstrates that a subset of bacteria from the Enterobacteriaceae bacterial family induce cellular death and membrane blebs in a variety of cell types via a type V secretion-system dependent mechanism. Here, we report that ShlA-family cytolysins from Proteus mirabilis and Serratia marcescens were required to induce membrane blebbling and cell death. Blebbing and cellular death were blocked by an antioxidant and RIP-1 and MLKL inhibitors, implicating necroptosis in the observed phenotypes. Additional genetic studies determined that an IgaA family stress-response protein, GumB, was necessary to induce blebs. Data supported a model where GumB and shlBA are in a regulatory circuit through the Rcs stress response phosphorelay system required for bleb formation and pathogenesis in an invertebrate model of infection and proliferation in a phagocytic cell line. This study introduces GumB as a regulator of S. marcescens host-pathogen interactions and demonstrates a common type V secretion system-dependent mechanism by which bacteria elicit surface morphological changes on mammalian cells. This type V secretion-system mechanism likely contributes bacterial damage to the corneal epithelial layer, and enables access to deeper parts of the tissue that are more susceptible to infection.
- Occurrence of β-Lactam Resistance Genes and Plasmid-Mediated Resistance Among Vibrios Isolated from Southwest Coast of India. [Journal Article]
- MDMicrob Drug Resist 2019 Jun 20
- Antimicrobial resistance (AMR) is a serious global threat driven by the overuse of drugs in humans, animals, as well as the contamination of natural environments with antimicrobial residues. In recen…
Antimicrobial resistance (AMR) is a serious global threat driven by the overuse of drugs in humans, animals, as well as the contamination of natural environments with antimicrobial residues. In recent years, the rise of community-acquired infections resistant to antibiotics has drawn renewed attention to the environmental compartment, in particular for pathogens found in aquaculture systems. We quantified the prevalence of antibiotic resistance in Vibrios isolated from the Cochin Estuary as well as the adjoining shrimp farms, and seafood from markets. A total of 280 Vibrio strains were subjected to antimicrobial susceptibility testing and screened for the presence of blaTEM, blaCTX-M, and blaNDM-1 genes. All strains identified were resistant to at least three antimicrobials, and the percentage of drugs resistant per strain ranged from 16% up to 60%. All the strains from the estuary were resistant to amoxicillin, ampicillin, cephalothin, and colistin. Similarly, strains isolated from seafood were resistant to enrofloxacin, furazolidone, and trimethoprim, and all strains from shrimp farms were resistant to colistin. Plasmid-mediated antibiotic resistance was observed in 21% of the strains. In addition, the presence of blaNDM-1 gene was confirmed in 22.85% of the strains. The presence of multiple resistant phenotypes in vibrios, including resistance to last-resort compounds in domestic food sources, raises serious concerns for public health in the Cochin Estuary. Although localized in nature, our findings also have vital implications for the spread of AMR internationally, given the prominence of South India for seafood exports.
- Phenotypic & genotypic study of antimicrobial profile of bacteria isolates from environmental samples. [Journal Article]
- IJIndian J Med Res 2019; 149(2):232-239
- CONCLUSIONS: This study results showed high rate of occurrence of antimicrobial resistance and their determinants in Gram-negative bacteria isolated from different environmental sources.
- Prevalence of Enteropathogens in Outpatients with Acute Diarrhea from Urban and Rural Areas, Southeast China, 2010-2014. [Journal Article]
- AJAm J Trop Med Hyg 2019 Jun 17
- Acute diarrhea is an important public health issue. Here, we focused on the differences of enteropathogens in acute diarrhea between urban and rural areas in southeast China. Laboratory- and sentinel…
Acute diarrhea is an important public health issue. Here, we focused on the differences of enteropathogens in acute diarrhea between urban and rural areas in southeast China. Laboratory- and sentinel-based surveillance of acute diarrhea (≥ 3 loose or liquid stools/24 hours) was conducted at 16 hospitals. Fecal specimens were tested for bacterial (Aeromonas sp., Campylobacter sp., diarrheagenic Escherichia coli, Plesiomonas shigelloides, non-typhoidal Salmonella, Shigella sp., Vibrio sp., and Yersinia sp.) and viral (adenovirus, astrovirus, Norovirus, Rotavirus, and Sapovirus) pathogens. Descriptive statistics were used. Between January 1, 2010, and December 31, 2014, 4,548 outpatients with acute diarrhea were enrolled (urban, n = 3,220; rural, n = 1,328). Pathogens were identified in 2,074 (45.6%) patients. Norovirus (25.7%), Vibrio parahaemolyticus (10.2%), enteroaggregative Escherichia coli (EAEC) (8.8%), group A Rotavirus (7.0%), and enterotoxigenic Escherichia coli (ETEC) (5.6%) were the most common pathogens. Enteropathogens were less common in urban than in rural areas (42.0% versus 54.4%, P < 0.001). In urban areas, EAEC and ETEC were more common in high-income than in middle-income regions. Interventions targeting the most common enteropathogens can substantially reduce the burden of acute diarrhea in southeast China.
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- Gallium(III) Nitrate Inhibits Pathogenic Vibrio splendidus Vs by Interfering with the Iron Uptake Pathway. [Journal Article]
- JMJ Microbiol Biotechnol 2019 Jun 10
- It is well known that iron is critical for bacterial growth and pathogenic virulence. Due to chemical similarity, Ga3+ competes with Fe3+ for binding to compounds that usually bind Fe3+, thereby inte…
It is well known that iron is critical for bacterial growth and pathogenic virulence. Due to chemical similarity, Ga3+ competes with Fe3+ for binding to compounds that usually bind Fe3+, thereby interfering with various essential biological reactions. In our present study, gallium(III) nitrate [Ga(NO3)3] could repress the growth of V. splendidus Vs without complete inhibition. In the presence of Ga(NO3)3, the secretion of homogentisic acid-melanin (HGAmelanin) in V. splendidus Vs cells could be increased by 4.8-fold, compared to that in the absence of Ga(NO3)3. HGA-melanin possessed the ability to reduce Fe3+ to Fe2+. In addition, HGA-melanin increased the mRNA levels of feoA and feoB, genes coding Fe2+ transport system proteins to 1.86- and 6.1-fold, respectively, and promoted bacterial growth to 139.2%. Similarly, the mRNA expression of feoA and feoB was upregulated 4.11-fold and 2.71-fold in the presence of 640 μM Ga(NO3)3, respectively. In conclusion, our study suggested that although Ga(NO3)3 could interfere with the growth of V. splendidus Vs, it could also stimulate both the production of Fe3+-reducing HGA-melanin and the expression of feoA and feoB , which facilitate Fe2+ transport in V. splendidus Vs.