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The genus Shewanella consists of Gram-negative proteobacteria that are ubiquitously distributed in environment. As the members of this genus have rapidly increased within the past decade, several species have become emerging pathogens worldwide, attracting the attention of the medical community. These species are also associated with severe community- and hospital-acquired infections. Patients infected with Shewanella spp. had experiences of occupational or recreational exposure; meanwhile, the process of infection is complex and the pathogenicity is influenced by a variety of factors. Here, an exhaustive internet-based literature search was carried out in PUBMED using terms “Achromobacter putrefaciens,” “Pseudomonas putrefaciens,” “Alteromonas putrefaciens” and “Shewanella” to search literatures published between 1978 and June 2022. We provided a comprehensive review on the epidemiology, clinical features and pathogenicity of Shewanella, which will contribute a better understanding of its clinical aetiology, and facilitate the timely diagnosis and effective treatment of Shewanella infection for clinicians and public health professionals.

The epidemiology of bloodstream infections caused by Shewanella spp. is not well defined. Our objective was to define the incidence and determinants of Shewanella spp. bloodstream infections by using population-based surveillance in Queensland, Australia during 2000‒2019. The incidence was 1.0 cases/1 million persons annually and was highest during summer and in the tropical Torres and Cape region. Older persons and male patients were at highest risk. At least 1 concurrent condition was documented in 75% of case-patients, and 30-day all cause case-fatality rate was 15%. Aging populations in warm climates might expect an increasing burden of these infections.

ABSTRACT Shewanella species have been identified as progenitors of several clinically important antibiotic resistance genes. The aim of our study was to analyze Shewanella baltica strains isolated from the gut contents of wild Atlantic mackerel (Scomber scombrus) for the presence of both known and novel variants of antibiotic resistance genes (ARGs), using Illumina-based whole-genome sequencing (WGS). Thirty-three S. baltica strains were isolated from Atlantic mackerel collected in the northern North Sea. WGS revealed the presence of several new variants of class C and class D beta-lactamases. Nearly 42% (14/33) of the strains carried the mobile colistin resistance gene mcr-4.3. To understand the genetic context of mcr-4.3, we determined the complete genome sequence of strain 11FHM2, using a combination of Oxford Nanopore- and Illumina-based sequencing. The complete genome sequence is 5,406,724 bp long, with one contig representing a chromosome of 5,068,880 bp and three contigs representing novel plasmids (pSBP1, 194,145 bp; pSBP2_mcr4, 86,727 bp; and pSBP3, 56,972 bp). Plasmid pSBP2_mcr4 contains the mobile colistin resistance gene mcr-4.3, as well as the mercury resistance operon merRPAT. Plasmid pSBP1 carries genes encoding resistance against copper, zinc, chromium, and arsenic. Plasmid pSBP3 does not carry any antibiotic or heavy metal resistance genes. Analysis of the flanking region of mcr-4.3 suggests that a phage integrase may be involved in the mobilization of mcr-4.3 in Shewanella spp. Our results provide insights into the mobile mcr-4.3 present in Shewanella spp. and highlight the importance of the marine environment in the emergence and dissemination of clinically important resistance genes. IMPORTANCE We identified two new plasmids in Shewanella baltica isolated from wild Atlantic mackerel (Scomber scombrus) collected from the northern North Sea, one plasmid carrying the mcr-4.3 gene for colistin resistance and the operon merRPAT for mercury resistance and the other carrying multiple heavy metal resistance genes. The marine environment has been recognized as a source of new resistance genes that are found in human pathogens. Selection pressure from heavy metals is seen in the marine environment, especially associated with human activities, such as waste discharge, mining, and in aquaculture settings. This would help maintain and disseminate these plasmids in the environment. Our study provides insights into the mobilization of colistin resistance genes in Shewanella spp. and highlights the importance of the marine environment in the emergence and dissemination of clinically important antibiotic resistance genes.

Bacteria with carbapenem or tigecycline resistance have been spreading widely among humans, animals and the environment globally, being great threats to public health. However, bacteria co-carrying drug resistance genes of carbapenem and tigecycline in Shewanella and Acinetobacter species remain to be investigated. Here, we detected nine blaNDM-1-carrying Shewanella spp. isolates as well as three A. portensis isolates co-harboring tet(X3) and blaNDM-1 from seventy-two samples collected from a dairy farm in China. To explore their genomic characteristic and transmission mechanism, we utilized various methods, including PCR, antimicrobial susceptibility testing, conjugation experiment, whole-genome sequencing, circular intermediate identification and bioinformatics analysis. Clonal dissemination was found among three A. portensis, of which tet(X3) and blaNDM-1 were located on a novel non-conjugative plasmid pJNE5-X3_NDM-1 (333,311 bp), and the circular intermediate ΔISCR2-tet(X3)-blaNDM-1 was identified. Moreover, there was another copy of tet(X3) on the chromosome of A. portensis. It was verified that blaNDM-1 could be transferred to Escherichia coli C600 from Shewanella spp. by conjugation, and self-transmissible IncA/C2 plasmids mediated the transmission of blaNDM-1 in Shewanella spp. strains. Stringent surveillance was warranted to curb the transmission of such vital resistance genes. [ABSTRACT FROM AUTHOR]

Shewanella baltica is the dominant bacterium that causes spoilage of seafood. RpoS is an alternative sigma factor regulating stress adaptation in many bacteria. However, the detailed regulatory mechanism of RpoS in S. baltica remains unclear. This study aims to investigate the regulatory function of RpoS on spoilage activity and adhesion ability in S. baltica. Results revealed that RpoS had no effect on the growth of S. baltica, but positively regulated the spoilage potential of S. baltica accompanied by a slower decline of total volatile basic nitrogen, lightness, and the sensory score of fish fillets inoculated with rpoS mutant. RpoS negatively regulated the adhesion ability, which was manifested in that the bacterial number of rpoS mutant adhered to stainless steel coupon was higher than that of the S. baltica in the early stage, and the biofilm formed on glass slide by rpoS mutant was thicker and tighter compared with S. baltica. Transcriptomic analysis showed that a total of 397 differentially expressed genes were regulated by RpoS. These genes were mainly enrichment in flagellar assembly, fatty acid metabolism/degradation, and RNA degradation pathways, which were associated with motility, biofilm formation and cold adaptation. This study demonstrated that RpoS is a primary regulator involved in flagellar assembly mediated biofilm formation and cold adaptation-related spoilage activity of S. baltica. Our research will provide significant insights into the control of microbiological spoilage in seafood. [ABSTRACT FROM AUTHOR]

The epidemiology of bloodstream infections caused by Shewanella spp. is not well defined. Our objective was to define the incidence and determinants of Shewanella spp. bloodstream infections by using population-based surveillance in Queensland, Australia during 2000‒2019. The incidence was 1.0 cases/1 million persons annually and was highest during summer and in the tropical Torres and Cape region. Older persons and male patients were at highest risk. At least 1 concurrent condition was documented in 75% of case-patients, and 30-day all cause case-fatality rate was 15%. Aging populations in warm climates might expect an increasing burden of these infections. [ABSTRACT FROM AUTHOR]

Bacteria with carbapenem or tigecycline resistance have been spreading widely among humans, animals and the environment globally, being great threats to public health. However, bacteria co-carrying drug resistance genes of carbapenem and tigecycline in Shewanella and Acinetobacter species remain to be investigated. Here, we detected nine blaNDM-1-carrying Shewanella spp. isolates as well as three A. portensis isolates co-harboring tet(X3) and blaNDM-1 from seventy-two samples collected from a dairy farm in China. To explore their genomic characteristic and transmission mechanism, we utilized various methods, including PCR, antimicrobial susceptibility testing, conjugation experiment, whole-genome sequencing, circular intermediate identification and bioinformatics analysis. Clonal dissemination was found among three A. portensis, of which tet(X3) and blaNDM-1 were located on a novel non-conjugative plasmid pJNE5-X3_NDM-1 (333,311 bp), and the circular intermediate ΔISCR2-tet(X3)-blaNDM-1 was identified. Moreover, there was another copy of tet(X3) on the chromosome of A. portensis. It was verified that blaNDM-1 could be transferred to Escherichia coli C600 from Shewanella spp. by conjugation, and self-transmissible IncA/C2 plasmids mediated the transmission of blaNDM-1 in Shewanella spp. strains. Stringent surveillance was warranted to curb the transmission of such vital resistance genes.

Different Shewanella species are isolated both from healthy and from diseased fish. To date, contemporary methods do not provide sufficient insight to determine species and detail differentiation between tested strains. Bacteria isolated from cultured (n = 33), wild (n = 12) and ornamental (n = 6) fish, as well as several reference strains, were tested by 16S rRNA gene sequencing, ERIC‐PCR and pulsed‐field gel electrophoresis (PFGE) assays. Our study indicates that isolates collected from freshwater fish were genetically diverse. Based on 16S rRNA gene sequences, bacteria were clustered into groups S. putrefaciens, S. xiamenensis and S. oneidensis. Some isolates were classified only to genus Shewanella; thus, 16S rRNA gene analyses were not enough to determine the species. ERIC‐PCR revealed 49 different genotype profiles indicating that the method might be useful for differentiation of Shewanella isolates irrespectively to species identification, contrary to PFGE which is not suitable for Shewanella typing. [ABSTRACT FROM AUTHOR]

The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10–37 °C), pH (4–8), salinity (0%–2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent.

Shewanella sp. O23S is a dissimilatory arsenate reducing bacterial strain involved in arsenic transformations within the abandoned gold mine in Zloty Stok (SW Poland). Previous physiological studies revealed that O23S may not only release arsenic from minerals, but also facilitate its immobilization through co-precipitation with reduced sulfur species. Given these uncommon, complementary characteristics and the application potential of the strain in arsenic-removal technologies, its genome (~5.3 Mbp), consisting of a single chromosome, two large plasmids (pSheA and pSheB) and three small plasmid-like phages (pSheC-E) was sequenced and annotated. Genes encoding putative proteins involved in heavy metal transformations, antibiotic resistance and other phenotypic traits were identified. An in-depth comparative analysis of arsenic respiration (arr) and resistance (ars) genes and their genetic context was also performed, revealing that pSheB carries the only copy of the arr genes, and a complete ars operon. The plasmid pSheB is therefore a unique natural vector of these genes, providing the host cells arsenic respiration and resistance abilities. The functionality of the identified genes was determined based on the results of the previous and additional physiological studies, including: the assessment of heavy metal and antibiotic resistance under various conditions, adhesion-biofilm formation assay and BiologTM metabolic preferences test. This combined genetic and physiological approach shed a new light on the capabilities of O23S and their molecular basis, and helped to confirm the biosafety of the strain in relation to its application in bioremediation technologies.

Application of natural preservative agents has improved storability of aquatic products due to their antimicrobial properties. Recently, a combination of chitosan and nisin has been proven effective for preservation of Pseudosciaena crocea stored at 4 °C. However, few studies are available on the antimicrobial potential of this combination against Shewanella spp. in Pseudosciaena crocea . In this study the antimicrobial performance of 1% chitosan, 1% chitosan +0.4% nisin and 1% chitosan +0.6% nisin against two isolates Shewanella putrefaciens DHS01 and Shewanella algae DHS02 was compared. The results revealed that with the synergy of 0.6% nisin, 1% chitosan presented significant inhibitory effects on growth and biofilm formation of these two species. By inhibiting growth and biofilm formation of Shewanella putrefaciens and Shewanella algae , this combination was considered capable of reducing amino acids loss of Pseudosciaena crocea and accumulation of spoilage products like VBN, putrescine and cadaverine. Simultaneously, we proposed a new method to monitor the growth of Shewanella putrefaciens and Shewanella algae in Pseudosciaena crocea by analysis of phospholipid acids. [ABSTRACT FROM AUTHOR]

The spoilage potential of Shewanella putrefaciens and S. baltica isolated from spoiled refrigerated Litopenaeus vannamei was evaluated by in vitro assays for trimethylamine oxide reduction, extracellular hydrolytic enzymes and biofilm formation, and in vivo inoculation into surface-sterilised shrimp followed by microbial, biochemical and sensory analyses during storage for 5 days at 4 °C. S. baltica displayed higher spoilage potential than S. putrefaciens both in vitro and in vivo. Shrimp co-inoculated with them had one-day shorter shelf life than those mono-inoculated, based on the results of bacterial density, volatile base nitrogen, trimethylamine, volatile organic compounds and sensory analysis, which strongly suggests cooperation of Shewanella species in shrimp spoilage. Exogenous cyclo-(L-Pro-L-Leu) boosted bacterial growth, extracellular protease and collagenase activities, and biofilm formation of S. putrefaciens and S. baltica at least before they entered the stationary phase, indicating that cyclo-(L-Pro-L-Leu)-dependent quorum sensing, a recently suggested communication mechanism between them, contributes to the cooperation. [ABSTRACT FROM AUTHOR]

Lactobionic acid (LBA) is a novel antibacterial agent that has attracted much interest in recent years. However, the study on the antibacterial effect of LBA on spoilage bacteria is rare. This study aims to investigate the antibacterial activity and mechanism of LBA on Shewanella baltica and Shewanella putrefaciens , which are the common spoilage microorganisms in chilled seafood. The results demonstrated that LBA was an effective bacteriostat against S. baltica and S. putrefaciens , with the minimum inhibitor concentration (MIC) of 8 mg/mL. Both the two Shewanella species could be completely killed by LBA at 2 MIC. LBA damaged the cell membrane integrity and increased outer membrane permeability, causing the increase in protein leakage and conductivity, which was supported by the bacterial morphology observed with scanning electron microscopy. Besides, LBA could interact with the bacterial genome DNA, resulting in the dysfunction of cell function. Moreover, LBA exhibited an effectively inhibitory effect on slowing down microbial growth, melanosis and lipid oxidation rate in refrigerated shrimp. These results suggest that LBA would be a promising antibacterial compound used in seafood. • Lactobionic acid shows antibacterial activity against S. baltica and S. putrefaciens. • Lactobionic acid can damage cell membrane integrity and cause protein leakage. • Lactobionic acid can retard genome DNA migrate and quench the fluorescence intensity. • Lactobionic acid exhibits a preservative effect on Pacific white shrimp. [ABSTRACT FROM AUTHOR]

The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10-37 °C), pH (4-8), salinity (0%-2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent. [ABSTRACT FROM AUTHOR]

Shewanella species have been identified as progenitors of several clinically important antibiotic resistance genes. The aim of our study was to analyze Shewanella baltica strains isolated from the gut contents of wild Atlantic mackerel (Scomber scombrus) for the presence of both known and novel variants of antibiotic resistance genes (ARGs), using Illumina-based whole-genome sequencing (WGS). Thirty-three S. baltica strains were isolated from Atlantic mackerel collected in the northern North Sea. WGS revealed the presence of several new variants of class C and class D beta-lactamases. Nearly 42% (14/33) of the strains carried the mobile colistin resistance gene mcr-4.3 . To understand the genetic context of mcr-4.3 , we determined the complete genome sequence of strain 11FHM2, using a combination of Oxford Nanopore- and Illumina-based sequencing. The complete genome sequence is 5,406,724 bp long, with one contig representing a chromosome of 5,068,880 bp and three contigs representing novel plasmids (pSBP1, 194,145 bp; pSBP2_mcr4, 86,727 bp; and pSBP3, 56,972 bp). Plasmid pSBP2_mcr4 contains the mobile colistin resistance gene mcr-4.3 , as well as the mercury resistance operon merRPAT . Plasmid pSBP1 carries genes encoding resistance against copper, zinc, chromium, and arsenic. Plasmid pSBP3 does not carry any antibiotic or heavy metal resistance genes. Analysis of the flanking region of mcr-4.3 suggests that a phage integrase may be involved in the mobilization of mcr-4.3 in Shewanella spp. Our results provide insights into the mobile mcr-4.3 present in Shewanella spp. and highlight the importance of the marine environment in the emergence and dissemination of clinically important resistance genes. IMPORTANCE We identified two new plasmids in Shewanella baltica isolated from wild Atlantic mackerel (Scomber scombrus) collected from the northern North Sea, one plasmid carrying the mcr-4.3 gene for colistin resistance and the operon merRPAT for mercury resistance and the other carrying multiple heavy metal resistance genes. The marine environment has been recognized as a source of new resistance genes that are found in human pathogens. Selection pressure from heavy metals is seen in the marine environment, especially associated with human activities, such as waste discharge, mining, and in aquaculture settings. This would help maintain and disseminate these plasmids in the environment. Our study provides insights into the mobilization of colistin resistance genes in Shewanella spp. and highlights the importance of the marine environment in the emergence and dissemination of clinically important antibiotic resistance genes.

The genus Shewanella consists of Gram-negative proteobacteria that are ubiquitously distributed in environment. As the members of this genus have rapidly increased within the past decade, several species have become emerging pathogens worldwide, attracting the attention of the medical community. These species are also associated with severe community- and hospital-acquired infections. Patients infected with Shewanella spp. had experiences of occupational or recreational exposure; meanwhile, the process of infection is complex and the pathogenicity is influenced by a variety of factors. Here, an exhaustive internet-based literature search was carried out in PUBMED using terms " Achromobacter putrefaciens ," " Pseudomonas putrefaciens ," " Alteromonas putrefaciens " and " Shewanella " to search literatures published between 1978 and June 2022. We provided a comprehensive review on the epidemiology, clinical features and pathogenicity of Shewanella , which will contribute a better understanding of its clinical aetiology, and facilitate the timely diagnosis and effective treatment of Shewanella infection for clinicians and public health professionals.

Shewanella baltica is the dominant bacterium that causes spoilage of seafood. RpoS is an alternative sigma factor regulating stress adaptation in many bacteria. However, the detailed regulatory mechanism of RpoS in S. baltica remains unclear. This study aims to investigate the regulatory function of RpoS on spoilage activity and adhesion ability in S. baltica . Results revealed that RpoS had no effect on the growth of S. baltica , but positively regulated the spoilage potential of S. baltica accompanied by a slower decline of total volatile basic nitrogen, lightness, and the sensory score of fish fillets inoculated with rpoS mutant. RpoS negatively regulated the adhesion ability, which was manifested in that the bacterial number of rpoS mutant adhered to stainless steel coupon was higher than that of the S. baltica in the early stage, and the biofilm formed on glass slide by rpoS mutant was thicker and tighter compared with S. baltica . Transcriptomic analysis showed that a total of 397 differentially expressed genes were regulated by RpoS. These genes were mainly enrichment in flagellar assembly, fatty acid metabolism/degradation, and RNA degradation pathways, which were associated with motility, biofilm formation and cold adaptation. This study demonstrated that RpoS is a primary regulator involved in flagellar assembly mediated biofilm formation and cold adaptation-related spoilage activity of S. baltica . Our research will provide significant insights into the control of microbiological spoilage in seafood., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Zhang, Chen, Pan, Liu and Liu.)

Abstract: A cryptic plasmid pSFKW33 from psychrotrophic bacterium Shewanella sp. 33B, an isolate from the Gulf of Gdansk (the Baltic Sea), was sequenced and characterized. It is an 8021bp circular molecule with 38% GC content, which shows a distinctive nucleotide sequence without homology to other known plasmids. The nucleotide sequence analysis predicts eight open reading frames. The deduced amino acid sequence of ORF-1 shared significant similarity with the phage integrase protein from Pseudomonas putida GB-1. The ORF2 product showed some similarity with the hypothetical protein Shal_1786 from Shewanella halifaxensis HAW-EB4. The ORF-3 product revealed high amino acid sequence homology with the Escherichia coli replication initiation protein similar to pi protein of R6K plasmid. Five repeat regions (three perfect 22-bp repeats and two imperfect motifs), a putative ribosome binding site, and −10 and −35 promotor sequences were identified upstream of the ORF-3 (rep). The rep module is very similar to several theta replicating iteron family plasmids, suggesting that pSFKW33 replication follows the same course. The ORF-5 product revealed significant identity with the entry exclusion protein 1 of plasmid pIS2 from enteropathogenic strain E. coli 0111:H. The ORF-6 product showed significant identity with the putative transcriptional regulator protein from Shewanella benthica KT99 belonging to HTH-XRE-family protein. The ORF-8 encoded protein that showed some similarity with the hypothetical protein KT99_00146 from Shewanella benthica KT99. The ORF-4 and ORF-7 encoded putative proteins of 189 and 118 amino acid residues, respectively, with no homologies to any known proteins. The absolute copy number of pSFKW33 was estimated to be five copies per chromosome by real-time PCR. [Copyright &y& Elsevier]

Abstract: Biosorption of copper and cobalt by Shewanella spp. was investigated in this study. The biosorption capabilities of Shewanella spp. for copper and cobalt were monitored at different ion concentrations (0.002M, 0.07M and 0.2M), biomass dosages (50, 100 and 150 (×104 CFU/ml)) and pH (values 2–8) in batch mode. At optimum concentration (0.002M/3.86gl−1), biosorbent dosage (150×104 CFU/ml) and solution pH 6.5, Shewanella spp. recorded maximum copper and cobalt uptakes of 38% and 27%, respectively. The kinetic data obtained at different concentrations suggested that the biosorption rate was fast and in most cases the biosorption took place within 8h followed by a slow attainment of equilibrium and the Langmuir sorption model fitted the data well with very high correlation efficiencies (>0.95). The results obtained in this study suggest that biosorbents, with further research, can in future be viewed as suitable sorbents in the recovery of precious metals such as copper after being discharged as effluent or as a result of mineral processing. In managing water resources, it is important that metallic species such as copper and cobalt be removed from water or reduced to acceptable levels since these metal species may cause ill-health effects to humans and livestock if the required concentration levels are exceeded. The required levels should fall within with World Health Organization (WHO) water quality guidelines and the water quality standards for various purposes (e.g. agriculture, drinking, domestic, water-reuse) as prescribed by individual countries. [Copyright &y& Elsevier]

The occurrence of the two Shewanella species found in clinical specimens, Shewanella algae and Shewanella putrefaciens, correlates with the temperature and salinity of seawater. This means that Shewanella infections occur in warm climates or during especially warm summers in temperate climates. The infections described most commonly involve ears, skin and soft tissue, with or without bacteraemia. Primary bacteraemia with a fulminant course is also seen in immunocompromised patients. Important differential characteristics between the two species include the ability of S. algae to produce mucoid colonies withβ-haemolysis on sheep blood agar, to grow at 42°C and in NaCl 6% w/v, and to reduce nitrite, and an inability to produce acid from maltose, all of which are in contrast to the characteristics of S. putrefaciens. Automated identification systems fail to differentiate between S. algae and S. putrefaciens, as S. algae is not included in the databases of these systems. Presumably for this reason, most Shewanella infections reported during recent years have been attributed to S. putrefaciens. However, when extensive phenotypic characterisation is performed, most human infections are seen to be caused by S. algae. As the two species seem to have different pathogenic potential for humans, correct identification is important, and this is possible in routine clinical microbiology laboratories. [ABSTRACT FROM AUTHOR]

Nervous necrosis virus (NNV) (genus: Betanodavirus) attacks aquacultured fish. Biocontrol may prevent and control the disease caused by NNV infection. Shewanella strain 0409 was isolated from the microbiome of grouper intestines, and its culture supernatant (CS0409) could inhibit NNV replication in vitro. The present study elucidated the antiviral mechanism of Shewanella strain 0409 against NNV in vitro. In NNV-infected GF-1 cells, CS0409 reduced both NNV RNA synthesis and the percentage of cells expressing NNV RNA-dependent RNA polymerase (RdRp) within 24 hpi. However, NNV RdRp activity was not inhibited by CS0490 treatment. The most favorable time for CS0409 treatment in NNV-infected GF-1 cells was the period of viral adsorption, which revealed a high inhibition level of NNV RNA synthesis. Shewanella strain 0409 produced ammonium in CS0409. When ammonium in CS0409 was removed by heating with evaporation, the anti-NNV activity of CS0409 decreased. Moreover, ammonium in CS0409 inhibited the acidification of acidic organelles. Furthermore, the morphology of NNV virions changed to empty particles after exposure to pH 5 and 6, indicating that NNV uncoating required the acidic environment of endosomes. Therefore, ammonium in CS0409 is responsible for the anti-NNV activity in vitro by inhibiting the acidification of endosomes and then suppressing NNV uncoating. • Culture supernatant (CS0409) of Shewanella strain 0409 inhibited NNV replication. • CS0409 inhibited NNV RNA synthesis but not NNV RdRp activity. • Shewanella strain 0409 produced ammonium (NH 4 +) in CS0409. • Anti-NNV activity of CS0409 disappeared when NH 4 + in CS0409 was removed. • NH 4 + in CS0409 inhibited endosomal acidification, thus suppressing NNV uncoating. [ABSTRACT FROM AUTHOR]

Nervous necrosis virus (NNV), belonging to the genus Betanodavirus , causes mass mortality of many species of marine and freshwater fish at the larval and juvenile stages. Biocontrol is a potential strategy for the prevention and control of diseases associated with NNV infection. A bacterial strain, 0409, was isolated from the microbiome of grouper intestines, and the bacterial culture supernatant (CS0409) was found to suppress NNV RNA synthesis and reduce NNV titers. The aim of the present study was to elucidate how the bacterial strain 0409 antagonized NNV in vitro and in vivo. The 16S rDNA of strain 0409 had high sequence identity to Shewanella spp. The anti-NNV substances in CS0409 were heat stable, resistant to protease and nuclease activity, widely pH-tolerant, hydrophilic, and had molecular weights of <3 kDa. CS0409 exhibited anti-NNV effects, but not by neutralizing NNV or blocking the viral receptor on GF-1 cells. The anti-NNV activity of CS0409 was present when NNV-infected GF-1 cells were treated with CS0409 prior to 2 h post infection (hpi) and had to be cultured in CS0409-supplemented medium throughout the entire course of the experiment. Once CS0409 was removed from the culture medium of infected cells, the anti-NNV effect was abrogated. Moreover, CS0409 could induce cBB cells to express Mx gene, which could inhibit NNV RNA synthesis. Furthermore, groupers that were fed with strain 0409 for 2 months showed lower morbidity and mortality after NNV challenge compared with the mock-fed groupers. Therefore, strain 0409 has the potential to be a beneficial bacterium for biocontrol against NNV. • The strain 0409 was isolated from the microbiome of grouper intestines. • The 16S rDNA sequence of stain 0409 had high identity to Shewanella spp. • The culture supernatant of strain 0409 antagonized NNV in GF-1 cells. • The culture supernatant of strain 0409 induced Mx gene expression in cBB cells. • Feeding with strain 0409 protected groupers from NNV challenge. [ABSTRACT FROM AUTHOR]

Shewanella sp. O23S is a dissimilatory arsenate reducing bacterial strain involved in arsenic transformations within the abandoned gold mine in Zloty Stok (SW Poland). Previous physiological studies revealed that O23S may not only release arsenic from minerals, but also facilitate its immobilization through co-precipitation with reduced sulfur species. Given these uncommon, complementary characteristics and the application potential of the strain in arsenic-removal technologies, its genome (~5.3 Mbp), consisting of a single chromosome, two large plasmids (pSheA and pSheB) and three small plasmid-like phages (pSheC-E) was sequenced and annotated. Genes encoding putative proteins involved in heavy metal transformations, antibiotic resistance and other phenotypic traits were identified. An in-depth comparative analysis of arsenic respiration (arr) and resistance (ars) genes and their genetic context was also performed, revealing that pSheB carries the only copy of the arr genes, and a complete ars operon. The plasmid pSheB is therefore a unique natural vector of these genes, providing the host cells arsenic respiration and resistance abilities. The functionality of the identified genes was determined based on the results of the previous and additional physiological studies, including: the assessment of heavy metal and antibiotic resistance under various conditions, adhesion-biofilm formation assay and BiologTM metabolic preferences test. This combined genetic and physiological approach shed a new light on the capabilities of O23S and their molecular basis, and helped to confirm the biosafety of the strain in relation to its application in bioremediation technologies. [ABSTRACT FROM AUTHOR]

Shewanella spp. are Gram-negative, rod-shaped, motile bacteria that are widely distributed in marine and freshwater environments. The bacteria are present in the physiological microflora of fish from temperate waters and are known as fish spoilage species. From clinically healthy fish and from fish with skin ulcerations, Shewanella spp. is regularly isolated, indicating a possible role as fish pathogen. In this study, 74 isolates of Shewanella spp. were analysed. For species identification, biochemical techniques, 16S rRNA sequencing, MALDI-TOF MS and the Sherlock Microbial Identification System (MIS) based on the composition of fatty acid ethyl esters were compared. The phylogenetic relationship, cytotoxicity in vitro and resistance against antibiotics were tested. The most reliable method for species identification was 16S rRNA sequencing. From diseased fish, clinically healthy fish and the aquatic environment, different Shewanella species were isolated. This indicates that Shewanella spp. is widespread in the aquatic milieu and acts as a secondary pathogen. The virulence of Shewanella spp. is probably not depending on the species but on the isolate itself. Many isolates of Shewanella spp. were showing multiresistances against antibiotic substances, especially in samples derived from retailers and in routine diagnostics, all Shewanella spp. should therefore be tested for resistances against antibiotic agents., (© 2017 John Wiley & Sons Ltd.)