Shewanella phaeophyticola sp. nov. and Vibrio algarum sp. nov., isolated from marine brown algae.

Two Gram-stain-negative, rod-shaped bacteria, designated as strains KJ10-1T and KJ40-1T, were isolated from marine brown algae. Both strains were catalase-positive, oxidase-positive, and facultative aerobic. Strain KJ10-1T exhibited optimal growth at 25 °C, pH 7.0, and 3 % NaCl, whereas strain KJ40-1T showed optimal growth at 25 °C, pH 7.0, and 2 % NaCl. The respiratory quinones of strain KJ10-1T were ubiquinone-8, ubiquinone-7, menaquinone-7, and methylated menaquinone-7, while the respiratory quinone of strain KJ40-1T was only ubiquinone-8. As major fatty acids, strain KJ10-1T contained C16 : 0, C17 : 1 ω8c, iso-C15 : 0, and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and strain KJ40-1T contained C16 : 0 and summed features 3 and 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The major polar lipids in strain KJ10-1T were phosphatidylethanolamine, phosphatidylglycerol, and an unidentified aminolipid, whereas those in strain KJ40-1T were phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. The DNA G+C contents of strains KJ10-1T and KJ40-1T were 42.1 and 40.8 mol%, respectively. Based on 16S rRNA gene sequences, strains KJ10-1T and KJ40-1T exhibited the closest relatedness to Shewanella saliphila MMS16-UL250T (98.6 %) and Vibrio rumoiensis S-1T (95.4 %), respectively. Phylogenetic analyses, based on both 16S rRNA and 92 housekeeping genes, showed that the strains formed distinct phylogenic lineages within the genera Shewanella and Vibrio. Digital DNA-DNA hybridization and orthologous average nucleotide identity values between strain KJ10-1T and other Shewanella species, as well as between strain KJ40-1T and other Vibrio species, were below the thresholds commonly accepted for prokaryotic species delineation. Based on the phenotypic, chemotaxonomic, and phylogenetic data, strains KJ10-1T and KJ40-1T represent novel species of the genera Shewanella and Vibrio, respectively, for which the names Shewanella phaeophyticola sp. nov. and Vibrio algarum sp. nov. are proposed, respectively. The type strains of S. phaeophyticola and V. algarum are KJ10-1T (=KACC 22589T=JCM 35409T) and KJ40-1T (=KACC 22588T=JCM 35410T), respectively.

Genomic analysis reveals high intra-species diversity of Shewanella algae.

Shewanella algae is widely distributed in marine and freshwater habitats, and has been proved to be an emerging marine zoonotic and human pathogen. However, the genomic characteristics and pathogenicity of Shewanella algae are unclear. Here, the whole-genome features of 55 S. algae strains isolated from different sources were described. Pan-genome analysis yielded 2863 (19.4 %) genes shared among all strains. Functional annotation of the core genome showed that the main functions are focused on basic lifestyle such as metabolism and energy production. Meanwhile, the phylogenetic tree of the single nucleotide polymorphisms (SNPs) of core genome divided the 55 strains into three clades, with the majority of strains from China falling into the first two clades. As for the accessory genome, 167 genomic islands (GIs) and 65 phage-related elements were detected. The CRISPR-Cas system with a high degree of confidence was predicted in 23 strains. The GIs carried a suite of virulence genes and mobile genetic elements, while prophages contained several transposases and integrases. Horizontal genes transfer based on homology analysis indicated that these GIs and prophages were parts of major drivers for the evolution and the environmental adaptation of S. algae. In addition, a rich putative virulence-associated gene pool was found. Eight classes of antibiotic-associated resistance genes were detected, and the carriage rate of ß-lactam resistance genes was 100 %. In conclusion, S. algae exhibits a high intra-species diversity in the aspects of population structure, virulence-associated genes and potential drug resistance, which is helpful for its evolution in pathogenesis and environmental adaptability.

Shewanella nanhaiensis sp. nov., a marine bacterium isolated from sediment of South China Sea, and emended descriptions of Shewanella woodyi, Shewanella hanedai and Shewanella canadensis.

A Gram-stain-negative, motile, facultative anaerobic and rod-shaped bacterium, designated strain NR704-98T, was isolated from marine sediment of the northern South China Sea. Cells were positive for oxidase and catalase activity. Growth was observed at 4-30 °C (optimum 20-25 °C), at pH 6-9 (pH 7) and with 0.5-7 % NaCl (2 %). The 16S rRNA gene-based phylogenetic analysis revealed that the nearest phylogenetic neighbours of strain NR704-98T were Shewanella woodyi MS32T (97.9 %), Shewanella hanedai 281T (97.1 %), Shewanella sediminis HAW-EB3T (96.8 %) and Shewanella canadensis HAW-EB2T (96.7 %). Based on the results of phylogenomic analysis, the average nucleotide identity and the digital DNA-DNA hybridization values between strain NR704-98T and the previously mentioned type strains of species of the genus Shewanella were in the range of 74.9-93.1 % and 20.6-51.4 %, respectively. The respiratory quinones were Q-7 and Q-8. The predominant fatty acids (>10 %) of strain NR704-98T were C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and iso-C15 : 0. Phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminophospholipids and five unidentified lipids were detected in strain NR704-98T. Based on the phylogenetic and phenotypic characteristics, strain NR704-98T is considered to represent a novel species of the genus Shewanella, for which the name Shewanella nanhaiensis sp. nov. is proposed. The type strain is NR704-98T (=KCTC 82799T=MCCC 1K06091T).

Shewanella cyperi sp. nov., a facultative anaerobic bacterium isolated from mangrove sediment.

Two Gram-stain-negative, motile, facultatively anaerobic, rod-shaped strains, FJAT-53720T and FJAT-53726, were isolated from rhizosphere sediment of plant Cyperus malaccensis. Phylogenetic analysis based on their 16S rRNA gene sequences revealed that strains FJAT-53720T and FJAT-53726 were affiliated to the genus Shewanella (forming an independent cluster) with the highest sequence similarity to the type strain of Shewanella algae. Optimum growth of both strains was observed at 30 °C and pH 7. The respiratory quinones were Q-7, Q-8 and MK-7. The polar lipid profile included phosphatidylmethyl ethanolamine, phosphatidylethanolamine, diphosphatidylglycerol, one unidentified aminophospholipid and four unknown phospholipids. The major fatty acids of strains FJAT-53720T and FJAT-53726 were iso-C15:0, C17 : 1 ω8c and summed feature 3. The genomic DNA G+C content of strain FJAT-53720T was 55.6 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between FJAT-53720T and FJAT-53726 were 97.4 and 77.9 %, confirming that they were similar species and hence FJAT-53720T was selected for further analysis. The ANI and dDDH values between FJAT-53720T and other members of the genus Shewanella were below the cut-off level (95-96 %; 70 %) for species delineation. Based on the above results, FJAT-53720T represents a novel species of the genus Shewanella, for which the name Shewanella cyperi sp. nov. is proposed. The type strain is FJAT-53720T (=KCTC 82444T=GDMCC 1.2207T).

Phylogenomic analysis reveals a two-stage process of the evolutionary transition of Shewanella from the upper ocean to the hadal zone.

Shewanella strains are characterized by versatile metabolic capabilities, resulting in their wide distribution in the ocean at different depths. Considering that particle sedimentation is an important dynamic process in the ocean, we hypothesized that hadal Shewanella species evolved from the upper ocean. In this study, we isolated three novel Shewanella strains from deep-sea sediments in the Southwest Indian Ocean. Genome sequencing indicated that strains YLB-06 and YLB-08 represent two novel species in the genus Shewanella. Through phylogenomic analysis, we showed that speciation and genomic changes in marine Shewanella strains are related to water depth. We further confirmed the aforementioned hypothesis and revealed a two-stage process of the evolutionary transition of Shewanella from the upper ocean to the hadal zone by comparative genomics and gene gain/loss analysis. Finally, the transcriptomic analysis demonstrated that recently obtained genes are strictly repressed and may thus play a minor role in the response to environmental changes.

First isolation and whole-genome sequencing of a Shewanella algae strain from a swine farm in Brazil.

BACKGROUND: Infections caused by Shewanella spp. have been increasingly reported worldwide. The advances in genomic sciences have enabled better understanding about the taxonomy and epidemiology of this agent. However, the scarcity of DNA sequencing data is still an obstacle for understanding the genus and its association with infections in humans and animals. RESULTS: In this study, we report the first isolation and whole-genome sequencing of a Shewanella algae strain from a swine farm in Brazil using the boot sock method, as well as the resistance profile of this strain to antimicrobials. The isolate was first identified as Shewanella putrefaciens, but after whole-genome sequencing it showed greater similarity with Shewanella algae. The strain showed resistance to 46.7% of the antimicrobials tested, and 26 resistance genes were identified in the genome. CONCLUSIONS: This report supports research made with Shewanella spp. and gives a step forward for understanding its taxonomy and epidemiology. It also highlights the risk of emerging pathogens with high resistance to antimicrobial formulas that are important to public health.

First case of Shewanella indica isolated from a Bryde's whale (Balaenoptera edeni) stranded in the northern Beibu Gulf, China.

The purpose of this study was to culture and characterise bacteria from an intact abscess on the skin of a dead Bryde's whale (Balaenoptera edeni) which stranded in the northern Beibu Gulf, China. To grow bacteria, samples from the abscess were added to blood agar. After incubation, yellowish mucous colonies were visualized. The bacterium was firstly recognised as Shewanella algae by the VITEK® 2 System. However, by using 16S rRNA gene sequencing the bacterium was finally identified as S. indica. To characterise the bacterium, antibiotic susceptibility and virulence factors, such as hemolysis and biofilm formation were investigated. The bacterium is capable of ß-hemolysis and biofilm formation and it is also sensitive to several different classes of antibiotics, such as ß-lactams, quinolones, and aminoglycosides. To date there have been no reports of this bacterium causing infections in humans or animals. However, in this study we described the first case of S. indica isolated from an intact abscess on the back of a Bryde's whale.

Description of Shewanella salipaludis sp. nov., isolated from a salt marsh.

A Gram-stain-negative and flagellated bacterial strain, SHSM-M6T, was isolated from salt marsh from Yellow Sea, Republic of Korea. Neighbor-joining phylogenetic tree of 16S rRNA gene sequences showed that strain SHSM-M6T belongs to the genus Shewanella. 16S rRNA gene sequence similarity values between strain SHSM-M6T and the type strains of Shewanella species were <98.0%. The average nucleotide identity and DNA-DNA hybridization values between genomic sequences of strain SHSM-M6T and the type strains of Shewanella species were <73.3 and 20.7%, respectively. Strain SHSM-M6T contained MK-6 as predominant menaquinone and Q-7 and Q-8 as the predominant ubiquinones. The novel strain contained C16:1ω7c and/or C16:1ω6c, iso-C15:0 and C16:0 as major fatty acids. Major polar lipids of strain SHSM-M6T were phosphatidylethanolamine, phosphatidylglycerol, one unidentified lipid, one unidentified aminolipid and one unidentified phospholipid. Differential phenotypic properties of strain SHSM-M6T, together with its phylogenetic and genetic distinctiveness, revealed that strain SHSM-M6T is separated from recognized Shewanella species. On the basis of the data presented, strain SHSM-M6T is considered to represent a novel species of the genus Shewanella, for which the name Shewanella salipaludis sp. nov. is proposed. The type strain is SHSM-M6T (=KACC 19901T = NBRC 113646T).

Shewanella insulae sp. nov., isolated from a tidal flat.

A Gram-stain-negative, aerobic, non-spore-forming, motile by single polar flagellum and ovoid or rod-shaped bacterial strain, designated JBTF-M18T, was isolated from tidal-flat sediment collected from the Yellow Sea, Republic of Korea. The neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain JBTF-M18T fell within the clade comprising the type strains of Shewanella species. Strain JBTF-M18T exhibited 16S rRNA gene sequence similarity values of 97.1-98.8 % to the type strains of S. loihica, S. aquimarina, S. waksmanii and S. marisflavi and of less than 96.9 % to the type strains of the other Shewanella species. The average nucleotide identity and digital DNA-DNA hybridization values between strain JBTF-M18T and the type strains of S. waksmanii and S. loihica were 72.0 and 89.5% and 18.9 and 38.1 %, respectively. DNA-DNA relatedness values between strain JBTF-M18T and the type strains of S. aquimarina and S. marisflavi were 14 and 19 %, respectively. The DNA G+C content of strain JBTF-M18T from genomic sequence data was 52.9 %. Strain JBTF-M18Tcontained MK-6 as the predominant menaquinone and Q-7 and Q-8 as the predominant ubiquinones. It had iso-C15 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and C16 : 0 as the major fatty acids. The major polar lipids of strain JBTF-M18T were phosphatidylethanolamine and phosphatidylglycerol. Distinguished phenotypic properties, along with the phylogenetic and genetic distinctiveness, revealed that strain JBTF-M18T is separated from recognized Shewanella species. On the basis of the data presented, strain JBTF-M18T is considered to represent a novel species of the genus Shewanella, for which the name Shewanella insulae sp. nov. is proposed. The type strain is JBTF-M18T (=KACC 19869T=NBRC 113583T).

The strains of bioluminescent bacteria isolated from the White Sea finfishes: genera Photobacterium, Aliivibrio, Vibrio, Shewanella, and first luminous Kosakonia.

Bioluminescence is a spectacular feature of some prokaryotes. In the present work, we address the distribution of bioluminescence among bacteria isolated from the White Sea finfishes. Luminous bacteria are widely distributed throughout the World Ocean. Many strains have been isolated and described for tropical latitudes, while Nordic seas still remain quite a white spot in studying bioluminescence of bacteria. We describe the strains related to the two main genera of luminous bacteria, Photobacterium and Aliivibrio, as well as Shewanella and Vibrio. They are related to families Vibrionaceae and Shewanellaceae of the Gammaproteobacteria class. Here, we at the first time, report the bioluminescence of the Enterobacteriaceae Kosakonia cowanii. Moreover, we applied the polyphasic approach to identify and describe the isolated microorganisms. The data on sequencing, diversity of cell fine structure, and light emission spectra at room temperature on the solid medium are discussed. The bacteria are characterized by features in their light emission spectra. It may reflect possible molecular mechanisms of bioluminescence as well as features of bacterial composition. The obtained data expands the existing body of knowledge about the bioluminescence spread among the bacteria of Nordic latitudes and provides complex information that is crucial for their precise identification.

Shewanella polaris sp. nov., a psychrotolerant bacterium isolated from Arctic brown algae.

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901T, was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901T was affiliated with the genus Shewanella, showing the highest sequence similarity to the type strain of Shewanella litoralis (97.5%), followed by those of Shewanella vesiculosa, Shewanella livingstonensis and Shewanella saliphila (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C16 : 1 ω7с and/or C16 : 1 ω6с), C16 : 0, C18 : 0, iso-C15 : 0 and C17 : 1 ω8с and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar Shewanella species, within the genus Shewanella, for which the name Shewanella polaris sp. nov. is proposed. The type strain is SM1901T (=KCTC 72047T=MCCC 1K03585T).

Shewanella khirikhana sp. nov. - a shrimp pathogen isolated from a cultivation pond exhibiting early mortality syndrome.

Early mortality syndrome (EMS) in cultivated shrimp is of complex aetiology. One of the causes is acute hepatopancreatic necrosis disease (AHPND) caused by unique Vibrio isolates that carry two Pirvp toxin genes, but other causes of EMS remain mostly unexplained. Here, we describe the discovery of a Shewanella isolate TH2012T from an EMS/AHPND outbreak pond and demonstrate its virulence for shrimp (the mean lethal concentration of 105 colony-forming units per millilitre by immersion challenge) accompanied by distinctive histopathology, particularly of the ventral nerve cord and lymphoid organ but also including the digestive tract. On the basis of its complete genome sequence, multilocus phylogenetic trees, digital DNA-DNA hybridization analysis and differential phenotypic characteristics, we propose that Shewanella isolate TH2012T represents a novel species, separated sufficiently from the type strains S. litorisediminis and S. amazonensis to justify naming it Shewanella khirikhana sp. nov. Analysis of the TH2012T genome revealed no homologues of the Pirvp toxin genes but revealed a number of other potential virulence factors. It constitutes the first Shewanella isolate reported to be pathogenic to shrimp.

The Shewanella genus: ubiquitous organisms sustaining and preserving aquatic ecosystems.

The Gram-negative Shewanella bacterial genus currently includes about 70 species of mostly aquatic γ--proteobacteria, which were isolated around the globe in a multitude of environments such as surface freshwater and the deepest marine trenches. Their survival in such a wide range of ecological niches is due to their impressive physiological and respiratory versatility. Some strains are among the organisms with the highest number of respiratory systems, depending on a complex and rich metabolic network. Implicated in the recycling of organic and inorganic matter, they are important components of organism-rich oxic/anoxic interfaces, but they also belong to the microflora of a broad group of eukaryotes from metazoans to green algae. Examples of long-term biological interactions like mutualism or pathogeny have been described, although molecular determinants of such symbioses are still poorly understood. Some of these bacteria are key organisms for various biotechnological applications, especially the bioremediation of hydrocarbons and metallic pollutants. The natural ability of these prokaryotes to thrive and detoxify deleterious compounds explains their use in wastewater treatment, their use in energy generation by microbial fuel cells and their importance for resilience of aquatic ecosystems.

Shewanella maritima sp. nov., a facultative anaerobic marine bacterium isolated from seawater, and emended description of Shewanella intestini.

A Gram-stain-negative, motile, facultative anaerobic rod-shaped marine bacterium, designated strain D4-2T, was isolated from a sample of seawater collected at Dong-do marina, Dokdo Island, in the East Sea of the Republic of Korea. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain D4-2T was affiliated with members of genus Shewanella and closely related to Shewanella intestini XMDDZSB0408T (97.4%), followed by Shewanella gelidii RZB5-4T (96.7 %) and Shewanella inventionis KX27T (96.1 %). D4-2T has a single circular chromosome of 4.72 Mbp with a DNA G+C content of 44.5 mol%. Average nucleotide identity (ANI) and in silico DNA-DNA hybridization (DDH) values between strain D4-2T and the previously mentioned type strains of species of the genus Shewanella were in range of 69-83.8 % and 20.5-21.7 %, respectively. Growth was observed at 10-36 °C (optimum 29-32 °C), at pH 6-9 (optimum pH 7), and with 1-6% NaCl (optimum 2%). The predominant fatty acids (>10 %) of D4-2T were iso-C15:0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c). The respiratory quinones were Q-7, Q-8, MK-7 and MMK-7. Phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid, an unidentified aminolipid and four unidentified lipids were detected in D4-2T. On the basis of phenotypic, chemotaxonomic and molecular properties, D4-2T represents a novel species of the genus Shewanella, for which the name Shewanella maritima sp. nov. is proposed with D4-2T as the type strain (=KCTC 72040T=JCM 33294T).

Shewanella decolorationis LDS1 Chromate Resistance.

The genus Shewanella is well known for its genetic diversity, its outstanding respiratory capacity, and its high potential for bioremediation. Here, a novel strain isolated from sediments of the Indian Ocean was characterized. A 16S rRNA analysis indicated that it belongs to the species Shewanella decolorationis It was named Shewanella decolorationis LDS1. This strain presented an unusual ability to grow efficiently at temperatures from 24°C to 40°C without apparent modifications of its metabolism, as shown by testing respiratory activities or carbon assimilation, and in a wide range of salt concentrations. Moreover, S. decolorationis LDS1 tolerates high chromate concentrations. Indeed, it was able to grow in the presence of 4 mM chromate at 28°C and 3 mM chromate at 40°C. Interestingly, whatever the temperature, when the culture reached the stationary phase, the strain reduced the chromate present in the growth medium. In addition, S. decolorationis LDS1 degrades different toxic dyes, including anthraquinone, triarylmethane, and azo dyes. Thus, compared to Shewanella oneidensis, this strain presented better capacity to cope with various abiotic stresses, particularly at high temperatures. The analysis of genome sequence preliminary data indicated that, in contrast to S. oneidensis and S. decolorationis S12, S. decolorationis LDS1 possesses the phosphorothioate modification machinery that has been described as participating in survival against various abiotic stresses by protecting DNA. We demonstrate that its heterologous production in S. oneidensis allows it to resist higher concentrations of chromate.IMPORTANCEShewanella species have long been described as interesting microorganisms in regard to their ability to reduce many organic and inorganic compounds, including metals. However, members of the Shewanella genus are often depicted as cold-water microorganisms, although their optimal growth temperature usually ranges from 25 to 28°C under laboratory growth conditions. Shewanella decolorationis LDS1 is highly attractive, since its metabolism allows it to develop efficiently at temperatures from 24 to 40°C, conserving its ability to respire alternative substrates and to reduce toxic compounds such as chromate or toxic dyes. Our results clearly indicate that this novel strain has the potential to be a powerful tool for bioremediation and unveil one of the mechanisms involved in its chromate resistance.

Shewanella psychromarinicola sp. nov., a psychrophilic bacterium isolated from pelagic sediment of the Ross Sea (Antarctica), and reclassification of Shewanella arctica Kim et al. 2012 as a later heterotypic synonym of Shewanella frigidimarina Bowman et al. 1997.

Two Gram-stain-negative, rod-shaped, facultatively anaerobic, iron-reducing bacterial strains, designated M2T and R106, were isolated from pelagic surface-sediment of the Ross Sea, Antarctica. The 16S rRNA gene sequence analysis revealed that strains M2T and R106 were affiliated to the genus Shewanellaand formed a distinct subline in a robust clade encompassing Shewanella vesiculosa, Shewanella livingstonensis, Shewanella arcticaand Shewanella frigidimarinawith a range of sequence similarities of 98.1-98.9 %. Overall genome relatedness indices indicated that M2T and R106 represented a single genomic species, which was clearly distinguishable from the phylogenetically close relatives with lower values of species delineation thresholds. Cells of M2T grew optimally at 10-15 °C and pH 6.5 in the presence of 3.0-4.0 % (w/v) sea salts. The polar lipids of M2T comprised phosphatidylglycerol, phosphatidylethanolamine, two unidentified aminophospholipids, an unidentified aminolipid and an unidentified phospholipid. Quinones were Q-7, Q-8, MK-7 and MMK-7. The major cellular fatty acids (>10 %) were C16 : 1ω7c and/or C16 : 1ω6c, C16 : 0 and C17 : 1ω8c. The DNA G+C content was 42.2 mol%. On the basis of the phenotypic, phylogenetic, genomic and chemotaxonomic features, we propose the name Shewanellapsychromarinicola sp. nov. with the type strain M2T (=KCCM 43257T =JCM 32090T) and the reclassification of S. arcticaas a later heterotypic synonym of S. frigidimarina.

Multilocus Sequence Analysis, a Rapid and Accurate Tool for Taxonomic Classification, Evolutionary Relationship Determination, and Population Biology Studies of the Genus Shewanella.

The genus Shewanella comprises a group of marine-dwelling species with worldwide distribution. Several species are regarded as causative agents of food spoilage and opportunistic pathogens of human diseases. In this study, a standard multilocus sequence analysis (MLSA) based on six protein-coding genes (gyrA, gyrB, infB, recN, rpoA, and topA) was established as a rapid and accurate identification tool in 59 Shewanella type strains. This method yielded sufficient resolving power in regard to enough informative sites, adequate sequence divergences, and distinct interspecies branches. The stability of phylogenetic topology was supported by high bootstrap values and concordance with different methods. The reliability of the MLSA scheme was further validated by identical phylogenies and high correlations of genomes. The MLSA approach provided a robust system to exhibit evolutionary relationships in the Shewanella genus. The split network tree proposed twelve distinct monophyletic clades with identical G+C contents and high genetic similarities. A total of 86 tested strains were investigated to explore the population biology of the Shewanella genus in China. The most prevalent Shewanella species was Shewanella algae, followed by Shewanella xiamenensis, Shewanella chilikensis, Shewanella indica, Shewanella seohaensis, and Shewanella carassii The strains frequently isolated from clinical and food samples highlighted the importance of increasing the surveillance of Shewanella species. Based on the combined genetic, genomic, and phenotypic analyses, Shewanella upenei should be considered a synonym of S. algae, and Shewanella pacifica should be reclassified as a synonym of Shewanella japonicaIMPORTANCE The MLSA scheme based on six housekeeping genes (HKGs) (gyrA, gyrB, infB, recN, rpoA, and topA) is well established as a reliable tool for taxonomic, evolutionary, and population diversity analyses of the genus Shewanella in this study. The standard MLSA method allows researchers to make rapid, economical, and precise identification of Shewanella strains. The robust phylogenetic network of MLSA provides profound insight into the evolutionary structure of the genus Shewanella The population genetics of Shewanella species determined by the MLSA approach plays a pivotal role in clinical diagnosis and routine monitoring. Further studies on remaining species and genomic analysis will enhance a more comprehensive understanding of the microbial systematics, phylogenetic relationships, and ecological status of the genus Shewanella.

Molecular evidence of a toxic effect on a biofilm and its matrix.

Shewanella oneidensis MR-1 wild-type and a hyper-adhesive mutant CP2-1-S1 are used as model organisms and Cr(vi) is selected as a toxic chemical to study biofilm and toxic chemical interactions. Biofilms are cultured in a microfluidic device for in situ time-of-flight secondary ion mass spectrometry imaging. This approach is viable for studying biofilms' responses to antimicrobial resistance.

Shewanella submarina sp. nov., a gammaproteobacterium isolated from marine water.

A curved-rod-shaped bacterium was isolated from a marine (100 m depth) water sample collected from Bay of Bengal, Visakhapatnam, India. Strain NIO-S14T, was Gram-stain-negative, motile and pale-yellow. NIO-S14T was able to grow aerobically and anaerobically and could utilize a number of organic substrates. Major fatty acids were C12 : 0, iso-C13 : 0, C14 : 0, iso-C15 : 0, C16 : 0 and C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3). NIO-S14T contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminophospholipids and six unidentified lipids as polar lipids. The DNA G+C content of NIO-S14T was 47.9 mol%. The 16S rRNA gene sequence comparisons indicated that the isolate represented a member of the family Shewanellaceae within the class Gammaproteobacteria. According to the results of 16S rRNA gene sequence analysis, NIO-S14T was closely related to Shewanella coralliiwith a pair-wise sequence similarity of 99.26 %. On the basis of the sequence comparison, NIO-S14T clustered with Shewanella coralliiand together they clustered with Shewanella mangroviand seven other species of the genus Shewanella but were distantly related. DNA-DNA hybridization between NIO-S14T and Shewanella corallii DSM 21332Trevealed a relatedness of 35 %. Distinct morphological, physiological and genotypic differences from these previously described taxa supported the classification of NIO-S14T as a representative of a novel species of the genus Shewanella, for which the name Shewanellasubmarina sp. nov. is proposed. The type strain of Shewanellasubmarina is NIO-S14T (=MTCC 12524T=KCTC 52277T=LMG 30752T).

Multilocus sequence typing of Shewanella algae isolates identifies disease-causing Shewanella chilikensis strain 6I4.

The genus Shewanella is rapidly expanding, with new species being discovered frequently. Four species have been identified as pathogenic to humans, with Shewanella algae being most relevant. Evaluation of the clinical significance of Shewanella spp. still suffers from the imprecision of species identification. In addition, the origin of S. algae strains causing disease is unclear. To shed light upon these questions we re-identified reported S. algae isolates on the species level based on the analysis of the partial sequences of the 16S rRNA and gyrB genes in combination with multilocus sequence typing that included six housekeeping loci. The analysis of a collection of 23 S. algae isolates of clinical and environmental origin, the publicly available genome sequences of six additional S. algae strains and type strains of closely-related species showed the existence of a remarkable haplotypic diversity within the S. algae clade. Three of the analyzed strains are suggested to be assigned to a species different from S. algae. A clinical isolate was thus reclassified as S. chilikensis, thereby constituting the first known case of human infection by this species. Our study emphasizes the application of high resolution molecular markers for species identification. The taxonomic resolution of the S. algae clade is still unclear.