The genus Shewanella has been studied since 1931 with regard to a variety of topics of relevance to both applied and environmental microbiology. Recent years have seen the introduction of a large number of new Shewanella-like isolates, necessitating a coordinated review of the genus. In this work, the phylogenetic relationships among known shewanellae were examined using a battery of morphological, physiological, molecular and chemotaxonomic characterizations. This polyphasic taxonomy takes into account all available phenotypic and genotypic data and integrates them into a consensus classification. Based on information generated from this study and obtained from the literature, a scheme for the identification of Shewanella species has been compiled. Key phenotypic characteristics were sulfur reduction and halophilicity. Fatty acid and quinone profiling were used to impart an additional layer of information. Molecular characterizations employing small-subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in some cases. As a result, DNA-DNA hybridization and sequence analyses of a more rapidly evolving molecule (gyrB gene) were performed. Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of closely related strains. With this polyphasic approach, in addition to the ten described Shewanella species, two new species, Shewanella oneidensis and 'Shewanella pealeana', were recognized; Shewanella oneidensis sp. nov. is described here for the first time.

Plasmid-mediated resistance to quinolones is increasingly reported in studies of Enterobacteriaceae. Using a PCR-based strategy, a series of gram-negative species were screened for qnrA-like genes. Shewanella algae, an environmental species from marine and fresh water, was identified as its reservoir. This is a one of the very few examples of progenitor identification of an acquired antibiotic resistance gene.

A chromosome-encoded beta-lactamase gene from Shewanella algae clinical isolate KB-1 was cloned and expressed in Escherichia coli. It encoded the Ambler class D enzyme OXA-55, sharing less than 55% identity with any other oxacillinases. Although conferring a narrow-spectrum beta-lactam resistance phenotype, OXA-55 had carbapenem-hydrolyzing activity that mirrored the reduced susceptibility to imipenem observed in S. algae KB-1. Very similar oxacillinases were found in other S. algae isolates.

A Gram-staining-negative, motile, non-spore-forming and rod-shaped bacterial strain, 20-23R(T), was isolated from intestine of bensasi goatfish, Upeneus bensasi, and its taxonomic position was investigated by using a polyphasic study. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain 20-23R(T) belonged to the genus Shewanella. Strain 20-23R(T) exhibited 16S rRNA gene sequence similarity values of 99.5, 99.2, and 97.5% to Shewanella algae ATCC 51192(T), Shewanella haliotis DW01(T), and Shewanella chilikensis JC5(T), respectively. Strain 20-23R(T) exhibited 93.1-96.0% 16S rRNA gene sequence similarity to the other Shewanella species. It also exhibited 98.3-98.4% gyrB sequence similarity to the type strains of S. algae and S. haliotis. Strain 20-23R(T) contained simultaneously both menaquinones and ubiquinones; the predominant menaquinone was MK-7 and the predominant ubiquinones were Q-8 and Q-7. The fatty acid profiles of strain 20-23R(T), S. algae KCTC 22552(T) and S. haliotis KCTC 12896(T) were similar; major components were iso-C(15:0), C(16:0), C(16:1) �s7c and/or iso-C(15:0) 2-OH and C(17:1) �s8c. The DNA G+C content of strain 20-23R(T) was 53.9 mol%. Differential phenotypic properties and genetic distinctiveness of strain 20-23R(T), together with the phylogenetic distinctiveness, revealed that this strain is distinguishable from recognized Shewanella species. On the basis of the data presented, strain 20-23R(T) represents a novel species of the genus Shewanella, for which the name Shewanella upenei sp. nov. is proposed. The type strain is 20-23R(T) (=KCTC 22806(T) =CCUG 58400(T)).

Plasmid-carried quinolone resistance genes, like qnrA, are widespread in Enterobacteriaceae. To gain insight into its little-understood native functions, we studied the effect of environmental conditions on chromosomal qnrA expression in Shewanella algae. Among conditions of DNA damage, oxidative and osmotic stress, starvation, heat, and cold, only cold shock increased gene expression, as measured by quantitative reverse transcription-PCR (qRT-PCR). Induction was graded and occurred during growth arrest, suggesting that qnrA may contribute to the adaptation of Shewanella to low temperatures.

A Gram-negative, facultatively anaerobic, rod-shaped, catalase- and oxidase-positive bacterium, motile by means of a single polar flagellum and designated strain KJW27(T), was isolated from the marine sediment of Karwar jetty, west coast of India. The strain was �]-haemolytic and grew with 0-10 % (w/v) NaCl, at 10-45 �XC and at pH 6.5-10, with optimum growth with 2 % (w/v) NaCl, at 37 �XC and at pH 7.5. The major fatty acids were iso-C??:? (22.2 %), C??:?�s8c (21 %), summed feature 3 (comprising C??:?�s7c and/or C??:?�s6c; 10.2 %), C??:? (7.1 %), iso-C??:? (5.6 %) and C??:? (4.4 %). The DNA G+C content was 51.2 mol%. Phylogenetic analysis based on 16S rRNA and gyrB gene sequences showed that strain KJW27(T) forms a lineage within the genus Shewanella and is closely related to Shewanella algae ATCC 51192(T) (98.8 %), Shewanella haliotis DW01(T) (98.8 %) and Shewanella chilikensis JC5(T) (98.2 %). Sequence identity with other members of this genus ranges from 92.2 to 96.4 %. The DNA-DNA relatedness of strain KJW27(T) with S. algae ATCC 51192(T), S. haliotis DW01(T) and S. chilikensis JC5(T) was 52, 44 and 33 %, respectively. The phenotypic, genotypic and DNA-DNA relatedness data indicate that strain KJW27(T) should be distinguished from S. algae ATCC 51192(T), S. haliotis DW01(T) and S. chilikensis JC5(T). On the basis of the data presented in this study, strain KJW27(T) represents a novel species, for which the name Shewanella indica sp. nov. is proposed. The type strain is KJW27(T) (= KCTC 23171(T) = BCC 41031(T) = NCIM 5388(T)).

Shewanella algae B516 produces avaroferrin, an asymmetric hydroxamate siderophore, which has been shown to inhibit swarming motility of Vibrio alginolyticus. We aimed to elucidate the biosynthesis of this siderophore and to investigate how S. algae coordinates the production of avaroferrin and its two symmetric counterparts. We reconstituted the reaction in vitro with the main enzyme AvbD and the putative biosynthetic precursors, and demonstrate that multispecificity of this enzyme results in the production of all three cyclic hydroxamate siderophores that were previously isolated as natural products from S. algae. Surprisingly, purified AvbD exhibited a clear preference for the larger cadaverine-derived substrate. In live cells, however, siderophore ratios are maximized toward avaroferrin production, and we demonstrate that these siderophore ratios are the result of a regulation on substrate pool level, which may allow rapid evolutionary adaptation to environmental changes. Our results thereby give insights into a unique evolutionary strategy toward metabolite diversity.

The presence of SXT/R391-related integrating conjugative elements (ICEs) in bacterial strains isolated from fish obtained from marine aquaculture environments in 2001 to 2010 in the northwestern Iberian Peninsula was studied. ICEs were detected in 12 strains taxonomically related to Vibrio scophthalmi (3 strains), Vibrio splendidus (5 strains), Vibrio alginolyticus (1 strain), Shewanella haliotis (1 strain), and Enterovibrio nigricans (2 strains), broadening the known host range able to harbor SXT/R391-like ICEs. Variable DNA regions, which confer element-specific properties to ICEs of this family, were characterized. One of the ICEs encoded antibiotic resistance functions in variable region III, consisting of a tetracycline resistance locus. Interestingly, hot spot 4 included genes providing resistance to rifampin (ICEVspPor2 and ICEValPor1) and quaternary ammonium compounds (QACs) (ICEEniSpa1), and variable region IV included a mercury resistance operon (ICEVspSpa1 and ICEEniSpa1). The S exclusion group was more represented than the R exclusion group, accounting for two-thirds of the total ICEs. Mating experiments allowed ICE mobilization to Escherichia coli strains, showing the corresponding transconjugants' rifampin, mercury, and QAC resistance. These results show the first evidence of ICEs providing rifampin and QAC resistances, suggesting that these mobile genetic elements contribute to the dissemination of antimicrobial, heavy metal, and QAC resistance determinants in aquaculture environments.

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.

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