Molecular and phenotypic characterization of nonmotile Gram-negative bacteria associated with spoilage of freshwater fish

Abstract

Aims: Characterization of nonmotile bacteria associated with freshwater fish spoilage and that phenotypically resembled Psychrobacter spp. Methods and Results: A population of 44 nonmotile Gram-negative rods could not be assigned to the genus Psychrobacter on the basis of a definitive test (transformation assay). Conventional and commercial phenotypic systems did not help in identification. A second extensive phenotypic analysis using different temperatures and media confirmed these isolates as nonmotile although electron microscopic examination showed that all but two had one to four polar flagella and other appendages. On the basis of numerical taxonomy, this population was divided into six clusters, one of them consisting of five fluorescent strains. Sequencing of fluorescent and non fluorescent representative strains from each cluster demonstrated that strains from five clusters had between 97AE8 and 98AE8% sequence homology with Pseudomonas fragi IFO 3458. This and an unknown strain from deep sea were the closest organisms (80AE9% sequence homology) to one aflagellated representative strain of the remaining cluster. Conclusions: Oxidase-positive, nonmotile, nonfermenter Gram-negative rods isolated from freshwater fish can be wrongly ascribed to the genus Psychrobacter. Significance and Impact of the Study: Molecular methods are necessary for the identification of environmental isolates and species with an incomplete phenotypic description. This work emphasizes the need for a sound description of Ps. fragi based on molecular and phenotypic characterization.

POLYMERASE CHAIN REACTION‐BASED ASSAYS FOR THE DETECTION AND DIFFERENTIATION OF POULTRY SIGNIFICANT PSEUDOMONADS

“…Wild‐type isolates were identified by plating on differential media, Gram‐staining and biochemical assays. Wild‐type isolates were also identified by sequencing 1.45 kb of the 16s rRNA gene using published procedures and primers (Garcia‐Lopez et al. 1996).…”

A proteomic analysis of Psychrobacter articus 273‐4 adaptation to low temperature and salinity using a 2‐D liquid mapping approach

“…Psychrobacter is a "cold-loving" bacterium, which has been isolated from various sources, including sea water [1,2], sediments [3,4], coast [5], soil [6], permafrost [7], ice [8][9][10], refrigerators [11], animals [12,13], and food [13][14][15][16][17]. Psychrobacter 273-4 examined in this work was isolated from a 20 000-40 000-year-old Siberian permafrost core [18], which is characterized by low temperature (2107C), low water activity (aw = 0.85-0.9), poor nutrition, and high salinity.…”

Characterisation ofPseudomonas spp. isolated from foods

“…Indeed, the genus is considered a major producer of the volatile compounds responsible for off-flavour compounds (aldehydes, ketones and esters) (Gram and Huss, 1996;Franzetti et al, 2001) and Pseudomonas fragi appears the most to blame for fructy-odor production, a consequence of amino acid degradation (Molin and Ternstrom, 1986;Miller et al, 1993;Tryfinopoulou et al, 2002;Garcia-Lopez et al, 2004).…”