Abstract
The current taxonomic positions of psychrotrophic bacterial strains isolated from seafood and housed in the Kodiak Seafood Culture Collection (KSCC) were determined based on membrane fatty acid profiles and compared with profiles for representative American Type Culture Collection (ATCC) strains. Gram-positive organisms had a high percentage (64–96%) of branched-chain fatty acids, except for Streptococcus faecium . Gram-negative, oxidase-negative isolates were composed of 38–69% of saturated fatty acids and 19–50% of unsaturated fatty acids. Hydroxyl fatty acids were present in all the gram-negative, oxidase-positive isolates and the branched-chain fatty acids were <1–74%. Of the 33 strains tested, 55% were identified to species with a similarity index (SI) >0.5 and <0.1 SI in range of the first rank. Strains of Pseudomonas fluorescens and those belonging to the Enterobacteriaceae were responsible for this lower percentage. The modern taxonomic positions of three KSCC strains were found to be Shewanella putrefaciens , Psychrobacter immobilis and Myroides odoratus . Sherlock MIS proved to be an effective and rapid technique in the identification of bacteria associated with seafood.
Highlights
Lipids compose almost 50% of the cytoplasmic membrane of bacterial cells and are composed of unique fatty acids of straight chains and branched chains (Suutari and Laakso, 1994)
Gram-negative, oxidase-negative isolates were composed of 38–69% of saturated fatty acids and 19–50% of unsaturated fatty acids
Saturated straight- and branched-chain fatty acids were prominent in Staphylococcus epidermidis and S. xylosus but differed quantitatively and qualitatively (Table 3)
Summary
Lipids compose almost 50% of the cytoplasmic membrane of bacterial cells and are composed of unique fatty acids of straight chains (saturated, unsaturated, cyclopropane and hydroxylated) and branched chains (saturated, unsaturated or hydroxylated iso-, anteiso- and ω-alicyclic) (Suutari and Laakso, 1994). Some microbiology researchers conclude the MIS is accurate, efficient, reproducible, and rapid and correctly identifies clinical bacteria (Kunitsky et al, 2005; Himelbloom et al, 2011). Others report that this system cannot be used for sub-grouping of bacteria since the typing capability of MIS is genus- and/or species-dependent (Osterhout et al, 1991; Birnbaum et al, 1994; Steele et al, 1997; Odumeru et al, 1999). The objective of this research was to establish the fatty acid profiles of bacteria previously detected in Alaska seafood products and to assess the ability of the MIS to accurately identify this select group.
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