Domain: Bacteria, Phylum: Proteobacteria, Class: Gammaproteobacteria, Order: Alteromonadales, Family: Shewanellaceae, Genus: Shewanella(1)
Description and significance
Shewanella baltica (baltica of the Baltic Sea) is both an aerobic and anaerobic bacterium. Shewanella is the sole genus in the Shewanellaceae family of marine bacteria. Shewanella baltica are H2S-producing bacterial isolated from marine fish (mainly cod, plaice, and flounder) caught from the Baltic Sea. In aerobic conditions, the Black Sea strains of S. baltica absorbed significant quantities of Fe(III) from its medium, then reducing it to Fe (II) in anaerobic conditions. Under anaerobic conditions, S. baltica also oxidizes organic matter from the reduction of nitrate and sulfur compounds as well. S. baltica also has putrefaciens capable of high-rate azoreduction and humus reduction under anaerobic conditions.(3) S. baltica produces a black precipitate of FeS when grown on TSI agar medium.(4)
Cell structure and Metabolism
Shewanella baltica is gram-negative, shaped like a short straight rod, and has motility by polar flagellation. S. baltica is also catalase negative and oxidase positive. Its metabolism is strictly respiratory and it can reduce several electron acceptors. S. baltica produces N-acetyl-b-glucosaminidase consitutively, and lacks chymotrypsin production as well as the ability to use glycogen, gentiobiose, cellobiose, sucrose, d-gluconate, and citrate as carbon sources and energy.
Shewanella baltica can grow at 4°C, but not at 37°C. Due to its temperate nature, S. baltica has been found to play a major role in the spoilage of aerobically stored fish in ice. S. baltica is a marine bacteria and found mainly in the waters of the Baltic Sea, near Denmark. During the summer months, the mesophilic human pathogenic Shewanella algae dominates as the H2S-producing bacterial population. In the winter, however, after ice storage, a shift in the Shewanella species was found, and most of the H2S-producing strains were identified as S. baltica.(2)
Shewanella baltica is hypothesized to be able to produce substances that suppress the growth of other bacteria when cultured from fish that was stored for more than 7 days at 0°C.
Currently, Shewanella baltica is being studied for its ability to outgrow other Shewanella species and high G+Cmol% Shewanella species on fish in 0°C for more than 7 days. S. baltica has also been predicted to have a period where it remains dormant, and then explodes into a growth spurt due to it's dormancy during the summer.
(2)"Influence of acetate and CO2 on the TMAO-reduction reaction by Shewanella baltica." Debevere J, Devlieghere F, van Sprundel P, De Meulenaer B. Int J Food Microbiol. 2001 Aug 15
(3)"Identification of Shwanella baltica as the Most Important H2S-Productting Species during Iced Storage of Danish Marine Fish" Vogel, Venkateswaran, Satomi, Gram Danish Institue for Fisheries Research, Department of Seafood Research 2005 July 2
(4)"Reclassification of Shewanella putrefaciens Owen's genomic group II as Shewanella baltica sp. nov." Ziemke, Hofle, Lalucat, Rossello-Mora International Journal of Systematic Bacteriology 1998