OPTIMIZATION OF CULTURE CONDITIONS FOR ENUMERATION OF H₂S BACTERIA IN THE FLESH OF SEAFISH

Abstract

H2S bacteria of seafish flesh are weakly halophilic and require on average 1.68% NaCl according to statistical studies. Enumeration is optimal on PCA‐H2S(a PCA medium supplemented with sulfur sources and increased NaCl concentrations) incubated at 25C. Total aerobic bacteria can be counted simultaneously on this medium. The proportion of H2S bacteria relative to total aerobic bacteria increased slightly during prolonged storage of the fish, but was highly variable. Models relating H2S bacterial counts to spoilage of fish are sigmoidal and showed that when the count exceeds 10,000 CFU/g, whole or filleted fish stored in ice at 0C are unfit for consumption. Shewanella putrefaciens accounted for 69% of the H2S bacteria at the fifth day of storage and 100% at the fifteenth.

Low salinity activates a virulence program in the generalist marine pathogen Photobacterium damselae subsp. damselae

“…This system was first described in E. coli as an additional anaerobic respiration system that uses trimethylamine N -oxide (TMAO) and biotin sulfoxide as alternative electron acceptors ( 58 ). Of note, it has been reported in a previous study that Pdd is capable of reducing TMAO to TMA (trimethylamine) ( 59 ). Additionally, genes involved in glucolysis/gluconeogenesis, pyruvate and acetate metabolism were upregulated at 3% NaCl ( Table 1 ).…”