The ability of Gram-positive bacteria to form biogenic amines from different sources has been well documented; however, this ability and the spoilage potential of Gram-positive bacteria from marine sources have not been investigated. Therefore, this study aimed to evaluate the spoilage potential and the potential to form biogenic amines of 228 Gram-positive bacteria isolated from subtropical marine fish through their abilities to utilize organic and inorganic sulphur-containing sources, reduce trimethylamine oxide (TMAO) to trimethylamine (TMAO) and decarboxylate histidine, lysine and ornithine. Strains of Brevibacillus borstelensis (two), Streptococcus uberis (one), Vagococcus fluvialis (two) utilized sodium thiosulphate, cysteine and methionine. However, strains varied in sulphur source utilization. Exiguobacterium acetylicum (one), Exiguobacterium spp. (one), Carnobacterium spp. (one), Brev. borstelensis (two), Streptococcus uberis (two) and Vagococcus fluvialis (two) reduced TMAO. Histidine was not decarboxylated by any Gram-positive bacteria. Lysine and ornithine were decarboxylated mainly by strains of Staphylococcus warneri (eight), Staphylococcus epidermidis (seven) and Micrococcus luteus (two). This study found that Gram-positive bacteria of marine source were weak spoilers, however they had good potential to produce some biogenic amines and their potential was strain-dependent
