THE USE OF SELENOANALOGUES AS SPECIFIC INHIBITORS OF THIOAMINOACID METABOLISM BY SEDIMENTARY BACTERIA

Selenoanalogues of the thioaminoacids, methionine and cysteine, were t ested for their ability to inhibit microbial utilisation of the thioam inoacids in intertidal sediments. Concentrations of 40 mug selenoanalo gue . ml-1 sediment slurry were required to inhibit turnover of the co rresponding thioaminoacid. Selenomethionine (40 mug . ml-1) inhibited turnover of [methyl-C-14]methionine but not turnover Of L-[U-C-14]cyst eine; while selenocystine (40 mug . ml-1) inhibited turnover Of L-[U-C -14;]Cysteine but not [methyl-C-14]methionine. The inhibition of thioa mino acid turnover by the selenoanalogues was, therefore, specific. Th e selenoanalogues provide tools to examine the importance of the thioa minoacids during carbon flow in natural environments.