0000000001012958
AUTHOR
Emilie Chambellon
Experimental conditions affect the site of tetrazolium violet reduction in the electron transport chain of Lactococcus lactis
The reduction of tetrazolium salts to coloured formazans is often used as an indicator of cell metabolism during microbiology studies, although the reduction mechanisms have never clearly been established in bacteria. The objective of the present study was to identify the reduction mechanisms of tetrazolium violet (TV) in Lactococcus lactis using a mutagenesis approach, under two experimental conditions generally applied in microbiology: a plate test with growing cells, and a liquid test with non-growing (resting) cells. The results showed that in both tests, TV reduction resulted from electron transfer from an intracellular donor (mainly NADH) to TV via the electron transport chain (ETC), …
Methylthioacetaldehyde, a possible intermediate metabolite for the production of volatile sulphur compounds from L-methionine by Lactococcus lactis
Volatile sulphur compounds (VSCs) production from L-methionine was studied in Lactococcus lactis. In vitro studies with radiolabelled L-methionine and resting cells of L. lactis revealed that L-methionine was initially converted to alpha-keto-gamma-methylthiobutyrate (KMBA) by a transamination reaction. A part of KMBA was subsequently chemically converted to methylthioacetaldehyde, methanethiol and dimethylsulphides. Chemical conversion of KMBA to methylthioacetaldehyde was dependent on pH, Mn(II) and oxygen. Since methanethiol and dimethylsulphide production was highly related to that of methylthioacetaldehyde, the latter compound was proposed as being an intermediate in VSCs production by…