The genetic basis of tetrathionate respiration in Salmonella Typhimurium

Lehrstuhl für Bakteriologie, Max von Pettenkofer-Institut für Hygiene und Medizinische Mikrobiologie, Pettenkoferstr. 9a, D-80336 Munich, Germany.
Molecular Microbiology (Impact Factor: 4.42). 05/1999; 32(2):275-87. DOI: 10.1046/j.1365-2958.1999.01345.x
Source: PubMed


A range of bacteria are able to use tetrathionate as a terminal respiratory electron acceptor. Here we report the identification and characterization of the ttrRSBCA locus required for tetrathionate respiration in Salmonella typhimurium LT2a. The ttr genes are located within Salmonella pathogenicity island 2 at centisome 30.5. ttrA, ttrB and ttrC are the tetrathionate reductase structural genes. Sequence analysis suggests that TtrA contains a molybdopterin guanine dinucleotide cofactor and a [4Fe-4S] cluster, that TtrB binds four [4Fe-4S] clusters, and that TtrC is an integral membrane protein containing a quinol oxidation site. TtrA and TtrB are predicted to be anchored by TtrC to the periplasmic face of the cytoplasmic membrane implying a periplasmic site for tetrathionate reduction. It is inferred that the tetrathionate reductase, together with thiosulphate and polysulphide reductases, make up a previously unrecognized class of molybdopterin-dependent enzymes that carry out the reductive cleavage of sulphur-sulphur bonds. Cys-256 in TtrA is proposed to be the amino acid ligand to the molybdopterin cofactor. TtrS and TtrR are the sensor and response regulator components of a two-component regulatory system that is absolutely required for transcription of the ttrBCA operon. Expression of an active tetrathionate reduction system also requires the anoxia-responsive global transcriptional regulator Fnr. The ttrRSBCA gene cluster confers on Escherichia coli the ability to respire with tetrathionate as electron acceptor.

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    • "In particular, reactive oxygen species generated by neutrophils (PMNs) during inflammation can react with endogenous thiosulfate to form tetrathionate, a respiratory electron acceptor (21). The ability to respire tetrathionate has been mapped to the ttrRSBCA locus, which is located in SPI-2 (22). Under anaerobic conditions in which thiosulphate was oxidized to tetrathionate, S. typhimurium displays a growth advantage in comparison to resident microbiota under the same conditions (21). "
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    • "In this context, the aim of this study was the development and in-house validation of an open-formula diagnostic realtime PCR for detection of Salmonella in different meat products chosen according with Commission Regulation (EC) No. 2073 of 15 November 2005 on microbiological criteria for foodstuffs. The assay employed specific primers and a probe target within the ttrRSBCA locus, in Salmonella (Malorny et al. 2004a; Hensel et al. 1999). The original protocol (Malorny et al. 2004a) was modified with the inclusion of a new, easy to prepare Internal Amplification Control (IAC) which was added to every reaction mixture, to avoid false negative results (Abdulmawjood et al. 2002; Hoorfar et al. 2004b; Hoorfar et al. 2003). "
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