The ortho-cleavage pathways of catechol and 3-chlorocatechol are central catabolic pathways of Pseudomonas putida that convert aromatic and chloroaromatic compounds to tricarboxylic acid (TCA) cycle intermediates. They are encoded by the evolutionarily related catBCA and clcABD operons, respectively. Expression of the cat and clc operons requires the LysR-type transcriptional activators CatR and ClcR, respectively, and the inducer molecules cis,cis-muconate and 2-chloro-cis,cis-muconate, respectively. The regulation of the cat and clc promoters has been well studied, but the extent to which these operons are repressed by growth in TCA cycle intermediates has not been explored. We demonstrate by transcriptional fusion studies that the expression from the clc promoter is repressed when the cells are grown on succinate, citrate, or fumarate and that this repression is ClcR dependent and occurs at the transcriptional level. The presence of these organic acids did not affect the expression from the cat promoter. In vitro transcription assays demonstrate that the TCA cycle intermediate fumarate directly and specifically inhibits the formation of the clcA transcript. No such inhibition was observed when CatR was used as the activator on either the cat or clc template. Titration studies of fumarate and 2-chloromuconate show that the fumarate effect is concentration dependent and reversible, indicating that fumarate and 2-chloromuconate most probably compete for the same binding site on ClcR. This is an interesting example of the transcriptional regulation of a biodegradative pathway by the intracellular sensing of the state of the TCA cycle.Pseudomonas putida is able to use a wide variety of chlorinated and nonchlorinated aromatics as sole sources of carbon and energy (15,17). Nonchlorinated aromatics such as aniline, benzene, phenol, cinnamate, anthranilate, tryptophan, benzoate, and mandelate are all converted to catechol, which is catabolized to tricarboxylic acid (TCA) cycle intermediates by the central ortho-cleavage pathway (15). The catechol pathway is encoded by the catBCA and pcaD genes. Likewise, chlorinated aromatics such as chloroaniline, chlorophenoxyacetate, chlorophenol, chloronaphthalene, chlorosalicylate, chlorotoluene, chlorobiphenyl, chlorobenzoate, and chlorobenzene are funneled to chlorocatechol, which is converted to TCA cycle intermediates by the central, modified ortho pathway (17). Three operons encoding plasmid-encoded chlorocatechol pathways have been identified: the clcABD operon, isolated from plasmid pAC27 of P. putida (11) and plasmid pWR1 of Pseudomonas sp. strain B13 (36); the tcbCDEF operon, isolated from plasmid pP51 of Pseudomonas sp. strain P51 (38); and the tfdCDEF operon, isolated from plasmid pJP4 of Ralstonia eutropha JMP134 (formerly Alcaligenes eutrophus JMP134) (35, 41). The catechol and chlorocatechol operons are regulated by LysR-type transcriptional activators that are typically divergently transcribed from their structural genes (6,21,37,38). Because these pathways have si...

Background: Universal screening of all neonates has for long been recognized as the most effective method to detect congenital hypothyroidism. However, various maternal as well as perinatal factors can influence the cord blood TSH levels. Objectives:To evaluate the effect of perinatal factors on cord blood TSH level variations in neonates born in a rural tertiary care institution in South India. Methods:A cross-sectional study was done in 430 term neonates at birth to analyse the cord blood TSH levels and a repeat TSH estimation was done on 3 rd postnatal day for those having abnormal values. The values were statistically analysed with respect to maternal, paternal and perinatal parameters.

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