Unveiling the molecular basis for pleiotropy in selected rif mutants of Escherichia coli: Possible role for Tyrosine in the Rif binding pocket and fast movement of RNA polymerase.

Rifampicin (RIF) is still a first line of antibiotic in the treatment of bacterial diseases, in particular the Mycobacterial infections. The antimicrobial activity of RIF is attributed to its ability to inhibit transcription by binding to the β subunit of bacterial RNA polymerase (encoded by rpoB). Continued use of this drug resulted in the emergence of RIF resistant rpoB mutations in a high frequency that compels the use of RIF almost exclusively in drug combinations.

Microarray based transcriptome profile data of ∆ and ∆ strains of .

The data presented in this article shows the microarray based transcriptome profiles of ∆ and ∆ strains of . The mutation namely, was isolated spontaneously in the background of ∆ strain (over-produces colanic acid capsular polysaccharide) as a suppressor for over-production of colanic acid capsular polysaccharide (Meenakshi and Munavar, 2015) [1]. The strains were grown in LB medium at 30 °C overnight in duplicates.

A putative curved DNA region upstream of in plays a key role in transcriptional regulation by H-NS.

It is well established that in , the histone-like nucleoid structuring (H-NS) protein also functions as negative regulator of transcription. However, the exact mode of regulation of transcription by H-NS has not been studied extensively. Here, we report the multicopy effect of dominant-negative alleles on the transcription of based on expression of transcriptional fusion in ∆, ∆, ∆ and strains.

Evidence for up and down regulation of 450 genes by rpoB12 (rif) mutation and their implications in complexity of transcription modulation in Escherichia coli.

Analyses of mutations in rpoB subunit of Escherichia coli that lead to resistance to rifampicin have been invaluable in providing insight into events during transcription continue to be discovered. Earlier we reported that rpoB12 suppresses over-expression of cps genes in Δlon mutant of E. coli, by interfering with the transcription of rcsA.

Glu of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme.

As of date the two temperature sensitive mutations isolated in pheST operon include pheS5 (G →A ) and pheT354. Recently, we reported that G of pheS defines a hot spot for intragenic suppressors of pheS5. In this investigation, in 13 independent experiments, a collection of temperature sensitive mutants were isolated by localized mutagenesis.

Suppression of capsule expression in Δlon strains of Escherichia coli by two novel rpoB mutations in concert with HNS: possible role for DNA bending at rcsA promoter.

Analyses of mutations in genes coding for subunits of RNA polymerase always throw more light on the intricate events that regulate the expression of gene(s). Lon protease of Escherichia coli is implicated in the turnover of RcsA (positive regulator of genes involved in capsular polysaccharide synthesis) and SulA (cell division inhibitor induced upon DNA damage). Failure to degrade RcsA and SulA makes lon mutant cells to overproduce capsular polysaccharides and to become sensitive to DNA damaging agents.

G673 could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli.

The pheS5 Ts mutant of Escherichia coli defined by a G293 → A293 transition, which is responsible for thermosensitive Phenylalanyl-tRNA synthetase has been well studied at both biochemical and molecular level but genetic analyses pertaining to suppressors of pheS5 were hard to come by. Here we have systematically analyzed a spectrum of Temperature-insensitive derivatives isolated from pheS5 Ts mutant and identified two intragenic suppressors affecting the same base pair coordinate G673 (pheS19 defines G673 → T673 ; Gly225 → Cys225 and pheS28 defines G673 → C673 ; Gly225 → Arg225). In fact in the third derivative, the intragenic suppressor originally named pheS43 (G673 → C673 transversion) is virtually same as pheS28.

Screening of indigenous oxalate degrading lactic acid bacteria from human faeces and South Indian fermented foods: assessment of probiotic potential.

Lactic acid bacteria (LAB) have the potential to degrade intestinal oxalate and this is increasingly being studied as a promising probiotic solution to manage kidney stone disease. In this study, oxalate degrading LAB were isolated from human faeces and south Indian fermented foods, subsequently assessed for potential probiotic property in vitro and in vivo. Based on preliminary characteristics, 251 out of 673 bacterial isolates were identified as LAB.

Evidence for involvement of UvrB in elicitation of 'SIR' phenotype by rpoB87-gyrA87 mutations in lexA3 mutant of Escherichia coli.

An unconventional DNA repair termed SIR (SOS Independent Repair), specific to mitomycin C (MMC) damage elicited by a combination of specific Rif(R) (rpoB87) and Nal(R) (gyrA87) mutations in SOS un-inducible strains of Escherichia coli was reported by Kumaresan and Jayaraman (1988). We report here that the rpoB87 mutation defines a C(1565)→T(1565) transition changing S(522)→F(522) and gyrA87 defines a G(244)→A(244) transition changing D(82)→N(82). The reconstructed lexA3 rpoB87 gyrA87 strain (DM49RN) exhibited resistance to MMC but not to UV as expected.