Rel-dependent decrease in the expression of ribosomal protein genes by inhibition of the respiratory electron transport chain in .

In this study, we demonstrated that both the expression of most ribosomal protein genes and the amount of ribosomes were decreased in the Δ mutant of , in which the major terminal oxidase ( cytochrome oxidase) of the respiratory electron transport chain (ETC) is inactivated, compared to those in the wild-type strain. Deletion of the gene encoding the major (p)ppGpp synthetase in the background of the Δ mutant restored the reduced expression of ribosomal protein genes, suggesting that inhibition of the respiratory ETC leads to the Rel-dependent stringent response (SR) in this bacterium. Both a decrease in the expression of ribosomal protein genes by overexpression of and the increased expression of in the Δ mutant relative to the wild-type strain support the Rel-dependent induction of SR in the Δ mutant.

Mycobacterial Regulatory Systems Involved in the Regulation of Gene Expression Under Respiration-Inhibitory Conditions.

Mycobacterium tuberculosis is the causative agent of tuberculosis. M. tuberculosis can survive in a dormant state within the granuloma, avoiding the host-mounting immune attack.

Negative regulation of the acsA1 gene encoding the major acetyl-CoA synthetase by cAMP receptor protein in Mycobacterium smegmatis.

Acetyl-CoA synthetase (ACS) is the enzyme that irreversibly catalyzes the synthesis of acetyl-CoA from acetate, CoA-SH, and ATP via acetyl-AMP as an intermediate. In this study, we demonstrated that AcsA1 (MSMEG_6179) is the predominantly expressed ACS among four ACSs (MSMEG_6179, MSMEG_0718, MSMEG_3986, and MSMEG_5650) found in Mycobacterium smegmatis and that a deletion mutation of acsA1 in M. smegmatis led to its compromised growth on acetate as the sole carbon source.

Activation of the SigE-SigB signaling pathway by inhibition of the respiratory electron transport chain and its effect on rifampicin resistance in Mycobacterium smegmatis.

Using a mutant of Mycobacterium smegmatis lacking the major aa cytochrome c oxidase of the electron transport chain (Δaa), we demonstrated that inhibition of the respiratory electron transport chain led to an increase in antibiotic resistance of M. smegmatis to isoniazid, rifampicin, ethambutol, and tetracycline. The alternative sigma factors SigB and SigE were shown to be involved in an increase in rifampicin resistance of M.

Functional characterization of HigBA toxin-antitoxin system in an Arctic bacterium, Bosea sp. PAMC 26642.

Toxin-antitoxin (TA) systems are growth-controlling genetic elements consisting of an intracellular toxin protein and its cognate antitoxin. TA systems have been spread among microbial genomes through horizontal gene transfer and are now prevalent in most bacterial and archaeal genomes. Under normal growth conditions, antitoxins tightly counteract the activity of the toxins.

Regulation of the Gene Encoding the Major Isocitrate Lyase in Mycobacterium smegmatis.

Mycobacterium smegmatis has two isocitrate lyase (ICL) isozymes (MSMEG_0911 and MSMEG_3706). We demonstrated that ICL1 (MSMEG_0911) is the predominantly expressed ICL in M. smegmatis and plays a major role in growth on acetate or fatty acid as the sole carbon and energy source.

Induction of the Operon Encoding the Quinol Oxidase Under Respiration-Inhibitory Conditions by the Major cAMP Receptor Protein MSMEG_6189 in .

The respiratory electron transport chain (ETC) of is terminated with two terminal oxidases, the cytochrome oxidase and the cytochrome quinol oxidase. The quinol oxidase with a higher binding affinity for O than the oxidase is known to play an important role in aerobic respiration under oxygen-limiting conditions. Using relevant () and () mutant strains of , we demonstrated that Crp1 plays a predominant role in induction of the operon under ETC-inhibitory conditions.

The Partner Switching System of the SigF Sigma Factor in and Induction of the SigF Regulon Under Respiration-Inhibitory Conditions.

The partner switching system (PSS) of the SigF regulatory pathway in has been previously demonstrated to include the anti-sigma factor RsbW (MSMEG_1803) and two anti-sigma factor antagonists RsfA and RsfB. In this study, we further characterized two additional RsbW homologs and revealed the distinct roles of three RsbW homologs [RsbW1 (MSMEG_1803), RsbW2 (MSMEG_6129), and RsbW3 (MSMEG_1787)] in the SigF PSS. RsbW1 and RsbW2 serve as the anti-sigma factor of SigF and the protein kinase phosphorylating RsfB, respectively, while RsbW3 functions as an anti-SigF antagonist through its protein interaction with RsbW1.

Overexpressed L20 Rescues 50S Ribosomal Subunit Assembly Defects of -Deletion in .

The BipA (BPI-inducible protein A) protein is highly conserved in a large variety of bacteria and belongs to the translational GTPases, based on sequential and structural similarities. Despite its conservation in bacteria, is not essential for cell growth under normal growth conditions. However, at 20°C, deletion of causes not only severe growth defects but also several phenotypic changes such as capsule production, motility, and ribosome assembly, indicating that it has global regulatory properties.

Tripartite Regulation of the Operon Involved in Glycerol Catabolism by GylR, Crp, and SigF in Mycobacterium smegmatis.

The () gene encoding glycerol-3-phosphate dehydrogenase was shown to be crucial for to utilize glycerol as the sole carbon source. The gene likely forms the operon together with and , encoding a glycerol facilitator and glycerol kinase, respectively. The () gene, whose product belongs to the IclR family of transcriptional regulators, was identified 182 bp upstream of It was demonstrated that GylR serves as a transcriptional activator and is involved in the induction of expression in the presence of glycerol.

Dual control of RegX3 transcriptional activity by SenX3 and PknB.

The mycobacterial SenX3-RegX3 two-component system consists of the SenX3 sensor histidine kinase and its cognate RegX3 response regulator. This system is a phosphorelay-based regulatory system involved in sensing environmental P levels and induction of genes required for P acquisition under P-limiting conditions. Here we demonstrate that overexpression of the kinase domain of PknB (PknB-KD) inhibits the transcriptional activity of RegX3 of both and (RegX3 and RegX3, respectively).

Alanine dehydrogenases in mycobacteria.

Since NAD(H)-dependent L-alanine dehydrogenase (EC 1.1.4.

A response regulator of the OmpR family is part of the regulatory network controlling the oxidative stress response of Rhodobacter sphaeroides.

As a free-living bacterium Rhodobacter sphaeroides needs to respond to many environmental stresses. Oxidative stress, membrane stress or heat stress induce the ompR-1 gene encoding a protein of the OmpR family. Overexpression of OmpR-1 results in increased resistance to organic peroxides and diamide.

Roles of Alanine Dehydrogenase and Induction of Its Gene in Mycobacterium smegmatis under Respiration-Inhibitory Conditions.

Here we demonstrated that the inhibition of electron flux through the respiratory electron transport chain (ETC) by either the disruption of the gene for the major terminal oxidase ( cytochrome oxidase) or treatment with KCN resulted in the induction of encoding alanine dehydrogenase in A decrease in functionality of the ETC shifts the redox state of the NADH/NAD pool toward a more reduced state, which in turn leads to an increase in cellular levels of alanine by Ald catalyzing the conversion of pyruvate to alanine with the concomitant oxidation of NADH to NAD The induction of expression under respiration-inhibitory conditions in is mediated by the alanine-responsive AldR transcriptional regulator. The growth defect of by respiration inhibition was exacerbated by inactivation of the gene, suggesting that Ald is beneficial to in its adaptation and survival under respiration-inhibitory conditions by maintaining NADH/NAD homeostasis. The low susceptibility of to complex inhibitors appears to be, at least in part, attributable to the high expression level of the quinol oxidase in when the - branch of the ETC is inactivated.

Roles of three FurA paralogs in the regulation of genes pertaining to peroxide defense in Mycobacterium smegmatis mc 155.

Mycobacterium smegmatis mc 155 has three genes (MSMEG_6383, furA1; MSMEG_3460, furA2; MSMEG_6253, furA3) encoding FurA (ferric-uptake regulator A) paralogs. Three FurA paralogs in M. smegmatis are functionally redundant and negatively regulate expression of a subset of genes involved in peroxide detoxification such as ahpC, katG1 and katG2, as well as their own genes.

Goldfish, Carassius auratus, as an infection model for studying the pathogenesis of Edwardsiella piscicida.

This study demonstrates the feasibility of using goldfish as an infection model to investigate the pathogenesis of Edwardsiella piscicida. Goldfish were found to be susceptible to acute E. piscicida-induced disease and died in a dose-dependent manner.

Inhibition of the DevSR Two-Component System by Overexpression of Mycobacterium tuberculosis PknB in Mycobacterium smegmatis.

The DevSR (DosSR) two-component system, which is a major regulatory system involved in oxygen sensing in mycobacteria, plays an important role in hypoxic induction of many genes in mycobacteria. We demonstrated that overexpression of the kinase domain of Mycobacterium tuberculosis (Mtb) PknB inhibited transcriptional activity of the DevR response regulator in Mycobacterium smegmatis and that this inhibitory effect was exerted through phosphorylation of DevR on Thr180 within its DNA-binding domain. Moreover, the purified kinase domain of Mtb PknB significantly phosphorylated RegX3, NarL, KdpE, TrcR, DosR, and MtrA response regulators of Mtb that contain the Thr residues corresponding to Thr180 of DevR in their DNA-binding domains, implying that transcriptional activities of these response regulators might also be inhibited when the kinase domain of PknB is overexpressed.

Edwardsiella piscicida lacking the cyclic AMP receptor protein (Crp) is avirulent and immunogenic in fish.

Edwardsiella piscicida is a Gram-negative pathogen that generally causes lethal septicemia in marine and freshwater fish. We generated a E. piscicida CK216 Δcrp mutant to investigate various biological roles related to this organism, including pathogenesis.

Identification and characterization of the genes encoding carbon monoxide dehydrogenase in Terrabacter carboxydivorans.

Terrabacter carboxydivorans is able to grow aerobically at low concentrations of carbon monoxide (CO) as a sole source of carbon and energy. The genes for carbon monoxide dehydrogenase (CO-DH) were cloned from T. carboxydivorans and analyzed.

Functional characterization of the cutI gene for the transcription of carbon monoxide dehydrogenase genes in Mycobacterium sp. strain JC1 DSM 3803.

Carbon monoxide dehydrogenase (CO-DH) in Mycobacterium sp. strain JC1 is a key enzyme for the carboxydotrophic growth, when carbon monoxide (CO) is supplied as a sole source of carbon and energy. This enzyme is also known to act as nitric oxide dehydrogenase (NO-DH) for the detoxification of NO.

Regulation of a polyamine transporter by the conserved 3' UTR-derived sRNA SorX confers resistance to singlet oxygen and organic hydroperoxides in Rhodobacter sphaeroides.

Singlet oxygen is generated by bacteriochlorophylls when light and oxygen are simultaneously present in Rhodobacter sphaeroides. Singlet oxygen triggers a specific response that is partly regulated by the alternative sigma factor RpoHI/HII. The sRNA RSs2461 has previously been identified as an RpoHI/HII-dependent sRNA and is derived from the 3' UTR of the mRNA for an OmpR-type transcriptional regulator.

Regulation Mechanism of the ald Gene Encoding Alanine Dehydrogenase in Mycobacterium smegmatis and Mycobacterium tuberculosis by the Lrp/AsnC Family Regulator AldR.

Unlabelled: In the presence of alanine, AldR, which belongs to the Lrp/AsnC family of transcriptional regulators and regulates ald encoding alanine dehydrogenase in Mycobacterium smegmatis, changes its quaternary structure from a homodimer to an octamer with an open-ring conformation. Four AldR-binding sites (O2, O1, O4, and O3) with a consensus sequence of GA/T-N2-NWW/WWN-N2-A/TC were identified upstream of the M. smegmatis ald gene by means of DNase I footprinting analysis.

Regulation of the ahpC gene encoding alkyl hydroperoxide reductase in Mycobacterium smegmatis.

The ahpC (MSMEG_4891) gene encodes alkyl hydroperoxide reductase C in Mycobacterium smegmatis mc2155 and its expression is induced under oxidative stress conditions. Two well-defined inverted repeat sequences (IR1 and IR2) were identified in the upstream region of ahpC. Using a crp (cAMP receptor protein: MSMEG_6189) mutant and in vitro DNA-binding assay, it was demonstrated that the IR1 sequence serves as a Crp-binding site and that Crp functions as an activator in the regulation of ahpC expression.

Construction of target-specific virus-like particles for the delivery of algicidal compounds to harmful algae.

Harmful algal blooms (HABs) can lead to substantial socio-economic losses and extensive damage to aquatic ecosystems, drinking water sources and human health. Common algicidal techniques, including ozonation, ultrasonic treatment and dispersion of algae-killing chemicals, are unsatisfactory both economically and ecologically. This study therefore presents a novel alternative strategy for the efficient control of deleterious algae via the use of host-specific virus-like particles (VLPs) combined with chemically synthesized algicidal compounds.