An open reading frame upstream from the nifH gene of Klebsiella pneumoniae

An open reading frame upstream from nifHDK operon of Klebsiella pneumoniae had been described. The orientation of this open reading frame is opposite to that of nifHDK and sequence homology was found between the open reading frame promoter and the promoter of nifHDK operon. A recombinant plasmid carrying the promoter region of the open reading frame fused to the beta-galactosidase gene was constructed. Strains of E.coli were transformed with the plasmid containing this open reading frame promoter-lacZ fusion or co-transformed with it and a plasmid carrying the nifA gene. An appreciable activity of beta-galactosidase was found in strains which received both plasmids, indicating that the promoter of the open reading frame can be activated by the product of nifA gene. Thus, the open reading frame found between nifHDK operon and nifJ behaves just like other nif genes of K.pneumoniae in requiring the product of nifA as the positive effector for expression

Role of the PAS2 domain of the NifL regulatory protein in redox signal transduction

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Substitutions in the redox-sensing PAS domain of the NifL regulatory protein define an inter-subunit pathway for redox signal transmission

The Per-ARNT-Sim (PAS) domain is a conserved a/ß fold present within a plethora of signalling proteins from all kingdoms of life. PAS domains are often dimeric and act as versatile sensory and interaction modules to propagate environmental signals to effector domains. The NifL regulatory protein from Azotobacter vinelandii senses the oxygen status of the cell via an FAD cofactor accommodated within the first of two amino-terminal tandem PAS domains, termed PAS1 and PAS2. The redox signal perceived at PAS1 is relayed to PAS2 resulting in conformational reorganization of NifL and consequent inhibition of NifA activity. We have identified mutations in the cofactor-binding cavity of PAS1 that prevent 'release' of the inhibitory signal upon oxidation of FAD. Substitutions of conserved ß-sheet residues on the distal surface of the FAD-binding cavity trap PAS1 in the inhibitory signalling state, irrespective of the redox state of the FAD group. In contrast, substitutions within the flanking A'a-helix that comprises part of the dimerization interface of PAS1 prevent transmission of the inhibitory signal. Taken together, these results suggest an inter-subunit pathway for redox signal transmission from PAS1 that propagates from core to the surface in a conformation-dependent manner requiring a flexible dimer interface

BacS: An Abundant Bacteroid Protein in \u3cem\u3eRhizobium etli\u3c/em\u3e Whose Expression Ex Planta Requires \u3cem\u3enifA\u3c/em\u3e

Rhizobium etli CFN42 bacteroids from bean nodules possessed an abundant 16-kDa protein (BacS) that was found in the membrane pellet after cell disruption. This protein was not detected in bacteria cultured in tryptone-yeast extract. In minimal media, it was produced at low oxygen concentration but not in a mutant whose nifA was disrupted. N-terminal sequencing of the protein led to isolation of a bacS DNA fragment. DNA hybridization and nucleotide sequencing revealed three copies of the bacS gene, all residing on the main symbiotic plasmid of strain CFN42. A stretch of 304 nucleotides, exactly conserved upstream of all three bacS open reading frames, had very close matches with the NifA and sigma 54 consensus binding sequences. The only bacS homology in the genetic sequence databases was to three hypothetical proteins of unknown function, all from rhizobial species. Mutation and genetic complementation indicated that each of the bacS genes gives rise to a BacS polypeptide. Mutants disrupted or deleted in all three genes did not produce the BacS polypeptide but were Nod+ and Fix+ on Phaseolus vulgaris

A novel function of the key nitrogen-fixation activator NifA in beta-rhizobia: Repression of bacterial auxin synthesis during symbiosis

Rhizobia fix nitrogen within root nodules of host plants where nitrogenase expression is strictly controlled by its key regulator NifA. We recently discovered that in nodules infected by the beta-rhizobial strain Paraburkholderia phymatum STM815, NifA controls expression of two bacterial auxin synthesis genes. Both the iaaM and iaaH transcripts, as well as the metabolites indole-acetamide (IAM) and indole-3-acetic acid (IAA) showed increased abundance in nodules occupied by a nifA mutant compared to wild-type nodules. Here, we document the structural changes that a P. phymatum nifA mutant induces in common bean (Phaseolus vulgaris) nodules, eventually leading to hypernodulation. To investigate the role of the P. phymatum iaaMH genes during symbiosis, we monitored their expression in presence and absence of NifA over different stages of the symbiosis. The iaaMH genes were found to be under negative control of NifA in all symbiotic stages. While a P. phymatum iaaMH mutant produced the same number of nodules and nitrogenase activity as the wild-type strain, the nifA mutant produced more nodules than the wild-type that clustered into regularly-patterned root zones. Mutation of the iaaMH genes in a nifA mutant background reduced the presence of these nodule clusters on the root. We further show that the P. phymatum iaaMH genes are located in a region of the symbiotic plasmid with a significantly lower GC content and exhibit high similarity to two genes of the IAM pathway often used by bacterial phytopathogens to deploy IAA as a virulence factor. Overall, our data suggest that the increased abundance of rhizobial auxin in the non-fixing nifA mutant strain enables greater root infection rates and a role for bacterial auxin production in the control of early stage symbiotic interactions

The nitric oxide response in plant-associated endosymbiotic bacteria

Nitric oxide (NO) is a gaseous signalling molecule which becomes very toxic due to its ability to react with multiple cellular targets in biological systems. Bacterial cells protect against NO through the expression of enzymes that detoxify this molecule by oxidizing it to nitrate or reducing it to nitrous oxide or ammonia. These enzymes are haemoglobins, c-type nitric oxide reductase, flavorubredoxins and the cytochrome c respiratory nitrite reductase. Expression of the genes encoding these enzymes is controlled by NO-sensitive regulatory proteins. The production of NO in rhizobia–legume symbiosis has been demonstrated recently. In functioning nodules, NO acts as a potent inhibitor of nitrogenase enzymes. These observations have led to the question of how rhizobia overcome the toxicity of NO. Several studies on the NO response have been undertaken in two non-dentrifying rhizobial species, Sinorhizobium meliloti and Rhizobium etli, and in a denitrifying species, Bradyrhizobium japonicum. In the present mini-review, current knowledge of the NO response in those legume-associated endosymbiotic bacteria is summarized

PERBANDINGAN MASKER COKELAT DENGAN MASKER BERAS MERAH TERHADAP KELEMBABAN KULIT WAJAH KERING

Abstract The study aims to determine whether there is an effect of the use of chocolate mask to moisture dry skin, and brown rice as a mask treatment group comparisons.The population used in this study is the dry skin in older women, aged 35-45 years old. Sampling was done by purposive sampling, which is done by taking the characteristics or properties of a previously unknown population with the purpose of research. The method used is the experimental method. The number of samples taken in this study is 10 people. These samples were divided into 2 groups: group A by 5 people using the chocolate mask and group B by 5 people using the mask of brown rice. Each sample was given treatment 1 week 2 treatments were performed during treatment 8 times. Based on the theoretical description, it can be formulated research hypotheses that: there is the effect of using chocolate mask to moisture dry skin. This study used a research instrument with a score sheet moisture content that can be read on the use of a skin analyzer test. This tool is used to determine the level of moisture in dry skin. Having obtained the research data, test requirements analysis and data analysis to test for normality and homogeneity test, using a test average of one party. Analysis of the data indicates t = 9.230. At the significant level = 0.05 and degrees of freedom (df = 8), the table = 2.31 ​​declared tcount> t table, the null hypothesis (Ho) is rejected. There is the effect of using chocolate mask to moisture dry skin. The result of this study are expected to increase the development of courses Facial Skin Care and Cosmetics Traditional Makeup Studies Program, Department of Family Welfare, Faculty of Engineering, State University of Jakarta. Key words; chocolate, mask, moisture, dry skin, brown rice, treatment   Abstrak Penilitan ini bertujuan untuk mengetahui apakah terdapat pengaruh dari penggunaan masker cokelat terhadap kelembaban kulit wajah kering, dan perawatan masker beras merah sebagai kelompok perbandingan.Populasi yang digunakan pada penelitian ini yaitu kulit wajah kering pada wanita dewasa, usia 35-45 tahun. Pengambilan sampel dilakukan dengan purposive sampling, yaitu pengambilan yang dilakukan berdasarkan ciri-ciri atau sifat populasi yang diketahui sebelumnya dengan tujuan penelitian. Metode yang digunakan adalah metode eksperimen.Banyaknya sampel yang diambil dalam penelitian ini yaitu 10 orang. Sampel ini dibagi menjadi 2 kelompok, yaitu kelompok A sebanyak 5 orang yang menggunakan masker cokelat dan kelompok B sebanyak 5 orang yang menggunakan masker beras merah. Masing-masing sampel diberikan perlakuan 1 minggu 2 kali perawatan yang dilakukan selama 8x perlakuan. Berdasarkan deskripsi teoritis, maka dapat dirumuskan hipotesis penelitian bahwa : terdapat pengaruh penggunaan masker cokelat terhadap kelembaban kulit wajah kering.Penelitian ini menggunakan instrumen lembar penelitian dengan nilai skor kadar kelembaban yang dapat dibaca pada penggunaan alat skin analyzer test. Alat ini digunakan untuk mengetahui tingkat kelembaban pada kulit wajah kering.Setelah diperoleh data hasil penelitian, dilakukan uji prasyarat analisis dan analisa data dengan uji normalitas dan uji homogenitas, menggunakan uji rata-rata satu pihak. Analisa data menunjukan thitung = 9,230. Pada taraf signifikan = 0,05 dan derajat kebebasan (dk = 8) maka ttabel = 2,31 dinyatakan thitung > ttabel,maka hipotesis nol (Ho) ditolak. Dengan demikian terdapat pengaruh penggunaan masker cokelat terhadap kelembaban kulit wajah kering.Diharapkan dari hasil penelitan ini dapat memberikan manfaat bagi pengembangan mata kuliah Perawatan Kulit Wajah dan Kosmetika Tradisional di Program Studi Tata Rias, Jurusan Ilmu Kesejahteraan Keluarga, Fakultas Teknik, Universitas Negeri Jakarta. Kata Kunci; cokelat, masker,  kelembaban,  kulit wajah kering, perawatan, beras merah