Induction of monoamine oxidase A-mediated oxidative stress and impairment of NRF2-antioxidant defence response by polyphenol-rich fraction of Bergenia ligulata sensitizes prostate cancer cells in vitro and in vivo

Prostate cancer (PCa) is a major cause of mortality and morbidity in men. Available therapies yield limited outcome. We explored anti-PCa activity in a polyphenol-rich fraction of Bergenia ligulata (PFBL), a plant used in Indian traditional and folk medicine for its anti-inflammatory and antineoplastic properties. PFBL constituted of about fifteen different compounds as per LCMS analysis induced apoptotic death in both androgen-dependent LNCaP and androgen-refractory PC3 and DU145 cells with little effect on NKE and WI38 cells. Further investigation revealed that PFBL mediates its function through upregulating ROS production by enhanced catalytic activity of Monoamine oxidase A (MAO-A). Notably, the differential inactivation of NRF2-antioxidant response pathway by PFBL resulted in death in PC3 versus NKE cells involving GSK-3β activity facilitated by AKT inhibition. PFBL efficiently reduced the PC3-tumor xenograft in NOD-SCID mice alone and in synergy with Paclitaxel. Tumor tissues in PFBL-treated mice showed upregulation of similar mechanism of cell death as observed in isolated PC3 cells i.e., elevation of MAO-A catalytic activity, ROS production accompanied by activation of β-TrCP-GSK-3β axis of NRF2 degradation. Blood counts, liver, and splenocyte sensitivity analyses justified the PFBL safety in the healthy mice. To our knowledge this is the first report of an activity that crippled NRF2 activation both in vitro and in vivo in response to MAO-A activation. Results of this study suggest the development of a novel treatment protocol utilizing PFBL to improve therapeutic outcome for patients with aggressive PCa which claims hundreds of thousands of lives each year.

Partial characterization of novel inulin-like prebiotic fructooligosaccharides of Sechium edule (Jacq.) Sw. (Cucurbitaceae) tuberous roots

The fruits and aerial parts of Sechium edule (Jacq.) Sw. (Cucurbitaceae) are a popular cook vegetable being used in different parts of the world with ethnomedicinal and pharmacological values. However, the beneficial health attributes of the tuberous roots have been less exploited. The present study aimed to determine the prebiotic potentiality of the storage carbohydrates from this part. The carbohydrate fractions were harvested by hot-water, cold-water, hot-acid, hot-alkali, and hot 80% ethanol treatments following the standard protocol. The fractions were tested for in vitro prebiotic efficacy, hypocholesterolemic and antioxidant potentials, and in vivo health attributes in Swiss albino mice. The partial characterization was performed by high-performance thin-layer chromatography (HPTLC) and spectroscopic analyses by Fourier-transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The highest prebiotic index was observed in hot-water and ethanol (Et-OH) fractions with the antioxidant IC₅₀ values of 35.46 ± 0.33 and 32.56 ± 0.48 µg/ml, respectively. The HPTLC, FT-IR, and ESI-MS analyses showed that the hot-water and Et-OH carbohydrate fractions are rich in low-degree polymerizing inulin-like fructooligosaccharides (FOS). The fractions had a significant prebiotic index, hypocholesterolemic, and antioxidant activities. The synbiotic combination of the fractions with the probiotic LAB improved gut colonization and gut immune enhancement with significantly lowered triglycerides, serum LDL, and serum VLDL cholesterols. A significantly enhanced HDL cholesterol level proves its health beneficial attributes comparable to the commercial inulin prebiotics. Thus, this plant's novel inulin-like FOS may substitute the high-cost commercial prebiotics for our daily life. PRACTICAL APPLICATIONS: Prebiotics are low-degree polymerizing oligosaccharide food ingredients having multifaceted health benefits. For this reason, there is an ever-increasing global demand for such novel prebiotics. Therefore, finding out some novel prebiotic from conventional food sources may provide an alternative dietary source to fulfill the consumer demand. Sechium edule is a famous cook vegetable used by many ethnic communities across the globe. For the first time, the study revealed novel inulin-like fructooligosaccharides in the tuberous roots having hypocholesterolemic and synbiotic efficacy with GRAS lactic acid bacteria.

Detection, Isolation and Partial Characterization of Antifungal Compound(s) Produced by Pediococcus acidilactici LAB 5

Pediococcus acidilactici LAB 5 produces antifungal compound(s), as well as bacteriocin, which was isolated from vacuum packed fermented meat. This bacterium exhibits varying degrees of antifungal activity against a number of food and feed borne molds and plant pathogenic fungi, such as Alternaria solani, Aspergillus fumigaus, A. parasiticus, Cladosporium herbarum, Colletotrichum acutatum, Curvularia lunata, Fusarium oxysporum, Microsporium sp, Mucor sp, and Penicillium sp. The production of antifungal compound(s) showed a great degree of media specificity and it was strictly restricted to MRS agar media. No production of antifungal compounds was detected in TGE, and TGE+ Tween 80 plates, though the latter supported the highest amount of bacteriocin production at 37°C after 24 hrs. Antifungal compound produced by LAB 5 was extracted using diethyl ether. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the compound were determined against Curvularia lunata. Chemically the antifungal substance was a phenolic compound with aromatic unsaturation, as evidenced by UV and IR spectroscopy. This is the first report of the production of antifungal compounds by Pediococcus acidilactici LAB 5.

Longterm storage of post-packaged bread by controlling spoilage pathogens using Lactobacillus fermentum C14 isolated from homemade curd

One potent lactic acid bacterial strain C14 with strong antifungal activity was isolated from homemade curd. Based on morphological as well as biochemical characters and 16S rDNA sequence homology the strain was identified as Lactobacillus fermentum. It displayed a wide antimicrobial spectrum against both Gram-positive and Gram-negative pathogenic bacteria, and also against number of food spoilage, plant and human pathogenic fungi. The cell free supernatant (CFS) of the strain C14 was also effective against the fungi tested. Inhibition of radial growth of Penicillium digitatum, Trichophyton rubrum and Mucor sp. was noticed in the presence of CFS of C14 even at low concentration (1%). More than 94.3 ± 1.6% and 91.5 ± 2.2% inhibition of conidial germination of P. digitatum and Mucor sp. were noticed in the presence of 10-fold-concentrated CFS of C14. Massive deformation of the fungal mycelia was observed by SEM studies, and losses of cellular proteins and DNA are also evident upon its treatment with C14. HPLC analysis revealed the presence of phenyl lactic acid, lactic acid along with some unidentified compounds in the antifungal extract. Challenge experiment showed immense potential of the strain C14 in preventing the spoilage of bread samples caused by Mucor sp. and Bacillus subtilis. The bread samples remained fresh upto 25 days even after inoculation with Mucor sp. (3.7 × 104 spores /ml) and B. subtilis (4.6 × 104 CFU /ml). Along with the antifungal properties, the isolated lactic acid bacterial strain also showed very good antioxidant activities. Unchanged level of liver enzymes serum glutamic pyruvic transaminase and serum glutamic oxaloacetic transaminase in albino mice upon feeding with C14 also suggested non-toxic nature of the bacterial isolate.

Sunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity

BACKGROUND

Nanotechnology is now regarded as a distinct field of research in modern science and technology with multifaceted areas including biomedical applications. Among the various approaches currently available for the generation of metallic nanoparticles, biogenic synthesis is of increasing demand for the purpose of green nanotechnology. Among various natural sources, plant materials are the most readily available template-directing matrix offering cost-effectiveness, eco-friendliness, and easy handling. Moreover, the inherent pharmacological potentials of these medicinal plant extracts offer added biomedical implementations of the synthesized metal nanoparticles.

RESULTS

A robust practical method for eco-friendly synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum (Tulsi) as both reducing and capping agent, under the influence of direct sunlight has been developed without applying any other chemical additives. The nanoparticles were characterized with the help of UV-visible spectrophotometer and transmission electron microscopy (TEM). The prepared silver nanoparticles exhibited considerable antibacterial activity. The effects were more pronounced on non-endospore-forming Gram-positive bacteria viz., Staphylococcus aureus, Staphylococcus epidermidis, and Listeria monocytogenes than endospore-forming species Bacillus subtilis. The nanoparticles also showed prominent activity on Gram-negative human pathogenic Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and plant pathogenic Pantoea ananatis. A bactericidal mode of action was observed for both Gram-positive and Gram-negative bacteria by the nanoparticles.

CONCLUSIONS

We have developed a very simple, efficient, and practical method for the synthesis of silver nanoparticles using aqueous leaf extract of O. sanctum under the influence of direct sunlight. The biosynthesis of silver nanoparticles making use of such a traditionally important medicinal plant without applying any other chemical additives, thus offers a cost-effective and environmentally benign route for their large-scale commercial production. The nanoparticles dispersed in the mother solution showed promising antibacterial efficacy. Graphical AbstractSunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity.

Chronic inflammation and cancer: potential chemoprevention through nuclear factor kappa B and p53 mutual antagonism

Activation of nuclear factor-kappa B (NF- κB) as a mechanism of host defense against infection and stress is the central mediator of inflammatory responses. A normal (acute) inflammatory response is activated on urgent basis and is auto-regulated. Chronic inflammation that results due to failure in the regulatory mechanism, however, is largely considered as a critical determinant in the initiation and progression of various forms of cancer. Mechanistically, NF- κB favors this process by inducing various genes responsible for cell survival, proliferation, migration, invasion while at the same time antagonizing growth regulators including tumor suppressor p53. It has been shown by various independent investigations that a down regulation of NF- κB activity directly, or indirectly through the activation of the p53 pathway reduces tumor growth substantially. Therefore, there is a huge effort driven by many laboratories to understand the NF- κB signaling pathways to intervene the function of this crucial player in inflammation and tumorigenesis in order to find an effective inhibitor directly, or through the p53 tumor suppressor. We discuss here on the role of NF- κB in chronic inflammation and cancer, highlighting mutual antagonism between NF- κB and p53 pathways in the process. We also discuss prospective pharmacological modulators of these two pathways, including those that were already tested to affect this mutual antagonism.

Vermicomposting of Tea Factory Coal Ash: metal accumulation and metallothionein response in Eisenia fetida (Savigny) and Lampito mauritii (Kinberg)

Earthworms can accumulate heavy metals in their intestines to a great extent. Impact of feed materials and duration of metal exposure on natural activity of earthworms are rather unclear; this investigation therefore addresses the impact of metal rich Tea Factory Coal Ash (TFCA) on reproduction, composting and metal accumulation ability of Eisenia fetida and Lampito mauritii. Earthworm count and cocoon production increased significantly during vermicomposting. pH of the vermicomposted mixtures shifted toward neutrality, total organic C decreased substantially and total N enhanced significantly compared to composting. High heavy metal (Mn, Zn, Cu, As) accumulation was recorded in the intestine of both the earthworm species. Moreover, gradual increase in the metal-inducible metallothionein concentration indicated the causal mechanism of metal accumulation in these species. TFCA+cow dung (CD) (1:1) were most favorable feed mixture for E. fetida and TFCA+CD (1:2) were good for L. mauritii in regard to metal accumulation and compost quality.

Phosphate solubilizing ability of Emericella nidulans strain V1 isolated from vermicompost

Phosphorus is one of the key factors that regulate soil fertility. Its deficiencies in soil are largely replenished by chemical fertilizers. The present study was aimed to isolate efficient phosphate solubilizing fungal strains from Eisenia fetida vermicompost. Out of total 30 fungal strains the most efficient phosphate solubilizing one was Emericella (Aspergillus) nidulans V1 (MTCC 11044), identified by custom sequencing of beta-tubulin gene and BLAST analysis. This strain solubilized 13 to 36% phosphate from four different rock phosphates. After three days of incubation of isolated culture with black Mussorie phosphate rock, the highest percentage of phosphate solubilization was 35.5 +/- 1.01 with a pH drop of 4.2 +/- 0.09. Kinetics of solubilization and acid production showed a linear relationship until day five of incubation. Interestingly, from zero to tenth day of incubation, solubility of soil phosphate increased gradually from 4.31 +/- 1.57 to 13.65 +/- 1.82 (mg kg(-1)) recording a maximum of 21.23 +/- 0.54 on day 45 in respect of the V1 isolate. Further, enhanced phosphorus uptake by Phaseolus plants with significant pod yield due to soil inoculation of Emericella nidulans V1 (MTCC 11044), demonstrated its prospect as an effective biofertilizer for plant growth.

A comparative antibacterial evaluation of raw and processed Guñjā (Abrus precatorius Linn.) seeds

Background:

Seed of Guñjā (Abrus precatorius Linn.), a known poisonous drug, is used extensively in various ayurvedic formulations with great therapeutic significance. Ayurveda recommends the administration of Guñjā in diseases like Indralupta (alopecia), Śotha (edema), Kṛmi (helminthes), Kuṣṭha (skin diseases), Kaṇḍu (itching), Prameha (urinary disorders) etc., after being treated with specific Śodhana (purification) procedures.

Objective:

To assess the antimicrobial action of of raw and Śhodhita (Processed) Guñjā seeds

Methods:

Guñjā seeds after being processed with Godugdha (cow's milk), Nimbu swarasa (Lemon juice), Kāñjī (Sour gruel) and water, as the media, were evaluated for its antibacterial effect against clinically important bacterial strains using agar well diffusion method.

Results:

Aqueous extracts of raw seeds of Guñjā exert its antibacterial effect on both Gram positive, as well as Gram negative bacteria but none of the Śodhita Guñjā seeds showed any bactericidal effect on any bacterial strains. Chloroform extracts of all the Śodhita Guñjā seed extracts could inhibit bacterial growth but with variations

Conclusion:

The study displayed that chloroform extracts of raw and śodhita samples for bacterial study were much sensitive than the aqueous extracts.

A new pentacyclic triterpene with potent antibacterial activity from Limnophila indica Linn. (Druce)

A new pentacyclic triterpenoid constituent, characterized as 3-oxo-olean-12(13),18(19)-dien-29α-carboxylic acid (1) on the basis of detailed spectral studies, was isolated from the aerial parts and roots of Limnophila indica (Scrophulariaceae). Compound 1 exhibited considerable antibacterial activity against three Gram-positive bacteria viz. Bacillus subtilis, Staphylococcus aureus and Listeria monocytogenes (MICs within a range of 25-30 μg/ml) and moderate activity against four Gram-negative bacteria Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and Pantoea ananatis (MICs within a range of 30-100 μg/ml). The plant pathogenic bacterium P. ananatis and human pathogenic S. typhimurium responded at comparatively higher concentrations of the compound 1, which were 75 and 100 μg/ml respectively. The compound inhibited the growth of Gram-positive B. subtilis and Gram-negative P. aeruginosa completely with a clear bactericidal mode of action at their MIC values. The compound upon treatment on both B. subtilis and P. aeruginosa released substantial amount of nucleic acid in the external medium and also effected the change of morphology towards pleomorphicity, thereby indicating its probable action on cell membrane. Furthermore, the triterpenoid 1 was found not to inhibit a probiotic lactic acid bacterium Lactococcus lactis subsp. lactis LABW4 under in vitro condition and to possess no toxicity in Swiss albino mice.

Effect of fungicides and insecticides on growth and enzyme activity of four cyanobacteria

Cyanobacterial populations introduced into crop fields as biofertilizer become non-target organisms for the pesticides and fungicides applied in the field. Effect of four commonly used pesticides viz. Bagalol, Mancozeb (fungicides), Thiodan and Phorate (insecticides) was studied on growth and different enzymes of four cyanobacterial species viz. Nostoc ellipsosporum, Scytonema simplex, Tolypothrix tenuis, and Westiellopsis prolifica. EC 50 concentration of each pesticide was determined for all cyanobacteria. Bagalol and Thiodan were found to be the most toxic. Both the fungicides and insecticides inhibited the activity of nitrogenase and glutamine synthetase (GS) at EC 50 concentration in all the four species studied. Bagalol incurred maximum inhibition of nitrogenase and GS activity on N. ellipsosporum and S. simplex while Thiodan and Phorate had maximum effect on T. tenuis, and W. prolifica. Mancozeb had lesser effect on all the above enzymes. One catabolic enzyme of carbohydrate metabolism, isocitrate dehydrogenase (ICDH) and one anabolic enzyme isocitrate lyase (ICL), which is related to glyoxylate pathway as well as gluconeogenesis, were also assayed. Cell free extracts of cyanobacteria treated with pesticides for 7 days show a drastic reduction of ICDH activity. ICL activity was induced in the organisms when treated with pesticides.

Evaluation of the antimicrobial potential of two flavonoids isolated from limnophila plants

The antimicrobial potential of two bioflavonoids, i.e., 5,7-dihydroxy-4',6,8-trimethoxyflavone (1) and 5,6-dihydroxy-4',7,8-trimethoxyflavone (2), isolated from Limnophila heterophylla Benth. and L. indica (Linn.) Druce (Scrophulariaceae), respectively, were evaluated against the microbial strains Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Alternaria solani, and Candida albicans. Compounds 1 and 2 exhibited moderate but broad antimicrobial activities against both Gram-positive and Gram-negative bacteria and also against the fungal pathogens. Moreover, the mechanism of action of 1 and 2 on the cellular functions or structures of some of the microorganisms was studied. Compound 1 showed a bactericidal effect against E. coli and S. aureus (MICs of 200 and 250 μg/ml, resp.), while compound 2 was found to effectively kill B. subtilis by cell lysis. The growth of A. solani and C. albicans was inhibited by compounds 1 and 2, respectively. The effects of the flavonoids on the cellular structures and the carbohydrate metabolic pathways were studied by scanning electron microscopy (SEM) of the treated cells and by assessing the specific activity of key enzymes of the pathways, respectively. At sublethal doses, they enhanced the activity of gluconeogenic fructose bisphosphatase, but decreased the activity of phosphofructokinase and isocitrate dehydrogenase, the key enzymes of the EmbdenMeyerhofParnas pathway and the tricarboxylic acid cycle, respectively.

Inactivation of indispensable bacterial proteins by early proteins of bacteriophages: implication in antibacterial drug discovery

Bacteriophages utilize host bacterial cellular machineries for their own reproduction and completion of life cycles. The early proteins that phage synthesize immediately after the entry of their genomes into bacterial cells participate in inhibiting host macromolecular biosynthesis, initiating phage-specific replication and synthesizing late proteins. Inhibition of synthesis of host macromolecules that eventually leads to cell death is generally performed by the physical and/or chemical modification of indispensable host proteins by early proteins. Interestingly, most modified bacterial proteins were shown to take part actively in phage-specific transcription and replication. Research on phages in last nine decades has demonstrated such lethal early proteins that interact with or chemically modify indispensable host proteins. Among the host proteins inhibited by lethal phage proteins, several are not inhibited by any chemical inhibitor available today. Under the context of widespread dissemination of antibiotic-resistant strains of pathogenic bacteria in recent years, the information of lethal phage proteins and cognate host proteins could be extremely invaluable as they may lead to the identification of novel antibacterial compounds. In this review, we summarize the current knowledge about some early phage proteins, their cognate host proteins and their mechanism of action and also describe how the above interacting proteins had been exploited in antibacterial drug discovery.

Survival, nodulation and N2 fixation ability of root nodule bacteria under different nutritional regimes

Eleven strains of Rhizobium and five strains of Bradyrhizobium were examined for their viability as well nodulation and nitrogen fixation ability after storage under different conditions for two years. The storage conditions comprised lateritic soil, lateritic soil plus 1% mannitol, lateritic soil plus 0.1% yeast extract, lateritic soil plus 1% mannitol and 0.1% yeast extract, organic soil, organic soil plus 1% mannitol, organic soil plus 0.1% yeast extract, organic soil plus 1% mannitol and 0.1% yeast extract, and sterile distilled water. All the slow growing strains showed better viability than the fast growing strains in any of these conditions. The survived strains maintained their nodulation ability about 50-60% after one year and 40-50% after two years of preservation as compared to control, but the nodulation ability in sterile distilled water was very poor. Acetylene reduction activity in the nodules was found to be 70-90% and 50-70% after 12 and 24 months of preservation, respectively. The strains retained their phenotypic characters like antibiotic resistance and salt tolerance up to their highest survivability in respective nutritional condition.

Antimicrobial activity of saponins from Acacia auriculiformis

Acaciaside A and B, two acylated bisglycoside saponins originally isolated from the funicles of Acacia auriculiformis, are known to have antihelminthic activity. Their antifungal and antibacterial activities were investigated. Complete inhibition of conidial germination of Aspergillus ochraceous and Curvularia lunata was recorded at 300 microg/ml or less whereas to inhibit the growth of Bacillus megaterium, Salmonella typhimurium and Pseudomonas aeruginosa 700 microg/ml or higher concentrations of the mixture was required. Two catabolic enzymes, phosphofructokinase and isocitrate dehydrogenase, responded differentially in fungi and bacteria against sublethal concentrations of the compound when assayed from their cell free extracts. An increased specific activity of the enzymes in bacteria and a decrease activity in fungi indicate a possible different mechanism of inhibition of saponins on the organisms tested.

An epidemiological study of the risk factors of occupational diseases in coal handling plant of a thermal power station

Anthropometry and morbidity profile of fifty randomly selected workers of coal handling plant at a thermal power station of West Bengal having at least five years experience were studied. The mean value of their age, duration of present job and Body Mass Index (BMI) were 34.8 years, 7.86 years and 19.24 respectively. As they were exposed to coal dust (Av. concentration 300-350 mg/M3 of air), warmth (Ambient temperature 40 +/- 5 degrees C), humidity (Relative humidity 80 +/- 5%) and noise [Av. 80 dB(A)], respiratory system was most commonly (72%) effected followed by greying of hair (5.6%), Cloth dusters used by some could not render any discernable protective effect. Addiction was also prevent (62%). Use of proper protective equipments (PPE) supplemented by adequate preplacement and periodic medical examination followed by successful rehabilitation were suggested.

A study of energetics of cooperative interaction using a mutant lambda-repressor

A lambda-repressor mutant, S228N, which is defective in tetramer formation in the free state but retains full cooperativity, was studied in detail. Isolated single operator-bound S228N repressor shows association properties similar to those of the wild-type repressor. Fluorescence anisotropy studies with dansyl chloride-labeled repressor show a dimer-monomer dissociation constant of around 10(-5) M. The structure of the mutant repressor was studied by circular dichroism, acrylamide quenching and sulfhydryl reactivity at protein concentrations of < or =10(-6) M, where it is predominantly monomeric. The results suggest no significant perturbations in the structure of the S228N mutant repressor from that of the wild-type repressor. Urea denaturation studies also indicate no significant change in the stability of the repressor. The results were used to calculate energetics of loop formation in the cooperative binding process.

Amino acid changes in the repressor of bacteriophage lambda due to temperature-sensitive mutations in its cI gene and the structure of a highly temperature-sensitive mutant repressor

The mutant cIts genes from seven different lambdacIts phages carrying tsU50, tsU9, tsU46, ts1, tsU51, tsI-22 and ts2 mutations were cloned in plasmid. The positions of these mutations and the resulting changes of amino acids in the repressor were determined by DNA sequencing. The first four mutations mapping in the N-terminal domain show the following changes: I21S, G53S, A62T and V73A, respectively. Of the three remaining mutations mapping in the C-terminal domain, cItsI-22 and cIts2 show N207T and K224E substitutions respectively, while the mutant cItsU51 gene carries F141I and P153L substitutions. Among these ts repressors, CIts2 having the charge-reversal change K224E was overexpressed from tac promoter in a plasmid and purified, and its structure and function were studied. Operator-binding studies suggest that the ts2 repressor is somewhat defective in monomer-dimer equilibrium and/or cooperativity even at permissive temperatures and loses its operator-binding ability very rapidly above 25 degrees C. Comparative studies of fluorescence and CD spectra, sulfhydryl group reactivity and elution behaviour in size-exclusion HPLC of both wild-type and ts2-mutant repressors at permissive and non-permissive temperatures suggest that the C-terminal domain of the ts2 repressor carrying a K224E substitution has a structure that does not favor tetramer formation at non-permissive temperatures.

Identification of an early positive regulatory gene of mycobacteriophage L1

Among 14 temperature-sensitive, growth-defective mutants of mycobacteriophage L1 showing a lysis-defective phenotype at 42 degrees C, six are, in addition, defective in phage DNA synthesis at 42 degrees C. In the present study, we show that one of the latter six mutants, L1G27ts901, is also defective in the synthesis of both an L1-specific exonuclease (a representative delayed early protein), and of RNA in both the delayed early and late periods but not in the immediate early period. The results of a temperature-shift experiment suggest that the synthesis of L1 exonuclease is regulated by G27 at the level of transcription. Furthermore, the temperature-sensitive defect in delayed early and late RNA synthesis could be largely overcome when the L1G27ts901-infected culture was shifted from 32 to 42 degrees C at 10 min but not at zero time post-infection. These results suggest that the primary effect of the G27ts901 mutation is to make the phage defective in transcription of delayed early genes at 42 degrees C, and the defect in late RNA synthesis by this mutant is a secondary effect which is caused by its inability to express regulatory gene products. We conclude that G27 is involved in the positive regulation of expression of the delayed early genes of L1 at the transcriptional level.

Role of the C-terminal tail region in the self-assembly of lambda-repressor

Acrylamide quenching of the tryptophan fluorescence of the lambda-repressor at different protein concentrations indicates that one of the three tryptophan residues, W129, W142, and W230, undergoes a change in environment upon self-assembly, from dimer to associated species. Quenching data suggest that this tryptophan residue is inaccessible to low concentrations of acrylamide and is blue-shifted in the associated form. In the dimer, this tryptophan residue is highly accessible to acrylamide and is red-shifted. NBS oxidation, at protein concentrations which favor the associated form, showed that this tryptophan is also significantly protected from NBS oxidation. HPLC peptide mapping of NBS-oxidized lambda-repressor, amino acid analysis, and sequencing indicate that the protected, blue-shifted tryptophan is tryptophan 230. A mutant repressor (F235C) was specifically labeled at Cys 235 with an environment-sensitive probe, acrylodan. The acrylodan fluorescence of the labeled F235C lambda-repressor undergoes a significant blue-shift, accompanied by fluorescence enhancement, upon protein association. Along with other genetic evidence, these results suggest involvement of the C-terminal tail region in the self-assembly of the lambda-repressor.

Isolation, characterization, and mapping of temperature-sensitive mutations in the genes essential for lysogenic and lytic growth of the mycobacteriophage L1

Forty temperature-sensitive mutations affecting lytic growth and eight affecting both establishment and maintenance of lysogeny of the temperate mycobacteriophage L1 have been isolated. All of the latter mutations form one complementation group and map within a very short region around the 15% coordinate of the L1 genome; these affect a single gene, cl, coding for the L1 repressor. The former 40 mutations form 28 complementation groups, identifying 28 different genes, G1-G28, essential for the lytic growth of L1. These genes have been mapped using the Gts mutations. Of the 28 Gts mutants, 14 are defective in host lysis at 42 degrees but not at 32 degrees while the other 14 can lyse the host at both temperatures. Among the former 14 Gts mutants, 6 are also defective in L1 DNA synthesis at 42 degrees, and they map in two different clusters, 4 around 65% and 2 around 84% of the L1 genome.

A fluorescence anisotropy study of tetramer-dimer equilibrium of lambda repressor and its implication for function

Tetramer-dimer equilibrium of lambda repressor has been studied by fluorescence anisotropy techniques. We have chosen 1-dimethylamino naphthalene-5-sulfonyl chloride (dansyl chloride)-labeled repressor to study the dissociation-association equilibrium, because of relatively long life-time of the probe (> 10 ns). Polarization of the dansyl-labeled repressor decreases with decreasing protein concentrations in the range of 20 to 0.2 microM. The decrease of anisotropy was shown to be due to reversible dissociation of the protein. Size exclusion high-performance liquid chromatography studies and polyacrylamide gel electrophoresis under native conditions (Ferguson plot) confirmed that at around 20 microM concentrations the repressor exists in predominantly tetrameric form, whereas in lower concentrations it exists in predominantly dimer form. A dissociation constant of 2.3 +/- 0.9 microM was estimated in 0.1 M potassium phosphate, pH 8.0, at 25 degrees C. A stoichiometric amount of isolated single operator shifted the tetramer-dimer equilibrium toward the dimer. Increased ionic strength had only a modest effect on the dissociation constant. The thermodynamic constants for the dissociation reaction calculated from the Van't Hoff plot was +26.6 kcal/mol for delta H and +64.7 e.u. for delta S. The rotational correlation times derived from isothermal Perrin plot indicated elongated dimers and tetramers.

Multiphasic denaturation of the lambda repressor by urea and its implications for the repressor structure

Urea denaturation of the lambda repressor has been studied by fluorescence and circular dichroic spectroscopies. Three phases of denaturation could be detected which we have assigned to part of the C-terminal domain, N-terminal domain and subunit dissociation coupled with further denaturation of the rest of the C-terminal domain at increasing urea concentrations. Acrylamide quenching suggests that at least one of the three tryptophan residues of the lambda repressor is in a different environment and its emission maximum is considerably blue-shifted. The transition in low urea concentration (midpoint approximately 2 M) affects the environment of this tryptophan residue, which is located in the C-terminal domain. Removal of the hinge and the N-terminal domain shifts this transition towards even lower urea concentrations, indicating the presence of interaction between hinge on N-terminal and C-terminal domains in the intact repressor.

An operator-induced conformational change in the C-terminal domain of the lambda repressor

4,4'-bis(1-anilino-8-naphthalenesulfonic acid (Bis-ANS), an environment-sensitive fluorescent probe for hydrophobic region of proteins, binds specifically to the C-terminal domain of lambda repressor. The binding is characterized by positive cooperativity, the magnitude of which is dependent on protein concentration in the concentration range where dimeric repressor aggregates to a tetramer. In this range, positive cooperativity becomes more pronounced at higher protein concentrations. This suggests a preferential binding of Bis-ANS to the dimeric form of the repressor. Binding of single operator OR1 to the N-terminal domain of the repressor causes enhancement of fluorescence of the C-terminal domain bound Bis-ANS. The binding of single operator OR1 also leads to quenching of fluorescence of tryptophan residues, all of which are located in the hinge or the C-terminal domain. Thus two different fluorescent probes indicate an operator-induced conformational change which affects the C-terminal domain. The significance of this conformational change with respect to the function of lambda repressor has been discussed.

Isolation and preliminary characterization of Escherichia coli mutants resistant to lethal action of the bacteriophage lambda P gene

Both spontaneous and NTG-induced mutants of Escherichia coli 594 insensitive to the lethal action of lambda P gene were isolated and called rpl (resistant to P lethality). These mutants were of two types, showing different phenotypes. On type I rpl mutants, lambda cl- and lambda v1v3 did not plate, while lambda vir, lambda cl- c17, lambda imm434, and lambda imm21 did; plasmid pMR45 carrying the lambda P gene could not complement lambda imm21P- phage in type I mutants. On the other hand, the type II rpl mutants support the growth of all the above phages including lambda cl-. Neither type of rpl mutation affects growth of the bacteria.

Bacteriophage lambda P gene shows host killing which is not dependent on lambda DNA replication

Bacteriophage lambda, having a mutation replacing glycine by glutamic acid at the 48th codon of cro, kills the host under N- conditions; we call this the hk mutation. In lambda N-N-cl-hk phage-infected bacteria, the late gene R is expressed to a significant level, phage DNA synthesis occurs with better efficiency, and the Cro activity is around 20% less, all compared to those in lambda N-N-cl-hk(+)-infected bacteria. Segments of lambda DNA from the left of pR to the right of tR2, carrying cro, cII, O, P, and the genes of the nin5 region from the above hk and hk+ phages, were cloned in pBR322. Studies with these plasmids and their derivatives having one or more of the lambda genes deleted indicate that the hk mutation is lethal only when a functional P gene is also present. When expression of P from pR is elevated, due to the deletion of tR1, host killing also occurs without the hk mutation. We conclude that the higher levels of P protein, produced either (1) when cro has the hk mutation or (2) when tR1 is deleted, are lethal to the host. We also show that due to the hk mutation, the Cro protein becomes partially defective in its negative regulation at pR, resulting in the expression of P to a lethal level even in the absence of N protein-mediated antitermination. This P protein-induced host killing depends neither on lambda DNA replication nor on any other gene functions of the phage.

Enzymes of carbohydrate metabolism in fast-growing Rhizobium grown on hexoses or succinate

Enzymatic evidence supports that succinate mediates repression of hexose-catabolising enzymes in fast-growing Rhizobium sp. (Cicer arietinum). Enzymes of the Embden-Myerhof-Parnas, Entner-Doudoroff and pentose phosphate pathways were found present in hexose-grown cells but not in succinate-grown cells. These however could be induced by the presence of hexoses.

Structure and function of the repressor of bacteriophage lambda. III. Molecular cloning of the high-affinity mutant cI gene of lambda and studies of the properties of the clones

The high-affinity mutant cI gene of lambda cIha (Nag et al. 1984) was cloned in the multicopy plasmid pBR322. In the resulting plasmid, pMD 102, a lacUV5 promoter was inserted giving the lacUV5-cIha fusion plasmid pMD 205. Bacteria carrying pMD 102 and pMD 205 contain 2.5 and 15 times, respectively, the level of repressor in a monolysogen of lambda cIha. Results of the study of certain properties of the bacteria carrying these plasmids suggest that the ha repressor also has a higher affinity for the virulent mutant operators as well as the prm promoter of lambda.

Structure and function of the repressor of bacteriophage lambda. II. Isolation and characterization of a lambda mutant which produces repressor having higher affinity for operators

By mutagenizing a lambda cIts (lambda cI857) lysogen, a lambda mutant has been isolated with a wild-type phenotype. This mutant phage lysogenizes with low efficiency and produces a low burst. Though the initial rates of repressor synthesis in Escherichia coli after infection with wild-type and mutant lambda are the same, the maximum level of repressor that is synthesized in the latter case is only about 30% of that synthesized in the former. Virulent lambda plates on the lysogen of mutant lambda with slightly less efficiency producing very tiny plaques. Operator-binding studies made in vitro with purified mutant and wild-type repressors show that the binding curve of the former repressor is a rectangular hyperbola while that of the latter is sigmoid. The half-lives of the complexes of mutant and wild-type repressors with right operator are 133 and 27 min, respectively. All these results suggest that the mutant repressor possibly has a higher affinity for the operators. This mutant has been named lambda cIha (ha = high affinity).

A simple procedure for large-scale preparation of pure plasmid DNA free from chromosomal DNA from bacteria

A very simple, inexpensive procedure for preparing pure plasmid DNA from bacteria is described. In this method, lysozyme-induced spheroplasts are made in presence of 833 micrograms/ml of ethidium bromide which are then lysed by a mixture of Brij 58 and sodium deoxycholate, and the lysate is centrifuged at 48,000 g for 25 min whereby about 99.9% of total chromosomal DNA is pelleted. From the supernatant containing plasmid DNA, the proteins are removed by phenol extraction and the major part of RNA by CaCl2 precipitation, and finally the small amount of residual RNA is removed by RNase treatment. The average yield of pBR322 DNA from 1 liter of amplified culture by this procedure is 2 to 2.5 mg and the preparation is highly pure, containing only about 0.005% of total yield as chromosomal DNA contaminant. Moreover, the substrate activity and the transforming ability of the plasmid DNA prepared by this method remain unaffected.

Studies on polylysogens containing lambda N-cI- prophages. II. Role of high multiplicities in lysogen formation by lambda N-cI- phage

Results of the experiments presented in this paper show that lambda N-cI- phage can lysogenize a nonpermissive host Escherichia coli when it infects at very high multiplicities (around 100), and lambda N-cI-cII- and lambda cIII-N-cI- lysogenize poorly at similar high multiplicities. The latter two phages lysogenize with appreciable frequency when either lambda N-cI- or lambda int-cN-cI-cII- is used as helper. The phages, lambda N-cI-, lambda N-cI-cII-, and lambda cIII-N-cI- can lysogenize also at relatively low m.o.i. of 20 in presence of the above lambda int-c helper, and the lambda int-cN-cI-cII- phage alone forms converted lysogens at an m.o.i. as low as 12. All these results suggest that the establishment of prophage integration by lambda N-cI- is positively regulated, like lambda N+cI+ phage, by the cII/cIII-promoted expression of the int gene of lambda, and under the N- condition, high multiplicities are needed to provide optimum levels of cII and cIII products, especially the latter.

An Escherichia coli mutant with a temperature-sensitive function affecting bacteriophage Qbeta RNA replication

We report the isolation of E. coli mutant capable of supporting replication of bacteriophage Qbeta at 33 degrees, but not at 40 degrees. Coliphages f2, R23, fd, and yamma formed plaques on mutant cells at both temperatures. Temperature-shift experiments showed that bacteriophage Q beta replication was blocked in the mutant within the first 20-30 min of infection. The defect did not prevent translation of the Qbeta polymerase gene or assembly of catalytically active Qbeta replicase molecules. In fact, mutant cells infected at 40 degrees hyperinduced replicase active both in vivo and in vitro. However, zone sedimentation of the in vivo RNA product showed it to consist of partially double-stranded material sedimenting at 9 S, with little or no viral 32S RNA. The 9S RNA was also found, along with a predominant peak of 32S RNA in parental cells infected at 40 degrees, but not in cells infected at 33 degrees. It thus appears that the temperature-sensitive component is required for viral RNA replication, but not for other RNA synthesis catalyzed by the replicase. Uninfected mutant cells grew normally at 40 degrees in nutrient broth, but not in glucose- or glycerol-minimal media. Revertants selected for their abillity to grow in minimal medium at 40 degrees also supported bacteriophage Qbeta replication at 40 degrees.

Heat-sensitive DNA-binding activity of the cI product of bacteriophage lambda

The binding of lambda gene cI product to lambda DNA was studied at temperatures from 0 degrees C to 46 degrees C. Binding activity of the products of cIts mutants was higher at 22 degrees C than at 0 degrees C, 26 degrees C or 30 degrees C. Both cI+ and cIts products lost DNA-binding activity at 46 degrees C, but after subsequent cooling to 22 degrees C, they regained 50-100% of their activity.

Metabolism of Inositol Phosphates: I. Phytase Synthesis during Germination in Cotyledons of Mung Beans, Phaseolus aureus

The degradation of phytin in germinating mung bean seeds has been found to be associated with the increased activity of phytase in the cotyledon. In the differentiated embryo the increase of this activity is very low all throughout the growth periods studied. Phytase appears in the cotyledon during germination. No activity has been detected in the cotyledons of unsoaked seeds. Cycloheximide (10(-6) M) inhibits the appearance of phytase by 61% during 24 and 48 hours after the start of germination. This phytase increase is dependent on the synthesis of new RNA in the cotyledon. Synthesis of DNA is not detected in the cotyledon during germination.