New bacteriophages active on strains of Hyphomicrobium

Fifty-five lytic bacteriophages isolated from water and soil samples were active on many strains of the genus Hyphomicrobium. The optimal isolation procedure was an adsorption method in which samples from a habitat similar to that of the respective host bacterium were used as the phage inoculum. According to the morphology and nucleic acid type these bacteriophages belonged to different families: Myoviridae (type A1: five phages); Styloviridae (type B1: 33 phages; type B2: eight phages) and Podoviridae (type C1: nine phages). The Styloviridae (type B1) appeared in two morphological variants (tails flexible or rigid). All phages investigated were specific for the genus Hyphomicrobium and were unable to lyse members of other genera of hyphal, budding bacteria (e.g. Hyphomonas, Pedomicrobium, genus D, genus T). The host specificity of 42 phages was tested with 156 Hyphomicrobium strains: 122 strains were lysed by at least one of these phages, but 34 Hyphomicrobium strains were not susceptible. Morphotype B1 phages with identical morphology could be distinguished according to their host-range properties on prophage-containing Hyphomicrobium strains. With regard to differences in morphology and host range, 25 phages were selected for more detailed investigations. From these phages DNA was isolated; the melting transition midpoints (Tm) ranged from 67 to 93 degrees C. The upper and higher values suggested the presence of DNA modifications. Six different adsorption patterns could be distinguished among the Hyphomicrobium phages. Preferred attachment sites were the proximal pole of the mother cell, the hyphal tip, the distal pole of the bud, and the distal pole of the swarmer cell.     

l-Serine production using a resting cell system of Hyphomicrobium strains

Twenty-six strains of methylotrophic hyphomicrobia were examined for their ability to produce l-serine from methanol and glycine in a resting cell reaction. l-Serine productivity of over 5 mg/ml was observed in 7 strains, and Hyphomicrobium sp. NCIB10099 was found to exhibit the highest productivity. Under optimized conditions using this bacterium, 45 mg/ml l-serine was produced from 100 mg/ml glycine and 88 mg/ml methanol in 3 d. The high l-serine degrading activity of the bacterium was entirely suppressed by adding an appropriate amount of CdCl₂ (ca. 1 mM), resulting in an enhanced conversion ratio of glycine to l-serine (ca. 100% molar conversion).     

两株链霉菌对非洲菊生长和生理生化指标的影响

本研究以非洲菊(Gerbera jamesonii)为试材,采用不同浓度的脱叶链霉菌FT05W和深蓝链霉菌ZEA17I孢子悬浮液浇灌盆栽非洲菊,筛选出非洲菊的最佳施用浓度,探索两株链霉菌对非洲菊生长和生理生化指标的影响,为非洲菊生产上科学合理施用链霉菌提供理论依据.结果 表明:脱叶链霉菌FT05W和深蓝链霉菌ZEA17...     

Some physiological studies in two species of phytophthora

Summary The paper deals with some physiological studies viz., (1) Production of enzymes (2) Effect of chemicals and sugar solutions and (3) Utilization of amino acids, by two species ofPhytophthora i.e.,Phytophthora palmivora Butler andP. parasitica Dast. var.macrospora Ashby., isolated from rotten fruits ofAchras sapota andAnona squamosa respectively.In the study of production of extra-cellular enzymes, it was found that both the isolates ofPhytophthora produced enzymes like inulase, amidase, emulsin and diastase in small quantity.Among the various chemicals and salt solutions used to study their effects in the formation of sporangia; it was observed that these were remarkably produced in abundance by both the species ofPhytophthora specially in the chemical solutions like sodium chloride, potassium nitrate, sodium thiosulphate and potassium permanganate. On the other hand, chemical solutions like strontium sulphate, potassium chromate, ammonium oxalate, zinc sulphate, copper sulphate, potassium sulphate, strontium nitrate and ferrous sulphate completely ceased the sporangial development. Among the various sugar solutions tried, dextrose, galactose, glucose, laevulose and fructose accelerated sporangial formation.An attempt was also made to study the effect of various amino acids singly or in combination on growth and sporulation. Both the isolates under study, utilized L-Arganine monohydrochloride and DL-Aspartic acid, hence these were growth promoters. It is interesting to note that the growth of the isolates was good, only when DL-Norleucine and DL-Methionine (both growth inhibitors) were provided in combination.Forms a part of Senior author's M.Sc. (Agriculture) Thesis, University of Poona, (Poona) India.Respectively, Ex-Jr. Res. Fellow, I.C.A.R. New Delhi; Professor of Plant Pathology and Principal, College of Agriculture, Junagad (Gujarat); and Plant Pathologist, Wheat Rust Research Station, Mahabaleshwar (Poona), India.     

Evidence for the existence of isocitrate lyase activity in methylotrophic Hyphomicrobium strains

Abstract Isocitrate lyase activities were detected in a range of 0.096–0.212 units mg⁻¹ in cell-free extracts of all tested Hyphomicrobium strains grown on methanol as a sole carbon source, although the activities were rapidly lost during storage at 4 °C. When cell-free extracts were incubated with dithiothreitol, after storage the recovery of activity was observed, indicating the involvement of a labile sulfhydryl group in the enzyme. This confirmed the distribution of unstable isocitrate lyase in the genus Hyphomicrobium , and, contrary to previous observations, the operation of the ic ⁺-serine pathway was suggested for the assimilation of one-carbon compounds.     

Two component systems: physiological effect of a third component

Signal transduction systems mediate the response and adaptation of organisms to environmental changes. In prokaryotes, this signal transduction is often done through Two Component Systems (TCS). These TCS are phosphotransfer protein cascades, and in their prototypical form they are composed by a kinase that senses the environmental signals (SK) and by a response regulator (RR) that regulates the cellular response. This basic motif can be modified by the addition of a third protein that interacts either with the SK or the RR in a way that could change the dynamic response of the TCS module. In this work we aim at understanding the effect of such an additional protein (which we call "third component") on the functional properties of a prototypical TCS. To do so we build mathematical models of TCS with alternative designs for their interaction with that third component. These mathematical models are analyzed in order to identify the differences in dynamic behavior inherent to each design, with respect to functionally relevant properties such as sensitivity to changes in either the parameter values or the molecular concentrations, temporal responsiveness, possibility of multiple steady states, or stochastic fluctuations in the system. The differences are then correlated to the physiological requirements that impinge on the functioning of the TCS. This analysis sheds light on both, the dynamic behavior of synthetically designed TCS, and the conditions under which natural selection might favor each of the designs. We find that a third component that modulates SK activity increases the parameter space where a bistable response of the TCS module to signals is possible, if SK is monofunctional, but decreases it when the SK is bifunctional. The presence of a third component that modulates RR activity decreases the parameter space where a bistable response of the TCS module to signals is possible.     

Comparative Analysis of Denitrifying Activities of Hyphomicrobium nitrativorans,Hyphomicrobium denitrificans,and Hyphomicrobium zavarzinii

Hyphomicrobium spp. are commonly identified as major players in denitrification systems supplied with methanol as a carbon source. However, denitrifying Hyphomicrobium species are poorly characterized, and very few studies have provided information on the genetic and physiological aspects of denitrification in pure cultures of these bacteria. This is a comparative study of three denitrifying Hyphomicrobium species, H. denitrificans ATCC 51888, H. zavarzinii ZV622, and a newly described species, H. nitrativorans NL23, which was isolated from a denitrification system treating seawater. Whole-genome sequence analyses revealed that although they share numerous orthologous genes, these three species differ greatly in their nitrate reductases, with gene clusters encoding a periplasmic nitrate reductase (Nap) in H. nitrativorans, a membrane-bound nitrate reductase (Nar) in H. denitrificans, and one Nap and two Nar enzymes in H. zavarzinii. Concurrently with these differences observed at the genetic level, important differences in the denitrification capacities of these Hyphomicrobium species were determined. H. nitrativorans grew and denitrified at higher nitrate and NaCl concentrations than did the two other species, without significant nitrite accumulation. Significant increases in the relative gene expression levels of the nitrate (napA) and nitrite (nirK) reductase genes were also noted for H. nitrativorans at higher nitrate and NaCl concentrations. Oxygen was also found to be a strong regulator of denitrification gene expression in both H. nitrativorans and H. zavarzinii, although individual genes responded differently in these two species. Taken together, the results presented in this study highlight the potential of H. nitrativorans as an efficient and adaptable bacterium that is able to perform complete denitrification under various conditions.     

Dimethylsulfone as a growth substrate for novel methylotrophic species of Hyphomicrobium and Arthrobacter

Dimethylsulfone is a major product of the chemical oxidation in the atmosphere of the principal biogenic sulfur gas, dimethylsulfide, but no studies have been reported on the mechanisms for its microbiological degradation. Three novel strains of bacteria have been isolated from enrichment cultures provided with dimethylsulfone as the only carbon and energy substrate. These are novel facultatively methylotrophic species of Hyphonmicrobium and Arthobacter, capable of growth on a range of one-carbon substrates. Cell-free extracts contained activities of enzymes necessary for a reductive/oxidative pathway for dimethylsulfone degradation: membrane-bound-dimethylsulfone and dimethylsulfoxide reductases, dimethylsulfide monooxygenase, and methanethiol oxidase. Enzymatic evidence is also presented for the subsequent oxidation of formaldehyde by formaldehyde and formate dehydrogenases in the Hyphomicrobium strain and by a dissimilatory ribulose monophosphate cycle in the Arthrobacter strains. The strains also grew on dimethylsulfoxide and dimethylsulfide, and dimethylsulfide-grown bacteria oxidized dimethylsulfide and dimethylsulfoxide but not dimethylsulfone. Formaldehyde assimilation was effected in the Hyphomicrobium strain by the serine pathway, but enzymes of the ribulose monophosphate cycle for formaldehyde assimilation were present in the Arthrobacter strains grown on dimethylsulfone. In contrast, one of the Arthrobacter strains was shown to switch to the serine pathway during growth on methanol. Growth yields on dimethylsulfone and formaldehyde were consistent with the occurrence of the serine pathway in Hyphomicrobium strain S1 and the ribulose monophosphate cycle in Arthrobacter strain TGA, and with the proposed reductive pathway for dimethylsulfone degradation in both.     

The ligamentum infundibulo-cornuale in the pig: morphological and physiological studies of the smooth muscle component

The ligamentum infundibulo-cornuale (LIC) in the pig runs along the anterolateral side of the tubal isthmus, connecting the uterotubal junction and the edge of the infundibulum and has a comparatively well-developed muscular component running under the mesothelium. The well-vascularized smooth muscle cells held close cell-to-cell contacts and received innervation by adrenergic and cholinergic-like nerve terminals. Isolated LIC preparations, collected during oestrus showed a rhythmic spontaneous motility in vitro, the frequency and the relative amplitude of the contractions being highest during the preovulatory period. In vitro, noradrenaline and adrenaline elicited contractile (alpha) and relaxatory (beta) responses, while isoprenaline induced only beta-responses, as demonstrated by pretreatment with selective blockers. Oxytocin, PGF2 alpha and PGE2 always increased the muscular activity of the LIC. Indomethacin inhibited, in a concentration-dependent and reversible manner, the spontaneous motility of the porcine LIC, which could be fully restored by PGF2 alpha, indicating an endogenous local synthesis of prostaglandins in the tissue. The present results suggest that, in the pig, the LIC consists of a well-arranged, richly innervated bulk of smooth muscle which shows rhythmic spontaneous activity at the time of ovulation that could assist ova pick-up.     

Comparative studies on metal biosorption by two strains of Cladosporium cladosporioides

Two strains of a fungus, Cladosporium cladosporioides 1 and C. cladosporioides 2 showed different metal biosorption properties. Strain 1 showed preferential sorption of gold and silver, while strain 2 could bind metals such as copper and cadmium in addition to gold and silver. Strain 1 had a cell-wall hexosamine content of 0.1%. X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR) analyses indicated that nitrogen was not involved in metal biosorption by the strain. In strain 2 the cell-wall hexosamine content was 150 times that of strain 1. These results indicated that hexosamine was responsible for non-specific metal binding while cell-wall polymers other than hexosamines had a role in conferring selectivity in precious-metal binding.     

The mescaline or strychnine spikes as a tool for physiological and pharmacological studies

The all-or-nothing spikes elicited by antidromic, afferent, or direct electrical stimulation of a cortical area treated with mescaline or strychnine were studied. These potentials are most probably originated in nonsynaptic dentritic membranes and their changes in amplitude and latency can be an index of the excitability of these structures. Several factors are considered as sources of error when measurements of such parameters are made to follow their changes in different experimental conditions. When these sources of error can be eliminated, the frequency, amplitude and latency of those spikes can be taken as an index of the variations in cortical excitability under some physiological conditions. Another use of these giant potentials can be for the study of humoral and pharmacological agents.     

Glyoxylate conversion by Hyphomicrobium species grown on allantoin as nitrogen source

Glyoxylate, formed as a result of allantoin degradation, is converted by Hyphomicrobium species to glycerate via tartronate semialdehyde. Glyoxylate carboligase and tartronate semialdehyde reductase, the two enzymes involved, are present only in cells grown on allantoin as nitrogen source.     

Screening terrestrial and aquatic strains of Dunaliella from the eco-taxonomical perspective: a comparative study on fatty acid compositions as habitat indicators

Journal of Applied Phycology - The integration of taxonomic and ecological traits is a more balanced approach in the systematic identification of living organisms. We isolated ten strains of...     

Purification and properties of penicillinases from two strains of Bacillus licheniformis: a chemical, physicochemical and physiological comparison

1. The penicillinases formed by penicillinase-constitutive mutant strains from two closely related varieties (749 and 6346) of Bacillus licheniformis have been isolated, characterized and compared. They are chemically, physicochemically and immunologically very similar, but differ enzymologically in absolute and relative activity on, and affinity for, different penicillins and cephalosporins. 2. The molecular weights of both types are approx. 23000. Neither enzyme contains any cyst(e)ine. However, in most other respects they show little resemblance to any of the other penicillinases so far isolated. 3. Their properties, whether isolated from cells (to which approx. 50% of the activity is normally bound) or from the culture supernatant, appear to be similar. However, the molecular weight of a preparation of enzyme from strain 749/C obtained from the culture supernatant was found to be significantly (over 20%) higher than that obtained from cells alone. 4. With benzylpenicillin, the enzyme from strain 749 has V_max. approx. 6 times higher than that of the enzyme from strain 6346, but this difference is `compensated' by its affinity being 6 times lower. Thus, at the very low biologically effective concentrations of penicillin met with under natural conditions, where neither type of enzyme is more than a fraction saturated with its substrate, the antibiotic is hydrolysed at the same rate by both. As expected, the penicillin-sensitivities of single cells from the two strains were found to be identical. 5. It is suggested that the concept of `physiological efficiency' (defined as V_max. divided by K_m), applied to enzymes acting naturally under conditions of poor saturation with their substrates, may be useful for expressing their biological function in vivo.     

Molecular characterization of dichloromethane-degrading Hyphomicrobium strains using 16S rDNA and DCM dehalogenase gene sequences

A phylogenetic analysis of 6 strains of dichloromethane (DCM) utilizing bacteria was performed. Based on the almost complete 16S rDNA sequence determination, all strains clustered together and showed high sequence similarity to Hyphomicrobium denitrificans, except for the strain MC8b, which is only moderately related to them and probably represents a distinct species. The 16S rDNA-based phylogenetic tree was compared to the one obtained from the DNA sequence data of the dcmA gene coding DCM dehalogenase, the key enzyme of DCM utilization. The topology of the two trees is in good agreement and may suggest an ancient origin of DCM dehalogenase, but also raises questions about the original role of the enzyme.