The effect of sulfide on the blue-green algae of hot springs II. Yellowstone National Park

In the Mammoth Springs (Yellowstone National Park) waters with near neutral pH and soluble sulfide (H₂S, HS^–, S^2–) of over 1–2 mg/liter (30–60M) are characterized by substrate covers of phototrophic bacteria (Chloroflexus and aChlorobium-like unicell) above 50C and by a blue-green alga (Spirulina labyrinthiformis) below this temperature.Synechococcus. Mastigocladus, and other blue-green algae typical of most hot springs of western North America are excluded, apparently by sulfide. The sulfide-adaptedSpirulina photosynthesized at maximum rates at 45C and at approximately 300 to 700Ein/m²/sec of visible radiation. Sulfide (0.6–1.2 mM) severely poisoned photosynthesis of nonadapted populations, but those continuously exposed to over 30M tolerated at least 1 mM without inhibition. A normal¹⁴C-HCO₃ photoincorporation rate was sustained with 0.6–1 mM sulfide in the presence of DCMU (7M) or NH₂OH (0.2 mM), although both of these photosystem II inhibitors prevented photoincorporation without sulfide. Other sulfur-containing compounds (S₂O₃ ^2– SO₃ ^2–, S₂O₄ ^2– thioglycolic acid cysteine) were unable to relieve DCMU inhibition. The lowering of the photoincorporation rate by preferentially irradiating photosystem I was also relieved by sulfide. The most tenable explanation of these results is that sulfide is used as a photo-reductant of CO₂, at least when photosystem II is inhibited. It is suggested that in some blue-green algae photosystem II is poisoned by a low sulfide concentration, thus making these algae sulfidedependent if they are to continue photosynthesizing in a sulfide environment. Presumably a sulfidecytochrome reductase enzyme system must be synthesized for sulfide to be used as a photo-reductant.     

Host factor for coliphage Q beta RNA replication: presence in procaryotes and association with the 30S ribosomal subunit in Escherichia coli.

Summary The Host Factor required for in vitro coliphage Q RNA replication, a heat-stable RNA binding protein present in uninfectedEscherichia coli, has been detected by both immunological and functional tests inAcinetobacter calcoaceticus, Klebsiella pneumoniae, Pseudomonas aeruginosa andPseudomonas putida. It was not detectable by these criteria inBacillus stearothermophilus, Bacillus subtilis, Caulobacter crescentus, Micrococcus lysodeikticus, Rhodopseudomonas capsulata orSaccharomyces cerevisiae. InEscherichia coli the Host Factor protein has been shown to be associated with ribosomes. It is demostrated here that this association is specific for the 30S ribosomal subunit.     

Physical and genetical characterisation of a second sex factor, SCP2, for Streptomyces coelicolor A3(2)

Summary Covalently closed circular (ccc) DNA of uniform monomer size (c. 18×10⁶ daltons) and restriction endonuclease cleavage pattern was isolated from strains of S. coelicolor A3(2) of differing constitution in respect of the SCP1 sex factor: SCP1⁺, SCP1, SCP1^- and NF (integrated SCP1). No such ccc DNA was found in strains of S. lividans 66 or S. parvulus ATCC 12434 whether or not they contained SCP1. These results confirmed that the 18×10⁶ dalton plasmid is not, and does not include, SCP1, which has not so far been isolated by any of a variety of methods.Genetic data served to identify a second sex factor, SCP2, postulated to be present in SCP2⁺ state in the starting strains and to be capable of mutation to a variant form, SCP2^*, with enhanced sex factor activity. From SCP2^* strains, SCP2^- cultures were isolated, at an average spontaneous frequency of about 0.8%. Crosses of pairs of SCP1^- SCP2^- strains were almost, but not completely, sterile; thus SCP1 and SCP2 probably contribute nearly all the fertility naturally occurring in the A3(2) strain. The two sex factors share the property of exerting an effect that may be comparable with lethal zygosis caused by F in E. coli: it is shown by SCP1-carrying strains against SCP1^-, or SCP2^* (but not SCP2⁺) strains against SCP2^- and is revealed as a narrow zone of growth inhibition surrounding the plasmid-carrying culture on a background of the appropriate plasmid-negative strain.Genetically defined SCP^2- strains lacked the ccc DNA found in SCP2⁺ and SCP2^* strains. Thus this DNA apparently represents the SCP2 sex factor. A preliminary restriction endonuclease cleavage map of SCP2 was constructed, with single sites for EcoRI and HindIII, four sites for SalPI (=PstI) and more than 20 sites for SalGI (SalI).     

Nuclear cytochrome-deficient mutants of Neurospora crassa: isolation, characterization, and genetic mapping.

Summary We have isolated twenty-six nuclear, singlegene cytochrome-deficient mutants of Neurospora crassa as an initial step toward the study of the structural components and regulatory mechanisms involved in the biogenesis of the mitochondrial cytochrome system. These mutants, together with two previously described mutants, cyt-1 and cyt-2, have been classified into six distinct groups on the basis of cytochrome phenotype: a) cytochrome aa ₃ deficiency (due to mutations affecting loci designated cya); b) cytochrome b deficiency (cyb-1 locus); c) cytochrome b deficiency with a partial deficiency of cytochrome aa ₃ (cyb-2 locus); d) deficiency of both cytochromes aa ₃ and b (cyt loci); e) deficiency of both cytochromes aa ₃ and c (cyt-2 locus); and f) partial deficiency of cytochromes aa ₃ and c (cyt-12 locus).Four of seven mutations affecting cya loci have been mapped and are located on linkage groups I, II, V, and VI. It is not yet known whether these genes code for structural components of cytochrome oxidase or have a regulatory function that affects synthesis or assembly of the enzyme. The cyb-1 and cyb-2 genes are located on linkage groups V and VI, respectively, and appear to code for regulatory elements that control the biogenesis of cytochromes b and aa ₃ . The positions of the cyt mutations that cause a simultaneous deficiency of cytochromes aa ₃ and b are dispersed throughout the genome, except for two gene clusters on the left arm of linkage group I. Some of these mutants may be deficient in mitochondrial protein synthesis. Two mutations, cyt-2 and cyt-12, are located on linkage groups VI and II, respectively, and appear to affect genes that code for components of a regulatory system that controls the biogenesis of cytochromes aa ₃ and c.     

Absolute configuration of heteroxanthin and diadinoxanthin

The absolute configurations of heteroxanthin ((3S,5S,6S,3′R)- 7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,5,3′,6′-tetrol) ex Euglena gracilis and of diadinoxanthin ((3S,5R,6S,3′R)-5,6-epoxy-7′,8′-didehydro-5,6-dihydro-β,β-carotene-3,3′-diol) from the same source have been established by chemical reactions, hydrogen bonding studies, ¹H NMR and CD. Two previously unknown carotenoids (artefacts?) from Trollius europaeus, assigned the structures (3S,5S,6S,3′S,5′R,6′R)-6,7-didehydro-5,6,5′,6′-tetrahydro-β,β -carotene-3,5,6,3′,5′-pentol and its 5R epimer, served as useful models.     

Can cell walls bending round xylem vessels control water flow?

Vascular bundles of petioles below wilted leaves of Nymphoides peltata (S.G. Gmel. O. Kuntze) were frozen intact and freeze-fractured for electron microscopy. Cell walls in them appeared drawn in against the helical thickenings of xylem vessels. By contrast, walls round vessels which had been frozen in vascular bundles below turgid leaves, and walls round vessels which had been fixed, embedded and sectioned, were straight or bulged outwards slightly. Walls bulged outwards slightly also from cut vessels filled with sucrose solution before freezing. Movement of vessel walls could produce the clicks audible when water cavitates in vessels, and might explain a variable resistance to the flow of water through plants.     

Surgical Management of Epilepsy

Therapy with anticonvulsant drugs reduces the frequency and severity of seizures in many but not all epileptic patients. Unfortunately, in a significant number control remains poor even when maximal doses of multiple anticonvulsant drugs are given. Some of these patients are candidates for surgical treatment of epilepsy. The operative management of convulsive disorders is a well-established technique and is available in some centers. In selected cases, such operations are both safe and effective, with good longterm improvement or complete control in 76 percent of patients. We have summarized the 24-year experience with surgical operation for epilepsy at the University of Washington Medical Center.     

Myocardial Revascularization in Patients 70 Years of Age and Older

Myocardial revascularization has been carried out by us in 67 patients 70 years of age or older. Advanced coronary artery disease was found at angiography in more than two thirds of the patients. The postoperative morbidity and mortality compare very favorably with those in younger patients. The early and late mortality in the 67 patients was 4.5 percent and 6.0 percent, respectively. Fifty-seven survivors have been followed an average of 21 months; for most patients there has been a pronounced improvement in clinical classification. Properly selected, patients of advanced age can undergo successful revascularization surgical procedures. The adequacy of function of the left ventricle, proper timing of the surgical operation and an aggressive yet realistic approach seem to be major determinants for a good result.     

Identification of the oligonucleotide and oligopeptide involved in an RNA--protein crosslink induced by ultraviolet irradiation of Escherichia coli 30 S ribosomal subunits.

When 30 S ribosomal subunits are irradiated with ultraviolet light, we have found that an RNA-protein crosslinking reaction occurs whose primary target is protein S7. This paper describes the identification of the oligopeptide and oligonucleotide at the crosslinking point, by direct analysis (a) of the peptide remaining attached to an oligonucleotide (after total digestion of the RNA in the crosslinked complex with ribonucleases A and T₁, followed by digestion with trypsin), and (b) of the nucleotides remaining attached to the crosslinked protein (after digestion of the RNA in the complex with ribonuclease T₁ alone).The crosslinking site was found to lie within a single short peptide, Ser-Met-Ala-Leu-Arg (positions 113 to 117 in the S7 sequence), with methionine as the probable amino acid concerned. The principal RNA site was found to lie within an oligonucleotide three to six bases long, the underlined portion of the partially ordered sequence $\text{C-U-A-C-}\text{A-A-U-G.G.C}\text{-G}$ in section P of the 16 S RNA. The methodology involved has been designed with a view to being generally applicable in future RNA-protein crosslinking studies, where several proteins are simultaneously attached to the RNA.     

A measure of the denseness of a phylogenetic network

Summary The concept of phylogenetic denseness bears critically on the accuracy of evolutionary pathways inferred from experimentally sequenced proteins isolated from extant species. In this paper I develop an objective measure,, of denseness to supplement previous intuitive concepts and which permits one to use this concept in comparing the quality of different evolutionary reconstructions. This measure is used to examine several published phylogenetic trees: insulin, a-hemoglobin,-hemoglobin, myoglobin, cytochromec, and the parvalbumin family. The paper emphasizes 1) the importance of denseness in accurately estimating the number of nucleotide replacements which separate homologous sequences when this estimation is made by the method of parsimony, 2) the value of this concept in assessing the quality of those estimates, and 3) the use of this concept as a biologically practical heuristic method for identifying poorly studied regions in a phylogenetic tree, whether or not the tree was obtained by the parsimony method.