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HUMIC substances are heterogeneous high-molecular-weight organic materials which are ubiquitous in terrestrial and aquatic environments. They are resistant to microbial degradation1 and thus are not generally considered to be dynamically involved in microbial metabolism, especially in anoxic habitats. However, we show here that some microorganisms found in soils and sediments are able to use humic substances as an electron acceptor for the anaerobic oxidation of organic compounds and hydrogen. This electron transport yields energy to support growth. Microbial humic reduction also enhances the capacity for microorganisms to reduce other, less accessible electron acceptors, such as insoluble Fe(III) oxides, because humic substances can shuttle electrons between the humic-reducing microorganisms and the Fe(III) oxide. The finding that microorganisms can donate electrons to humic acids has important implications for the mechanisms by which microorganisms oxidize both natural and contaminant organics in anaerobic soils and sediments, and suggests a biological source of electrons for humics-mediated reduction of contaminant metals and organics.

In a previous publication1 we described the results of an investigation into the spatial distribution of cosmic electromagnetic noise radiation at 5 metres wave-length. We have recently been engaged in an attempt to make a more detailed determination by using a more sensitive receiver of narrower beam-width. An interesting new feature which has emerged from these latter experiments is the occurrence of short - period irregular fluctuations which have been found to be associated with the direction of Cygnus. This region, which is a secondary peak in the cosmic noise distribution, appears to be unique in being char¬acterized by short-period variations of marked amplitude in the intensity of power flux.

REDUCTION of the soluble, oxidized form of uranium, U(VI), to insoluble U(IV) is an important mechanism for the immobilization of uranium in aquatic sediments and for the formation of some uranium ores1–10. U(VI) reduction has generally been regarded as an abiological reaction in which sulphide, molecular hydrogen or organic compounds function as the reductant1,2,5,11. Microbial involvement in U(VI) reduction has been considered to be limited to indirect effects, such as microbial metabolism providing the reduced compounds for abiological U(VI) reduction and microbial cell walls providing a surface to stimulate abiological U(VI) reduction1,12,13. We report here, however, that dissimilatory Fe(III)-reducing microorganisms can obtain energy for growth by electron transport to U(VI). This novel form of microbial metabolism can be much faster than commonly cited abiological mechanisms for U(VI) reduction. Not only do these findings expand the known potential terminal electron acceptors for microbial energy transduction, they offer a likely explanation for the deposition of uranium in aquatic sediments and aquifers, and suggest a method for biological remediation of environments contaminated with uranium.

The interstellar medium in our vicinity forms an elongated cavity of X-ray-emitting gas, extending up to 200 pc from the Sun. The gas inside this local bubble is very hot (~ 10^6 K) and tenuous (electron density n _e ≈ 0.005 cm^(−3)), and is typical of material in the coronal phase of the interstellar medium, thought to occur when hot stars or supernovae blow out holes in cooler and denser interstellar gas. Little is known about turbulent density fluctuations in the coronal gas, but its physical state is important in understanding cosmic ray confinement and the energy balance of interstellar material, as well as the scattering of radio emission from compact sources. To probe turbulence in the local interstellar medium, we have made scintillation measurements at 50 MHz (6 m wavelength) of emission from the nearby pulsar 0950 + 08, which happens to lie near the edge of the local bubble. From the scintillation bandwidth we deduce the amplitude of the electron-density fluctuation spectrum in the coronal gas alone, and find it to be an order of magnitude lower than for any previously measured interstellar line of sight. We conclude that the interior of the bubble is relatively quiescent and that high levels of plasma turbulence—if they exist—must be localized to the cavity boundary.

The observation of Bragg diffraction from supernanometre regions of 'amorphous' silicon reveals the existence of crystalline clusters too small to be observed by X-ray diffraction in bulk. The clusters are imaged by high-resolution transmission electron microscopy. These observations support a submicrocrystalline model for the structure of non-crystalline solids.

THE genomes of several mammalian species contain at least two α globin loci and a single β globin locus so that the ratio of α- to β-globin genes is 2 : 1 or more1–3. Despite this difference in number of genes, reticulocytes from these species synthesise equal numbers of α- and β-globin chains indicating that compensatory regulation must occur. Cytoplasmic mRNA is an intermediate between the gene and globin protein, and it has been suggested that the cellular α/β mRNA ratio is an important factor in achieving balanced globin synthesis4–6. We report here an excess of 30% α mRNA on reticulocyte polysomes of rabbits, mice, and sheep. Our data also illustrate the potential for errors in studies in which only poly(A)+ RNA is assayed.

ACTIN and myosin have been found in many non-muscle cells1. They are presumed to function in the generation of the force required in the various expressions of cytoplasmic or cell motility. Although both have been found in association with the plasma membrane2–5, nothing is known about the nature or consequences of this association. Equally uncertain is the mechanism of movement of secretory granules : synaptic vesicles, for example, are transported along neurones at high rates (up to 20 cm d−1)6, probably in association with microtubules7. Roles for actomyosin in this process8 and in exocytosis9 have been proposed. We have used a new approach to the problem of actomyosin-membrane interaction, and report here the binding of actin and myosin in vitro to a purified cytoplasmic membrane component.

THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1–7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8–12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically.

Aeromagnetic profiles show two types of smooth magnetic zone in the South Atlantic symmetrically positioned about the Mid-Atlantic Ridge. The first borders the continental margins off Argentina and the Union of South Africa and the second extends over part of the Argentine-Brazil and Angola-Cape basins. The origin of the first zone may be related to the tectonic and/or diagenetic processes associated with the initial rifting of South America from Africa and the second can be simply explained by seafloor spreading during Middle-Late Cretaceous time when the polarity of the Earth's field was relatively constant.

MICROEARTHQUAKE activity in the median valley of the Mid-Atlantic Ridge near 36°30′N has been monitored using expendable radio-sonobuoy arrays. Similar techniques have been used by Reid et al.1 in the Gulf of California, Macdonald and Mudie2 near the Galapagos spreading centre and recently by Reid and Macdonald3 near fracture zones A and B shown in Fig. 1 (ref. 4). This study provides area coverage not obtained by Reid and Macdonald whose experiment was confined to the fracture zone regions. A new method of sonobuoy position determination was used that provides relative buoy locations (locations with respect to each other) to within ±10 m. The ultimate positioning capability in latitude and longitude depends on the accuracy of the primary navigation system available. Satellite navigation can yield absolute positions to within ±100 m. An estimated actual accuracy of ±200 m is ascribed to the experiments reported here. Accuracy of this order allows correlation of epicentre locations with topographic features of similar scale size. Recently acquired bathymetric data (K. C. Macdonald and colleagues, in preparation) indicate that significant features of the ridge near 36°30′N, such as transform faults and valley walls, can be defined by scale sizes of some hundreds of metres, A total of 112 events definitely attributable to seismic activity were recorded in 72 h of listening, yielding an average rate of occurrence of 1.5 events h−1.

The potential contribution of microbial metabolism to the magnetization of sediments has only recently been recognized. In the presence of oxygen, magnetotactic bacteria can form intracellular chains of magnetite while using oxygen or nitrate as the terminal electron acceptor for metabolism1. The production of ultrafine-grained magnetite by magnetotactic bacteria in surficial aerobic sediments may contribute significantly to the natural remanent magnetism of sediments2–4. However, recent studies on iron reduction in anaerobic sediments suggested that bacteria can also generate magnetite in the absence of oxygen5. We report here on a sediment organism, designated GS-15, which produces copious quantities of ultrafine-grained magnetite under anaerobic conditions. GS-15 is not magnetotactic, but reduces amorphic ferric oxide to extracellular magnetite during the reduction of ferric iron as the terminal electron acceptor for organic matter oxidation. This novel metabolism may be the mechanism for the formation of ultrafine-grained magnetite in anaerobic sediments, and couldaccount for the accumulation of magnetite in ancient iron formations and hydrocarbon deposits.

DURING studies of the pulse radiolysis of aqueous solutions of pyrimidines and related substances, we have observed the formation of short-lived organic species which are formed by reactions other than those of the free radicals H, OH and e−aq produced by the radiolysis of the solvent. On the basis of the evidence presented here, we believe that these molecular transient species are the result of acid-base reactions between the pyrimidines and the radiolytic yield of hydroxide ions. These processes, although unlikely to lead to permanent products, are important in the pulse technique where the correct interpretation of a transient absorption is vital.

PALAEOMAGNETIC studies of deep sea cores have shown that the history of geomagnetic polarity reversal is recorded in sea floor sediments1–8. The local extinction of certain species of Radiolaria can be related to palaeomagnetic polarity reversals1,4,8, and specifically there is an association of the Brunhes–Matuyama polarity reversal at 0.7 × 106 yr ago with the ψ/X radiolaria boundary4,8. Another such extinction has been suggested4,9; occurring within the Olduvai Normal polarity event about 2 × 106 yr ago, approximates the Plio/Pleistocene chronostratigraphic boundary defined by Ericson10,11 for oceanic sediments. Although this chronostratigraphic age assignment may be correct, the relationship of the geomagnetic polarity time scale to the biostratigraphic units used to define Plio/Pleistocene geological history has not been demonstrated. This results primarily from the lack of appropriate palaeontological criteria in deep sea cores which can be correlated with the standard (type) sections of the Pliocene/Pleistocene of Italy.

After a progression of machines extending over several years, Perhapsatron S-3 shows, by magnetic probe measurements, more symmetrical detachment of the current channel from the walls. Problems and possible improvements in the apparatus are discussed. (M.H.R.)

THERE has long been an interest in developing mouse stocks carrying chromosome inversions for mutation testing. This interest stems from the fact that heterozygosity for a paracentric inversion, that is, a structural rearrangement in which a chromosome segment that does not include the centromere is rotated through 180°, results in suppression of recombination in the inversion region. This is caused by the failure of recovery of the products of single crossovers in this region, because dicentric chromatids and acentric fragments are produced that either fail to give functional meiotic products or result in the formation of unbalanced zygotes which are generally eliminated. Recombination between the pair of chromosomes concerned is, therefore, confined to any crossovers in the non-inverted regions and to the rare two-strand double crossovers which may occur within the inversion region if it is a long one. This property of inversion heterozygotes enables the recovery, in the progeny, of the structurally normal homologue largely intact and any recessive mutation located on it can be readily detected if suitable genetically marked stocks are used. In the simplest case, when the mutation is a recessive lethal and the inversion is located in the X chromosome, detection is either by the absence of half the males, or if the inversion itself is marked by a recessive lethal (as in the C1B method devised by Muller for Drosophila melanogaster), by the absence of all the males.

RECENT investigations on the incorporation of metal ions into porphyrins solubilized in aqueous detergent solutions have revealed two factors having a marked influence on the reaction-rate. The first is related to the charge on the detergent and has been termed the electrostatic effect ; the second is concerned with the presence of certain chelating agents, and has been termed the co-ordination effect.

THE corpuscles of Stannius, supposedly endocrine glands, are peculiar to teleostean fishes. Their function is uncertain1, but Rasquin2 has suggested that they are concerned in osmoregulation. Unequivocal evidence that the interrenal tissue of teleosts is the homologue of the adrenal cortex3,4 strongly suggests that a role other than production of corticosteroids be attributed to the corpuscles of Stannius. In order to supply direct evidence to support this assumption, procedures used in studies on interrenal tissue of Fundulus heteroclitus 4 were applied to corpuscles of Stannius collected from Pseudo-pleuronectes americanus. Sixty-one fish, caught in Niantic Bay and Long Island Sound, Conn., in December 1958 yielded 95 corpuscles of Stannius weighing 104.7 mgm. This tissue and 162 mgm. of mesonephric kidney which served as control tissue, were separately incubated with tritiated progesterone in a manner previously described4.

The current distribution in a discharge which compresses a longitudinal magnetic field originally set up in the tube by an external coil is described. The apparatus is described briefly. Contour plots of axial current density and magnetic field as a function of time are given. Also included are plots of magnetic fields as a function of radius at 2.5 μsec.

IT has recently been suggested by Roseman et al.1 that columns of ‘Amberlite IRA 400 (OH′)’ might be used for the separation of certain reducing and non-reducing carbohydrates. Our own experience with this resin suggests that very carefully controlled conditions would be necessary if reliable quantitative results are to be obtained. During an investigation of the non-volatile organic acid components of apple juice and cider, it has been found that sugars are extensively degraded by ‘Amberlite IRA 400’ used in the OH′ form, organic acids being the main products of degradation.

RECENTLY, there has been some discussion between Brady, Pethica, Cockbain and others regarding the form in which the Gibbs adsorption isotherm should be applied to surface-active electrolytes in the absence of any added electrolyte. Under such conditions, and assuming complete dissociation of the surf ace-active electrolytes, it has been shown, for example1, that the Gibbs equation (neglecting the correction for activities) may be written in the form where γ is the interfacial tension; c the concentration of surf ace-active electrolyte; A the area occupied per film ion at the interface; k the Boltzmann constant, and T the absolute temperature. This has been verified by Cockbain2 for sodium dodecyl sulphate at the oil-water interface. Other investigators, however, have found3,4 that the form theoretically applicable in the case of excess added electrolyte, namely, appears also to apply in practice to the case of no added electrolyte.

IN May, 1878, Mr. Church, who was at that time Professor of Mining at the University of Ohio, read a paper before the American Institute of Mining Engineers on the heat of the Comstock mines, which was subsequently, in an extended form, included in the author's volume on the Comstock lode, of which a review appeared in NATURE (vol. xxi. p. 511).

MAMMALIAN radiation genetics has been largely concerned with the effects of X- and γ-irradiation, about which much has been learned in recent years. Surprisingly little work has been done with neutrons, although it is known that fast neutrons of modal energy around 1 MeV are about six times as effective as acute X-irradiation for the induction of dominant lethal mutations in mouse spermatozoa, whether the neutron dose is administered at high or at low intensity1,2. For the assessment of human hazards from high linear energy transfer radiation, it is particularly important to investigate the effectiveness of chronic neutron exposures with respect to the induction of point mutations in immature germ-cells of mammals. An experiment of this type, using the specific locus method, is now in progress and has revealed a surprisingly high yield of mutations following fast neutron irradiation of mouse spermatogonia.

Nuclear Forces and the Few-Nucleon Problem Proceedings of the International Conference held at the Physics Department, University College, London, 8–11 July, 1959. Edited by T. C. Griffith and E. A. Power. Vol. 1: Pp. xiii + 1–340. Vol. 2: Pp. vii + 341–712. (London and New York: Pergamon Press, 1960.) 200s. per set of two volumes.

In their description of the solar radio emissions from the great sunspot of February 1946, Appleton and Hey1 pointed out that a number of sudden enhancements of intensity, observed at about 5 metres wave-length, occurred simultaneously with increases in D-layer ionization as indicated by fade-outs on long-distance radio-communication circuits. This increased ionization, which is believed to be due to enhanced solar ultra-violet radiations, strongly absorbs the radio communication waves (of the order of 20 metres wave-length) but does not produce any marked absorption of the solar radio emissions at wave-lengths of 5 metres or less.

WHEN a powder is compacted by a simple application of pressure, the density and strength of the compact so formed (measured after the pressure has been released) are determined by the pressure used, but ultimately they approach limiting values which are not exceeded by further increasing the pressure. The limiting density of the compact falls short of the density of the material of the powder by an appreciable margin, say 4–20 per cent, depending on the material used (Fig. 1).

THE discovery of electromagnetic 'noise' radiations at radio frequencies was first made by K. G. Jansky1 who, in a series of measurements at about 20 Mc. s. ( 15 m.) was able to establish the close connexion between the direction of greatest intensity and the centre of the galaxy. G. Reber2 later made measurements at 160 Mc./s. ( 2 m.), and he was able, by virtue of a narrower beam, to detect a number of subsidiary peaks. He found the intensity of radiation at this higher frequency was very much less ; he also suggested a probable explanation of the radiations, namely, the interactions in encounters between positive ions and free electrons released from interstellar gases by the photoelectric action of stellar radiations. The theoretical treatment for radiation arising from such encounters was first given by H. A. Kramers3 to account for continuous radiation in X-ray spectra. The cosmic noise radiation is not observable at frequencies lower than a few megacycles per second, owing to the screening action of the ionosphere.

Active Sodium and Chloride Transport by Anal Papillae of a Salt Water Mosquito Larva (Aedes campestris)

RECENTLY it was postulated that in haemoglobin and myoglobin the haem iron is bound to the apoprotein other than through histidine imidazole groups1. This conclusion, which does not appear to be warranted by evidence at present available, is based on the assumption that the pH at which half the haem is bound to the protein moiety can be identified with the pKL of the binding group. There is no theoretical reason why this should be so.

IN current estimates of the genetic hazard of ionizing radiations to man1,2 four important assumptions are made : (1) that the mutagenic effect of a given radiation dose to the gonads is independent of dose-rate ; (2) that the relationship of mutation-rate to accumulated dose is linear ; (3) that the spectrum of radiation-induced mutation is similar to the spectrum of spontaneous mutation, and (4) that a dose of about 30–80 rads induces as much mutation as occurs spontaneously per generation (‘doubling dose’). Assumptions (1), (2) and (3) derive largely from experiments with Drosophila ; assumption (4) derives in part from the fact that a spermatogonial doubling dose of this order was estimated for seven specific genes in the mouse from observations of the spontaneous mutation-rate3,4 and from experiments4 in which adult males were given a high X-ray dose at a high dose-rate (600 rads, 90 rads/min.), the validity of assumptions (1), (2) and (3) being presupposed.

AN article on “Seasonal Sunshine in Great Britain” by Mr. Charles Harding appeared in NATURE of March 20. The results were based on the 35-years' mean, 1881–1915. Comparing south-east England with south-west England and south Wales, Mr. Harding says that “the average sunshine for the year in south-east England is 4.49 hours a day, and in south-west England and south Wales, including the so-called Cornish Riviera, it is 4.28 hours. In the winter, south-east England has an average daily sunshine of 1.92 hours, and in south-west England and south Wales the value is 1.91 hours a day; in spring the hours of sunshine for the two districts are respectively 5.50 and 5.36; in summer 6.88 and 6.41, and in autumn 3.46 and 3.31 hours”.

IN continuation of previous work on the effects of radiations on liquids1, we have for some time been investigating the action of neutrons, alpha-, beta- and gamma-rays in inducing polymerization of a number of hydrocarbon compounds. Of the different methods used for observing the rate of polymerization—changes in colour, refractive index, viscosity, streaming polarization, etc.—we have found it convenient to follow the changes in density consequent on irradiation by means of a volume dilatometer. The sources of radiation were sometimes placed inside the bulb of the dilatometer, and sometimes surrounded it.

FOR more than a year we have been engaged in investigating the action of neutrons and rays: (a) in affecting the stability of colloids, and (b) in promoting chemical reactions. As sources of radiation we have used platinum containers filled with radium sulphate, or radium emanation sealed into glass tubes surrounded by a few millimetres of lead. Neutrons were obtained from sources similar to these to which metallic beryllium had been added. Since all the neutron sources used emitted rays, every titration was carried out in triplicate on (1) a non-irradiated control; (2) a specimen irradiated by rays alone; (3) a specimen irradiated by neutrons and rays from the same or an equal source. The strengths of the sources ranged from 30 mC to 150 mC and the periods of irradiation from a few hours to two weeks.