Activity of methanotrophic bacteria in Green Bay sediments

Abstract Sediment pore water samples obtained from a 19 m station in Green Bay in Lake Michigan were examined for levels of ambient dissolved methane and copper, and for the potential for in situ methane oxidation by methanotrophs found within surface sediments. The in situ methane concentration in the upper oxic sediment layer ranged from 20–150 μmol · 1⁻¹ at this station. The activity of methanotrophs and the kinetics of methane oxidation in these sediments were demonstrated by the uptake of radiolabeled methane. K_s values varied between 4.1–9.6 nmol · cm³ of sediment slurry. High V_max values (12.7–35.2 nmol · cm⁻³ · h⁻¹) suggest a large population of methanotrophs in the sediments. An average methane flux to the oxic sediments of 0.24 mol · m⁻² · year⁻¹ was calculated from the pore water methane gradients. Pore water concentrations of copper in the upper sediment layer ranged from 10–120 nmol · 1⁻¹. Based upon the copper concentration, other measured parameters, and equilibrium conditions defined by WATEQF4, an estimate for dissolved free Cu²⁺ concentration of 5–38 nmol · 1⁻¹ pore water was obtained. Several factors control the rate of methane oxidation, including oxygen, methane, and the bioavailability of free Cu²⁺.     

SULPHIDE PRODUCTION FROM SULPHATE-ENRICHED SEWAGE SLUDGES

SUMMARY: Sterilized raw sewage sludge enriched with sulphate and inoculated with pure strains of Desulphovibrio desulphuricans produced negligible sulphide. Unsterilized sludge supplemented with 7% (w/v) CaSO₄.2H₂O and inoculated with crude cultures of sulphate-reducing bacteria obtained from sewage yielded 1·0% S^2- (wt S^2- produced as H₂S/vol. of raw sludge) in 6 months at 30°. By repeated subculture more active cultures developed which produced 1% S^2- in 7 days and 1·2–1·9% in 28 days. Digested sludge yielded only 0·1% S^2-. In semicontinuous fermentations at 30°, raw sludge without added sulphate produced 20 times its own volume of gas containing 70% CH₄ and 30% CO₂. When 5% CaSO₄.2H₂O and an active crude culture of sulphate reducers were added, gas production decreased steadily to zero. There were no differences in pH, temperature and redox potential in sludges producing methane or sulphide. The chief cause of inhibition appeared to be the action of sulphide: 0·02% soluble sulphide (S^2-) totally inhibited methane formation; 0·01% S^2- initially decreased gas production by one-quarter but there was a slow recovery to normal, suggesting acclimatization of the methane-producing organisms to sulphide.
Linked fermentations, in which gas from a methane fermentation swept H₂S from a sulphide fermentation, gave a final gas mixture of about 60% CH₄, 30% CO₂ and 5–10% H₂S. The yield of sulphide depended on the rate of sweeping.     

RETENTION AND EXCHANGE OF POTASSIUM IN A SYNAPTOSOMAL FRACTION OF MOUSE BRAIN

Abstract— Myelin, synaptosomal and mitochondrial fractions obtained from homogenates of whole mouse brain contain K⁺ which can exchange with ⁴²K⁺ at 2º in 0·32 m -sucrose. The content and rates of exchange of K⁺ were greater at pH 8·2 than at 6·1. In the synaptosomal preparations, the rates of exchange and content of ⁴²K⁺ and K⁺ declined progressively with decreasing pH.
Of the total synaptosomal K⁺, 95 per cent could exchange with external ⁴²K⁺. At pH 7·5, 20 per cent of the K⁺ and 78 per cent of the Na⁺ appeared to reside in osmotically insensitive pools. Synaptosomal K⁺ at 2º was slowly displaced by NaCl (0·18 m ) and the rate of exchange between ⁴²K⁺ and K⁺ was retarded. KCI (0·18 m ) did not readily displace endogenous Na⁺. Synaptosomal K⁺ exchanged with exogenous K⁺ more rapidly than with exogenous Na⁺.
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K⁺ traverses the plasma membrane at 2º.     

The co-disposal of a model brewery wastewater with domestic refuse

By use of refuse columns, it was shown that, at appropriate organic loading rates, the co-disposal of a synthetic brewery wastewater with refuse stimulated methane production and did not reduce leachate quality, in terms of pH or volatile fatty acid concentrations. When the application rate was doubled, from imposed dilution rate ( D ) 0·025 to 0·056 h⁻¹, there was no breakthrough of volatile fatty acids and methane production was promoted. However, when the same total organic load was achieved by doubling the organic strength of the wastewater, but maintaining D = 0·025 h⁻¹, leachate quality was temporarily reduced, with elevated concentrations of acetate and propionate.     

Aspects of methane flow from sediment through emergent cattail (Typha latifolia) plants

We measured the flow of methane in Typha latifolia L. (cattail)-dominated wetlands from microbial production in anoxic sediment into, through, and out of emergent T. latifolia shoots (i.e. plant transport). The purpose was to identify key environmental and plant factors that might affect rates of methane efflux from wetlands to the Earth's atmosphere. Methane accumulated in leafy T. latifolia shoots overnight, reaching concentrations up to 10000 μl l⁻¹ (vs. atmospheric concentrations <4 μl l⁻¹), suggesting that lower stomatal conductance at night limits methane efflux from the plant into ambient air. Daytime light and (or) lower atmospheric humidity that induce convective gas flow through the plant coincided with ( a ) an increase in the rate of methane efflux from T. latifolia leaves to ambient air (from <0·1 to >2·0 μmol m⁻² (leaf) s⁻¹) and ( b ) a decrease in shoot methane concentration to <70 μl l⁻¹. Very short fluctuation in stomatal conductance during the day did not affect the methane efflux rate unless, possibly, the rate of photosynthesis decreased. A strong relationship between the maximum daily rate of methane efflux and shoot methane concentration (measured before the onset of convective gas flow) suggests T. latifolia plants behave like a capacitor (filling with methane at night, emitting the stored methane during the day). Experimentally cutting leaves (to prevent pressurization) reduced plant capacitance for methane.     

Effect of feeding level and feeding frequency on specific dynamic action in Silurus meridionalis

The effect of feeding level ( F _L; 0·5 to 4% dry diet mass per wet fish body mass) and feeding frequency (once every 4 days to twice per day) on postprandial metabolic response was investigated in southern catfish Silurus meridionalis at 27·5° C. The results showed that there was no significant difference in the specific dynamic action (SDA) coefficient among the groups of different feeding levels ( P  > 0·05). The duration increased from 26·0 to 40·0 h and the peak metabolic rate increased from 207·8 to 378·8 mg O₂ kg⁻¹ h⁻¹ when the feeding level was increased from 0·5 to 4%. The relationship between the peak metabolic rate ( R _P, mg O₂ kg⁻¹ h⁻¹) and F _L could be described as: R _P = 175·4 + 47·3 F _L( r ² = 0·943, n  = 40, P  < 0·001). The relationship between the SDA duration ( D , h) and F _L could be described as D =30·97 F _L^0·248 ( r ²=0·729, n =40, P  < 0·001).     

Effect of plant succession, ploughing, and fertilization on the microbiological oxidation of atmospheric methane in a heathland soil

Abstract: The effect of plant succession on methane uptake was measured on intact soil cores collected from seven heathland sites. Six of the sites had undergone either secondary succession with grass or oak, ammonium fertilization or ploughing, while the seventh site was located in the native heathland. There was a positive relationship between methane uptake rate and time elapsed since the plant invasion had taken place in the native heathland. The native heathland site showed an insignificant atmospheric methane uptake of 0.01 mg CH₄ m⁻² d⁻¹, whereas the established oak brushwood (70 years old) and the grass invaded heathland (13 years old) showed rates of 1.36 mg CH₄ m⁻² d⁻¹ and 0.73 mg CH₄ m⁻² d⁻¹, respectively. In the fertilized heathland plot (112 kg N ha⁻¹ six years prior to this study) grass had become the dominating species and showed a methane oxidation rate of 0.28 mg CH₄ m⁻² d⁻¹. Ploughing of the heathland resulted in methane oxidation rates seven times the rates measured in the native heathland. The results suggested that an increased future atmospheric nitrogen deposition in heathlands and other nutrient poor ecosystems may have a stimulating effect on the soil sink for atmospheric methane.     

Effect of oxygen tension, salinity, temperature and organic matter concentration on the growth and nitrifying activity of an estuarine strain of Nitrosomonas

Abstract The effects of O₂ tension, temperature, salt concentration and organic matter concentration on the growth and nitrifying activity of Nitrosomonas N₃ isolated from Tay Estuary sediments have been investigated. Chemostat-grown cultures were able to grow and nitrify at dissolved O₂ concentrations as low as 0.1 mg O₂· 1⁻¹ (cell population densities were 15% of those obtained in fully aerated cultures). This bacterium was sensitive to reduced temperatures as chemostat-grown cultures washed out at growth temperatures below 15°C, at dilution rates > 0.025 · h⁻¹. Batch-grown cultures of Nitrosomonas N₃ were used to study the effects of NaCl and complex organic matter concentration on nitrifying activity. Maximum rates of NH⁺₄ oxidation were recorded at NaCl concentrations of 1% w/v, whilst tryptone soya broth (TSB), nutrient broth (NB), yeast extract broth (YEB) and peptone were inhibitory at concentrations > 10 mg · 1⁻¹.     

Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t ₀=–0·43 and K =0·12; and female: L ∞=115·1 cm, t ₀=–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O₂ kg^–1 h^–1 and 70·65±7·63 mg O₂ kg^–1 h^–1 respectively, and at 10° C were 25·43±1·31 mg O₂ kg^–1 h^–1 and 113·84±16·26 mg O₂ kg^–1 h^–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Osmoregulation during the development of glass eels and elvers

Drinking rates in glass eels and elvers of the European eel increased with environmental acclimation salinity from 0·07±0·02 (FW) to 0·70±0·09 μl g-¹ h-¹ (SW) at month 1 and from 1·12±0·42 (FW) to 12·85±1·05 ± l g-¹ h-¹ (SW) at month 5. Drinking rates increased with time in both FW and SW groups. FW acclimated eels when challenged acutely with SW increased drinking rate rapidly immediately upon transfer (0–15 min) and the magnitude of this response increased with developmental time from month 1 to month 5.     

A method for long-term measurement of respiration in intertidal fishes during simulated intertidal conditions

Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow-through respirometer system. The system allowed long-term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The M o ₂ of L. pholis , measured at 15° C, was 2·1 μmol O₂ g^–1 h^–1 during aquatic and 1·99 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the M co₂ were 1.67 and 1.59 μmol O₂ g^–1 h^–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The M o₂ of P. barbarus , measured at 28°C, was 4·05 μmol O₂ g^–1 h^–1 during aquatic and 3·44 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the Mco₂ were 3·29 μmol CO₂ g^–1 h^–1 and 2·63 μmol CO₂ g^–1 h^–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re-immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected.     

Pathogenicity of live bacteria and extracellular products of motile Aeromonas isolated from eels

The pathogenic activities in vitro and in vivo of live bacteria and extracellular products (ECP) of 24 motile Aeromonas strains were investigated. Most Aer. hydrophila and Aer. jandaei isolates were pathogenic for eels (LD₅₀ 10^5·4-10^7·6 cfu fish^-1) but no Aer. sobria , Aer. caviae and Aer. allosaccharophila caused mortality in eels at doses of > 10^8·4 cfu fish^-1. Of these Aeromonas strains, Aer. hydrophila and Aer. jandaei in particular produced elastases and haemolysins against fish erythrocytes. ECP from Aer. hydrophila and Aer. jandaei caused degenerative changes in fish cell lines and were strongly toxic for eels (LD⁵⁰ 1·0–3·2 μg (g fish)^-1) reproducing the symptoms associated with natural disease. ECP from non-pathogenic species were inactive on fish cell lines as well as being poorly lethal for eels (LD⁵⁰ > 9·2 μg (g fish)^-1). All these biological activities of Aeromonas ECP were lost after heat treatment. These findings indicate differences between pathogenic and non-pathogenic Aeromonas species with respect to the expression of virulence factors, and show that elastases, haemolysins and exotoxins play a leading role in the pathogenicity of motile Aeromonas for eels.     

Increased ELISA sensitivity using a modified extraction buffer for detection of Xanthomonas campestris pv. vesicatoria in leaf tissue

In vitro and in planta sensitivity of an indirect enzyme-linked immunoassaytechnique, using a monoclonal antibody specific for the lipopolysaccharide (LPS) of Xanthomonas campestris pv. vesicatoria , was increased 10-foldby using a newextraction buffer (gl of : KH₂PO₄, 2; NaHPO₄, 11·5; EDTAdisodium, 0·14; thimerosal, 0·02; and lysozyme, 0·2). The procedure improvedsensitivity without increasing background levels. In vitro , the limit of detection wasbetween 1×10⁷ and 1×10⁸ cells ml⁻¹ with the conventionalextraction buffer phosphate-buffered saline (PBS) and less than 1×10⁶ cells ml⁻¹ when lysozyme extraction buffer was substituted for PBS. In comparing 22 X. c.vesicatoria strains, absorbance readings were increased close to three-fold with the lysozymeextraction buffer as opposed to PBS. When leaf tissue extract was spiked with the bacterium, thelimit of detection was 1×10⁷ cfu ml⁻¹ and 1×10⁸ cfu ml⁻¹ with the lysozyme solution and PBS, respectively, as the extraction buffers. Whenusing the lysozyme extraction buffer in combination with a commercial amplification system, thelimit of detection was decreased to less than 1×10⁵ cfu ml⁻¹ in leaftissue. The addition of the lysozyme and EDTA to the phosphate buffer resulted in release of asignificant quantity of LPS and concomitant dramatic increase in sensitivity. The new procedure,termed lysozyme ELISA (L-ELISA), should increase sensitivity of ELISA reactions where LPS isthe reacting epitope.     

Protein synthesis, nitrogen excretion and long-term growth of juvenile Pleuronectes flesus

This study aimed to measure protein synthesis using a stable isotope method, investigate protein-nitrogen flux in a flatfish Pleuronectes flesus , and use the data to test the hypothesis that individual differences in growth efficiency were related to individual differences in protein-nitrogen flux mediated through differences in protein synthesis and degradation. Three measurements of protein-nitrogen flux via consumption, protein synthesis and nitrogenous excretion were made for individual flounder during a 212-day period and fractional rates of protein-nitrogen flux were scaled for a 50–g flounder to provide mean values for protein consumption (2·11 ± 0·21% day⁻¹), protein synthesis (2·08±0·23% day⁻¹), protein growth (0·71±0·06% day⁻¹) and protein degradation (1·37±0·24% day⁻¹). Mean rates of nitrogenous excretion were 0·142 mg N g⁻¹ day⁻¹ and 0·047 mg N g⁻¹ day⁻¹ for ammonia and urea, respectively. Individual flounder had different protein growth efficiencies and this was correlated negatively and significantly with mean rates of protein synthesis ( r - 0·70; P <0·05) and degradation ( r - 0·67; P < 0·05) and correlated positively and significantly with the efficiency of retaining synthesized protein ( r +0·63, P <0·05). This supported the proposed hypothesis that flounder which grow more efficiently achieve this through adopting a low protein turnover strategy.     

Fast locomotion of some African ungulates

Ten species of ungulate were filmed, galloping in their natural habitat. They ranged in size from Thomson's gazelle (about 20 kg) to giraffe (about 1000 kg). They were pursued to make them run as fast as possible. The films have been analysed to determine speed, stride frequency, stride and step lengths, and duty factors. The dependence of these quantities on body size is discussed.  

Summary:

Fast locomotion of zebra, giraffe, warthog and seven species of Bovidae has been studied. The animals were filmed from a pursuing vehicle while galloping in their natural habitat.
Stride frequency was more closely correlated with limb length (represented by hip height) than with body mass. Mean stride frequency was proportional to (hip height)^-0·51 and maximum stride frequency to (hip height) ^-0·63.
Maximum speed was between 10 and 14 m s ^-1 for all species except buffalo (7 m s ^-1). It was not significantly correlated with body mass.
Since the small species ran at least as fast as the large ones they attained higher Froude numbers. Relative stride length was approximately 1·8 (Froude number)^0·39 for all species, irrespective of size. Relative step length was approximately 0·65 (Froude number)^0·2, both for the fore feet and for the hind ones. The vertical forces exerted by the feet are proportional to (body weight)×(Froude number)^0·2 so the forces at maximum speed are larger multiples of body weight for small species than for large ones.     

Hydroacoustic measurement of swimming speed of North Sea saithe in the field

Saithe Pollachius virens , tracked diurnally with a split-beam echosounder, showed no relationship between size and swimming speed. The average and the median swimming speeds were 1·05 m s⁻¹(±0·09 m s⁻¹) and 0·93 m s⁻¹, respectively. However, ping-to-ping speeds up to 3·34 m s⁻¹ were measured for 25–29 cm fish, whose swimming speeds were significantly higher at night (1·08 m s⁻¹) than during the day (0·72 m s⁻¹). The high average swimming speed could be related to the foraging or streaming part of the population and not to potential weakness of the methodology. However, the uncertainty of target location increased with depth and resulted in calculated average swimming speeds of 0·15 m s⁻¹ even for a stationary target. With increasing swimming speed the average error decreased to 0 m s⁻¹ for speeds >0·34 m s⁻¹. Species identity was verified by trawling in a pelagic layer and on the bottom.     

Ammonium ion affecting tylosin production by Streptomyces fradiae NRRL 2702 in continuous culture

Nitrogen regulation in tylosin production by Streptomyces fradiae NRRL 2702 was studied in chemostat culture using a soluble synthetic medium. The maximum value of specific tylosin formation rate ( q _TYL) was 1·13 mg g⁻¹ h⁻¹ at the specific growth rate (μ) of 0·05 h⁻¹, and q _TYL decreased with increasing levels of the specific growth rate after reaching a rate of 0·1 h⁻¹. The optimum conditions for tylosin formation were that the specific ammonium ion uptake rate ( q _N) and μ were 0·13 mmol g⁻¹ h⁻¹ and 0·05 h⁻¹, respectively. The specific formation rates of threonine dehydratase (TDT) and tylosin were repressed by high levels of specific ammonium ion uptake rate. This study showed the adaptation to chemostat cultures of the nitrogen regulation of tylosin fermentations.     

In vitro analysis of intestinal absorption of cadmium and calcium in rainbow trout fed with calcium- and cadmium-supplemented diets

The protective effects of dietary Ca²⁺ supplementation against Cd accumulation in rainbow trout Oncorhynchus mykiss fed with Cd-contaminated food were evaluated in relation to chronic changes in intestinal absorption rates. The changes were measured ' in vitro '. The control diet contained c. 20 mg Ca²⁺ g⁻¹ food and 0·25 μg Cd g⁻¹ food; the experimental diets were supplemented with CaCO₃ and Cd(NO₃)₂·4H₂O to levels of 50 mg Ca²⁺ g⁻¹ food and 300 μg Cd g⁻¹ food, alone and in combination. The Ca²⁺ and Cd absorption rates were measured using radiotracers (⁴⁵Ca, ¹⁰⁹Cd) at total Ca²⁺ and Cd concentrations of 3·0 and 0·12 mmol l⁻¹, respectively in the intestinal saline. Chronically elevated dietary Cd caused a significant increase in Cd absorption rate by up to 10-fold at 30 days in the mid-intestine. The high Ca²⁺ diet prevented this up-regulation of Cd transport rate. Conversely, intestinal Ca²⁺ absorption was significantly increased by two- to five-fold by the Ca²⁺-supplemented diet at 30 days in both the mid- and posterior intestine, and this effect was eliminated when Cd was simultaneously elevated in the diet. Ca²⁺ and Cd probably interact at common pathways and transport mechanisms in the intestine, though independent pathways may also exist.