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1.
S L Percival 《Journal of industrial microbiology & biotechnology》1999,23(2):112-117
Little is known about the formation and effects of biofilms on stainless steel pipes in freshwater environments, particularly
as they are considered as a direct replacement for copper pipes for ‘problem’ water. There is some cause for concern especially
as stainless steel cannot claim the inherent biocidal potential of copper. As molybdenum is known to be leached out of stainless
steel grade 316, in very small amounts, a study was set up to see if molybdenum could retard the development of biofilms.
When a comparison of biofilm viable and total cell counts was made between pure molybdenum metal and stainless steel grade
304, it was found that cell counts were significantly higher (P < 0.05) on grade 304 stainless steel after 5 weeks exposure to flowing water (0.64 m s−1). Molybdenum (above a concentration of 1 g L−1) affected the growth rate of Acinetobacter sp, a pioneering bacterium of biofilms in potable water.
Received 18 February 1998/ Accepted in revised form 17 May 1999 相似文献
2.
Mattila K Weber A Salkinoja-Salonen MS 《Journal of industrial microbiology & biotechnology》2002,28(5):268-279
Paper machine biofilms formed in situ on stainless steel surfaces were studied. A robust flow cell was fitted to side stream (1.8 m s−1) of the spray water circuit of a paper machine. This on-site tool allowed for assessing the efficacy of antifoulants and
the adequacy of steel polishing under mill conditions. A rapid fluorescence-based assay was developed to quantify the biomass
of shallow biofilms on machine steel. The fluorescence matched the ATP content measured for the same biofilms. Electrolytic
polishing reduced the tendency of biofouling of 500 grit surface steel. Biofilm grew under machine conditions as clusters
on the steels, showing uniformly coccoid, filaments or short rods; only one cell type in each cluster. The biofilm clusters
excluded latex beads of 0.02 μm with hydrophilic or with hydrophobic surfaces from penetrating more than three to four layers
of cells. Under the high hydraulic flow at the machine (1.8 m s−1), the biofilm grew in 7 days 6–10 μm thick. The high flow rate guided the shape of the biofilm clusters emerging after the
primary attachment of cells. Adhered individual bacteria were the platform on steel to which solids such as paper machine
fines then accumulated. Journal of Industrial Microbiology & Biotechnology (2002) 28, 268–279 DOI: 10.1038/sj/jim/7000242
Received 04 October 2001/ Accepted in revised form 14 January 2002 相似文献
3.
Whereas the transfer of Listeria from surfaces to foods and vice versa has been well documented, little is known about the mechanism of bacterial transfer.
The objective of this work is to gain a better understanding of the forces involved in listerial biofilms adhesion using atomic
force microscopy (AFM). L. monocytogenes Scott A was grown as biofilms on stainless steel surfaces by inoculating stainless steel coupons with Listeria and incubating the coupons for 48 h at 32 °C with a diluted 1:20 tryptic soy broth. After growth, biofilms were equilibrated
over saturated salt solutions at a constant relative humidity (%RH) before measurement of adhesion forces using AFM. The effects
of contact time, loading force, and biofilm relative humidity (%RH) suggested that neither contact time, loading force nor
biofilm %RH had a significant effect on biofilm adhesiveness at a cellular level (P > 0.05). In a second set of experiments, the influence of material type on biofilm adhesiveness was evaluated using two different
colloidal probes (SiO2 and polyethylene). Results showed that the maximum pull-off force and retraction work needed to retract the cantilever for
glass (−85.42 nN and 1.610−15 J, respectively) were significantly lower than those of polyethylene (−113.38 nN and 2.7 × 10–15 J, respectively; P < 0.001). The results of this study suggest that Listeria biofilms adhere more strongly to hydrophobic surfaces than hydrophilic surfaces when measured at a cellular level. These
results provide important insights that could lead to new ways to remediate and avoid listerial biofilm formation in the food
industry. 相似文献
4.
Joseph P. Weir Dennis A. Keefe Jason F. Eaton Robert T. Augustine Dawn M. Tobin 《European journal of applied physiology and occupational physiology》1998,78(6):555-559
We examined the effect of fatigue of the quadriceps muscles on coactivation of the hamstring muscles and determined if the
response is different between two isokinetic speeds in ten males and ten females with no history of knee pathology. Electromyographic
data were recorded from the vastus lateralis and biceps femoris muscles during 50 maximal knee extensions at isokinetic speeds
of 1.75 rad · s−1 (100° · s−1) and 4.36 rad · s−1 (250° · s−1). A greater degree of coactivation was apparent at the higher speed, but the increase in coactivation of the hamstring muscles
was similar at both speeds. The results revealed that: (1) coactivation is greater at a higher isokinetic speed, and (2) coactivation
increases during fatigue, but the rate of increase is independent of contraction velocity.
Accepted: 15 June 1998 相似文献
5.
Submerged aquatic higher plants maintain acropetal water transport to the young leaves in active growth to satisfy their
demand for nutrients and hormones derived from the roots. We here present the first measurements of hydraulic properties for
a submerged plant, the monocotyledon Sparganium emersum Rehman. The hydraulic conductance per unit length, Kh, was measured in leaf segments without the leaf tip and shown to be greater in old, fully developed leaves (1.5 · 10−10 · m4 · MPa−1 · s−1) than in young leaves (1.0 · 10−10 · m4 · MPa−1 · s−1). In leaves with intact leaf tips, however, Kh was significantly greater in the youngest leaves, which suggests that the leaf tip with the hydathode influences resistance
and thus flow. Microscopy confirmed that the hydathodal area, which is an apical opening, undergoes structural changes with
leaf age; a matrix of microorganisms develops in the older leaves and probably restricts water flow by clogging the hydathodes.
The leaf specific conductivity expressing transport capacity relative to the leaf area supplied, of S. emersum (0.1 · 10−8 to 9 · 10−8 · m2 MPa−1· s−1) was within the same range as for various species of terrestrial ferns, vines and trees. This finding does not support the
traditional concept of functionally reduced vascular transport in
Received: 15 July 1996 / Accepted: 30 November 1996 相似文献
6.
Using the cell pressure probe, the effects of temperature on hydraulic conductivity (Lp; osmotic water permeability), solute
permeability (permeability coefficient, Ps), and reflection coefficients (σs) were measured on internodes of Chara corallina, Klein ex Willd., em R.D.W.. For the first time, complete sets of transport coefficients were obtained in the range between
10 and 35 °C which provided evidence about pathways of water and solutes as they move across the plasma membrane (water channel
and bilayer arrays). Test solutes used to check for the selectivity of water channels were monohydric alcohols of different
molecular size and shape (ethanol, n-propanol, iso-propanol, and tert-butanol) and heavy water (HDO). Within the limits of accuracy, Q10 values for Lp and for the diffusive water permeability (Pd) were identical (Q10 for Lp = 1.29 ± 0.17 (± SD; n = 15 cells) and Q10 for Pd = 1.25 ± 0.16 (n = 5 cells)). The Q10 values were equivalent to activation energies of Ea = 16.8 ± 6.4 and 16.6 ± 10.0 kJ · mol−1, respectively, which is similar to that of self-diffusion or of viscous flow of water. The Q10 values and activation energies for Ps of the alcohols were significantly larger (ethanol: Q10 = 1.68 ± 0.16, Ea = 37.1 ± 5.9 kJ · mol−1; n-propanol: Q10 = 1.75 ± 0.40, Ea = 43.1 ± 15.3 kJ · mol−1; iso-propanol: Q10 = 2.12 ± 0.42, Ea = 52.2 ± 14.6 kJ · mol−1; tert-butanol: Q10 = 2.13 ± 0.56, Ea = 51.6 ± 17.1 kJ · mol−1; ±SD; n = 5 to 6 cells). Effects of temperature on reflection coefficients were most pronounced. With increasing temperature, σs values of the alcohols decreased and those of HDO increased. The data indicate that water and solutes use different pathways
when crossing the membrane. Ordinary and isotopic water use water channels and the other test solutes use the bilayer array
(composite transport model of membrane). Changes in σs values with temperature were found to be a sensitive measure for the open/closed state of water channels. The decrease of
σs with temperature was theoretically predicted from the temperature dependence of Ps and Lp. Differences between predicted and measured values of σs allowed estimation of the bypass flow (slippage) of solutes through water channels which did not completely exclude test
solutes. The permeability of channels depended on the structure and size of test solutes. It is concluded that water channels
are much less selective than is usually thought. Since water channels represent single-file or no-pass pores, solutes drag
along considerable amounts of water as they diffuse across channels. This results in low overall values of σs. The σs of HDO was extremely low. Its response to temperature was opposite to that for the σs of the alcohols. This suggested a stronger effect of temperature on the hydraulic (osmotic) than on the diffusive water flow
across individual water channels, i.e. a differential sensitivity of different mechanisms to temperature.
Received: 10 October 1996 / Accepted: 2 December 1996 相似文献
7.
The development of biofilms of Pseudomonas aeruginosa PAO-1 was studied using modified Robbins devices. Biofilm development was measured using viable counts, acridine orange direct
counts (AODC), and a colorimetric method for exopolysaccharide (EPS). Biofilms reached their maximum population 24–72 h after
inoculation on coupons with no paint or on coupons coated with marine paint VC-18 without additives. Biofilms on stainless
steel contained higher numbers of total cells and of viable cells than biofilms on fiberglass or aluminum. Coating the surfaces
with marine paint VC-18 resulted in decreased numbers of cells on stainless steel but had little effect on numbers of cells
on fiberglass or aluminum. Addition to the paint of Cu or tributyltin (TBT), the active components in two types of antifouling
paints, inhibited the initial development of biofilms. However, by 72–96 h, most biofilms contained the same number of cells
as surfaces without additives as shown by both viable counts and AODC. Biofilms that formed on surfaces coated with Cu- or
TBT-containing paint did not synthesize more EPS, suggesting that P. aeruginosa PAO-1 does not respond to these compounds by synthesizing more EPS, which could bind the metal and protect the cells. Rather,
these biofilms may contain Cu- or TBT-resistant cells. TBT-resistant cells made up 1–10% of the viable counts in biofilms
on uncoated stainless steel, but in biofilms on stainless steel coated with marine paint containing TBT, TBT-resistant cells
made up as much as 50% of the population. For non-coated stainless steel surfaces, Cu-resistant cells initially made up the
majority of the population, but after 48 h they made up less than 1% of the population. On Cu-coated stainless steel, Cu-resistant
cells predominated through 48 h, but after 48 h they comprised less than 10% of the population. These results suggest that
the growth of TBT-resistant and Cu-resistant cells contributes to biofilms of P. aeruginosa PAO-1 at early stages of development but not at later stages.
Received 16 December 1997/ Accepted in revised form 9 March 1998 相似文献
8.
CO2 exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO2 concentration. The species had low CO2 exchange rates (maximum net photosynthesis: c. 0.45 μmol CO2 m−2 s−1; maximum dark respiration: c. 0.3 μmol CO2 m−2 s−1) and a very low light compensation point (7 μmol photons m−2 s−1 at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only
after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under
different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant.
Low photosynthetically active radiation (normally below 40 μmol photons m−2 s−1), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO2 assimilation were often measured in the absence of condensation phenomena.
Received: 22 September 1996 / Accepted: 26 April 1997 相似文献
9.
Water availability is an important factor limiting the productivity of desert plants but little is known about the impact
of water-limiting conditions on the physiology of plants in mesic environments. Riparian ecosystems of the western US receive
significantly more water than the surrounding desert environments but experience dramatic interannual fluctuations in water
availability because both stream flow and precipitation are highly variable over time. This variability results in different
growing conditions each year which may influence the physiology of riparian species such as Fremont cottonwood (Populus fremontii), the dominant, native canopy tree species in lowland southwestern US river systems. We wished to determine if the physiology
of this species varies among years, what climatic parameters are related to any observed physiological variation and if individuals
within a P. fremontii population differ in their physiological response to variation through time. We collected tree ring cores from a central
New Mexico cottonwood population and analyzed carbon isotope composition (δ13C) in each year from 1981 to 1995. We used δ13C analysis in this study because it allowed us to obtain multi-year estimates of physiological activity. During these years,
mean stream flow at our study site ranged over two orders of magnitude from 0.82 to 80.94 m3 s−1, precipitation ranged fourfold from 49 to 215 ccmm and mean temperature ranged from 20.5 to 22.6°C during the growing season.
δ13C varied from a low of −26.7‰ in 1984 to a high of −24.7‰ in 1981. Low δ13C values were associated with years in which stream flow and/or precipitation were high and temperature was low. The opposite
was true of years with high δ13C values. We observed a strong linear relationship between δ13C and stream flow during years when stream flow was <25 m3 s−1 but no significant relationship between these variables when stream flow was >25 m3 s−1. Additionally, there was a linear relationship between δ13C and precipitation during years when stream flow was <25 m3 s−1 but not in years when stream flow was >25 m3 s−1. These data suggest that above a threshold of total stream flow, increased flow does not influence physiology. Below this
threshold, precipitation can be an important water source. The ten individuals within our study population varied significantly
in mean δ13C values but responded to interannual variation in a similar manner (i.e., all individuals had low δ13C values when water was abundant). These results suggest that precipitation as well as stream flow are important factors influencing
the physiology of this riparian tree.
Received: 25 November 1998 / Accepted: 9 February 1999 相似文献
10.
Juozas Kulys Kastis Krikstopaitis Arturas Ziemys 《Journal of biological inorganic chemistry》2000,5(3):333-340
N -substituted phenothiazines (PTs) and phenoxazines (POs) catalyzed by fungal Coprinus cinereus peroxidase and Polyporus pinsitus laccase were investigated at pH 4–10. In the case of peroxidase, an apparent bimolecular rate constant (expressed as k
cat/K
m) varied from 1 ×107 M−1 s−1to 2.6×108 M−1 s−1 at pH 7.0. The constants for PO oxidation were higher in comparison to PT. pH dependence revealed two or three ionizable
groups with pK
a values of 4.9–5.7 and 7.7–9.7 that significantly affected the activity of peroxidase. Single-turnover experiments showed
that the limiting step of PT oxidation was reduction of compound II and second-order rate constants were obtained which were
consistent with the constants at steady-state conditions. Laccase-catalyzed PT and PO oxidation rates were lower; apparent
bimolecular rate constants varied from 1.8×105 M−1 s−1 to 2.0×107 M−1 s−1 at pH 5.3. PO constants were higher in comparison to PT, as was the case with peroxidase. The dependence of the apparent
bimolecular constants of compound II or copper type 1 reduction, in the case of peroxidase or laccase, respectively, was analyzed
in the framework of the Marcus outer-sphere electron-transfer theory. Peroxidase-catalyzed reactions with PT, as well as PO,
fitted the same hyperbolic dependence with a maximal oxidation rate of 1.6×108 M−1 s−1 and a reorganization energy of 0.30 eV. The respective parameters for laccase were 5.0×107 M−1 s−1 and 0.29 eV.
Received: 20 September 1999 / Accepted: 24 February 2000 相似文献
11.
P. Pfeiffer B. M. Culik 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(2):143-148
We used a still-water swim channel in conjunction with open-flow oxygen and carbon dioxide respirometry to examine the energy
requirements of river-otters (Lutra lutra L.) swimming voluntarily underwater in Neumünster Zoo (Germany). While at rest on land (5 °C), river-otters had a respiratory
quotient of 0.77 and a resting metabolic rate of 4.1 W kg−1. This increased to an estimated 6.4 W kg−1 during rest in water (11–15 °C) and to 12.3 W kg−1 when the animals were feeding in the channel. River-otters swimming under water preferred a mean speed of 0.89 m s−1, and their energy requirements attained 11.6 W kg−1. Cost of transport, however, was minimal at 1.3 m s−1 and amounted to 0.95 J N−1 m−1.
Accepted: 3 November 1997 相似文献
12.
Water conductance of the cuticular membrane (CM) of mature sweet cherry fruit (Prunus avium L. cv. Sam) was investigated by monitoring water loss from segments of the outer pericarp excised from the cheek of the fruit.
Segments consisted of epidermis, hypodermis and several cell layers of the mesocarp. Segments were mounted in stainless-steel
diffusion cells with the mesocarp surface in contact with water, while the outer cuticular surface was exposed to dry silica
(22 ± 1 °C). Conductance was calculated by dividing the amount of water transpired per unit area and time by the difference
in water vapour concentration across the segment. Conductance values had a log normal distribution with a median of 1.15 × 10−4 m s−1 (n=357). Transpiration increased linearly with time. Conductance remained constant and was not affected by metabolic inhibitors
(1 mM NaN3 or 0.1 mM carbonylcyanide m-chlorophenylhydrazone) or thickness of segments (range 0.8–2.8 mm). Storing fruit (up to 42 d, 1 °C) used as a source of
segments had no consistent effect on conductance. Conductance of the CM increased from cheek (1.16 ± 0.10 × 10−4 m s−1) to ventral suture (1.32 ± 0.07 × 10−4 m s−1) and to stylar end (2.53 ± 0.17 × 10−4 m s−1). There was a positive relationship (r2=0.066**; n=108) between conductance and stomatal density. From this relationship the cuticular conductance of a hypothetical astomatous
CM was estimated to be 0.97 ± 0.09 × 10−4 m s−1. Removal of epicuticular wax by stripping with cellulose acetate or extracting epicuticular plus cuticular wax by dipping
in CHCl3/methanol increased conductance 3.6- and 48.6-fold, respectively. Water fluxes increased with increasing temperature (range
10–39 °C) and energies of activation, calculated for the temperature range from 10 to 30 °C, were 64.8 ± 5.8 and 22.2 ± 5.0 kJ
mol−1 for flux and vapour-concentration-based conductance, respectively.
Received: 23 March 2000 / Accepted: 28 July 2000 相似文献
13.
Christophe Sandt Truis Smith-Palmer Jonathan Comeau David Pink 《Applied microbiology and biotechnology》2009,83(6):1171-1182
The Raman spectra, water content, and biomass density of wild-type (WT) Pseudomonas aeruginosa PAO1, small colony variant (SCV) PAO1, and Pseudoalteromonas sp. NCIMB 2021 biofilms were compared in order to determine their variation with strain and species. Living, fully submerged
biofilms were analyzed in situ by confocal Raman microspectroscopy for up to 2 weeks. Water to biomass ratios (W/BRs), which
are the ratios of the O–H stretching vibration of water at 3,450 cm−1 to the C–H stretching band characteristic of biomass at 2,950 cm−1, were used to estimate the biomass density and cell density by comparison with W/BRs of protein solutions and bacterial suspensions,
respectively, on calibration curves. The hydration within SCV biofilm colonies was extremely heterogeneous whereas W/BRs were
generally constant in young WT biofilm colonies. The mean biomass in biofilm colonies of WT or colony cores of SCV was typically
equivalent to 16% to 27% protein (w/v), but was 10% or less for NCIMB 2021. The corresponding cell densities were 7.5 to >10 × 1010 cfu mL−1 for SCV, while the maximum cell density for NCIMB biofilms was 2.8 × 1010 cfu mL−1. 相似文献
14.
J. Hall I. A. Macdonald P. J. Maddison J. P. O''Hare 《European journal of applied physiology and occupational physiology》1998,77(3):278-284
This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise
on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water
temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h−1. Oxygen consumption (V˙O2) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing
speed both in water and on land. At 3.5 km · h−1
V˙O2 was similar across procedures [χ = 0.6 (0.05) l · min−1]. At 4.5 and 5.5 km · h−1
V˙O2 was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm:
0.8 and 0.9 l · min−1, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at
4.5 and 5.5 km · h−1 (P ≤ 0.003). The HR-V˙O2 relationship showed that at a V˙O2 of 0.9 l · min−1, HR was higher in water at 36°C (115 beats · min−1) than either on land (100 beats · min−1) or in water at 28°C (99 beats · min−1). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h−1 was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was
27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data
has implications for therapists working in hydrotherapy pools.
Accepted: 3 September 1997 相似文献
15.
Inhibiting sulfate-reducing bacteria in biofilms by expressing the antimicrobial peptides indolicidin and bactenecin 总被引:3,自引:0,他引:3
A Jayaraman F B Mansfeld T K Wood 《Journal of industrial microbiology & biotechnology》1999,22(3):167-175
To identify novel, less-toxic compounds capable of inhibiting sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris and Desulfovibrio gigas in suspension cultures were exposed to several antimicrobial peptides. The bacterial peptide antimicrobials gramicidin S,
gramicidin D, and polymyxin B as well as the cationic peptides indolicidin and bactenecin from bovine neutrophils decreased
the viability of both SRB by 90% after a 1-h exposure at concentrations of 25–100 μg ml−1. To reduce corrosion by inhibiting SRB in biofilms, the genes for indolicidin and bactenecin were expressed in Bacillus subtilisBE1500 and B. subtilis WB600 under the control of the constitutive alkaline protease (apr) promoter, and the antimicrobials were secreted into the culture medium using the apr signal sequence. Bactenecin was also synthesized and expressed as a fusion to the pro-region of barnase from Bacillus amyloliquefaciens. Concentrated culture supernatants of B. subtilis BE1500 expressing bactenecin at 3 μg ml−1 decreased the viability of Escherichia coli BK6 by 90% and the reference SRB D. vulgaris by 83% in suspension cultures. B. subtilis BE1500 and B. subtilis WB600 expressing bactenecin in biofilms also inhibited the SRB-induced corrosion of 304 stainless steel six to 12-fold in
continuous reactors as evidenced by the lack of change in the impedance spectra (resistance polarization) upon addition of
SRB and by the reduction in hydrogen sulfide and iron sulfide in batch fermentations with mild steel. A 36-fold decrease in
the population of D. vulgaris in a B. subtilis BE1500 biofilm expressing bactenecin was also observed. This is the first report of an antimicrobial produced in a biofilm
for in vivo applications and represents the first application of a beneficial, genetically-engineered biofilm for combating corrosion.
Received 27 October 1998/ Accepted in revised form 21 February 1999 相似文献
16.
A.-W. Pan J. He Y. Kinouchi Hisao Yamaguchi Hiroshi Miyamoto 《European journal of applied physiology and occupational physiology》1997,75(5):388-395
The present study investigated the mechanism of diving bradycardia. A group of 14 healthy untrained male subjects were examined
during breath-holding either out of the water (30–33°C), in head-out immersion, or in whole-body submersion (27–29°C) in a
diving pool. Blood velocity, blood volume flow in the carotid artery, diastolic blood pressure and electrocardiogram were
measured and recorded during the experiments. The peak blood velocity increased by 13.6% (P < 0.01) and R-wave amplitude increased by 57.1% (P < 0.005) when the subjects entered water from air. End-diastolic blood velocity in the carotid artery increased significantly during breath-holding, e.g. increased from 0.20 (SD 0.02) m · s−1 at rest to 0.33 (SD 0.04) m · s−1 (P < 0.001) at 50.0 s in breath-hold submersion to a 2.0-m depth. Blood volume flow in the carotid artery increased by 26.6%
(P < 0.05) at 30 s and 36.6% (P < 0.001) at 40 s in breath-hold submersion to a 2.0-m depth. Diastolic blood pressure increased by 15.4% (P < 0.01) at 60 s during breath-holding in head-out immersion. Blood volume flow, and diastolic blood pressure increased significantly more and faster during breath-holding in submersion than out of the
water. There was a good negative correlation with the heart rate: the root mean square correlation coefficient r was 0.73 (P < 0.001). It was concluded that an increased accumulation of blood in the aorta and arteries at end-diastole and decreased
venous return, caused by an increase in systemic peripheral resistance during breath-holding, underlies diving bradycardia.
Accepted: 22 November 1996 相似文献
17.
To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending
on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 μmol m−2 s−1) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a
control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 μmol m−2 s−1. The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 μmol m−2 s−1 and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300–1600 μmol m−2 s−1). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite
content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase
and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 μmol m−2 s−1 or in the glasshouse than in plants grown at 330 μmol m−2 s−1. Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar
under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 μmol m−2 s−1 can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate.
This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase
and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate.
This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
Received: 15 November 1999 / Accepted: 27 January 2000 相似文献
18.
E. J. Olguín S. Galicia R. Camacho G. Mercado T. J. Pérez 《Applied microbiology and biotechnology》1997,48(2):242-247
The use of untreated sea water supplemented with anaerobic effluents from digested pig waste and sodium bicarbonate was evaluated
as a low-cost medium for semi-continuous cultivation of a mixed culture of two Spirulina strains in outdoor raceways under temperate climatic conditions (pond temperature in the range 21–26 °C and light intensity
in the range 225–957␣μE m−2 s−1). The mixed culture had a predominant population (86.6 ± 3.9%) of an atypical Spirulina strain consisting of straight filaments, which appeared spontaneously after the strain with helicoidal trichomes had been
subcultured. Morphological studies for the identification of the type and size of trichomes of the two strains (HF and SF)
were carried out. The proportions of the two strains were observed to be stable during the monitoring period (30 days). Three
different sets of semicontinuous cultures were carried out. Sets 1 and 2 were operated under regime 1 (a single addition of
anaerobic effluents at time zero and no pH control) during the same season (June and July) of different years. Set 3 was operated
under regime 2 (semi-continuous addition of anaerobic effluents and pH control) during the autumn. A minimum productivity
of 3.6 g m−2 day−1 was obtained at one of the lowest temperatures (22.1 °C) and light intensities (245 μE m−2 s−1) and a maximum productivity of 10.9 g m−2 day−1 was observed at the highest temperature (25 °C) and highest average light intensity (618 μE m−2 s−1) registered for sets 1 and 2. The protein content in the Spirulina biomass harvested from these two sets varied from 17% to 65.6%. In set 3, a maximum productivity of 9.0 g m−2 day−1 was recorded at an average temperature of 24.4 °C and at an average light intensity of 668 μE m−2 s−1. The protein content in this set under regime 2 varied within a narrower range than in set 1 and set 2 (from 34.8% to 49.1%),
apparently because of a continuous availability of ammonia nitrogen at a level of 30–50 mg l−1. However, in terms of the removal of ammonia nitrogen and chemical oxygen demand, regime 1 was more efficient than regime␣2.
Received: 3 September 1996 / Received revision: 19 February 1997 / Accepted: 7 March 1997 相似文献
19.
Malaysia is the world’s leading producer of palm oil products that contribute US$ 7.5 billion in export revenues. Like any
other agro-based industries, it generates waste that could be utilized as a source of organic nutrients for microalgae culture.
Present investigation delves upon Isochrysis sp. culture in POME modified medium and its utilization as a supplement to Nanochloropsis sp. in rotifer cultures. The culture conditions were optimized using a 1 L photobioreactor (Temp: 23°C, illumination: 180 ∼ 200 μmol
photons m−2s−1, n = 6) and scaled up to 10 L outdoor system (Temp: 26–29°C, illumination: 50 ∼ 180 μmol photons m−2s−1, n = 3). Algal growth rate in photobioreactor (μ = 0.0363 h−1) was 55% higher compared to outdoor culture (μ = 0.0163 h−1), but biomass production was 1.3 times higher in outdoor culture (Outdoor = 91.7 mg m−2d−1; Photobioreactor = 69 mg m−2d−1). Outdoor culture produced 18% higher lipid; while total fatty acids (FA) was not significantly affected by the change in
culture systems as both cultures yield almost similar concentrations of fatty acids per gram of sample (photobioreactor = 119.17 mg
g−1; outdoor culture = 104.50 mg g−1); however, outdoor cultured Isochrysis sp. had 26% more polyunsaturated fatty acids (PUFAs). Rotifers cultured in Isochrysis sp./ Nanochloropsis sp. (1:1, v/v) mixture gave similar growth rate as 100% Nanochoropsis sp. culture (μ = 0.40 d−1), but had 45% higher counts of rotifers with eggs (t = 7, maximum). The Isochrysis sp. culture successfully lowered the nitrate (46%) and orthophosphate (83%) during outdoor culture. 相似文献
20.
Yun Hee Kang Jong Ahm Shin Myung Sook Kim Ik Kyo Chung 《Journal of applied phycology》2008,20(2):183-190
In integrated multi-trophic aquaculture (IMTA), seaweeds have the capacity to reduce the environmental impact of nitrogen-rich
effluents in coastal ecosystems. To establish such bioremediation systems, selection of suitable seaweed species is important.
The distribution and productivity of seaweeds vary seasonally based on water temperature and photoperiod. In Korea, candidate
genera such as Pophyra, Laminaria, and Undaria grow from autumn to spring. In contrast, Codium grows well at relatively high water temperatures in summer. Thus, aquaculture systems potentially could capitalize on Codium’s capacity for rapid growth in the warm temperatures of late summer and early fall. In this study, we investigated ammonium
uptake and removal efficiency by Codium fragile. In laboratory experiments, we grew C. fragile under various water temperatures (10, 15, 20, and 25°C), irradiances (dark, 10, and 100 μmol photons m−2 s−1), and initial ammonium concentrations (150 and 300 μM); in all cases, C. fragile exhausted the ammonium supply for 6 h. At 150 μM of , ammonium removal efficiency was greatest (99.5 ± 2.6%) when C. fragile was incubated at 20°C under 100 μmol photons m−2 s−1. At 300 μM of , removal efficiency was greatest (86.3 ± 2.1%) at 25°C under 100 μmol photons m−2 s−1. Ammonium removal efficiency was significantly greater at 20 and 25°C under irradiance of 100 μmol photons m−2 s−1 than under other conditions tested. 相似文献