Substrate affinity from bacterial strains and distribution water biofilms

Biodegradable dissolved organic carbon (BDOC) is almost the only limiting factor of bacterial growth in drinking water. Two representative bacterial strains were isolated from a two-column reactor for the determination of BDOC (from respectively the first and the second column) and used to estimate their growth kinetics in two different types of water: finished water from a water treatment plant and water collected at the outlet of the first column of the BDOC reactor. K _s, the substrate saturation constant, was calculated by analogy with Michaelis-Menten enzyme kinetics, and for each strain a lower K _s value was observed for the type of water that it normally receives.
K _s for in situ biofilms, from both first and second column and the same types of water, were also calculated according to a technique which uses a curve-matching method with kinetic results from the non-steady-state experiments. In this case, the results were similar for the first and second column biofilms. However, a higher affinity was observed for finished water than for the water from the outlet of the first column in both biofilms.     

Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation

The study examined the relationships between whole tree hydraulic conductance ( K _tree) and the conductance in roots ( K _root) and leaves ( K _leaf) in loblolly pine trees. In addition, the role of seasonal variations in K _root and K _leaf in mediating stomatal control of transpiration and its response to vapour pressure deficit ( D ) as soil-dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K _root declined faster than K _leaf. Although K _tree depended on soil moisture, its dynamics was tempered by the elongation of current-year needles that significantly increased K _leaf when REW was below 50%. After accounting for the effect of D on g _s, the seasonal decline in K _tree caused a 35% decrease in g _s and in its sensitivity to D , responses that were mainly driven by K _leaf under high REW and by K _root under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K _tree and g _s and the acclimation of trees to changing environmental conditions.     

Surface free energies of oral streptococci and their adhesion to solids

Abstract The adhesion of 3 strains of oral streptococci from a buffered suspension onto 3 different solid substrata was studied. Representative strains of streptococci were selected on the basis of their surface free energy ( γ _b), namely Streptococcus mitis L1 ( γ _b= 37 mJ·m⁻²), Streptococcus sanguis CH3 (95 mJ·m⁻²) and Streptococcus mutans NS (117 mJ·m⁻²). Solid substrata were also selected on basis of their surface free energy ( γ _s), and included polytetrafluorethylene ( γ _s= 20 mJ·m⁻²), polymethylmethacrylate (53 mJ·m⁻²) and glass (109 mJ·m⁻²). Bacterial adhesion was measured as the number of bacteria adhering per cm² at equilibrium. Equilibrium was usually obtained within 20 min. S. sanguis CH3, having an intermediate surface free energy did not show a clear preference for any of the 3 solids. S. mitis L1, however, the lowest surface free energy strain, adhered in highest numbers to the low energy solid PTFE, whereas the highest γ _b strain, S. mutans NS, adhered in highest numbers to the highest γ _s solid, glass. Calculation of the interfacial free energy of adhesion ( ΔF _adh) for each bacterial strain showed that this parameter was predictive of bacterial adhesion to solid substrata.     

Stomata of trees growing in CO2-enriched air show reduced sensitivity to vapour pressure deficit and drought

Stomatal conductance ( g _s) and photosynthetic rate ( A ) were measured in young beech ( Fagus sylvatica ), chestnut ( Castanea sativa ) and oak ( Quercus robur ) growing in ambient or CO₂-enriched air. In oak, g _s was consistently reduced in elevated CO₂. However, in beech and chestnut, the stomata of trees growing in elevated CO₂ failed to close normally in response to increased leaf-to-air vapour pressure deficit (LAVPD). Consequently, while g _s was reduced in elevated CO₂ on days with low LAVPD, on warm sunny days (with correspondingly high LAVPD) g _s was unchanged or even slightly higher in elevated CO₂. Furthermore, during drought, g _s of beech and chestnut was unresponsive to [CO₂], over a wide range of ambient LAVPD, whereas in oak g _s was reduced by an average of 50% in elevated CO₂. Stimulation of A by elevated CO₂ in beech and chestnut was restricted to days with high irradiance, and was greatest in beech during drought. Hence, most of the additional carbon gain in elevated CO₂ was made at the expense of water economy, at precisely those times (drought, high evaporative demand) when water conservation was most important. Such effects could have serious consequences for drought tolerance, growth and, ultimately, survival as atmospheric [CO₂] increases.     

Sap salinity effects on xylem conductivity in two mangrove species

Xylem sap salinity and conductivity were examined in two mangrove ecosystem tree species . For Avicennia germinans , extracted xylem sap osmotic potentials ranged from −0.24 to −1.36 MPa versus −0.14 to −0.56 MPa for Conocarpus erectus. Xylem sap of Conocarpus did not vary in osmotic potential between sites nor between predawn and midday. In Avicennia , values were more negative at midday than predawn, and also more negative at hypersaline than hyposaline sites. After removing embolisms, specific conductivity ( K _s) was measured as a function of salinity of the artificial xylem sap perfusion. For both species the lowest K _s values, about 70% of the maximum K _s, were obtained when stems were perfused with deionized water (0 m m ; 0.0 MPa) or with a 557-m m saline solution (−2.4 MPa). Higher K _s values were obtained in the range from −0.3 to −1.2 MPa, with a peak at −0.82 ± 0.08 MPa for Avicennia and −0.75 ± 0.08 MPa for Conocarpus . The variations in K _s values with minima both at very low and very high salt concentrations were consistent with published results for swelling and shrinking of synthetic hydrogels, suggesting native hydrogels in pit membranes of vessels could help regulate conductivity.     

Major differences between glutamate-fermenting species isolated from chemostat enrichments at different dilution rates

Abstract From chemostat enrichments conducted at dilution rates of 0.025, 0.12 and 0.25 h⁻¹ glutamate- and aspartate-fermenting bacteria were isolated. The dominant aspartate-fermenting strains in all these enrichments belonged to the genus Campylobacter , whereas 3 dissimilar types of glutamate-fermenting bacteria predominated at the different dilution rates. One of these strains was identified as Clostridium cochlearium . The remaining two were designated as strain DKglu16 (glutamate → acetate + propionate + ammonium + carbon dioxide) and DKglu21 (glutamate → acetate + formate + ammonium + carbon dioxide). Grown in continuous culture under glutamate limitation, strain DKglu16 (μ_max= 0.13 h⁻¹; K _s= 1.9 μM) outcompeted C. cochlearium (μ_max= 0.36 h⁻¹; K _s= 7 μM) at low dilution rates, but was outgrown at higher rates of dilution (0.044 h⁻¹). In glutamate-limited continuous culture the competitiveness of strain DKglu16 increased considerably when lactate was added to the feed in addition to glutamate.     

Fluoride inhibits root water transport and affects leaf expansion and gas exchange in aspen (Populus tremuloides) seedlings

The effects of sodium fluoride (0.3, 5 and 10 m M NaF) on root hydraulic conductivity, and gas exchange processes were examined in aspen ( Populus tremuloides Michx.) seedlings grown in solution culture. A long-term exposure of roots to NaF significantly decreased root hydraulic conductivity ( L _p) and stomatal conductance ( g _s). Root absorbed NaF significantly affected electrolyte leakage in leaf tissues and substantially restricted leaf expansion. NaF did not significantly affect leaf chlorophyll contents but decreased net photosynthesis ( P _n). A short-term exposure of excised roots to 5 m M NaF and KF significantly decreased root water flow ( Q _v) with a concomitant decline in root respiration and reduced g _s when applied through intact roots or excised stems. The same molar concentration of NaCl also decreased Q _v and g _s in intact seedlings, but to a lesser extent than NaF or KF, and did not significantly affect root respiration. The results suggest that fluoride metabolically inhibited Q _v or L _p, probably by affecting water channel activity. We suggest that the metabolic inhibition of L _p by root-absorbed fluoride affected gas exchange and leaf expansion in aspen seedlings.     

Anaerobic degradation of 3,4,5-trimethoxybenzoate by a defined mixed culture of Acetobacterium woodii, Pelobacter acidigallici, and Desulfobacter postgatei

Abstract Acetobacterium woodii was continuously grown on 3,4,5-trimethoxybenzoate as pure culture or in commensalistic combination with Pelobacter acidigallici and Desulfobacter postgatei . Under pure culture conditions the following growth parameters were determined: μ _max= 0.112 h⁻¹, K _s= 1.07 mM, Y _max= 35 g/mol, and m = 0.22 mmol·g⁻¹·h⁻¹. In coculture with P. acidigallici the affinity for the substrate increased and the K _s value was found to be 135 μM. Under batch culture conditions mixed populations of A. woodii, P. acidigallici , and D. postgatei completely mineralized 3,4,5-trimethoxybenzoate to CO₂, whereas under continuous culture conditions more than 3 mM acetate remained unused.     

A chromosomal chloramphenicol acetyltransferase determinant from a probiotic strain of Bacillus clausii

The mechanism of resistance to chloramphenicol was studied in four strains of Bacillus clausii included in a probiotic mixture, which is administered to humans for prevention of gastrointestinal side effects due to oral antibiotic therapy. By cloning experiments, a chloramphenicol acetyltransferase (CAT) gene, cat _Bcl , coding for a putative 228-amino acid CAT protein was identified in B. clausii SIN. The deduced amino acid sequence displayed from 31% to 85% identity with 56 CAT proteins from other Gram-positive bacterial strains. The cat _Bcl gene was also detected by PCR in the three other B. clausii strains resistant to chloramphenicol, whereas it was absent in the three control strains susceptible to chloramphenicol. Pulse-field gel electrophoresis of total DNA digested by I-CeuI followed by hybridization with a cat -specific probe as well as unsuccessful repeated attempts of in vitro transfer of chloramphenicol resistance to various recipient cells indicated that cat _Bcl was chromosomally located in all four resistant B. clausii strains.     

Correlations of stomatal conductance with hydraulic and chemical factors in several deciduous tree species in a natural habitat

Recent research in whole-plant stomatal physiology, conducted largely with potted plants in controlled environments, suggests that stomatal conductance ( g _s) might be more closely linked to plant chemical variables than to hydraulic variables. To test this in a field situation, seasonal g _s was examined in relation to a number of plant and environmental variables in 11 temperate, deciduous forest tree species. Stomatal conductance was generally better correlated with environmental variables (air temperature, vapor pressure deficit, PPFD) than with plant variables, and slightly better correlated with plant hydraulic variables (shoot water and osmotic potentials) than with plant chemical variables (xylem sap ABA concentration, xylem sap pH). We examined a model, developed previously for maize, which describes regulation of g _s by xylem sap ABA concentration with leaf water status acting to modify stomatal sensitivity to the ABA signal. This model explained slightly more variation in seasonal g _s in the forest trees than did single plant variables but not more variation than most single environmental variables. Response surface models, especially those incorporating environmental variables, were more consistently successful at explaining g _s across species.     

Responses of apple leaf stomata: a model for single leaves and a whole tree

Abstract. An empirical model of stomatal response to environmental factors was developed from measurements of stomatal conductance ( g _s) made in a leaf chamber under controlled conditions. Results presented in a companion paper (Warrit, Landsberg & Thorpe, 1980) indicated that the model could be written in terms of only two factors, photon flux density ( Q _p) and leaf to air vapour pressure gradient ( D ). The response of Q _p was hyperbolic and that to D linear; combining these the equation of the model is where g _r is a reference conductance, α is the slope of the response to D and β indicates the sensitivity of g _s response to Q _p. Values of α were 0.20 and 0.30 kPa⁻¹ in June and August; the corresponding values of β were 59 and 79 μmol m⁻² s⁻¹.
The model was tested against mean values of g _s obtained with a porometer in the field, using environmental measurements as inputs. Correspondence between measured and calculated values was good. Transpiration rates were calculated from the Penman-Monteith equation, with stomatal resistance values calculated from the model, and compared with gravimetric measurements of tree water use. It was shown that transpiration could be calculated with acceptable accuracy. The effects of variations in stomatal resistance on transpiration rates under a range of conditions were explored using the model and the Penman- Monteith equation.     

Molecular Cloning and Characterization of a Lobster Gαs Protein Expressed in Neurons of Olfactory Organ and Brain

Abstract: We have isolated from an American lobster ( Homarus americanus ) olfactory organ cDNA library a clone, lobGα_s, with >70% identity to mammalian and arthropod Gα_s sequences. In genomic Southern blots, a fragment of lobGα_s detected only one band, suggesting the lobsters have a single Gα_s gene. In brain and olfactory organ, lobGα_s mRNA was expressed predominantly in neurons, including many of the neuronal cell body clusters of the brain. Gα_s protein was also expressed broadly, appearing on western blots as a band of 51.8 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory organ, and aesthetasc hairs. These results suggest that lobGα_s plays a role in a wide variety of signal transduction events. Its presence in the olfactory aesthetasc hairs, which are almost pure preparations of the outer dendrites of the olfactory receptor neurons, and the expression of lobGα_s mRNA in the olfactory receptor neurons of the olfactory organ indicate that lobGα_s may mediate olfactory transduction. That virtually all ORNs express lobGα_s mRNA equally predicts that hyperpolarizing odor responses mediated by cyclic AMP are a property of all lobster olfactory receptor neurons.     

Responses of apple leaf stomata to environmental factors

Abstract. Stomatal conductances ( g _s) were measured on the leaves of 3–4 year old Golden Delicious trees and of seedlings of two other cultivars. Measurements were made on container grown trees in the field with a diffusion porometer in 1975 and 1976, and in controlled conditions in a leaf chamber in the laboratory in 1976. Stomatal densities in the Golden Delicious leaves were assessed from scanning electron micrographs. Stomatal density on extension shoot leaves was higher than on other leaf types after June.
The response to irradiance shown by both the porometer and the leaf chamber results could be described by a rectangular hyperbola: where g _max is maximum conductance and β indicates the sensitivity of g_s to photon influx density ( Q _p). The values of β were in the range 60–90 μmol m⁻² s⁻¹.
There was no evidence that apple stomata are sensitive to temperature per se, but g _s was reduced by increasing leaf to air vapour pressure deficits ( D ). There was a linear relationship between g _s and D which was not attributable to feed-back to leaf water potential (ψ_L) as the latter did not affect g _s until a threshold of about −2.0 to −2.5 MPa was reached. Conductance generally declined with increasing ambient CO₂ concentration.     

The Effect of Temperature, Pressure and Chlorine Concentration of Spray Washing Water on Numbers of Bacteria on Lamb Carcases

Combined analysis of three experiments showed that when lamb carcases with initial bacterial numbers of between logi₁₀3.29 and 4.22/cm² were spray washed, statistically significant reductions in bacterial numbers of log₁₀O.5 were obtained when the spray wash water temperature was > 57°C, and reductions of log₁₀1.0 were obtained when the temperature was ≥ 80°C. Reductions at all temperatures were enhanced by log₁₀0.66 when the water contained 30 µg/ml chlorine, but increasing the concentration to 450 µg/ml reduced bacterial numbers only by a further log₁₀0–29. At highly contaminated sites increasing the duration of spraying from 30 to 120 s significantly increased the reductions obtained when water containing added chlorine was used. Reductions in bacterial numbers after spray washing with pressures of 3.5, 5.6. 7.7 kg/cm² were not significantly different.     

Biochemical studies on the cell wall degradation of Fusarium oxysporum f. sp. lycopersici race 2 by its own lytic enzymes for its biocontrol

An exhaustive cell wall fractionation of Fusarium oxysporum f. sp. lycopersici race 2 ( Fol 2) with alkali in a sequential procedure yields only three polysaccharide fractions: F1_s (alkali and water soluble), F1₁ (alkali soluble and water insoluble) and F4 (alkali-insoluble residue). These fractions amounted respectively to 15, 1.3 and 52% of the cell wall and have been characterized by infra-red spectroscopy and gas liquid chromatography-mass spectrometry (GLC-MS). F1_s is a β-gluco-galacto-mannan, F1₁ is mainly composed of a β-1, 3-glucan and F4 is a β-1,3-glucan-chitin complex. The F1_s is a very complex polysaccharide and its hydrolysis requires the action of different enzymes. The lysis of the cell wall and its three fractions with lytic enzymes from Fol 2 has been studied and a correlation between the lysis of the cell wall and the lysis of these fractions was found. The amount of glucose, galactose and mannose in F1_s and cell wall hydrolysates were quantified by GLC and they indicated the hydrolysis of the gluco-galacto-mannan polysaccharide. In the hydrolysis of F4 and cell walls N -acetylglucosamine was also found and quantified. When chlamydospores of this fungus were treated with Fol 2 lytic enzymes, the sugars liberated were principally mannose and N -acetylglucosamine. These results indicate that Fol 2 produces during its autolysis the necessary enzymes to hydrolyse its own cell walls. This fact suggests that a biological control of Fol 2 with its own lytic enzymes, conveniently immobilized, could be developed.     

Night-time transpiration can decrease hydraulic redistribution

C₃ plants dominate many landscapes and are critically important for ecosystem water cycling. At night, plant water losses can include transpiration (E_night) from the canopy and hydraulic redistribution (HR) from roots. We tested whether E_night limits the magnitude of HR in a greenhouse study using Artemisia tridentata , Helianthus anomalus and Quercus laevis . Plants were grown with their roots split between two compartments. HR was initiated by briefly withholding all water, followed by watering only one rooting compartment. Under study conditions, all species showed substantial E_night and HR (highest minus lowest soil water potential [ Ψ _s] during a specified diel period). Suppressing E_night by canopy bagging increased HR during the nightly bagging period (HR_N) for A. tridentata and H. anomalus by 73 and 33% respectively, but did not affect HR_N by Q. laevis . Total daily HR (HR_T) was positively correlated with the Ψ _s gradient between the rooting compartments, which was correlated with light and/or atmospheric vapour pressure deficit (VPDa) the prior day. For A. tridentata , HR_T was negatively correlated with night-time VPDa. Ecological implications of the impact of E_night on HR may include decreased plant productivity during dry seasons, altered ecosystem water flux patterns and reduced nutrient cycling in drying soils.     

Xylem hydraulic characteristics of subtropical trees from contrasting habitats grown under identical environmental conditions

Five evergreen subtropical tree species growing under identical environmental conditions were investigated to establish which hydraulic properties are genotypically rigid and which show phenotypic plasticity. Maximum xylem-specific conductivity ( k _s) correlated well with the anatomical characteristics (conduit diameter and density) for the four angiosperms Tecomaria capensis , Trichilia dregeana , Cinnamomum camphora and Barringtonia racemosa ; the anatomy of the gymnosperm Podocarpus latifolius was not assessed. Huber values (functional xylem cross-sectional area : leaf area) varied inversely with k _s among species. Maximum leaf-specific conductivity was similar in the five unrelated species. Vulnerability of xylem to cavitation differed between species, as did the relationship between transpiration and water potential. Models of these parameters and isolated midday readings confirm that these trees operate at similar maximum leaf-specific conductivity ( k _l) values. The data are consistent with the hypothesis that conductivity characteristics ( k _l, k _s) are influenced by environment, whereas vulnerability to cavitation is genetically determined.     

DOUBLE PULSE LABELLING WITH 3H-THYMIDINE: A METHOD FOR CALCULATING CELL POPULATIO KINETICS

A method was developed for calculating cell population kinetics with the aid of double pulse labelling with ³H-TdR. The labelling index was measured from auto-radiographs of the oral epithelium of two groups of 30-day-old rats. One group was injected once with ³H-TdR the other twice, with a time interval of 90 min between injections. DNA synthesis time was calculated from the equation:
   
where T _s= synthesis time; LI₁= labelling index in the single-injected group; LI₂= labelling index in the double-injected group; and T _i= time interval between injections. Synthesis time in the palate was 4.8 hr and 7.6 hr in the tongue. Generation time was calculated from the equation: T _g= ( T _s/LI₁) × 100, where T _g= generation time. Generation time in the palate was 46.1 hr and 75.8 hr in the tongue     

Human Lymphocyte Proliferation: Dna Synthesis Time

Abstract. The DNA synthesis time ( T _s) of lymphocytes from spleens and lymph nodes of patients with Hodgkin's disease was determined by the double labeling method. ³H-TdR was administered in vivo and removed tissues minced in ¹⁴C-TdR in vitro. Lymphocytes from patients with lymphosarcoma and reticulum cell sarcoma were studied in a similar manner. Lymphocytes were divided into A cells, small with non-basophilic cytoplasm, B cells, small with basophilic cytoplasm, C cells, large with non-basophilic cytoplasm, and D cells, large with basophilic cytoplasm.
The T _s of splenic lymphocytes, in four samples not containing Reed-Sternberg cells, in hours, was: B 11.3; C , 7.9; D , 8.4; combined, 8.8. the T _s of B lymphocytes was significantly longer than that of C and D lymphocytes. A lymphocytes did not label sufficiently to measure T _s. C and D lymph node lymphocytes and lymphocytes in tissues containing Reed-Sternberg cells had a longer T _s than splenic C and D cells. the former was: B , 12.7; C , 11.7; D , 11.0; combined, 11.8. the latter was: B , 12.2; C , 11.3; D , 11.2; combined, 11.6. the T _s of Reed-Sternberg cells in one specimen of a splenic Hodgkin's tumor was 13.1 hr. Macrophage T _s was 10.7 and 15.1 hr. Lymphosarcoma cell T _s was 14.2 and 14.6 hr. Reticulum cell sarcoma cell T _s was 7.5 and 7.7 hr.
The following minimum times were calculated from observation of ³H-TdR only labeled mitotic figures: S to prophase, 71 min; S to metaphase, 75 min; S to telophase, 100 min.     

Characterization of Serotonin N-Acetyltransferase in the Lateral Eye of the Green Frog Rana perezi: Protective Action of EGTA

Abstract: The kinetics of seRotonin N -acetyltransferase (NAT) from the lateral eye of Rana perezi have been characterized. NAT from ocular tissue reached maximal activity at a phosphate buffer concentration of 250 m M and a pH of 6.5. Reaction linearity was highly conserved within the homogenate fraction range tested (0.033-0.33). The time course of ocular NAT reaction showed a high linearity at 25 and 35°C. K _m and V_max estimations for acetyl-CoA at a 10 m M tryptamine concentration were 63.3 μ M and 4.42 nmol/h per eye, respectively. Regardless of the acceptor amine (tryptamine or serotonin), the K _m was not affected by the acetyl-CoA concentration (50 or 250 μ M ), whereas the V _max was significantly increased at a 250 μ M acetyl-CoA concentration. Ocular NAT showed a higher affinity for serotonin ( K _m= 20.7 μ M ) than for tryptamine ( K _m= 48-60 μ M ); V _max however, was similar for both substrates. Acetyl-CoA does not protect ocular NAT; in contrast, the use of EGTA (4 m M ) in the assay is essential to protect the enzyme because NAT in ocular crude homogenate shows rapid inactivation. This result suggests that intracellular calcium levels are involved in the NAT inactivation mechanisms in frog ocular tissue.