Showing papers in "Soil Biology & Biochemistry in 1980"
TL;DR: The specificity of the infection of maize, wheat and rice roots by N2-fixing Azospirillum spp was studied using pots with unsterilized soil and in two field experiments and results were partially obscured by the unexpectedly high proportion of streptomycin-resistant strains isolated from within the roots of uninoculated plants.
Abstract: The specificity of the infection of maize, wheat and rice roots by N2-fixing Azospirillum spp was studied in four greenhouse experiments using pots with unsterilized soil and in two field experiments. In all experiments A. lipoferum was most frequently isolated from externally sterilized roots of maize, and A. brasilense nir− (nitrite reductase negative) from wheat and rice. In pot experiments, A. brasilense nir+ was isolated with moderate frequency from within maize roots but rarely from within wheat or rice roots. Inoculation of the pots with a mixture of representative strains of the three Azospirillum groups had no effect on the proportion of strains recovered from each plant species. In the field experiments, inoculation with spontaneous streptomycin-resistant mutants of two of the representative strains confirmed the apparent specificity of A. lipoferum for maize roots and of A. brasilense for wheat but the results were partially obscured by the unexpectedly high proportion of streptomycin-resistant strains isolated from within the roots of uninoculated plants.
300 citations
TL;DR: The fumigation-respirometric determination of soil biomass was modified to assess the effects of cultivation on the biomass in the upper 5 cm of intact soil samples and found the method suitable for comparative studies, but not for providing an absolute measure.
Abstract: The fumigation-respirometric determination of soil biomass was modified to assess the effects of cultivation on the biomass in the upper 5 cm of intact soil samples. We found the method suitable for comparative studies, but not for providing an absolute measure. The soil biomass increased during the growth of a wheat crop and then decreased to an approximately constant amount. The biomass was significantly greater where the soil had been direct-drilled than where it had been ploughed, probably because plant roots were more abundant after direct drilling. The size of the oil biomass in relation to substrate input is discussed.
271 citations
TL;DR: A modification of Marmur's method was used to isolate DNA, but difficulties in separating DNA from humic substances gave low yields and impure DNA.
Abstract: DNA has been isolated from the bacterial fraction of two soils. Numbers of bacteria, determined by fluorescence microscopy were 1.1 and 2.2·10 10 cells g −1 dry wt. The total amounts of bacterial DNA in these soils were 90 and 187 μg g −1 dry wt respectively. A modification of Marmur's method was used to isolate DNA, but difficulties in separating DNA from humic substances gave low yields and impure DNA. DNA could be partly separated from humic material in the presence of 8 m urea by ion-exchange chromatography on DEAE-Sepharose CL-6B. Final purification was obtained by chromatography on a hydroxyapatite column. When lowering the EDTA concentration in the saline-EDTA solution used for lysis, the amount of humic substances in the cell-free lysate after centrifugation was considerably decreased. The lysate could then be chromatographed directly on hydroxyapatite. Quantities up to 1.5 mg DNA high purity was isolated from 90 g wet soil (37 g dry wt). The isolated DNA was characterized by treatment with DNAse and absorption spectra. No uncommon bases were revealed by thin layer chromatography of the DNA hydrolysates. Melting curves of the isolated DNA showed a relatively broad melting profile, with half maximum hyperchromicity (T m ) near 90°C. Sedimentation coefficients determined by analytical ultracentrifugation showed that the isolated DNA had a high molecular weight, ranging from 2.3 to 10.1·10 5 daltons.
179 citations
TL;DR: C Cumulative CO2 measurements showed that microbial respiration was inhibited by grazing pressures higher than optimum values, suggesting that litter comminution by the animals was the main factor contributing to the enhancement of C mineralization.
Abstract: Fragmented (2–4 mm) and mechanically ground (0.1–0.2 mm) oak litter was inoculated with faeces of Oniscus asellus or Glomeris marginata and incubated in the laboratory. After 40 days microbial respiration rates were the same for both litter treatments. Woodlice or millipedes were then added in various numbers and CO2 evolution measured for a further 40 days. Microbial respiration in fragmented litter was initially increased to twice the control rates by four Oniscus and to 1.6 times control rates by six Glomeris but subsequently declined to rates slightly above controls. But in treatments with ten Oniscus respiration was depressed below the controls after 20 days. Cumulative CO2 measurements showed that microbial respiration was inhibited by grazing pressures higher than optimum values. Animals feeding on previously-ground litter produced a similar, but reduced response, suggesting that litter comminution by the animals was the main factor contributing to the enhancement of C mineralization. Disturbance of fragmented litter, either by Oniscus or by mechanical means, produced no significant changes in respiration. In ground-litter cultures there was a small enhancement of CO2 evolution for the first 10 days. Fungal standing crop was reduced to one-third of controls by Oniscus; the effects being particularly pronounced during the first 3 days of the experiment. Bacterial standing crop increased to a maximum of 10 times control levels.
147 citations
TL;DR: In this article, short-term changes in numbers and biomass of bacteria, determined by direct counts, are descrived for a subarctic mire and for the humus and mineral soil layers of pine forest podsol.
Abstract: Short-term changes in numbers and biomass of bacteria, determined by direct counts, are descrived for a subarctic mire and for the humus and mineral soil layers of pine forest podsol. For biomass, monthly fluctuations for 15 months are presented. Almost as large fluctuations in bacterial numbers were found during 2 weeks as were found during the whole year. Precipitation resulted in increases in bacterial biomass even when the soil moisture content was non-limiting for bacterial growth, but these increases did not last for more than 1–2 days. Observed rapid declines in bacterial numbers were interpreted as the result of grazing by the microfuana. Changes in cell sizes and shapes after rainfall indicated that even under favourable growth conditions only 15–30% of the bacteria were active. The increases in bacterial biomass were used to calculate a minimum production. For the bacteria in the peat the production over 9 days was 40% of the mean standing crop value per day. The corresponding values for the bacteria of the humus and mineral layer over 13 days were 19 and 15%. The average generation times, estimated from increases in numbers, were 39 h for the peat bacteria and 66 and 55 h for the bacteria of the humus and mineral layers respectively. Based on the number of falls of rain a yearly bacterial production value of 210 g d.w.m−2 was calculated for the forest site. This figure is discussed in relation to the yearly energy input through primary production.
134 citations
TL;DR: In this article, the authors assessed optimum and potentially deleterious physico-chemical conditions in the environment of the earthworm Eisenia foetida and found that the worms died within a week at pH values 9; optimum pH for gain in weight centered around 7.0.
Abstract: Survival and/or growth were used to assess optimum and potentially deleterious physico-chemical conditions in the environment of the earthworm Eisenia foetida. Maximum weight was gained between 20 and 29°C with horse manure or activated sludge as food. Maximum weight gain as a function of moisture in activated sludge occurred between 70 and 85%. All worms died within a week at pH values 9; optimum pH for gain in weight centered around 7.0 Soluble salts in excess of 0.5% were lethal, though ammonium acetate caused 100% mortality at a concentration of 0.1%; concentrations in manures contaminated by urine or cattle slurry may be lethal, while those present in noncontaminated manure, with an electrolytic conductivity of 1.5–3mmhos, support weight gain. Inorganic chemicals that are commonly used to coagulate sludges, often as a preliminary to land application, were innocuous at concentrations higher than those normally used at wastewater treatment plants. Anaerobically digested sludges are toxic to earthworms, and are characterized by low oxidation-reduction potentials; when placed upon a soil substrate the redox potential increases slowly, and though the sludge tested in this study was nontoxic at Eh values in excess of 250 mV, it provided insufficient nutriment to E. foetida to allow weight gain. With activated sludge as food, growth of E. foetida occurred more rapidly when soil was present, independently of whether it was placed as a substrate beneath the sludge or mixed into the sludge. Growth occurred more rapidly when activated sludge was placed on substrates which allowed drainage, though loam or ashed loam appeared superior to others, such as glass beads or sand; the growth promoting factor is related to the inorganic fraction of the soil.
117 citations
TL;DR: In this paper, it was shown that during plant decomposition, changes occurred in the concentrations of organic- 14 C and - 15 N in some of the soil components, these having been fractionated according to density and particle size.
Abstract: Medicago littoralis leaf material, labelled with 14 C and 15 N, and of C:N ratio 8.7:1, decomposed rapidly in a calcareous soil. One half of the plant-C and two thirds of the plant-N remained in the soil as organic residues after 34 days. The rates of decomposition and the changes in the distribution of organic- 14 C and - 15 N residues followed similar patterns. Incorporation of 14 C and 15 N into microbial cells, formed during plant breakdown, reached a maximum after 62 days. At this time the microbial biomass accounted for 21.9 and 23.3%, respectively, of residual organic- 14 C and - 15 N. Thereafter, the amounts of isotope-labelled biomass decreased with the percentage decrease slightly exceeding that of the total labelled soil residues. During plant decomposition, changes occurred in the concentrations of organic- 14 C and - 15 N in some of the soil components, these having been fractionated according to density and particle size. Especially evident was the rapid and extensive decrease of labelled material from the fine clay-size components. This was partly due to the decrease in the biomass- 14 C of this fraction. Changes in biomass- 14 C of some physical fractions were approximately reflected by changes in their numbers of viable microorganisms.
115 citations
113 citations
TL;DR: Correlation between counts from guts and food leaves indicated that the growth response was by the litter microflora and not indigenous gut symbionts, suggesting that the gut environment enhanced bacterial growth and viability.
Abstract: Bacteria from the food leaves and faeces of millipedes maintained in group cultures (12 animals) for 24 h were counted. Dilution plating and direct observation both showed significant increases in bacterial populations (10–100 fold) after passage through the gut. In cultures of single animals the increases were primarily the result of rapid growth in the midgut, though there was some evidence of further proliferation in the hindgut and faeces. The ratio of viable counts to direct counts was lower in litter than in the gut and faeces, suggesting that the gut environment enhanced bacterial growth and viability. Correlation between counts from guts and food leaves further indicated that the growth response was by the litter microflora and not indigenous gut symbionts.
113 citations
TL;DR: In this paper, the effect of NaCl on CO 2 evolution, ammonification, and nitrification was investigated in Sassafras sandy loam amended with finely ground alfalfa.
Abstract: Sodium chloride, at rates up to 100 mg g −1 , was added to a Sassafras sandy loam amended with finely-ground alfalfa to determine the effect of NaCl on CO 2 evolution, ammonification, and nitrification in a 14-week study. A NaCl concentration of 0.25 mg g −1 significantly reduced CO 2 evolution by 16% in unamended soil and 5% in alfalfa-amended soil. Increasing NaCl progressively reduced CO 2 evolution, with no CO 2 evolved from the soil receiving 100 mg NaCl g −1 . A 0.50 mg NaCl g −1 rate was required before a significant reduction in decomposition of the alfalfa occurred. The NO − 2 -N + NO − 3 -N content of the soil was significantly reduced from 40 to 37 μg g −1 at 0 and 0.25 mg NaCl g −1 , respectively in the unamended soil. In the alfalfa amended soil, nitrification was significantly reduced at 5 mg NaCl g −1 . At 10 mg NaCl g −1 , nitrification was completely inhibited, there being only 6 and 2 μg NO − 2 -N + NO − 3 -N g −1 in the alfalfa amended and unamended soil, respectively. In the alfalfa amended soil NH + 4 -N accumulated from 6 μg g −1 at the 0 NaCl rate to a maximum of 54 μg g −1 with 25 mg NaCl g −1 . These higher NH + 4 -N values resulted in a 0.5 unit increase in the pHw over that of the 0 NaCl rate in the alfalfa amended soil. At NaCl concentrations above 25 mg g −1 there was a reduction in NH + 4 -N. The addition of alfalfa to the soil helped to alleviate the adverse affects of NaCl on CO 2 evolution and nitrification.
106 citations
TL;DR: Mature pasture soils in the North Island, New Zealand, had 6–19 mycorrhizal propagules g−1 soil, and in a pot trial, mycor Rhizal inoculation of white clover plants increased shoot growth in seven eroded soils, by 1–12-fold.
Abstract: A method to assess the mycorrhizal inoculum infectivity of soils is described. Mature pasture soils in the North Island, New Zealand, had 6–19 mycorrhizal propagules g−1 soil. Of 31 samples taken from extensive areas of eroded soil around Gisborne and Masterton 22 had fewer than 1.0 mycorrhizal propagule g−1 soil, and 13 of these soils had less than 0.2 propagules g−1. In a pot trial, mycorrhizal inoculation of white clover plants increased shoot growth in seven eroded soils, by 1–12-fold.
TL;DR: The change in root dynamics is suggested to be an important reason for the decrease of fungal hyphae in forest soil after clear-cutting.
Abstract: The effect of clear-cutting on fluorescein diacetate (PDA) active and total fungal biomass was studied in three soil horizons of a coniferous forest in Sweden. Throughout the soil profile, fungal biomass decreased after felling. FDA-active hyphae decreased more in the mineral soil than in the organic soil. The effect of felling residues left at the time of clear-cutting appeared to be of only minor importance, since the decrease in fungal content was independent of the amount of slash left on the ground. However, the addition of slash generally gave greater amounts of FDA-active fungal mycelium compared to the treatment without slash. The change in root dynamics is suggested to be an important reason for the decrease of fungal hyphae in forest soil after clear-cutting.
TL;DR: In this paper, three biochemical procedures were used to determine microbial biomass in nine topsoils from a climosequence in tussock grasslands, and the results were significantly correlated with each other and with several soil properties, including organic C and total N contents and CO 2 production.
Abstract: Microbial biomass was determined by three biochemical procedures in nine topsoils from a climosequence in tussock grasslands. The pH values of the samples ranged from 4.4 to 6.2 and organic C contents from 2.5 to 20.0%. When determined by a chloroform-fumigation procedure, contents of biomass C and mineral-N (Min-N) flush ranged from 530–2780 and 59–167 μgg −1 dry soil respectively. Adenosine 5'-triphosphate (ATP) content ranged from 2.2 to 10.7 μg g −1 dry soil. All three estimates were significantly correlated with each other and with several soil properties, including organic C and total N contents and CO 2 production. They were not significantly correlated with any climatic factor. In spite of these significant correlations, the ratios of the biomass estimates varied appreciably in the different soils. The ratios of biomass C/Min-N flush ranged from 7.8 to 22.8 (average 12.5), biomass C/ATP from 163 to 423 (average 248) and Min-N flush/ATP from 12 to 35 (average 22). These ratios were mostly higher than those found elsewhere for Australian and English soils. The high biomass C/ATP and Min-N flush/ATP ratios did not appear to originate from inefficient extraction of “native” ATP or from the soils' P status. Based on these results, care in the use of factors for obtaining soil microbial biomass content from Min-N flush or ATP values is indicated.
TL;DR: In this paper, the amounts of Ca, K, Mg and P were measured in leaf litter contained in litter bags in a southeastern United States deciduous forest, and half of the litter was treated with naphthalene, a chemical that reduced microarthropod densities to about 10% of those found in untreated litter.
Abstract: The amounts of Ca, K, Mg and P were measured in leaf litter contained in litter bags in a southeastern United States deciduous forest. Half of the litter was treated with naphthalene, a chemical that reduced microarthropod densities to about 10% of those found in untreated litter. Phosphorus losses were significantly greater in untreated litter. After initial elemental losses, amounts of Ca, K and Mg generally increased in 9–12 month-old untreated litter, while naphthalene-treated litter generally showed no seasonal dynamics. Seasonal amounts of nutrients in forest litter depend upon elemental mobility, inputs of nutrients in rainfall, throughfall and particulates, and nutrient retention by forest floor biota. Microarthropods increase nutrient loss from forest litter by comminution; however, microbial stimulation as a result of microarthropod feeding activities appears to increase the nutrient retention capacities of forest litter.
TL;DR: An enzyme system having phosphotriesterase activity was partially purified from Flavobacterium sp.
Abstract: An enzyme system having phosphotriesterase activity was partially purified from Flavobacterium sp. by means of gel filtration and preparative gel isotachophoresis. Flavobacterium phosphotriesterase showed maximum activity between pH 8–10 and was unaffected by the presence of metal ions. Non-ionic detergents were potent and irreversible inhibitors of activity. Inhibition was also observed with mercurial thiol reagents and cysteine, although in the latter case inhibition could be reversed by oxidation in air or with K 3 Fe(CN) 6 . Activity was restricted towards substrates having electron withdrawing aromatic or heterocyclic leaving group such as parathion, paraoxon, diazinon and their analogues. Substrate analogues having the weakly electrophilic 4-aminophenyl group were not hydrolysed and in some cases acted as competitive inhibitors. Product inhibition by 4-nitrophenol (but not by the phosphorus containing moiety) was observed.
TL;DR: In this paper, the formation of nitrous oxide and dinitrogen by decomposition of NH2OH in soils was studied using 19 soils selected to obtain a wide range in properties.
Abstract: Soil properties affecting formation of nitrous oxide (N2O) and dinitrogen (N2) by chemical decomposition of hydroxylamine (NH2OH) in soils were studied using 19 soils selected to obtain a wide range in properties. It was found that production of N2O by chemical decomposition of NH2OH in soils is more rapid than production of N2 and that, except with calcareous soils, N2O production greatly exceeds N2 production. Studies of the correlations between various soil properties and formation of N2O and N2 by decomposition of NH2OH showed that production of N2O was very highly correlated with exchangeable and oxidized Mn in the soils studied, and that production of N2 was very highly correlated with pH, CaCO3 equivalent, exchangeable Ca2+, and oxidized Mn. Production of N2 in neutral and acidic soils was highly correlated with both exchangeable and oxidized Mn, and production of N2 in calcareous soils was significantly correlated with oxidized Fe. The deductions from these correlations that Mn compounds are involved in the reactions leading to formation of N2O and N2 by chemical decomposition of NH2OH in soils, and that CaCO3 and Fe compounds are involved in the reactions leading to formation of N2 in calcareous soils, were supported by studies of N2O and N2 production through reactions of Mn and Fe compounds with NH2OH in the presence and absence of CaCO3. Production of N2O via chemical decomposition of NH2OH in soils greatly exceeds production of N2O through chemical decomposition of nitrite (i.e. via chemodenitrification), and the amount of N2 produced by decomposition of NH2OH in most soils exceeds the amount produced by decomposition of nitrite. Work reported indicates that, if N2O is formed in soils through nonbiological transformations of NH2OH produced by soil microorganisms, very little of this gas is generated by the reaction of NH2OH with nitrite frequently postulated as a mechanism of N2O production in soils (NH2OH + HNO2 → N2O + 2H2O).
TL;DR: Sulphatase, urease and protease activities were studied in 12 New Zealand topsoils over 5 months during which the soils were held at 10, 18 and 25°C in pots sown with perennial ryegrass and in pots left fallow as discussed by the authors.
Abstract: Sulphatase, urease and protease activities were studied in 12 New Zealand topsoils over 5 months during which the soils were held at 10, 18 and 25°C in pots sown with perennial ryegrass and in pots left fallow Sulphatase activity in the planted soils showed little significant change over the period of examination In contrast, sulphatase activity in the fallow soils decreased significantly in almost every instance, the extent of the decrease becoming larger with increasing temperature Urease behaved similarly to sulphatase, except that in the planted soils several significant increases in activity occurred Protease activities proved to be very variable Because of this few significant differences in protease activity were recorded, although it showed the same trends as the other two enzymes It is suggested that temperature-dependent denaturation could have caused the decrease in enzyme activity in the fallow soils Replacement of activity lost in this manner by enzymes liberated from plants and microorganisms, and by intracellular enzymes, may have been responsible for the maintenance or increase of activity in the planted soils
TL;DR: In the surface 5 cm of a clay soil in 2 successive years, the microbial biomass, as measured by a fumigation-respiration technique, was constant as mentioned in this paper, and the biomasses in two clay soils were approximately ten times greater than that in a silt loam.
Abstract: In the surface 5 cm of a clay soil in 2 successive years the microbial biomass, as measured by a fumigation-respiration technique, was constant The biomasses in two clay soils were approximately ten times greater than that in a silt loam When straw from a preceding crop was chopped and left on the soil surface the biomass after 8 months was greater by a factor of two than that in soil where the straw had been burnt Where soil had been kept in grass for 9 yr, the biomass was greater by a factor of three than that in soil of the same kind that had been in arable cultivation for the previous 4 yr As the fumigation-respiration technique measured only the microbial and microfaunal contribution to the biomass, the total biomass can only be assessed by measuring the root contribution separately; when this was done the total biomass in the grassland was found to be greater by a factor of about six
TL;DR: In this article, the authors studied the dehydrogenase and invertase activities of three soils under flooded and non-flooded (60% water holding capacity) conditions.
Abstract: The dehydrogenase and invertase activities of three soils were studied under flooded and nonflooded (60% water holding capacity) conditions. Flooding increased (× 1.25 to 2.50) the dehydrogenase activity. In contrast, invertase activity decreased considerably upon flooding. The addition of rice straw increased the invertase activity under both water regimes, but dehydrogenase activity only under flooded conditions.
TL;DR: Aspects of the biology of C. minitans and its potential for control of S. sclerotiorum were investigated, with results believed to have resulted from low temperatures and dry conditions.
Abstract: Aspects of the biology of C. minitans and its potential for control of S. sclerotiorum were investigated. Temperatures below 7°C resulted in comparatively slow rates of germination and infection of sclerotia by C. minitans. The optimum temperature for germination, growth, infection of sclerotia, and destructive parasitism by C. minitans was 20°C. The optimum relative humidity for germination, growth and infection by C. minitans was above 95%. Autumn inoculations with suspensions of conidia, pycnidia and mycelium of C. minitans in the field resulted in negligible numbers of sclerotia remaining viable after 1 month. With culture-grown sclerotia 2 months were required for a similar reduction of sclerotial viability. In the absence of C. minitans mulching had no significant effect on sclerotial viability. In the presence of C. minitans mulching did, however, influence the viability and infection by C. minitans of culture-grown sclerotia. Populations of field sclerotia also differed from culture-grown sclerotia in that they harboured an internal population of microorganisms, which included C. minitans, and had a lower level of viability at the commencement of the treatments. A winter application of C. minitans did not result in significant infection of sclerotia nor in a reduction in viability of sclerotia. This failure is believed to have resulted from low temperatures and dry conditions.
TL;DR: Two regions of accelerated lysis of root tissue were demonstrated and are considered to be responsible for the two maxima in bacterial colonization of the root surface.
Abstract: Changes in root morphology during root growth and concurrent bacterial colonization of the root surface were studied. Wheat seedlings were grown in soil so that their roots grew along a removable transparent plate on which root growth was recorded daily. The root surface microflora of 10mm lengths of root that had grown over 24 h, was counted on agar-plates and by fluorescence microscopy. Two maxima in bacterial colonization of the seminal axis of 10-day-old roots were demonstrated between root tip and root base. Fluorescence microscopy was also used to estimate at intervals along the root axis the proportions of lysing epidermis and cortex cells based on staining of nuclei with acridine-orange. Two regions of accelerated lysis of root tissue were demonstrated and are considered to be responsible for the two maxima in bacterial colonization of the root surface.
TL;DR: Six bacteria and one fungus isolated from sclerotia of Sclerotium cepivorum, the causal agent of white rot of onions, produced diffusible antibiotics antagonistic to growth of S. cepvorum on potato dextrose agar, and all bacterial isolates appear to be Bacillus subtilis.
Abstract: Six bacteria and one fungus isolated from sclerotia of Sclerotium cepivorum, the causal agent of white rot of onions, produced diffusible antibiotics antagonistic to growth of S. cepivorum on potato dextrose agar. Three of the bacterial isolates applied as seed treatments to onions grown in non-sterile muck soil in a controlled environment chamber reduced the proportion of infections by S. cepivorum. Antagonists were further evaluated as seed treatments for field control of white rot on two onion cultivars grown on muck soil containing high levels of natural inoculum. Four of the bacterial isolates provided significant season-long protection on the partially-resistant cultivar Festival, and the best of these also provided significant protection on the susceptible cultivar Autumn Spice. The fungal antagonist has been identified as Penicillium nigricans, and all bacterial isolates appear to be Bacillus subtilis. The levels of protection provided by some of these latter isolates were comparable to those provided by chemical treatments and represent practical potential for field control of white rot.
TL;DR: Bacteria grown in synthetic media emit luminescence that is nearly identical in color with that of other luminescent bacteria, while the color of light from infected caterpillar is substantially red-shifted.
Abstract: The terrestrial nematode, Heterorhabitis bacteriophora contains symbiotic terrestrial bacteria which emit low but detectable luminescence in the symbiotic state. When the nematode is ingested by caterpillar larvae (or other insects), the bacteria are released into t he hemocoel, where they grow rapidly (doubling time of 3 h or less), reach high cell numbers (109 ml−1 greater), and are brightly luminous. The enzyme that catalyzes light emission is a typical bacterial luciferase as judged by its substrate requirements and the kinetics in vitro. Bacteria grown in synthetic media emit luminescence that is nearly identical in color with that of other luminescent bacteria, while the color of light from infected caterpillar is substantially red-shifted.
TL;DR: Biomass C values could change significantly at all storage temperatures, but generally least at −20°C, which was also the most suitable for retaining ATP contents, whereas 4°C was best for values of Min-N flush.
Abstract: The effects of 28 and 56 days' storage at 25°, 4° and −20°C on the microbial biomass content of four soils from tussock grasslands were studied by three biochemical procedures. Two of the procedures involved measurement of CO 2 and mineral-N (Min-N) production by chloroform-fumigated and unfumigated soil, and consequent estimation of biomass C and Min-N flush respectively. In the third, adenosine 5'-triphosphate (ATP) content was determined. Patterns of CO 2 production were often influenced by storage treatment. The use of fixed incubation periods for estimating the CO 2 flush of fumigated soil and the steady rate of CO 2 production by unfumigated soil did, however, give biomass C estimates that were generally similar to those calculated from individually determined incubation periods for each treatment and soil. Biomass C values could change significantly at all storage temperatures, but generally least at −20°C. Storage at −20°C was also the most suitable for retaining ATP contents, whereas 4°C was best for values of Min-N flush. Values of Min-N flush after storage of soil at −20°C decreased significantly in two of the soils but increased in another. No storage temperature was thus satisfactory for all three indices of microbial biomass. Generally, however, 4°C was adequate for short periods, and 25°C the least suitable.
TL;DR: Invertase, cellulase, phosphatases, protease and β-glucosidase were extracted from permanent pasture soil with 0.2 M phosphate buffer (pH 8) in the presence of ammonium and salmine sulphates as mentioned in this paper.
Abstract: Invertase, cellulase, phosphatases, protease and β-glucosidase were extracted from permanent pasture soil with 0.2 M phosphate buffer (pH 8) in the presence of 0.2 M EDTA. This extract was further treated with ammonium and salmine sulphates. Attempts were made to fractionate these enzyme activities by gel and anion-exchange chromatography. Specific activities were estimated in all fractions and some characteristics of the purified enzymes (optimum pH, temperature and substrate concentration, and K m and V max ) were investigated. The results indicated that extracted enzyme activities occurred partly in soil as a carbohydrate-enzyme complex and partly as a humo-carbohydrate complex.
TL;DR: The fluorochrome ethidium bromide combines with double-stranded DNA and fluoresces when excited by u.v. radiation to create EB, which strongly stained all eucaryotic and procaryotic cell types tested.
Abstract: The fluorochrome ethidium bromide (EB) combines with double-stranded DNA and fluoresces when excited by u.v. radiation.
When applied at aqueous concentrations ranging from 2 mg l−1 to Ig l−1 EB strongly stained all eucaryotic and procaryotic cell types tested. It concentrated preferentially in procaryotic cells containing DNA and in the nucleus and other cytoplasmic components of eucaryotic cells. It did not stain cell walls or inert materials, e.g. clay and sand, as intensely as material containing nucleic acid.
Potential applications for EB as a stain include the detection of plant root nuclei and the examination of bacteria and fungi in soil and mud preparations.
TL;DR: It is suggested that actinomycetes could be of importance in the nutrition, and ultimately metal concentration, of O. asellus as the association of micro-organisms in the feeding strategy of terrestrial isopods still requires a great deal of research.
Abstract: Claims by other authors as to the importance of coprophagy and micro-organisms in copper uptake by terrestrial isopods are largely unsubstantiated. This paper describes an expriment which shows that, at least in Oniscus asellus , Cu and Zn and rapidly assimilated irrespective of coprophagy. In contrast, Cd and Pb were not rapidly assimilated although Cd was more readily retained by animals not able to resort to coprophagy. Numbers of bacteria and fungi in the food supply and in both guts and faeces of O. asellus are related to animal activity and corophagy. Numbers of bacteria in faeces are higher than in original litter suggesting a stimulation during passage through the gut, in comparison numbers of fungi show the reverse. In the absence of corophagy numbers of micro-organisms are reduced in the litter, presumably by increased grazing. he ratio of actinomycetes: bacteria in the animal gut ranges from 0.024 to 0.247 and this ratio is affected by both corophagy and the food supply. The metal tolerance of the gut microflora increases as result of feeding on litter contaminated with metals, but is also affected by coprophagy. Although the association of micro-organisms in the feeding strategy of terrestrial isopods still requires a great deal of research it is suggested that actinomycetes could be of importance in the nutrition, and ultimately metal concentration, of O. asellus .
TL;DR: Adding nitrate did not disappear from two soils maintained under anerobiosis for 7 days at 1°C and the rate was markedly enhanced by glucose, but succinate and methanol were less stimulatory.
Abstract: Added nitrate did not disappear from two soils maintained under anerobiosis for 7 days at 1°C. Nitrate was reduced slowly at 7°C, and the rate increased with increasing temperature. The rate was markedly enhanced by glucose, but succinate and methanol were less stimulatory. Sewage effluent enhanced the rate to a small extent or inhibited the reduction. During the phase of rapid NO3− reduction, the population of denitrifying bacteria rose rapidly, but the cell density quickly declined as the rate of NO3− loss declined. From 1.8 to 8.4 pg of NO3−-N was reduced per denitrifying cell that proliferated during exponential NO3− reduction in soil. In culture, strains of Pseudomonas and Flavobacterium reduced 0.82–2.0 pg of NO3−-N per cell that appeared during exponential growth.