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[Background and aims] Microbe-assisted phytoremediation is particularly effective for organic pollutants. The leguminous shrub Cytisus striatus (Hill) Rothm. has been proposed as a candidate species for the rhizoremediation of hexachlorocyclohexane (HCH)-contaminated sites. The aim of this study was to improve the performance of this species using microbial inoculants., [Methods] C. striatus was grown in substrates contaminated with 0, 10 and 35 mg HCH kg−1 for 8 weeks. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 (isolated from a HCH-contaminated soil) on their own or in combination (ET, D4 and ETD4)., [Results] Inoculation with both bacterial strains (ETD4) resulted in decreased HCH phytotoxicity and improved plant growth. HCH-exposed plants inoculated with ETD4 presented a 120–160 % increase in root, and 140–160 % increase in shoot biomass, and led to a decrease in the activities of enzymes involved in anti-oxidative defence. APOD activity was reduced by up to 37 % in shoot tissues and 25 % in root tissues, and corresponding activities of SOD were reduced by up to 35 % and 30 %. HCH dissipation was enhanced in the presence of C. striatus but no significant effect of microbial inoculants was observed., [Conclusions] Inoculating C. striatus with this combination of bacterial strains is a promising approach for the remediation of HCH-contaminated sites.

Strains of Fusarium verticillioides produce mycotoxins such as fumonisins, which are common contaminants of maize and maize-based products worldwide and considered to be hazardous for human and animal health, due to their nephrotoxic, hepatotoxic, immunosuppressive and carcinogenic activity (references cited in Butron et al. 2006, Dalie et al. 2012). Biological control of Fusarium infection is therefore of great interest for food safety and could contribute towards reducing the use of toxic chemicals with fungicide activity. Many plant-associated bacteria, both epiphytes and endophytes, are widely recognized as agents of biological control against plant diseases and infections (Compant et al. 2010). Numerous phylogenetically diverse bacterial strains showing inhibitory activity against different fungi have been isolated (Bacon & Hinton 2002, Compant et al. 2005, Dalie et al. 2010, McSpadden Gardener 2007, Yoshida et al. 2012).

Strains of Fusarium verticillioides produce mycotoxins such as fumonisins, common contaminants of maize and maize-based products worldwide and considered to be hazardous for human and animal health. Biological control of Fusarium infection is of great interest for food safety The study describes the isolation and identification of a bacterial endophyte from kernels of the corn line A509 resistant to Fusarium. Initial studies on the inhibition of a fumonisin- producing Fusarium verticillioides by the isolated bacterial endophyte are also presented. The analysis include the growth of the bacterial strain and fungus in different media as well as the effect of bacterial metabolites on fungal growth.

Bromoxynil, frequently applied as bromoxynil octanoate, is a post-emergence herbicide, widely used for control of broad-leaved weeds on a variety of crops, particularly since the banning of atrazine in most countries. This study analysed the degradation of bromoxynil octanoate by microorganisms from non-organically managed agricultural soils developed over granite (G) and schist (S) as well as from an organically managed agricultural soil developed over granite (Go). As a means of analysing the role of the most abundant members of the soil microbial community, degradation of bromoxynil octanoate was evaluated in microcosms incubated with distinct amounts of soils. Furthermore, the effect of the herbicide on soil microbial communities (community level physiological profiles, CLPP) was analysed. Bromoxynil octanoate was rapidly degraded by microorganisms from the 3 soils and was no longer detectable three days after initiating the experiment. At this time, about half of the herbicide applied was present as the active compound, bromoxynil. Thereafter, bromoxynil was degraded more rapidly in G and S than in Go, in which the herbicide was still detectable 2 weeks after its application. In the short-medium term (3-15 days), the metabolites 3,5-dibromo-4-hidroxybenzamide (DBHB amide) and/or 3,5-dibromo-4- hidroxybenzoic acid were detected in all three soils. The most abundant members of the soil microbial communities were also able to degrade bromoxynil and its ester, though this degradation was slower, or incomplete, and bromoxymil and/or DBHB amide were detected 6 weeks after application. The herbicide had little effect on the functionality of the microbial communities in the soils.

The plant-microorganism-soil system of three pseudometallophytes (Betula celtiberica, Cytisus scoparius and Festuca rubra) growing in a Pb/Zn mine was characterised. Plant metal accumulation, soil metal fractions (rhizosphere and non-vegetated) and bacterial densities were determined. Total Cd, Pb and Zn in non-vegetated soils was up to 50, 3000 and 20,000 mg kg−1 dry weight, respectively. The residual fraction dominated non-vegetated soils, whereas plant-available fractions became important in rhizosphere soils. All plant species effectively excluded metals from the shoot. F. rubra presented a shoot:root transport factor of ≤0.2 and this population could be useful in future phytostabilisation trials. Culturable bacterial densities and diversity were low (predominantly Actinobacteria). Rhizosphere soils hosted higher total and metal-tolerant bacterial densities. Seventy-four metal-tolerant rhizobacteria were isolated, and characterised genotypically (BOX-PCR, 16S rDNA) and phenotypically [Cd/Zn tolerance, biosurfactant production and plant growth promoting (PGP) traits]. Several isolates resisted high concentrations of Cd and Zn, and only a few presented PGP traits. Fourteen isolates were evaluated for promoting plant growth of two species (Salix viminalis and Festuca pratensis). Thirteen inoculants enhanced growth of F. pratensis, while only three enhanced growth of S. viminalis. Growth enhancement could not always be related to isolate PGP traits. In conclusion, some isolates show potential application in phytostabilisation or phytoextraction techniques.

Bacterial strains were isolated from the rhizosphere of three populations of the Ni-hyperaccumulator Alyssum serpyllifolium subsp. lusitanicum (A. pintodasilvae; M, S, and L), one population of Ni-hyperaccumulator A. serpyllifolium subsp. malacitanum (A. malacitanum; SB), and one population of the non-hyperaccumulator A. serpyllifolium subsp. serpyllifolium (A. serpyllifolium; SN). Isolates were characterized genotypically by BOX-PCR genomic DNA fingerprinting and comparative sequence analysis of partial 16S rRNA gene, and phenotypically by their Ni tolerance (0–10 mM), presence of plant growth promoting traits (indoleacetic acid (IAA)-, siderophore-, or organic acid-production, and phosphate solubilization) or capacity to produce biosurfactants. Among the collection of rhizobacteria, 84 strains were selected (according to their BOX-PCR profiles and phenotypic characteristics) to assess their ability to modify Ni extractability from Ni-rich (serpentine) soils. Metabolites produced by 13 of the isolates mobilized soil Ni (originating from the rhizosphere of both Ni-hyperaccumulators and non-hyperaccumulator). In contrast, Ni extraction using culture medium filtrates which had supported the growth of 29 strains was significantly reduced. The remaining strains had no effect on Ni mobility. Bacterial induced Ni mobilization was not related to Ni resistance or the phenotypic traits tested. Isolates with potential use in phytoremediation techniques will be further studied in a plant-microorganism-soil system.

Inoculation of plants with their associated microorganisms is a promising strategy for improving phytoremediation of organic contaminants. Isolation and characterisation of these organisms from plants growing in contaminated sites will permit the identification of candidate strains for re-inoculation studies. The diversity of culturable endophytic and rhizoplane bacteria found in association with Cytisus striatus plants growing at a hexachlorocyclohexane (HCH)-contaminated site was studied. A total of 97 strains of endophytic bacteria were isolated from the root, stem and leaf tissues, and 49 from the rhizoplane. They were further characterised genotypically (BOX-PCR, 16S rDNA sequencing, presence of linA and linB genes) and phenotypically (trace metal tolerance, capacity to produce biosurfactants and plant growth promoting (PGP) traits). Proteobacteria and Actinobacteria dominated the isolate collection, and taxonomic diversity was strongly tissue-specific. The linA and linB genes were not detected in the isolate collection. The majority of isolates had at least one of the PGP traits tested, whereas biosurfactant-producing strains were less frequent. Resistance to more than one trace metal was generally restricted to endophytes isolated from shoot tissues. The PGP characteristics found in an important number of the bacterial isolates obtained in this study could be particularly useful for exploiting the phytoremediation potential of C. striatus.

Mining activities are important sources of trace elements in the environment. Tailings resulting from this type of activity tend to present high concentrations of trace elements and host metal-tolerant plants and their associated microorganisms. These plant-microbial associations may be of potential use in phytoremediation techniques. In this study, individuals of three plant species (Betula, Cytisus, Festuca) growing in a Pb/Zn mine in Rubiais (NW Spain) were sampled. Whole plants and their adhering soil, and nonvegetated soil, were collected. Bulk and rhizosphere soils were analysed for physico-chemical properties (pH, organic C/N, TOC, CEC, total metal (Cd, Pb and Zn) content, metal fractionation) and microbiological characteristics. Plant tissues were analysed for total metal content. All species excluded metals from shoot tissues, and Betula was found growing in the more contaminated points (hot spots). Plant-available fractions of metals (including less mobile metals such as Pb) were significantly higher in the rhizosphere. The number of colony forming units was determined in bulk and rhizosphere soils on mineral medium without metals or supplemented with increasing concentrations of Cd or Zn (0.1 or 1.0 mM Cd, 1 mM or 3 mM Zn). As expected, rhizosphere soils host higher total bacterial densities but also a higher proportion of metal-tolerant bacteria compared to nonvegetated soil. Of the three species, Cytisus hosts the highest densities of metal tolerant rhizobacteria. Eighty bacterial strains were isolated from rhizosphere soils. These strains were characterized by BOX-PCR profiling and comparative sequence analysis of 16S rRNA genes and screened for their ability to produce IAA, siderophores, biosurfactants and organic acids, to solubilise phosphate and for their Zn and Cd tolerance. Potentially useful metal-resistant or plant-growth promoting rhizobacteria will be selected for further plant inoculation studies in phytoremediation trials.

In this study we determine culturable microbial densities (total heterotrophs, ammonifiers, amylolytics and cellulolytics) and bacterial resistance to Co, Cr, and Ni in bulk and rhizosphere soils of three populations of the Ni-hyperaccumulator Alyssum serpyllifolium subsp. lusitanicum and the excluder Dactylis glomerata from ultramafic sites (two populations in Northeast (NE) Portugal (Samil (S), Morais (M)) and one population in Northwest (NW) Spain (Melide (L)). The relationship between bioavailable metal concentrations (H2O-soluble) and microbial densities were analysed. Significant differences in microbial densities and metal-resistance were observed between the two species and their three populations. The hyperaccumulator showed higher microbial densities (except cellulolytics) and a greater rhizosphere effect, but this was only observed in S and M populations. These populations of A. serpyllifolium also showed selective enrichment of Ni-tolerant bacteria at the rhizosphere where Ni solubility was enhanced (densities of Ni-resistant bacteria were positively correlated with H2O-soluble Ni). These rhizobacteria could solubilise Ni in the soil and potentially improve phytoextraction strategies.

[ES] Se estudió el efecto de la contaminación con altas cantidades de un residuo compuesto de isómeros de 1,2,3,4,5,6-hexaclorociclohexano (HCHs) (10, 50 y 100 g HCHs kg-1 suelo) sobre la densidad en el suelo de microorganismos heterótrofos, algas y cianobacterias fijadoras de N2 , sobre algunos microorganismos implicados en los ciclos de C y N (amonificantes, amilolíticos, y celulolíticos) así como sobre la capacidad de las comunidades microbianas edáficas para degradar varios sustratos carbonados (perfiles fisiológicos de las comunidades microbianas, CCLP). Estas propiedades microbianas se analizaron a las 2 semanas y los 2 y 4 meses de la aplicación del contaminante. También se estudió el efecto de la contaminación con HCHs aplicado a distintas concentraciones y en forma de partículas de distinto tamaño, sobre la respiración del suelo. A corto plazo tras la adición del contaminante al suelo, la densidad de los microorganismos heterótrofos aumentó, la abundancia de algas descendió y la población de cianobacterias no vario significativamente. A los 4 meses de la contaminación el efecto de las concentraciones de contaminante más altas (50 y 100 g HCHs kg-1 suelo) sobre los grupos microbianos mencionados fue negativo. El residuo de HCHs tuvo un efecto sobre la población amonificante similar a la observada en los microorganismos heterótrofos. Las densidades de amilolíticos y celulolíticos no se vieron afectadas o aumentaron, a corto plazo después de la adición de contaminante, aunque, a largo plazo (4 meses tras la contaminación) experimentaron una reducción con las concentraciones más altas de HCHs. A los dos meses de la contaminación, la capacidad de las comunidades microbianas del suelo para degradar sustratos carbonados (CCLP) se vio negativamente afectada por el residuo de HCHs. Cabe resaltar el descenso en la degradación de aminoácidos, que fue especialmente importante en los suelos con 50 y 100 g HCHs kg-1 suelo. El residuo de HCHs también afectó a la respiraci, [EN] The effect of heavy contamination with a residue composed of 1,2,3,4,5,6-hexachlorocyclohexane isomers (HCHs) (10, 50 and 100 g HCHs kg-1 soil) on the densities of cultivable soil heterotrophs, algae and N2 -fixing cyanobacteria, on soil microorganisms involved in the N and C cycles (ammonifiers, amylolytics and cellulolytics) as well as on the ability of soil microbial communities to degrade several C substrates (community level physiological profiles, CCLP) was studied. These microbial properties were analysed 2 weeks, and 2 and 4 months, after the soil was artificially contaminated. The effect of HCHs residue applied at different concentrations, and in the form of particles of different sizes on soil respiration was studied. The influence of the presence or absence of microorganisms from a long term polluted site on the effect of HCHs on soil respiration was also analysed. In the short term after the addition of the contaminant to the soil, the density of heterotrophs increased, the abundance of algae decreased, while the population of cyanobacteria did not change significantly. Four months after contamination the effect of the highest concentrations of HCHs (50 and 100 g HCHs kg-1 soil) on these microbial groups was negative. The HCH residue had a similar effect on the ammonifying population to that on heterotrophs. The densities of amylolytics and cellulolytics were either not modified, or were stimulated by the contaminant in the short term but, in the longer term (4 months after the contamination), were inhibited by HCHs applied at the highest concentrations. Two months after contamination, the ability of soil microbial communities to degrade C substrates (CCLP) was negatively affected by HCHs. It was noteworthy the decrease in the ability for degrading aminoacids, which was particularly important in the soils with 50 and 100 g HCHs kg-1 soil. HCHs also affected soil respiration but the effect depended on the HCH concentration, particle size of the conta

Microorganisms in heated (200°C, 1 h) soil not inoculated (H) or inoculated with 0.5% of fresh soil (Hi) and amended with wheat straw (Hi+WS) or poultry manure (Hi+PM) were determined during a 3-month soil incubation. Heating completely sterilised the soil, although the normal soil manipulation in the laboratory contaminated H with a few microbes. In the inoculated soil samples, whether amended or not, microbes were able to actively proliferate, but soil inoculation was essential to develop field microbial conditions. Organic amendment (WS or PM) neither inhibited microbial proliferation nor changed the order of the sizes of the various subgroups. Saprophytic bacteria predominated over the other microbial groups, followed by fungal propagules and actinomycetes; fungal mycelium was relatively well developed, whereas the numbers of photoautotrophs, cyanobacteria and algae were low. With regard to the N-mineralizers, there was a relatively high number of ammonifiers, while chemoautotrophic nitrifiers, both NH4+- and NO2−-oxidizers, were scarce. Microbial groups, however, differed in their response to treatment. In regard to the heterotrophic microbes, amendment with WS increased counts of fungal propagules and hyphae length, while bacteria, particularly actinomycetes and ammonifiers, were lowered; conversely, PM treatment favoured bacterial, actinomycetal, ammonifier and fungal mycelium development and propagule generation. All the autotrophic microbes, whether photo- or chemo-autotrophs, were decreased by the addition of organic residues and, in general, the effect was more negative with PM than with WS. The results indicated that WS could restore the numbers of fungi in the heated soil, but it could cause a reduction in other microbial groups, whereas PM increased the numbers of all the taxonomic groups and the ammonifiers. However, neither residue favoured the recovery of autotrophic C- and N-fixers and nitrifiers in the heated soil.

The effect of wildfire on soil microbes and extractable C (Cext) and N (Next) changed with respect to the time from burning and soil depth. Initially, microbial biomass C (Cmic) and N (Nmic) were drastically reduced in the soil surface layer (0–5 cm) and reduced by 50% in the subsurface (5–10 cm), whereas Cext increased by 62% in the surface layer and did not significantly change in the subsurface. These parameters were affected for the following 4 years, during which the average reductions in the soil surface and subsurface layers were, respectively, 60% and 50% for Cmic, 70% and 45% for Nmic, 60% and 40% for the ratio Cmic: organic C (Corg) and 70% and 30% for the ratio Nmic: total N (Ntot), while for Cext the surface layer was the only zone consistently affected and Cext decreased by up to 59%. Immediately after a fire, the Cext : Corg ratio increased by 3.5-fold and 2-fold in the surface and subsurface layers, respectively; thereafter for 2 years, it decreased in the surface layer (by up to 45%) while the effect on the subsurface layer was not consistent. The effect of burning on Next lasted 1 year, in which Next increased by up to 7- and 3-fold in the surface and subsurface layers, respectively, while the average Next : Ntot ratio doubled in the surface layer and increased by 34% in the subsurface. During the time in which each parameter was affected by burning, the soil factor explained a high percentage of variance in the fluctuations of Cmic, Nmic, Cmic : Corg and Nmic : Ntot, while those of Next and Next : Ntot, but not those of Cext and Cext : Corg depended on both the soil and its depth. In the burned soils similar patterns of response were found between the following parameters listed in pairs: Cmic and Nmic; Cmic : Corg and Nmic : Ntot; Cext and Next; and Cext : Corg and Next : Ntot. However, after the fire relationships found previously between the parameters studied and many other soils properties were either no longer evident, or were inverted. Alth

Physiological groups of soil microorganisms were investigated in a forest (Pinus pinaster Sol.) to asses their response to wildfire-induced soil changes. Microbial fluctuations were recorded 1 month and 1 year after the fire, both in the field and during controlled soil incubations. In both the burned and the unburned soil, starch-mineralizing microbes predominated over cellulose-mineralizing microbes; there were a relatively high number of ammonium-producers, whereas nitrite and nitrate producers were scarce. In the short term, burning produced a decreasing to nearly undetectable number in cellulase-producers whilst amylase-producers, and especially, ammonifying microbes increased, and the nitrifying groups did not change. One year after the wildfire, the burning effect was slightly overcome by cellulolytic microorganisms and the amylolytic population was slightly decreased; the improvement of ammonifiers was reduced, ammonium oxidizers were positively affected and nitrite oxidizers continued to be unaffected by the fire. The trends of populations during soil incubation indicated that, in the long term, the effect of burning will probably be nil on ammonifiers, somewhat negative on cellulolytic and amylolytic microbes and slightly positive on nitrite- and nitrate-formers.

Wheat straw or poultry Pinus-sawdust litter were added to a forest acid soil and changes in the microbial community were studied during a 3-month soil incubation. Soil amendment did not alter the relationships between microbial groups. In all the samples most microbes were aerobic heterotrophic bacteria which predominated over fungal propagules and actinomycetes; fungal hyphae were relatively well developed, whereas the densities of cyanobacteria and algae were relatively low. Among the N-cycle microbes, there was a relatively high number of ammonifiers, while both ammonium- and nitrite-oxidizers were scarce. Although soil amendment did not significantly alter the pattern of growth of most microbial groups, it drastically changed their numbers, alterations due to poultry addition being much more marked than those due to straw addition. Among the heterotrophic microbes, straw addition to soil increased fungal population but decreased bacteria and especially actinomycetes, while those that were able to carry-out ammonification were unaffected. Conversely, poultry manure addition favoured all the microbial groups, the increase in number following the order: bacteria > fungi > actinomycetes, the ammonium-producers being particularly stimulated. Autotrophic microbes, whether photo- or chemo-autotrophs, were decreased by straw and manure. The response of microbes indicated that the use of wheat straw could lead to a reduction in taxonomic and functional diversity in the microbial community and that, in general, poultry manure seems to be better for applying to soil.

Population fluctuations were increased by burning, which also modified the incubation patterns and the densities of several microbial groups, although without changing the order of their population sizes. In the short term, fire produced a sharp increase in microbes but affected the groups studied differently. Aerobic heterotrophic bacteria, including the acidophilic and sporulating ones, were stimulated by fire while cyanobacteria, algae and fungi (propagules as well as hyphae length) were clearly depressed. In the long term, the positive effect of fire on bacteria was nullified except on the sporulating ones; fungal propagules, but not mycelium, reached the unburned soil values, cyanobacteria and algae also increased. Soil incubation both improved the beneficial and diminished the negative fire effect on the microbiota

Microbial biomass and activity were determined in three Cambisols and two Rankers developed over different kinds of rocks. The soils contained 0·3−1·7 g C kg−1 soil as biomass, which represented 0·8−1·5% of the total C. Whether the fumigation-incubation or fumigation-extraction method was employed, non-significant differences were found in microbial biomass values. The microbial density, which ranged from 107 to 108 microorganisms g−1 soil, was drastically reduced by CHCl3-fumigation; however, the liberation of cell metabolites significantly increased the microbial growth rate. During 10 days of soil incubation at 25°C 0·1−0·2 g C kg−1 soil (0·1−0·5% of total soil C) was released and 1−5 mg N 100 g−1 soil (0·1−1·5% of total soil N) was mineralized. A significant increase (approximately threefold) in the average C and N mineralization was found as a consequence of microbial lysis by fumigation. The results indicated that these soils have a considerable quantity of microbial biomass but a relatively low metabolic activity and that C and N mineralization may be significantly improved when microbial constituents are liberated into the soil.

The physical and chemical characteristics of four composted urban refuses (one of them amended with CaCO3 during the composting process) from Spanish industrial composting plants were studied from the point of view of their use as organic fertilizers. The four composts were very fine in texture with low bulk density and high salinity. The pH was close to neutrality; the organic matter content ranged from 42 to 60% and the C/N ratio from 16 to 22 (7 for the amended urban refuse). Most of the total N was in organic forms; NH4+-N largely predominatedNO3−-N in the composts, except for the amended composted refuse where the predominant inorganic form was NO3−-N. Calcium was the most abundantnutrient followed by K, Na, Mg and P. Most of the Ca and Na were in available forms; available K and Mg were lower and available P very small. Total Al and Fe were extremely abundant followed by Zn, Mn, Pb, Cu, Cr, Ni and Cd. The percentage of available Mn was very high, followed by available Cu and Pb in two of the composts, and available Zn and Cd. Available Al, Fe, Ni and Cr were very low or negligible. Most of the total Zn, important percentages of total Pb, Mn, Al and Fe, but very low proportions of total Cr and Ni and only traces of Cd, were complexed with organic matter; these compounds seemed to be soluble organo-metallic complexes, except part of those formed by Al and Cd that could be stable complexes. Although the four composted refuses were unbalanced with regard to the main nutrients they all had potential agronomic value. Total C contents and C/N ratios in the three non-amended composts were in the range for stabilized composts; however, the NH4+-N content seemed to point to the presence of non-stabilized substances.

Viable microorganisms, soil respiration, and available N, Ca, Mg, Na, K, and P contents were determined in samples of five different forest soils collected in spring, summer, autumn, and winter. Viable microorganisms and soil respiration were positively correlated and showed a clear seasonal trend. The soils exhibited high microbial population values in spring and autumn and low values in summer and winter; total respiration values were largely higher in autumn than in the other seasons. Seasonal variations in available Ca, Na, and K contents were much more marked than those found for available N, Mg, and P. Available N and K and the microbial population showed similar seasonal trends whereas available Ca, Mg, Na, and P did not exhibit a distinguishable and uniform seasonal pattern. The quantities of available nutrients in soils followed the order Ca>K=Na>Mg>P>N. Soils developed over basic rocks showed higher values of both microbial density and microbial activity than those in soils developed over acid rocks. All the variables analysed were clearly related to the type of soil but varied with the date of sampling; a significant seasonal effect on the microbial population, microbial activity and available nutrients was detected in all the soils studied.

Lime was added to a forest acid soil rich in organic matter. During five weeks of initial incubation at room temperature (until the various limed soil samples reached stabilized pHs of 5.5, 6.0 or 6.51, there were rapid increases in the bacterial population, denitrifiers, and fungal mycelia, particularly in the heaviest limed sample. Conversely, nitrite oxidizers decreased to undetectable numbers regardless of the lime dose applied. At this time soil samples were amended with 5% of fresh soil. During 12 weeks of subsequent incubation at 28"C, the bacterial population was favoured by increasing soil pH; nevertheless, at the end of the incubation the positive effect was only significant at pH 6.0 and 6.5. By contrast fungi were depressed by raising the pH. Nitrifiers and denitrifiers were more numerous in the limed than in the unlimed soils but only in samples at pH 6.5 were the differences significant throughout the incubation period.

In poultry slurry bacteria, most of them being strict or facultative anaerobes, predominated over actinomycetes and fungi, and algae were in low densities. Most of the population could carry out proteolysis, ammonification, denitrification, anaerobic cellulolysis, anaerobic N2-fixation, amylolysis, pectolysis, reduction of sulphates and anaerobic mineralization of organic sulphur. Conversely there were few nitrifiers, aerobic cellulolytics, aerobic free-living N2-fixers and sulphur-oxidizers, and cyanobacteria, fungal hyphae and sulphide oxidizers were undetected. At the beginning of slurry storage, the population of viable microorganisms and most of the microbial groups abruptly declined. Thereafter, the viable population rapidly multiplied, being five-fold greater than its initial value after 14 weeks. This increase was mainly attributed to anaerobic bacteria, while aerobic heterotrophic bacteria, including the sporulating and acidophilic ones, actinomycetes and fungi were negatively affected. After the fall in numbers, proteolytics, ammonificants, amylolytics, anaerobic cellulolytics and anaerobic N2-fixers actively grew, regaining or even surpassing, their initial densities. Conversely aerobic free-living N2-fixers, ammonium-oxidizers, nitrite-oxidizers, aerobic cellulolytics, pectolytics and sulphur-oxidizers remained at densities significantly lower than their initial values. Only denitrifiers, algae and sulphate-reducers were favoured from the initial stage of the storage.

Principal components analysis has been applied to the total microbial population numbers and to taxonomic groups and the physiological groups involved in the C, N and S cycles in 10 humid zone soils developed over 7 different types of rock, the aim being to determine the relationships between the various groups and the factors influencing the distribution of microflora in these soils. Except for fungi, which are negatively correlated with certain other groups (algae especially), all the remaining groups are either not correlated or positively correlated with each other. The factor most influencing the density and functional diversity of the microbial population is depth within the profile, both density and diversity decreasing with increasing depth. In the surface horizons the distribution of microflora is controlled by the time of year and the associated changes in climatic conditions, with lack of humidity limiting the microbial population more than temperature. The time of year likewise determines the proteolytic and ammonification potential, whereas nitrification depends on the degree of differentiation of the profile. Denitrification and aerobic and anaerobic nitrogen fixing potential appear to be controlled by pH. Aerobic cellulolysis potential depends on the degree of evolution of the profile, with greatest potential in the least evolved soils, whereas the distribution of anaerobic cellulolytics seems to be determined by the type of parent rock.

Total microbial populations, bacteria, actinomycetes, fungi and algae of three samples of poultry excreta were studied. The physiological groups involved in C, N and S cycles have been determined. The results were compared with the common numbers in soils and organic wastes. Poultry excreta had a high density of micro-organisms. Bacteria, most of them being strict or facultative anaerobes, predominated. Actinomycetes and fungi were also in relatively high density. Fungi were mainly as propagules and their mycelium was nearly indetectable. Algae were in low density. A small percentage of aerobic bacteria was acidophilic or acid-tolerant, a lesser number was spore-forming, and cyanobacteria were not detected. Most of the microbial population had proteolytic, ammonificant, anaerobic cellulolytic, denitrificant and anaerobic nitrogen-fixing capacities, followed by amylolytics, pectolytics, sulphate reducers and anaerobic mineralizers of sulphur; whereas micro-organisms favoured by aerobic conditions as aerobic cellulolytic, aerobic free-living nitrogen fixers, ammonium oxidizers, nitrite oxidizers and sulphur oxidizers were in low densities, and sulphide oxidizers were not detected.

The average density of viable microorganisms in poultry pine-sawdust litter was 6·3 × 107/g dry material (DP); 1·6% of the population were aerobic heterotrophic bacteria. Acidophile bacteria, aerobic spore-forming bacteria, actinomycetes and fungi were, respectively 4·8 × 104, 8·1 × 104, 5·2 × 104 and 8·9 × 104 CFU/g DP. However the latter did not have a measurable mycelium. Algae were in low densities (18/g DP) and cyanobacteria were not detected. Most of the population had proteolytic and ammonificant capacities, but there were very few ammonium oxidizers and nitrite oxidizers. Denitrifiers were in relatively high density and the anaerobic free-nitrogen fixers were more abundant than the aerobic ones. Aerobic cellulolytics were scarce, but anaerobic cellulolytics, amylolytics and pectolytics showed a similar, and relatively high average density. Sulphate reducers and anaerobic mineralizers of organic sulphur were more abundant than the elementary-sulphur oxidizers, and sulphide oxidizers were not detected. Except for algae, microbial populations generally tended to decrease with time of use of the litter. This decline affected mainly nitrifiers, anaerobic and aerobic cellulolytics and amylolytics while sulphate reducers and anaerobic free-nitrogen fixers increased.

A study was conducted of the survival and multiplication of bacteria introduced into soil. In a loam, the populations of Rhizobium leguminosarum biovar phaseoti, R. meliloti, Agrobacterium tumefaciens, Micrococcus flavus, Corynebacterium sp., Pseudomonas sp. 2K and Pseudomonas sp. 1G declined by one to two orders of magnitude. Some of these species initially increased in numbers in this soil upon the addition of 0.1 or 1.0% glucose, but others did not proliferate. However, the populations of all species subsequently declined. The patterns of decline of A. tumefaciens, Pseudomonas sp. B4, Streptococcus faecalis and M.flavus in silt loam were similar. Because the patterns of decline of none of the test species were similar in unamended sterile soil or, except for M. flavus and S. faecalis, in sterile buffer, the reductions in population sizes were not a result of toxins already present in the soil or starvation, but were related to the activities of other microorganisms. The population size of an asporogenous strain of Bacillus subtilis declined markedly in nonsterile and sterile soil and in buffer, and it fell to a small number in nonsterile soil amended with 0.1% glucose. Because cellular slime molds, bacteriophages, bdellovibrios and myxobacteria were not found, they are not responsible for the reduction in numbers of the test species. Protozoa increased in number as the populations of the test species fell. The extents of decline of A. tumefaciens,Pseudomonas sp. 2K, Corynebacterium sp. and M. flavus were diminished if glucose-amended or unamended soil was treated with cycloheximide, a eucaryotic inhibitor. Antibiotic-producing and lytic microorganisms able to destroy the test species were present, their numbers varying with the test organism. It is suggested that the populations of bacteria introduced into soil may be reduced because of their susceptibility to predation, starvation or possibly antibiotic-producing or lytic microorganisms.

Agrobacterium tumefaciens, Pseudomonas sp. and Corynebacterium sp. grew in glucose-amended soil, but their populations subsequently declined. Protozoa multiplied as the numbers of cells of these species fell. The rise and subsequent fall in densities of the three bacterial species did not correlate with changes in the populations of lytic or antibiotic-producing organisms or in the lytic activity of the soil. Myxobacteria, bacteriophages and Bdellovibrio were not detected in the soil. The densities of the three bacterial species and indigenous bacteria were far greater and the subsequent falls in cell numbers were less marked in glucose-amended soil treated with cycloheximide and nystatin than in soil not receiving the two cucaryotic inhibitors. Addition of the two inhibitors caused a decline in the numbers of trophozoitcs and a rise in the numbers of protozoan cysts. The three bacterial species grew extensively after inoculation into sterile soil supplemented with glucose, but their population sizes were appreciably smaller and the numbers subsequently declined if the sterile soil also was inoculated with a mixture of prutozoa. The results suggest that predation by protozoa is a major factor limiting the growth and causing the decline of bacterial populations introduced into soil amended with readily-available organic nutrients.

l. Suelos– Física. Mecanismos de iluviación de arcilla en materiales calcáreos. Por J. Aguilar Ruiz, T. Rodríguez Rebollo y M. Simón Torres.-- l. Suelos-Química. Estudio cinético de la hidrólisis del parathión en extractos acuosos de un suelo alcalino típico de Almería. Por E. González Pradas, M. Villafranca Sánchez y F. del Rey Bueno.-- Determinación de Ca y Fe totales en suelos calizos por espectrometría de fluorescencia de rayos X. Por J. Moreno Caselles, M. T. Estañ Campello, M. Romero Conejero y F. Santacruz Carreño.-- Comparación de dos métodos de disolución alcalina para el estudio de los componentes no cristilinos del suelo. Por E. García-Rodeja Gavoso.-- Distribución de Pb, Cd, Cu y Cr entre distintas fases sólidas en algunos tipos de suelo. Por R. Cruz Cañadas, J. Rodríguez Sanchidrián y V. Cala Rivero.-- l. Suelos-Biología. Determinación del crecimiento de Rhizobium leguminosarum biovar trifolii bajo la acción del herbicida Amitrol. Por T. Mogollón, M. Flores y M. Cazorla.--l. Suelos-Génesis, clasificación y cartografía - Suelos desarrollados sobre sedimentos calizos no consolidados en el Valle del Guadalquivir. I: Descripción del medio y de los suelos de la zona. Por J. L. de Olmedo Pujol - Procesos edafogenésicos y edad de las formaciones tipo raña relacionadas con las estribaciones meridionales de los Montes de Toledo. Por R. Espejo Serrano.-- Contribución a la evaluación edáfica de suelos mediante el estudio del comportamiento de diversos metales pesados. Por V. Cala Rivera, R. Jiménez Ballesta, J. Rodríguez Sanchidrián y A. Guerra Delgado.-- l. Suelos-Fertilidad. Caracterización y fluctuación de parámetros fisicos y fisico-químicos en lodos de depuradoras. Por J. l. Moreno Sánchez, M. T. Hernández Fernández y F. Costa Yagüe.-- Caracterización y fluctuación del carbono y nitrógeno de lodos de depuradoras. Por M. T. Hernández Fernández, J.I. Moreno Sánchez y F. Costa Yagüe.-- Evolución de la microflora total y de los microorganismos nitrificantes de un

l. Suelos-Química Análisis de los procesos de alteración y neoformación en sistemas edáficos a partir de consideraciones termodinámicas de equilibrios solución-mineral. Por M. L. Fernández Marcos y F. Macías.-- Estudio de la materia orgánica y naturaleza de los compuestos hllmicos en suelos afectados por sales. Por P. Gómez, J. Gumuzzio y A. Polo.-- Factores formadores y características mineralógicas de suelos desarrollados sobre el Karst de Larra (Pirineo Occidental). Por J. López Martínez, J. Casas y J. L. Martín Vidales.-- Variación estacional de la composición de la disolución de suelos de Galicia en relación con el tipo de horizonte y material original. Por M. L. Fernández Marcos y F. Macías.-- Génesis, Clasificación y Cartografía Reconocimiento y evaluación de suelos del Valle del Guadalquivir: Zona Marmolejo-Menjibar (Jaén). l. Relaciones geomorfología-suelos. Por J. Gil, L. Corral y G. Paneque.-- Fertilidad Influencia del pH del suelo sobre el desarrollo y producción de la Piña tropical en Canarias, l.-Fertilidad del suelo y nutrición mineral. Por A. E. Carracedo Torres, C. E. Alvarez González, V. García García y C. García Corujo.-- Absorción de P por Rye-grass y el fósforo asimilable de suelos aluviales y autoctonos del Valle del Ebro. Por B. Eleizalde t y V. Hernando.-- ll. Biología Vegetal-Nutrición Evolución de los contenidos minerales de raíz, tallo y hoja de plantas de tomate como índices de nutrición. Por O. Carpena Artes, A. Masaguer Rodríguez y M. J. Sarro Casillas.-- Quelación por Dtpa de oligoelementos en suelos calizos. Ecuación modificada de Freundlich. Por J. Sánchez-Andréu, E. A. Gadea, M. Juárez y A. Gárate.-- Fisiología. Efecto de diversas concentraciones de nitratos y pH sobre el crecimiento de plántulas de capsicum annuum L. Var. acuminatum Fingerh H. Por l. Iglesias, T. Díaz, E. González y C. Rodríguez Bujan.-- Vitis Vinifera en el campo de Cartagena. II. Evolución de azllcares (Glucosa, fructosa y sacarosa), sustancias pécticas, ácidos o

I. Suelos. Física. Estudio de algunos factores que influyen en la formación de microagregados en los suelos del N.W. de España. Por E. Benito Rueda y F. Diaz-Fierros Viqueira.-- l. Suelos. Química. Comportamiento de la materia orgánica del suelo sometida a hidrolisis ácida: l. Seguimiento de la liberación de monómeros alfa-aminados. Por S. González Carcedo y M. C. Garcia Melus.-- Transformaciones del fósforo en suelos gallegos sometidos a incubación. Por M. C. Trasar Cepeda, F. Gil Sotres y F. Guilián Ojea.-- Dinámica de carbonatos en suelos desarrollados sobre areniscas. Por J. Batlle, J. R. Miñambres y J. L. Martin.-- Aplicación de técnicas de disolución selectiva al estudio de los componentes no cristalinos de una secuencia de sue los sobre granito en la Sierra de Ancares (Lugo, Galicia). Por E. García-Rodeja Gayoso y F. Macías Vázquez-- Movilización y fijación biológica de cationes en ecosistemas forestales. II: Dinámica del K en los horizontes superficiales del suelo. Por A. Garcia- Villaraco y F. Velasco de Pedro.--Determinación de la cinética de reacción del quelato Mnhedta en un suelo calizo mediante EUF (Electroultrafiltración). Por J. Sánchez-Andreu. Mª C. Sebastián Alafont, M. Juárez Sanz y J. Jordá Guijarro.-- l. Suelos. Biología. Estudio de la población microbiana de diversos tipos de suelo de zona húmeda (N.O. de España). Por Mª J. Acea y T. Carballas.--Distribución de la población microbiana de un podsol férrico húmico. Por Mª J. Acea y T. Carballas.-- l. Suelos. Génesis, Clasificación y Cartografía: Formaciones edáficas del sector N.E. de la provincia de Cuenca. (IV) Alfisoles. Por J. Batlle Sales, J. Gumuzzio Fernández y J. L. Martin de Vidales.--Suelos desarrollados sobre sedimentos calizos no consolidados en el Valle del Guadalquivir. II. Génesis y evaluación de los suelos. Por J. L. de Olmedo Pujol.-- Contribución al estudio micromorfológico de suelos de Galicia, sometidos a distintas condiciones de hidromorfia. Por M. C. Leiros de la Peña y .M.

Suelos-Química. Interacción del ácido 3,6-Dicloro-2-Metoxi-Benzoico (Dicamba) con montmorillonita, por G. Dios Cancela, A. Navarrete Guijosa y A. Jiménez López.-- Estabilidad de Beidellitas en función de su composición, por J. L. Martín de Vidales, R. Jiménez Ballesta, J. Casas y M. A. Hoyos.-- Caracterización de suelos en la Sierra del Pozo (Jaén) sector nor-oeste (Zona I), por J. González Parra, A. López Lafuente y C. González Huecas.-- Caracterización de suelos en la Sierra del Pozo (Jaén) sector central (Zona II), por J. González Parra, A. López Lafuente y C. González Huecas.-- Reacción con el FNa de los suelos de Galicia V. Relación con material de partida y los procesos edafogénesis, por E. García-Rodeja Gayoso, F. Macías Vázquez y F. Guitian Ojea.-- Morfología y propiedades químicas de suelos forestales de Argelia. Suelos bajo A bies numidica y Cedrus atlantica, por M. S. Martín, L. Corral y G. Paneque.-- Morfología y propiedades químicas de suelos forestales de Turquía. Suelos bajo A bies cilicica y Cedrus libani, por M. S. Martín, L. Corral y G. Paneque.-- l. Suelos.-Biología First results of a study of the microbial population of humid zone granitic soils, by M. J. Acea and T. Carballas.-- l. Suelos-Génesis Origen y desarrollo de la topografía en bolsas del material original de los suelos rojos de Aljarafe (Sevilla-Sur de España), por Juan L. de Olmedo Pujol.-- l. Suelos- Fertilidad. El fósforo en los purines de vacuno gallegos: 1) Contenido y distribución de las formas de fósforo, por F. Gil Sotres, F. Diaz-Fierros, Ma C. Leiros, T. Carballas, A. Cabaneiro, M. a C. Villar Celorio y M. Carballas.-- Il. Biología Vegetal-Nutrición Evolución del contenido de flavonoides en hoja de tomate en condiciones óptimas de nutrición, por E. Revilla, J. Serrano y M. J. Sarro.-- Estudio de la posible utilización de micorrizas V A como fertilizantes biológicos en dos suelos, por L. F. Cardona y J. A. Ocampo.-- Incidencia de la salinidad en uva de mesa de la vega media del

Suelos. Influencia de los factores formadores en la génesis de suelos de montaña en la provincia de Teruel, V., por A. Hoyos, Ma. L. Palomar, A.Ma. Moreno y C. Fernández.-- Características petroquímicas y. micromorfológicas de los Xerumbrepts de la Sierra de Guadarrama, por P. Arévalo t, J. Benayas y J. Gallardo.-- Predicción de parámetros climáticos de interés ecológico en Galicia. II., por A.M. MolIna, J. Juste, F. Ucieda, R. Retuerto y A. Carballeira.-- Naturaleza y utilidad de las relaciones suelo-relieve en una zona granodiorftica de la parte central del Valle de los Pedroches (Córdoba), por J. Torrent, M. A. Parra, L. Montealegre y J. Barrios.-- La fracción arcilla de suelos de alta montaña sobre rocas carbonatadas. IV Xerolls, por L. J. Alias y J. Fernández Bastida.-- La fracción arcilla de suelos de alta montaña sobre rocas carbonatadas. V. Borolls, por L. J. Alias Pérez y J. Hernández Bastida.-- Aspectos qufmico-agrfcolas de suelos representativos del marco Montilla-Moriles, I., por l. Sánchez, J. Gil, L. Corral, M. Medina y G. Paneque.-- Aspectos químico-agrícolas de suelos representativos del marco Montilla-Moriles. II., por l. Sánchez, J. Gil, M. Medina, L. Corral y G. Paneque.-- Aspectos químico-agrícolas de suelos representativos del marco Montilla-Moriles. Ill., por, l. Sánchez, J. Gil, L. Corral, M. Medina y G. Paneque.-- Aspectos químico-agrícolas de suelos representativos del marco Montilla-Moriles. IV., por, l. Sánchez, J. Gil, L. Corral, M. Medina y G. Paneque.-- Caracterización de la población microbiana de un purin de vacuno, por M. J. Acea y T. Carballas.-- Efecto de la humedad ambiental en la adsorción-desorción en fase gaseosa de Heptacloro· por suelos de la cuenca del Guadalquivir, por Eduardo Peris, Juan Cornejo y Pablo de Arambarri.-- Fertilidad de Suelos. Respuesta del maíz a las aplicaciones de fósforo en un suelo pardo con tendencia fersialftica, por P. Díaz Luis, Benigna Eleizalde, V. García y Amalia Díaz.-- Effect of different compos

The addition of cattle slurry to the soil brings about an increase in the number of microorganisms of the carbon and sulphur cycles, though the levels attained do not exceed normal large population densities. The dynamics of the rise depend on the chemical and microbial composition of the slurry and the process by which it is incorporated into the soil. The aerobic cellulolytic and pectinolytic populations are favoured in the long term, whereas the numbers of anaerobic cellulolytics and amylolytics increase rapidly on slurry treatment only to fall sharply shortly thereafter, and in the case of amylolytics these processes result in a net fall in population density. The rise in microbial populations after slurry treatment is due more to the added numbers of microorganisms present in the slurry itself than to the substrate stimulating a population growth, but whereas added elemental sulphur oxidizers survive, anaerobic microorganisms such as sulphate reducers and anaerobic organic sulphur mineralizers die off after a short time.

Soil microbial biomass, which generally comprises about 2-3% of the total organic carbon in soil. has been rccognized as an important source of nutrients because of its fast turnover (Jenkinson and Ladd, 1981). The C. N, P and S contents of biomass have been measured by fumigation procedures (Jenkinson and Powlson, ,1976); however, knowledge of other mineral nutrients in biomass is scarce (Sparling and Berrow. 1985). Our aim was to determine the quantities of available plant nutrients (N. P. K. Ca. Mg and Na) after the death of microorganisms by CH,CI fumigation.

The microbial populations of four composed urban refuses, one of them amended with CaCO3, have been studied. The physiological groups with greatest influence upon the evolution and fertility of the soil were determined. The results were compared with the common numbers in soils and organic wastes. Variations in soil microbial population and nitrite oxidizers attributable to the action of the added compost were also recorded. Composted urban refuses had a high microbial population. Bacteria, a small proportion of which were spore-forming, predominated, but actinomycetes and fungi were also in high densities; on the contrary, algae were absent, except in CaCO3-amended compost. Most of the population had preteolytic, ammonificant, amylolytic and aerobic cellulolytic capacities, followed by denitrifiers, sulphate reducers and elementary sulphur oxidizers. The densities of aerobic and anaerobic free-nitrogen fixers, anaerobic cellulolytics, pectolytics, anaerobic mineralizers of sulphur and sulphide oxidizers were low. An important feature was the lack of nitrifiers in the wastes studied, the only exception being the compost amended with CaCO3 which had a relatively high population of nitrifiers. The urban refuse composts did not substantially affect the soil microbial population and had a short-term, slightly-positive, effect over nitrite oxidizers. Composting with CaCO3 seemed to notably improve the nitrite oxidizer population of the soil.

The fumigation method was used to estimate microbial biomass C in four Haplumbrepts developed over different kinds of rock. In order to investigate the relationship between metabolic activity and microbial biomass and population density, CO2 release from the glucose-enriched and unenriched soils was measured during 28 days of incubation. Biomass C levels lay between 36 and 112 mg 100 g−1 of dry soil, and made up only a small proportion of total soil C (0.77–1.38%). Only a small fraction of this biomass was detected by counting viables, but the microbial population was nevertheless significantly correlated with the biomass determined by fumigation. Among the physico-chemical properties of the soils, microbial biomass and population size were both chiefly affected (favourably) by humidity, total C and N and Al gel content. Metabolic activity was slight, either because part of the micro-organisms are inactive or because of a limited supply of substrate (the organic matter present may be unsuitable as a substrate or protected from microbial attack). Percentage C mineralization was inversely related to organic matter, silt and Al gel contents, and likewise failed to exhibit positive correlation with respiration, the biomass determined by fumigation or the counted population. The metabolic activity of the biomass appeared to depend upon the quality and nature of soil organic matter rather than its quantity, which nevertheless controlled microbial population size. Neither microbial biomass estimates nor viable population counts faithfully reflected metabolic activity in the soils.

Variations in microbial population and nitrogen cycle microorganisms have been studied over one crop cycle in an acid Ranker over granite, under grass fertilized with cattle slurry and in the unfertilized soil. Cattle-slurry treatment brought about a great rise in total microbial population but affected different groups differently, though without changing the order of their population sizes. Bacteria were favoured, while the numbers of actinomycetes, fungi and algae were reduced, the latter especially. Slurry treatment increased the capacity for degradation and mineralization of nitrogen compounds by increasing the populations of proteolytics, ammonifiers and nitrifiers, though the latter group survived only briefly, their numbersfalling sharply again after a short time. The populations of denitrifiers and anaerobic free-nitrogen fixers also increased when slurry was applied, though much less strikingly than the groups mentioned above, whereas aerobic free-nitrogen fixers were depressed. Proteolytics, ammonifiers and denitrifiers were affected more by the first application of slurry than by the second, whereas the reverse was true of nitrifiers and anaerobic free-nitrogen fixers. All the groups studied except the algae tended to return to their initial population levels after some time.