Number Of Culturable Bacteria Research Articles

磷高效转基因大豆对根际微生物群落的影响

Farming is faced with the problems of excessive fertilizer use and the reduction of nutrient use efficiency.Phosphorus is one of the macronutrients necessary for plant growth and development.However,phosphorus is usually immobilized by organic substances or oxidized surfaces of iron-aluminum,and exists in the form of organic or inorganic phosphorus,which makes uptake from most soils difficult.It is well known that acid phosphatase increases the use efficiency of organic phosphorus by releasing inorganic phosphorus from organic phosphorus such as phytate.AtPAP15 encodes a purple acid phosphatase,which has been observed to have phytase activity,in Arabidopsis thaliana.AtPAP15 was over-expressed in transgenic soybean AP15-1 and its expression product was secreted into the rhizosphere because of the presence of a carrot extension gene signal peptide,and thus enhanced use of soil organic phosphorus.Previously,there have not been many reports of research concerning the effects of such nutrient-efficient transgenic plants on soil ecology.In this study,the effects of P-efficient transgenic soybean AP15-1 on soil ecology,especially on the rhizosphere microbial community,were investigated.Transgenic soybean AP15-1 and its receptor YC03-3 were planted in vent-netting greenhouse in 3 m × 5 m experimental plots with three replicates.Soybeans were planted in two successive spring and autumn seasons,and no manure,herbicide or pesticide was used.To ascertain if phytase activity in root exudates of transgenic soybean AP15-1 affects the soil microbe ecosystem,the rhizosphere and non-rhizosphere soil of AP15-1 and its receptor YC03-3 were collected at seedling,florescence and mature developmental stages and analyzed by plate culture count and BIOLOG-EcoPlate.The number of colony forming units(CFU) indicated that the number of culturable bacteria,fungi and actinomyces varied with seasons and development stages.There were no apparent differences in numbers of bacteria,fungi and actinomyces among rhizosphere and non-rhizosphere soil of AP15-1 and YC03-3.The absorbance of BIOLOG-EcoPlate at 590 nm and 750 nm was recorded using microplate spectrophotometer and the average well color development(AWCD) values were calculated.The curves of AWCD versus incubation time showed that the carbon metabolic activity of microbes in rhizosphere soil was higher than that in non-rhizosphere soil from the same season.However,statistical analysis indicated that no significant differences in carbon metabolic activity and carbon source preference were observed among rhizosphere and non-rhizosphere soils of AP15-1 and YC03-3.Statistical analysis of the calculated microbial abundance and diversity index also exhibited no distinct differences among rhizosphere and non-rhizosphere soils of AP15-1 and YC03-3.Principal component and clustering analyses revealed that the difference between the rhizosphere of AP15-1 and YC03-3 was less than that between rhizosphere and non-rhizosphere soil from the same season and at the same plant developmental stage.The effects of season and developmental stage on the community diversity of rhizosphere microbes were greater than that resulting from the genotype differences between AP15-1 and YC03-3.In conclusion,these results demonstrated that the P-efficient transgenic soybean AP15-1 planted in spring and autumn had no significant impact on the soil microbial numbers and community structures.

Bacterial communities in urban aerosols collected with wetted-wall cyclonic samplers and seasonal fluctuations of live and culturable airborne bacteria

Airborne transmission of bacterial pathogens from point sources (e.g., ranches, dairy waste treatment facilities) to areas of food production (farms) has been suspected. Determining the incidence, transport and viability of extremely low levels of pathogens require collection of high volumes of air and characterization of live bacteria from aerosols. We monitored the numbers of culturable bacteria in urban aerosols on 21 separate days during a 9 month period using high volume cyclonic samplers at an elevation of 6 m above ground level. Culturable bacteria in aerosols fluctuated from 3 CFU to 6 million CFU/L of air per hour and correlated significantly with changes in seasonal temperatures, but not with humidity or wind speed. Concentrations of viable bacteria determined by fluorescence staining and flow cytometry correlated significantly with culturable bacteria. Members of the phylum Proteobacteria constituted 98% of the bacterial community, which was characterized using 16S rRNA gene sequencing using DNA from aerosols. Aquabacterium sp., previously characterized from aquatic environments, represented 63% of all clones and the second most common were Burkholderia sp; these are ubiquitous in nature and some are potential human pathogens. Whole genome amplification prior to sequencing resulted in a substantial decrease in species diversity compared to characterizing culturable bacteria sorted by flow cytometry based on scatter signals. Although 27 isolated colonies were characterized, we were able to culture 38% of bacteria characterized by sequencing. The whole genome amplification method amplified DNA preferentially from Phyllobacterium myrsinacearum, a minor member of the bacterial communities, whereas Variovorax paradoxus dominated the cultured organisms.

Effects of Arbuscular Mycorrhizal Fungi Communities on Soil Quality and the Growth of Cucumber Seedlings in a Greenhouse Soil of Continuously Planting Cucumber

A pot experiment was performed to determine the effects of arbuscular mycorrhizal fungi (AMF) communities on soil properties and the growth of cucumber seedlings in a degraded soil that had been used for continuous cucumber monoculture in a greenhouse for 15 years. In the experiment, AMF communities (created by combining various AMF species that were found to be dominant in natural farm soil) were inoculated into the degraded soil, and then the soil was planted with cucumber. Inoculation with AMF communities did not affect soil pH but increased soil aggregate stability and decreased the concentrations of salt ions and electrical conductivity (EC) in the soil. Inoculation with AMF communities increased the numbers of culturable bacteria and actinomycetes but reduced the number of fungi. AMF communities increased plant growth, soluble sugar content, chlorophyll content, and root activity compared to non-mycorrhizal or a single AMF species treatments. Improvements of soil quality and plant growth were greatest with the following two communities: Glomus etunicatum + G. mosseae + Gigaspora margarita + Acaulospora lacunosa and G. aggregatum + G. etunicatum + G. mosseae + G. versiforme + G. margarita + A. lacunosa. The results suggested that certain AMF communities could substantially improve the quality of degraded soil.

Phyllopshere Bacterial Community Structure of Spinach (Spinacia oleracea) as Affected by Cultivar and Environmental Conditions at Time of Harvest

Modern molecular ecology techniques were used to demonstrate the effects of plant genotype and environmental conditions prior to harvest on the spinach epiphytic bacterial community. Three cultivars of spinach with different leaf topographies were collected at three different periods during the fall growing season. Leaf surface topography had an effect on diversity and number of culturable bacteria on the phylloepiphtyic community of spinach. Savoy cultivars, which had larger surface area and more stomata and glandular trichomes, where bacterial aggregates were observed, featured more diverse communities with increased richness and larger bacterial populations compared to flat-leaved cultivars. Bacterial community richness was compared using denaturant gradient gel electrophoresis (DGGE), while abundance was quantified using 16s rRNA primers for major phyla. The most diverse communities, both in richness and abundance, were observed during the first sampling period, immediately following a period of rapid spinach growth. Exposure to lower air and soil temperatures and decreased precipitation resulted in significantly reduced bacterial population size and bacterial community richness in November and December. This study describes the effect of the plant characteristics and environmental conditions that affect spinach microbiota population size and diversity, which might have implications in the survival of food and plant bacterial pathogens.

A Temperature-Controlled AGI-30 Impinger for Sampling of Bioaerosols

AGI-30 impingers are widely applied for the efficient collection of bioaerosols. However, these glass vessels are not protected against solar radiation and changing ambient temperature during sampling, which may impair the sampling efficiency by too high or low temperatures of the sampling liquid leading to early proliferation of microorganisms or ice formation. In order to reduce such disadvantages, an impinger holder was developed and tested under laboratory and field conditions, which insulates and controls the temperature of the impinger and the sampling liquid by means of a Peltier element. The influence of various ambient temperatures and relative humidities on the temperatures of tempered and untempered impinger liquids such as mineral oil, peptone water, and phosphate-buffered saline (PBS) during sampling periods of 30 min was investigated and compared. The type of sampling liquid greatly influenced the amount of residual liquid after sampling and the temperature in both the tempered and untempered impingers depended on the type of sample liquid, ambient temperature, and humidity. Mineral oil showed the lowest losses, followed by PBS and peptone water. Tempering of the impingers had some influence on the amount of losses. Tempering also strongly influenced the number of culturable bacteria (colony-forming unit [CFU]) in the sampling liquids. In the tempered impingers, three times higher CFU/m3 were found than in the untempered impingers. A great advantage of tempering was that sampling at ambient temperatures as low as −5°C was possible. However, in spite of insulation and tempering the impinger to a fixed value, the variance was rather high due to varying ambient temperature and relative humidity, which always have a strong influence on condensation and evaporation and therefore on the amount of sample liquid and the resulting number of CFU. Nevertheless, the temperature-controlled AGI-30 impinger is a step forward to more stable results.

Autotoxic Compounds from Rhizosphere Soil of Humulus lupulus L. Extracts: Identification and Biological Activity

Hop (Humulus lupulus L.) is a perennial herb that has been widely used in brewing around the world. Autotoxicity has been reported as one of the major problems hindering continuous hop cultivation. In this study, the autotoxic compounds from rhizosphere soil of hop fields at different time periods of hop cultivation were separated and identified by gas chromatography–mass spectrometry (GC–MS). From those compounds, one of the suspected bioactive compounds, 2,4‐bis(1,1‐dimethylethyl)‐phenol was selected, and its biological activity on hop seedling growth and effect on soil microbial populations were determined. The results of GC–MS analysis showed that the types of compounds found and their amount increased with the number of years hops had been cultivated. The results of a pot experiment showed that 2,4‐bis(1,1‐dimethylethyl)‐phenol significantly affected photosynthesis and hop seedling growth in a concentration‐dependent manner; generally, low concentrations enhanced photosynthesis and growth while high concentrations limited plant growth. The results of the pot experiment also indicated that 2,4‐bis(1,1‐dimethylethyl)‐phenol significantly decreased the numbers of culturable bacteria, fungi, actinomycetes, and the soil microbial community diversity index in the rhizosphere soil by the 7th d; however, the numbers of culturable bacteria, fungi, and actinomycetes of the rhizosphere soil significantly increased by 35 d after treatment. Furthermore, we verified the concentration of 2,4‐bis(1,1‐dimethylethyl)‐phenol by high performance liquid chromatography, which was in line with the concentration determined to be bioactive. These results suggest that 2,4‐bis(1,1‐dimethylethyl)‐phenol is involved in hops autotoxicity and that autotoxicity is the main deterrent to the success of hops replanting.

Effects of Jasmonic Acid, Ethylene, and Salicylic Acid Signaling on the Rhizosphere Bacterial Community of Arabidopsis thaliana

Systemically induced resistance is a promising strategy to control plant diseases, as it affects numerous pathogens. However, since induced resistance reduces one or both growth and activity of plant pathogens, the indigenous microflora may also be affected by an enhanced defensive state of the plant. The aim of this study was to elucidate how much the bacterial rhizosphere microflora of Arabidopsis is affected by induced systemic resistance (ISR) or systemic acquired resistance (SAR). Therefore, the bacterial microflora of wild-type plants and plants affected in their defense signaling was compared. Additionally, ISR was induced by application of methyl jasmonate and SAR by treatment with salicylic acid or benzothiadiazole. As a comparative model, we also used wild type and ethylene-insensitive tobacco. Some of the Arabidopsis genotypes affected in defense signaling showed altered numbers of culturable bacteria in their rhizospheres; however, effects were dependent on soil type. Effects of plant genotype on rhizosphere bacterial community structure could not be related to plant defense because chemical activation of ISR or SAR had no significant effects on density and structure of the rhizosphere bacterial community. These findings support the notion that control of plant diseases by elicitation of systemic resistance will not significantly affect the resident soil bacterial microflora.

Anti- Legionella activity of staphylococcal hemolytic peptides

A collection of various Staphylococci was screened for their anti- Legionella activity. Nine of the tested strains were found to secrete anti- Legionella compounds. The culture supernatants of the strains, described in the literature to produce hemolytic peptides, were successfully submitted to a two step purification process. All the purified compounds, except one, corresponded to previously described hemolytic peptides and were not known for their anti- Legionella activity. By comparison of the minimal inhibitory concentrations, minimal permeabilization concentrations, decrease in the number of cultivable bacteria, hemolytic activity and selectivity, the purified peptides could be separated in two groups. First group, with warnericin RK as a leader, corresponds to the more hemolytic and bactericidal peptides. The peptides of the second group, represented by the PSMα from Staphylococcus epidermidis, appeared bacteriostatic and poorly hemolytic.

Comparison of soil microorganism abundance and diversity in stands of European aspen (Populus tremulaL.) and hybrid aspen (Populus tremuloidesMichx. ×P. tremulaL.)

The use of short rotation forest tree species is increasing worldwide. The hybrid aspen (Populus tremuloides Michx. × P. tremula L.) is one of the suitable tree species under the climatic conditions of the Baltic region. The cultivation of these trees on former agricultural soils differs from agricultural practices with reduced soil tillage and is characterized by increased demand of nutrients, which in long term can cause changes in the soil microbial populations. The aim of our investigation was to compare soil microbial populations in hybrid aspen and European aspen (P. tremula L.) stands in four sampling plots with aspen age ranging from 10 to 46 years. The abundance and diversity of soil microbial populations were estimated by enumeration of micro- organisms (plate counts on three microbiological media) and by molecular methods (PCR, ARDRA, molecular identification of fungal isolates). Results showed that during long cultivation periods hybrid aspens reduced the number of culturable bacteria. The number of culturable filamentous fungi was statistically significantly increased only in one sampling plot in soil samples from hybrid aspen clones at a depth of 16-30 cm and only on one microbiological cultivation medium. The same was detected also with molecular methods in the case of fungal diversity estimated by Shannon-Weaver diversity indices in this sampling plot. None of the other characteristics of soil microbial populations, such as the number of yeasts and maltose utilizing bacteria on MEA, the number of yeasts and filamentous fungi on RBA, the total amount of soil DNA, fungal and bacterial diversity estimated by molecular biology methods, and species composition of filamentous fungi, was significantly affected by hybrid aspen. The identified filamentous fungi represented the following genera: Acremonium, Exophiala, Geomyces, Gibellulopsis, Gibberella, Hypocrea/Trichoderma, Leptosphaeria, Metarhizium, Mortierella, Nectria, Paecilomyces, Penicillium, Trichosporon, and others. The main conclusion was that cultivation of hybrid aspen as a short rotation forest tree in the Baltic region would not significantly affect the abundance and diversity of saprophytic soil microorganisms.

The presence of antibiotic resistant bacteria along the River Lagan

Abstract Antibiotic resistance (ABR) has now become a major public health issue. Relatively little work has been published on the incidence of ABR in environmental isolates within the environment, which is of importance to animal health, zoonotic transmission and human health. A study was performed to determine the diversity of total ABR (intrinsic + acquired resistance) in waterborne bacteria in a model watercourse system, namely the River Lagan, Northern Ireland, which is used a major source of drinking water by large populations of beef and dairy cattle. Total numbers of culturable bacteria at each sampling point ranged from 3.8 to 4.3 log colony forming units (cfu)/ml water, with a mean of 4. 1 ± 0.1 log cfu/ml. Total antibiotic resistance was observed to varying degrees and specific resistance levels were as follows with diminishing antibacterial effectiveness in the order: amikacin/aminoglycosides > carbapenems > fluoroquinolones > macrolides/tetracyclines/polymyxins > β-lactams/oxozolidones/rifampicin/trimethoprim/glycopeptides. Monitoring of the upstream ecology of waterways in terms of antibiotic susceptibility, from which agricultural animals gain their water, as well as the use of such water in agricultural crop irrigation is important, as well as the tracking of such organisms to their source may help determine the source of fecal pollution in aquatic ecosystems.

Bacterial diversity on the surface of potato tubers in soil and the influence of the plant genotype

The surface of tubers might be a reservoir for bacteria that are disseminated with seed potatoes or that affect postharvest damage. The numbers of culturable bacteria and their antagonistic potential, as well as bacterial community fingerprints were analysed from tubers of seven field-grown potato genotypes, including two lines with tuber-accumulated zeaxanthin. The plant genotype significantly affected the number of culturable bacteria only at one field site. Zeaxanthin had no effect on the bacterial plate counts. In dual culture, 72 of 700 bacterial isolates inhibited at least one of the potato pathogens Rhizoctonia solani, Verticillium dahliae or Phytophthora infestans, 12 of them suppressing all three. Most of these antagonists were identified as Bacillus or Streptomyces. From tubers of two plant genotypes, including one zeaxanthin line, higher numbers of antagonists were isolated. Most antagonists showed glucanase, cellulase and protease activity, which could represent mechanisms for pathogen suppression. PCR-DGGE fingerprints of the 16S rRNA genes of bacterial communities from the tuber surfaces revealed that the potato genotype significantly affected the Pseudomonas community structure at one site. However, the genotypes showed nearly identical fingerprints for Bacteria, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Bacillus and Streptomycetaceae. In conclusion, tuber-associated bacteria were only weakly affected by the plant genotype.

Bacterial community dynamics in horizontal flow constructed wetlands with different plants for high salinity industrial wastewater polishing

This study is focused on the diversity of bacterial communities from two series of horizontal subsurface flow constructed wetlands (CW) polishing high salinity tannery wastewater. Each series was planted with Arundo donax or Sarcocornia sp. in a substrate composed by expanded clay and sand. Chemical and biochemical oxygen demand removal efficiencies were similar in each series, varying between 58 and 67% (inlet COD 218 ± 28 mg L −1) and 60 and 77% (inlet BOD 5 37 ± 6 mg L −1), respectively. High numbers of culturable bacteria were obtained from substrate and root samples – 5.75 × 10 6-3.95 × 10 8 CFU g −1 recovered on marine agar and 1.72 × 10 7-8.46 × 10 8 CFU g −1 on nutrient agar. Fifty bacterial isolates were retrieved from the CW, related phylogenetically to Firmicutes, Actinobacteria, Bacteroidetes, α-, β-, and γ-Proteobacteria. Changes in the bacterial communities, from roots and substrate of each series, related to the plant species, hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). The clustering analysis suggested that a diverse and distinct bacterial community inhabits each series, which was related to the type of plant present in each CW.

Effect of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil

Electrokinetic remediation has been successfully used to remove organic contaminants and heavy metals within soil. The electrokinetic process changes basic soil properties, but little is known about the impact of this remediation technology on indigenous soil microbial activities. This study reports on the effects of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil. The main removal mechanism of diesel was electroosmosis and most of the bacteria were transported by electroosmosis. After 25 days of electrokinetic remediation (0.63 mA cm − 2 ), soil pH developed from pH 3.5 near the anode to pH 10.8 near the cathode. The soil pH change by electrokinetics reduced microbial cell number and microbial diversity. Especially the number of culturable bacteria decreased significantly and only Bacillus and strains in Bacillales were found as culturable bacteria. The use of EDTA as an electrolyte seemed to have detrimental effects on the soil microbial activity, particularly in the soil near the cathode. On the other hand, the soil dehydrogenase activity was enhanced close to the anode and the analysis of microbial community structure showed the increase of several microbial populations after electrokinetics. It is thought that the main causes of changes in microbial activities were soil pH and direct electric current. The results described here suggest that the application of electrokinetics can be a promising soil remediation technology if soil parameters, electric current, and electrolyte are suitably controlled based on the understanding of interaction between electrokinetics, contaminants, and indigenous microbial community.

Genetic and metabolic diversity of Arctic bacterioplankton during the post-spring phytoplankton bloom in Disko Bay, western Greenland

Changes in the genetic and metabolic diversity of the bacterioplankton in Disko Bay, western Greenland, were followed during the post-spring phytoplankton bloom. Samples were taken at different depths every 2 to 3 d from 1 to 23 June 2001. The highest bacterial abundance was found at the depth of the fluorescence maximum (FM). Average cell numbers at FM were around 6 × 10 5 cells ml -1 , but numbers were highly variable. Immediately following a rapid decline in the phyto- plankton biomass from 31 to 8 mg chl a m -3 , a peak in numbers of culturable bacteria was observed reaching 3 × 10 4 CFU ml -1 . Concomitant with the changes in phytoplankton biomass and bacterial culturability, the genetic diversity of the bacterioplankton communities changed as assessed by DGGE. At FM, DGGE fingerprints shifted between 6 and 8 June; however, they returned to the ini- tial profile between 10 and 14 June. Similarly, successional shifts in the diversity of the culturable bacteria were observed as the populations before and after the peak in CFUs were significantly dif- ferent. Accompanying the changes in genetic diversity, the metabolic diversity of the bacterial com- munities shifted and the communities became adapted to growth on refractory carbon sources such as cellulose and xylan. Our investigation thus demonstrates intimate links between phytoplankton and bacterioplankton and that the spring phytoplankton bloom strongly affects the genetic diversity and functional characteristics of the heterotrophic bacterial communities in Disko Bay.

Responses of indigenous microorganisms to a fungicidal mixture of mancozeb and dimethomorph added to sandy soils

The objective of this study was to assess changes in microbiological characteristics of loamy sand (LS) and sandy loam (SL) soils in response to a mixture of two fungicides, mancozeb (MB) and dimethomorph (DT), applied at three dosages of 15, 75 and 1500 mg kg −1 soil. Microbial activity, assessed by substrate-induced respiration, was either stimulated or unchanged by the first two dosages of MB + DT in both soils throughout 28 days. However, MB + DT at the concentration of 1500 mg kg −1 soil significantly decreased the respiration in LS soil. All MB + DT concentrations increased the total numbers of culturable bacteria, ammonification rate but did not change the numbers of nitrate-reducing bacteria in both soils. In comparison to acid and alkaline phosphatases and urease, dehydrogenase was most sensitive to MB + DT and its activity declined in both soils. Decreases in nitrate concentrations, the numbers of fungi, nitrifying and N 2-fixing bacteria were ascertained in both soils during the incubation time. Furthermore, slow growing K-strategists generally dominated in both soils after the treatment with MB + DT. Overall, the fungicidal preparation released at higher concentrations may disturb some non-target microbial groups inhabiting sandy soils. Consequently, to diminish an ecological hazard, careful application of MB + DT should be followed.

Ecology of pathogenic and non‐pathogenic Vibrio parahaemolyticus on the French Atlantic coast. Effects of temperature, salinity, turbidity and chlorophyll a

Vibrio parahaemolyticus is one of the principal bacterial causes for seafood-borne gastroenteritis in the world. In the present study, three sites located on the French Atlantic coast were monitored monthly for environmental parameters over 1 year. The presence of total and pathogenic V. parahaemolyticus in sediment, water and mussel samples was detected following enrichment by culture and real-time PCR (toxR gene, tdh, trh1 and trh2 virulence genes). Using generalized linear models, we showed that the presence of V. parahaemolyticus in water could be explained by a combination of mean temperature over the 7 days before the day of sampling (P < 0.001) and turbidity (P = 0.058). In mussels, an effect of chlorophyll a (P = 0.005) was detected when an effect of the mean salinity over the 7 days before sampling was significant for the sediment (P < 0.001). We did not detect any significant effect of phytoplanktonic blooms or of the number of culturable bacteria on V. parahaemolyticus presence. No sample was revealed positive for tdh. The presence of trh1 and trh2 was positively influenced by the mean temperature during the 2 days before the day of sampling (P < 0.001 and P = 0.032). The importance of these ecological parameters is discussed in relation to the biology of V. parahaemolyticus.

Effects of band-steaming on microbial activity and abundance in organic farming soil

Band-steaming of arable soil at 80–90 °C kill off weed seeds prior to crop establishment which allows an extensive intra-row weed control. Here we evaluated the side-effects of in situ band-steaming on soil respiration, enzyme activities, and numbers of culturable bacteria and fungi in an organic field soil. The results showed that mechanical disturbance created by band-steaming could be neglected as a mediator of microbial changes. Also, soil pH and water content was unaffected by band-steaming. Effects of band-steaming on in situ soil respiration and basal respiration, respectively, were insignificant or slightly stimulatory ( P < 0.05). Fluorescein diacetate hydrolysis and arylsulfatase activity were significantly ( P < 0.001) inhibited by 25 and 38%, respectively, and only showed weak recovery during 90 days after band-steaming. Bacterial colony-forming units increased after soil steaming whereas the number of fungal propagules was reduced by 50% ( P < 0.001). This reduction persisted at a level of 38% after 90 days ( P < 0.001). Evaluated in relation natural environmental stresses, band-steaming showed ecologically tolerable short-term effects, but with weaker recovery potential and therefore possible long-term effects. However, band-steaming affects only a minor volume of the plough layer (<10%) and long-term effects may be minimal due to annual tillage (mixing) of the soil. In conclusion, the side-effects on soil microbiology may not disqualify band-steaming as an option in organic farming systems.

Effect of Municipal Solid Waste Compost on Mine Soils As Evaluated by Chemical, Biological And Biochemical Properties of Soil

Composts are increasingly used in land rehabilitation because they can improve soil quality and reduce the need for inorganic fertilizers. Their use contributes to an integrated approach to waste management by promoting recycling of nutrients and minimizing final disposal of organic residues that, due to their composition, can pose problems to agricultural soils. We investigated whether compost from mixed municipal solid waste (MSW) could be used to remediate two soils from a mine contaminated with trace elements. One of the soils was less acidic and had a greater content of Cu and Zn while the other had more Pb and a lower pH. The effect of MSW was evaluated by plant growth, trace element leachability, ecotoxicity of soil leachates, and biological and biochemical properties of soils. Growth of perennial ryegrass (Lolium perenne L. cv. Victorian) was stimulated in the MSW compost-amended soils compared with respective controls or with acidic soil when limed. After ryegrass had been growing for 119 days, the amount of water-extractable Zn was lower in MSW compost-amended soils, while the opposite was true for water-extractable Cu. Water-extractable Pb increased following MSW compost application to one soil and decreased in the other. The greatest dehydrogenase activity was obtained in amended limed soil, while the number of culturable bacteria and fungi and the activities of cellulase and β-glucosidase were similar in soil that was limed or following MSW compost application. In contrast, urease activity was repressed in limed or MSW compost-amended soils. Leachates from unamended soils were toxic towards Daphnia magna. Liming the very acidic soil led to a decrease in the toxicity of the leachate, but it was only in MSW compost-amended soils that ecotoxicity was no longer detected.

Microbial characteristics of sandy soils exposed to diazinon under laboratory conditions

Changes in microbiological characteristics in response to diazinon, applied at three different dosages of 7, 35 and 700 mg kg−1 soil, were studied in pots filled with sandy soils of different texture. The insecticide dosages corresponded to the maximum predicted environmental concentration (PEC) in field conditions and five or hundred times this rate, respectively. To ascertain these changes, activities of selected soil enzymes, numbers of some microbial populations and bacterial community structure (r/K-strategists) were determined. Acid phosphatase activity and concentrations of ammonium ions either increased or were unaffected by the diazinon dosages. In contrast, nitrate ions, alkaline phosphatase, urease and especially dehydrogenase activities decreased in both soils treated with the higher dosages of the insecticide. The diazinon treatments increased the numbers of culturable bacteria and fungi; however, N-fixing bacteria and nitrifiers (but not denitrifiers) were decreased in both soils. When the high concentration of diazinon (100-times PEC) was added to the loamy sand soil (LS), simulating an undiluted chemical spill, the bacterial community structure shifted towards domination of K-strategists over time. However, r-strategists dominated in the community exposed to the same dosage of the insecticide in the sandy loam soil (SL). Generally, SL soil characteristics were more suitable for microbial activity and growth than those of LS soil were. The results indicate that except a situation of undiluted spill diazinon seems to be a non-hazardous chemical for the culturable soil microorganisms when applied at recommended concentrations.

Anti- Listeria innocua activity of silver functionalised textile prepared with plasma technology

Thin layers of silver particles (10–100 Å) were deposited by plasma technology on textiles mainly composed with cotton or polyester in order to obtain antimicrobial properties. The antimicrobial activity against a Listeria innocua strain (LRGIA 01) of these textiles was assessed following a protocol based on the ISO 20743-2005 standard. The number of cultivable bacteria on textiles was then monitored for 24 h. The microbial population after 24 h at 30 °C attained 10 7 CFU g −1 on control textiles while it did not exceed 10 3 CFU g −1 on plasma-treated textile. All plasma-treated with silver textiles were anti- Listeria (up to 7 log CFU g −1 decimal reductions of L. innocua populations) and this observation was confirmed by scanning electron microscopy. These textiles could thus have potential applications in food-processing industry to control cross-contaminations by L. monocytogenes.