[Periodicity of microbiological processes in the soil].
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Microbiological Phenomena↗
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Time-dependent distribution of surface-applied radionuclides and their recovery in maize during the growing season.
The spatial and temporal heterogeneity of field soils influences the fate and behavior of strongly sorbing pollutants and their entry into the food chain. We studied the redistribution of surface-applied 54Mn, 65Zn, 57Co, and 134Cs in the soil profile and their recovery in the aerial parts of maize grown on an untilled agricultural soil during the growing season. Radionuclides were more concentrated in the preferential flow paths (PFP) than in the soil matrix and their concentration decreased with time. The recovery of 54Mn in the aerial plant parts increased between pollen shed and maturity, while the recovery of 65Zn and 57Co did not show any significant difference, and the recovery of 134Cs decreased with time. The amount and distribution of rainfall, and the chemical, physical, and microbiological soil characteristics are the major factors influencing the variation of radionuclide recovery with time.
Plant Roots↗
Pollutant biodegradation: mountain or Mohammed.
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Bacterial Adhesion↗
[The prospects of using bacteria of the genus Rhodococcus and microbial surfactants for the degradation of oil pollutants].
The possibility of accelerating oil degradation by an enrichment culture of oil-oxidizing microorganisms in the presence of bacteria of the genus Rhodococcus and microbial surfactants was studied. It was shown that the degree of consumption of crude oil (2% v/v) after 192 h of enrichment culture growth reached 84%. Inoculation of the active hydrocarbon-oxidizing strain Rhodococcus erythropolis EK-1 and exogenous surfactants produced by Pseudomonas sp. PS-27 increased this degree to 90% and 93-94%, respectively. On the grounds of these results, efficient methods of purification of the environment from oil pollutants can be developed.
Biodegradation, Environmental↗
Human viruses in sediments, sludges, and soils.
Recent studies have provided a greater understanding of the movement of viruses in the environment by their attachment to solids. These studies have focused on solids-associated viruses present in wastewater discharged into the ocean and on viruses in sludge and wastewater that may be retained in soil following their land disposal. Such ocean or land disposal of wastewater and sludge may result in a discharge of one or more of 120 human enteric virus pathogens including those causing poliomyelitis, viral hepatitis A and acute gastroenteritis.Solids-associated viruses in effluents discharged into coastal waters accumulate in bottom sediments, which may contain 10 to 10 000 more virus per unit volume than the overlying seawater. Solids-associated viruses resuspended by water turbulence may be transported from polluted to distant non-polluted recreational or shellfish-growing water. Transmission of viruses causing hepatitis or gastroenteritis may result from contact by bathers or swimmers with these viruses in recreational waters, or from ingestion of raw or improperly cooked shellfish in which the solids-associated virus had been bioaccumulated.The land disposal of sludge and wastewater has a potential of causing infections in farm workers, contamination of crops, pollution of raw potable water sources or infiltration of ground water. Viruses retained on soils can be released by rain water and may contaminate ground water through lateral and vertical movements.
Adenoviridae↗
Gram-negative bacteria responsible for insoluble technetium formation and the fate of insoluble Tc in the water column above flooded paddy soil.
We studied the characteristic gram-stain of Tc insolubilizing bacteria using various antibiotics, and the fate of insoluble Tc in a water column above flooded paddy soil to clarify Tc behavior in paddy fields. The formation of insoluble Tc in water column samples was inhibited by the addition of antibiotics, especially reagents against gram-negative bacteria. For a sample without antibiotics, insoluble Tc formation increased with time, and the maximum amount of insoluble Tc was observed on day 4 of incubation with (95m)Tc. In contrast, concentrations of ferrous ion decreased with time. These results suggested that gram-negative bacteria were mainly responsible for insoluble Tc formation, and that these bacteria were able to transform soluble Tc to insoluble forms under oxidizing conditions.
Disasters↗
Biostimulation and bioaugmentation enhances aerobic biodegradation of dichloroethenes.
The accumulation of dichloroethenes (DCEs) as dominant products of microbial reductive dechlorination activity in soil and water represent a significant obstacle to the application of bioremediation as a remedial option for chloroethenes in many contaminated systems. In this study, the effects of biostimulation and/or bioaugmentation on the biodegradation of cis- and trans-DCE in soil and water samples collected from contaminated sites in South Africa were evaluated in order to determine the possible bioremediation option for these compounds in the contaminated sites. Results from this study indicate that cis- and trans-DCE were readily degraded to varying degrees by natural microbial populations in all the soil and water samples tested, with up to 44% of cis-DCE and 41% of trans-DCE degraded in the untreated soil and water samples in two weeks. The degradation rate constants ranged significantly (P<0.05) between 0.0938 and 0.560 wk(-1) and 0.182 and 0.401 wk(-1), for cis- and trans-DCE, respectively, for the various treatments employed. A combination of biostimulation and bioaugmentation significantly increased the biodegradation of both compounds within two weeks; 14% for cis-DCE and 18% for trans-DCE degradation, above those observed in untreated soil and water samples. These findings support the use of a combination of biostimulation and bioaugmentation for the efficient biodegradation of these compounds in contaminated soil and water. In addition, the results clearly demonstrate that while naturally occurring microorganisms are capable of aerobic biodegradation of cis- and trans-DCE, biotransformation may be affected by several factors, including isomer structure, soil type, and the amount of nutrients available in the water and soil.
Aerobiosis↗
Heavy metal toxicity to microbe-mediated ecologic processes: a review and potential application to regulatory policies.
Microorganisms are sensitive to heavy metal pollution as are other components of the biota. However, most studies on the interactions between microbes and heavy metals have been conducted in synthetic media or in altered (e.g., sterilized) environmental samples and usually have used only single species. Few studies have evaluated the effects of heavy metals on the activities of natural heterogeneous microbial populations, both autotrophic and heterotrophic, in terrestrial and aquatic environments. These latter studies have shown that heavy metals inhibit primary productivity, nitrogen fixation, the mineralization of carbon, nitrogen, sulfur, and phosphorus, litter decomposition, and enzyme synthesis and activity in soils, sediments, and surface waters. The potential adverse effects of heavy metals on such microbe-mediated ecologic processes need to be incorporated into the methodologies used by regulatory agencies, such as the U.S. Environmental Protection Agency, to prepare environmental risk assessments which, in turn, are used to formulate environmental criteria, such as the Water Quality Criteria, and to evaluate the safety to the environment of exposure to "new chemical substances," as mandated by the U.S. Toxic Substances Control Act of 1976. To provide appropriate data that can be assimilated into regulatory policy, it is essential that microbial ecotoxicity tests be standardized, are neither costly nor difficult to train personnel to conduct, and produce data that can be quantitated.
Bacteria↗
MALDI-TOF analysis of polymerase chain reaction products from methanotrophic bacteria.
Polymerase chain reaction (PCR) assays were designed to amplify 56- and 99-base regions of the pmoA gene from Methylosinus trichosporium OB3b and Methylomicrobium albus BG8, two species of methanotrophic bacteria that are of interest for monitoring bioremediation activity. The PCR product sizes are in a mass range that is accessible to analysis by MALDI-TOF mass spectrometry. A rapid purification procedure using commercially available reversed-phase cartridges was applied prior to MALDI-TOF analysis. A small aliquot (1.5%, 1.5 microL) from a single 100-microL PCR reaction was sufficient for reliable detection. No cross-amplification products were observed when primers designed for one bacterial species were used with genomic DNA of the other species. The methodology described here has potential to allow less expensive and faster characterization of the ability of microbial populations to destroy pollutants in groundwater and soil at contaminated industrial sites.
Biodegradation, Environmental↗
Overview of phytotechnologies.
Phytotechnologies are defined as: "The use of vegetation to contain, sequester, remove, or degrade inorganic and organic contaminants in soils, sediments, surface waters, and groundwater." This chapter is designed to provide the reader with a broad, introductory overview of phytotechnologies as well as environmental remediation in general. To familiarize the reader with the common acronyms, abbreviations, and parameters used in the environmental arena, an extensive list is provided for quick reference. Furthermore, due to the multi-disciplinary nature of phytotechnologies, a brief background on the pertinent information in plant physiology, soil microbiology, hydrogeology, and environmental engineering is provided as well. This covers the basic physiological processes occurring in the rhizosphere as well as in the plant system. Furthermore, these basic processes are related to the phytotechnology mechanisms that form the basis for the various applications used in the field today. Finally, basic design equations, site-specific considerations, and practical field implementation techniques are provided as well for the different applications.
Agriculture↗
The effect of nanometer dimension topographical features on the hygienic status of stainless steel.
Wear of food contact surfaces through abrasion may increase the surface roughness and introduce different topographical features. Both of these properties may enhance retention of soil and microorganisms and affect the surface cleanability. To test this hypothesis, stainless steel surfaces with topographical features and surface roughness (Ra) values simulating those of worn in-use surfaces were prepared. Surfaces were imaged and Ra values determined using atomic force microscopy (AFM). These ranged from 23 to 900 nm. Surfaces were sprayed with standardized cell suspensions of Pseudomonas aeruginosa or Staphylococcus aureus and allowed to air dry and were then cleaned using a nonionic detergent delivered via a manual linear cleaning device. There was a 2-log reduction in numbers attached after cleaning, but there was no significant difference (P > 0.05) between the cleanability of the surfaces in terms of the numbers of cells per unit area remaining after cleaning, although cells appeared to be retained within topographical features. Thus, the simulated effect of wear of a hygienic food contact surface did not affect its cleanability after a one-off microbiological soiling event. AFM provided hitherto unavailable information on the topography of worn stainless steel surfaces. In future work, the surfaces will be repeatedly challenged with an organic soil-microorganism mixture after cleaning events, to provide a more rigorous, realistic test.
Disinfection↗
Soil immobilization: new concept for biotreatment of soil contaminants.
A new concept for the development of microbial consortia for the degradation of persistent soil pollutants and for pollutant treatment is proposed. The concept defined as "soil immobilization" is based on the entrapment of soil particles, showing microbial activity in degrading the target pollutant, into a solid membrane with a large pore size distribution. The particular hydrodynamic and mass transfer properties of this system result in a very efficient process. A new type of bioreactor is proposed for carrying out the immobilized soil process. The performance of the system was tested by developing a microbial system for the mineralization of pentachlorophenol (PCP). The results show that the volumetric efficiency of the process for PCP mineralization in the immobilized soil bioreactor is 1-3 orders of magnitude higher than reported literature values. Chlorine and carbon atoms of PCP are both nearly completely (99%) mineralized.
Biodegradation, Environmental↗
Survival of luxAB-marked Alcaligenes eutrophus H850 in PCB-contaminated soil and sediment.
A rifampicin-resistant PCB-degrading Alcaligenes eutrophus H850 strain was marked with luxAB reporter genes and designated H850Lr. This strain was enumerated in soil by viable plating and counting of light-emitting colonies. The marked strain was also inoculated into soil and sediment microcosms contaminated with PCBs and treated with rhamnolipid biosurfactants produced by Pseudomonas aeruginosa UG2Lr or inoculated with the P. aeruginosa UG2Lr strain. A. eutrophus H850Lr exhibited similar survival in sandy loam soil in the absence or presence of PCBs over 56 days. Survival of A. eutrophus H850Lr in PCB-contaminated sediment was less than in sandy soil under the same incubation conditions. Addition of P. aeruginosa UG2 rhamnolipids to soil increased the culturable indigenous heterotrophic population, and numbers of A. eutrophus H850Lr cells. P. aeruginosa UG2Lr cells did not affect survival of A. eutrophus H850, as cell enumerations after 2 months were the same as in microcosms containing only A. eutrophus H850 inoculum. P. aeruginosa UG2Lr survived in soils as demonstrated by the slight decrease in CFU from 1 x 10(8) to 2 x 10(6) CFU cm-3 after 2 months. Direct extraction of DNA from soil and purification for use in PCR amplification using primers specific for the bphC gene detected 8 x 10(2) A. eutrophus H850Lr CFU g-1 soil in PCB-contaminated soils. Colony lifts of bacteria isolated from microcosms containing PCB-contaminated soil did not hybridize with LB400 bphC probe. However, enrichment of PCB-contaminated soil with biphenyl, followed by DNA extraction and probing with bphC gene probe detected indigenous PCB-degrading bacteria containing a similar gene sequence in PCB-contaminated sediment. This study demonstrates the usefulness of using the lux reporter system in monitoring bacterial survival in PCB-contaminated soils and sediments.
Alcaligenes↗
Influence of incubation temperature on activity of ligninolytic enzymes in sterile soil by Pleurotus sp. and Dichomitus squalens.
Solid state straw cultures of the white rot fungi Pleurotus sp. and Dichomitus squalens covered with a layer of sterile soil were incubated at 20 degrees C, 25 degrees C, 30 degrees C, and 34 degrees C. The activities of the extracellular enzymes laccase and manganese peroxidase (MnP) in the soil layers were measured over eight weeks. Pleurotus sp. produced high enzyme activity at low temperatures. Laccase was maximum at 25-30 degrees C and manganese peroxidase at 20 degrees C. D. squalens showed uniformly high levels of manganese peroxidase at 20-30 degrees C whereas at 34 degrees C, MnP was low and laccase showed an atypical time pattern. The discrepancy between low activity of the main enzyme, MnP, and high straw decomposition at 34 degrees C by D. squalens warrants further investigation of the enzyme inventory produced at that temperature.
Biodegradation, Environmental↗
Soya lecithin effects on the aerobic biodegradation of polychlorinated biphenyls in an artificially contaminated soil.
The effects of the phytogenic surfactant soya lecithin (SL) on the aerobic biodegradation of polychlorinated biphenyls (PCBs) spiked into a synthetic soil were studied. Soil was spiked with both biphenyl (4 g/kg) and Fenclor 42 (1,000 mg/kg) and treated in aerobic batch slurry-phase microcosms (17.5% w/v). Microcosms were prepared either with or without the exogenous aerobic PCB-dechlorinating bacterial co-culture ECO3 (inoculum:10(8) CFU/mL). In some inoculated microcosms, SL was added at 15 or 30 g/kg. Indigenous bacteria having the capability of metabolizing biphenyl and 2-chlorobenzoic acid were found to develop in the microcosms during the experiment, and were responsible for the significant PCB biodegradation and dechlorination observed in the uninoculated controls. The addition of ECO3 bacteria resulted in only a slight PCB biodegradation increase. In the presence of SL, a higher availability of biphenyl- and chlorobenzoic acid-degrading bacteria and higher PCB biodegradation and dechlorination yields were observed; the effects increased proportionally with the concentration of the applied SL. A significant decrease of soil ecotoxicity was also revealed in SL-supplemented microcosms. At both concentrations, SL was found to be a good carbon source for both the indigenous and ECO3 bacteria, as well as a product capable of enhancing the PCB bioavailability in the microcosms.
Aerobiosis↗
Evaluation of the interaction between biodegradation and sorption of phenanthrene in soil-slurry systems.
This work develops and utilizes a non-steady-state model for evaluating the interactions between sorption and biodegradation of hydrophobic organic compounds in soil-slurry systems. The model includes sorption/desorption of a target compound, its utilization by microorganisms as a primary substrate existing in the dissolved phase, and/or the sorbed phase in biomass and soil, oxygen transfer, and oxygen utilization as an electron acceptor. Biodegradation tests with phenanthrene were conducted in liquid and soil-slurry systems. The soil-slurry tests were performed with very different mass transfer rates: fast mass transfer in a flask test at 150 rpm, and slow mass transfer in a roller-bottle test at 2 rpm. The results of liquid tests indicate that biodegradation of the soil-soluble organic fraction did not significantly enhance the biodegradation rate. In the slurry tests, phenanthrene was degraded more rapidly than in liquid tests, but at a similar rate in both slurry systems. Modeling analyses with several hypotheses indicate that a model without biodegradation of compound sorbed to the soil was not able to account for the rapid degradation of phenanthrene, particularly in the roller-bottle slurry test. The model with sorbed-phase biodegradation and the same biokinetic parameters, but unique mass transfer coefficients, simulated the experimental data in both slurry tests most successfully. Reduced mass transfer resistance to bacteria attached to the soil is the most likely phenomenon accounting for rapid sorbed-phase biodegradation.
Adsorption↗
Evidence for high affinity nickel transporter genes in heavy metal resistant Streptomyces spec.
We have isolated 25 new strains of streptomycetes from soil samples of a polluted site at the former uranium mine, Wismut, in eastern Thuringia, Germany. The strains grew on medium containing 1 mM NiCl2 and thus were resistant to the heavy metal ion. Seven of the strains were further characterized. All of these strains were resistant to heavy metals in various degrees with up to 10 mM resistance against NiCl2 supplied with the liquid minimal growth medium. The high level of resistance prompted us to look for high affinity nickel transporter genes thought to provide a means to eliminate the excess nickel ions form the cells. Degenerate oligonucleotide primers derived from sequences of P-type ATPase transporter genes of Gram negative bacteria identified a fragment which shows deduced amino acid sequence similarities to known high affinity nickel transporters. Investigation of two genes obtained from the isolates Streptomyces spec. E8 and F4 showed high sequence divergence. This was unexpected since a transmissible plasmid had been thought to convey heavy metal resistance.
Amino Acid Sequence↗
Diversity of Bacillus thuringiensis in different habitats of northern Jordan.
A survey of Bacillus thuringiensis was conducted for 17 locations in Northern Jordan representing 12 different habitats. Eighty isolates were identified as B. thuringiensis in the majority of the tested samples. Results showed that soils contaminated with the slaughterhouses waste materials had the highest content of spore-forming bacteria [(4.05-2.2) 10(7) CFU/g)] and B. thuringiensis [(4.05-7.9) 10(7) CFU/g)] with a (5.5%-14.9%) and (5.2%-7.7%) of the total viable bacterial count, respectively. These bacteria were more abundant in soils contaminated with such animal by-products.
Abattoirs↗