Spatial and Temporal Shifts of Endophytic Bacteria in Conifer Seedlings of Abies religiosa (Kunth) Schltdl. & Cham.

Endophytes play an important role in plant development, survival, and establishment, but their temporal dynamics in young conifer plants are still largely unknown. In this study, the bacterial community was determined by metabarcoding of the 16S rRNA gene in the rhizoplane, roots, and aerial parts of 1- and 5-month-old seedlings of natural populations of Abies religiosa (Kunth) Schltdl. & Cham. In 1-month-old seedlings, Pseudomonas dominated aerial parts (relative abundance 71.6%) and roots (37.9%). However, the roots exhibited significantly higher bacterial species richness than the aerial parts, with the dissimilarity between these plant sections mostly explained by the loss of bacterial amplification sequence variants. After 5 months, Mucilaginibacter dominated in the rhizoplane (9.0%), Streptomyces in the roots (12.2%), and Pseudomonas in the aerial parts (18.1%). The bacterial richness and community structure differed significantly between the plant sections, and these variations were explained mostly by 1-for-1 substitution. The relative abundance of putative metabolic pathways significantly differed between the plant sections at both 1 and 5 months. All the dominant bacterial genera (e.g., Pseudomonas and Burkholderia-Caballeronia-Paraburkholderia) have been reported to have plant growth-promoting capacities and/or antagonism against pathogens, but what defines their role for plant development has still to be determined. This investigation improves our understanding of the early plant-bacteria interactions essential for natural regeneration of A. religiosa forest.

Application of young maize plant residues alters the microbiome composition and its functioning in a soil under conservation agriculture: a metagenomics study.

To increase our knowledge on how application of organic material alters soil microbial populations and functionality, shotgun metagenomic sequencing was used to determine the microbial communities and their potential functionality in an arable soil amended with young maize plants (Zea mays L.) in a laboratory experiment after 3 days. The relative abundance of bacterial and viral groups was strongly affected by organic material application, whereas that of the archaeal, protist and fungal groups was less affected. Cellulose degraders with copiotrophic lifestyle (e.g., Betaproteobacteria) were enriched in the amended soil, whereas the groups with slow growing oligotrophic and chemolithoautotrophic metabolism within Bacteria and Archaea were greater in the unamended than in the amended soil. The soil viral structure and richness were also affected. Caudovirales was the dominant viral family, with members of Siphoviridae enriched in the amended soil and members of Myoviridae in the unamended soil. More specialized metabolic traits related to both the degradation of complex C compounds and denitrification related genes were enriched in the young maize plant amended soil than in the unamended soil, whereas nitrification related genes were enriched in the latter. Copiotrophic life-style bacterial groups were enriched in the amended soil, whereas oligotrophic life-style bacterial groups in the unamended soil. Many bacterial and viral phylotypes were affected by the application of young maize plants, but the number of soil fungi, archaea and protists affected was smaller. Metabolic functionality was affected by the application of organic material as the relative abundance of genes involved in the denitrification process was higher in the maize plant amended soil than in the unamended soil and those involved in the nitrification process was higher in the unamended soil.

Bacteria in (vermi)composted organic wastes mostly survive when applied to an arable soil cultivated with wheat (Triticum sp. L.).

Composting and vermicomposting are an environmentally friendly way to reduce pathogens in organic wastes and generate a valuable product that provides nutrients for crops. However, how the bacterial community structure changes during these different processes and if the bacteria applied with the (vermi)composted products survive in an arable cultivated soil is still largely unknown. In this study, we monitored how the bacterial community structure changed during conditioning, composting with and without Eisenia fetida, and when the end-product was applied to arable soil cultivated with wheat Triticum sp. L. The organic wastes used were biosolid, cow manure, and a mixture of both. Large changes occurred in the relative abundance of some of the most abundant bacterial genera during conditioning, but the changes were much smaller during composting or vermicomposting. The bacterial community structure was significantly different in the organic wastes during conditioning and (vermi)composting but adding E. fetida had no significant effect on it. Changes in the relative abundance of the bacterial groups in the (vermi)composted waste applied to the arable soil cultivated with wheat were small, suggesting that most survived even after 140 days. As such, applying (vermi)composted organic wastes not only adds nutrients to a crop but also contributes to the survival of plant growth-promoting bacteria found in the (vermi)compost. However, putative human pathogens found in the biosolid also survived in the arable soil, and their relative abundance remained high but mixing the biosolid with cow manure reduced that risk. It was found that applying (vermi)composted organic wastes to an arable soil not only provides plant nutrients and adds bacteria with plant growth-promoting capacities, but some putative pathogens also survived.

The Bacterial Community Structure and Dynamics of Carbon and Nitrogen when Maize (Zea mays L.) and Its Neutral Detergent Fibre Were Added to Soil from Zimbabwe with Contrasting Management Practices.

Water infiltration, soil carbon content, aggregate stability and yields increased in conservation agriculture practices compared to conventionally ploughed control treatments at the Henderson research station near Mazowe (Zimbabwe). How these changes in soil characteristics affect the bacterial community structure and the bacteria involved in the degradation of applied organic material remains unanswered. Soil was sampled from three agricultural systems at Henderson, i.e. (1) conventional mouldboard ploughing with continuous maize (conventional tillage), (2) direct seeding with a Fitarelli jab planter and continuous maize (direct seeding with continuous maize) and (3) direct seeding with a Fitarelli jab planter with rotation of maize sunn hemp (direct seeding with crop rotation). Soil was amended with young maize plants or their neutral detergent fibre (NDF) and incubated aerobically for 56 days, while C and N mineralization and the bacterial community structure were monitored. Bacillus (Bacillales), Micrococcaceae (Actinomycetales) and phylotypes belonging to the Pseudomonadales were first degraders of the applied maize plants. At day 3, Streptomyces (Actinomycetales), Chitinophagaceae ([Saprospirales]) and Dyella (Xanthomonadales) participated in the degradation of the applied maize and at day 7 Oxalobacteraceae (Burkholderiales). Phylotypes belonging to Halomonas (Oceanospirillales) were the first degraders of NDF and were replaced by Phenylobacterium (Caulobacterales) and phylotypes belonging to Pseudomonadales at day 3. Afterwards, similar bacterial groups were favoured by application of NDF as they were by the application of maize plants, but there were also clear differences. Phylotypes belonging to the Micrococcaceae and Bacillus did not participate in the degradation of NDF or its metabolic products, while phylotypes belonging to the Acidobacteriaceae participated in the degradation of NDF but not in that of maize plants. It was found that agricultural practices had a limited effect on the bacterial community structure, but application of organic material altered it substantially.

Bacterial community structure within an activated sludge reactor added with phenolic compounds.

Biodegradation of phenolic compounds in bioreactors is well documented, but the changes in the bacterial populations dynamics during degradation were not that often. A glass bubble column used as reactor was inoculated with activated sludge, spiked with 2-chlorophenol, phenol and m-cresol after 28 days and maintained for an additional 56 days, while the 16S rRNA gene from metagenomic DNA was monitored. Proteobacteria (68.1%) dominated the inoculum, but the bacterial composition changed rapidly. The relative abundance of Bacteroidetes and Firmicutes decreased from 4.8 and 9.4 to <0.1 and 0.2% respectively, while that of Actinobacteria and TM7 increased from 4.8 and 2.0 to 19.2 and 16.1% respectively. Phenol application increased the relative abundance of Proteobacteria to 94.2% (mostly Brevundimonas 17.6%), while that of Bacteroidetes remained low (1.2%) until day 42. It then increased to 47.3% (mostly Leadbetterella 46.9%) at day 84. It was found that addition of phenolic compounds did not affect the relative abundance of the Alphaproteobacteria initially, but it decreased slowly while that of the Bacteroidetes increased towards the end.

Removal of Two High Molecular Weight PAHs from Soils with Different Water Content.

Polycyclic aromatic hydrocarbons (PAHs) such as benz[a]anthracene (BA) and dibenz[a,h]anthracene (DBA), which are considered toxic, are frequently found in contaminated soils in Mexico. A laboratory-scale study monitored the degradation of the mixture of these two PAHs in three soils from different Mexican states (Tabasco, Morelos and Veracruz), each with different organic matter content, particle size distribution and incubated under different water content conditions. The hydrocarbons were extracted using microwave digestion and quantified by GC/MS. The removal of the PAHs, the growth of aerobic bacteria and microbial activity were determined in soil samples with and without a bacterial growth inhibitor (HgCl2). The conclusion is that more than 90% of both contaminants was removed from the three soils, independently of the soil water content or the application of a bacterial growth inhibitor. Biological properties of the soils showed changes at the end of the experiment, but the results of the removal of PAHs were similar in the three soils.

Characterization of extracellular amylase produced by haloalkalophilic strain Kocuria sp. HJ014.

The haloalkaliphilic bacterium Kocuria sp. (HJ014) has the ability to produce extracellular amylase. The aim of this study was to purify and characterize this protein. The amylase enzyme with a specific activity of 753,502 U/mg was purified 5.7- fold using Sepharose 4B and Sephacryl S-300 gel filtration columns. The molecular weight of the enzyme was 45,000 Da as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The amylase showed maximum activity at pH 9 and 50°C in the presence of 3.5 M NaCl. The Km was 3.0 mg/ml and Vmax 90.09 U/ml. It was found that extracellular amylase from Kocuria sp. has a high industrial potential.

Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil.

In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic Candidatus Nitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils. Halobiforma, Halostagnicola, Haloterrigena, and Natronomonas were found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH.

454 pyrosequencing-based characterization of the bacterial consortia in a well established nitrifying reactor.

This present study aimed to characterize the bacterial community in a well-established nitrifying reactor by high-throughput sequencing of 16S rRNA amplicons. The laboratory-scale continuous stirred tank reactor has been supplied with ammonium (NH(4)(+)) as sole energy source for over 5 years, while no organic carbon has been added, assembling thus a unique planktonic community with a mean NH(4)(+) removal rate of 86 ± 1.4 mg NH(4)(+)-N/(L d). Results showed a nitrifying community composed of bacteria belonging to Nitrosomonas (relative abundance 11.0%) as the sole ammonia oxidizers (AOB) and Nitrobacter (9.3%) as the sole nitrite oxidizers (NOB). The Alphaproteobacteria (42.3% including Nitrobacter) were the most abundant class within the Proteobacteria (62.8%) followed by the Gammaproteobacteria (9.4%). However, the Betaproteobacteria (excluding AOB) contributed only 0.08%, confirming that Alpha- and Gammaproteobacteria thrived in low-organic-load environments while heterotrophic Betaproteobacteria are not well adapted to these conditions. Bacteroidetes, known to metabolize extracellular polymeric substances produced by nitrifying bacteria and secondary metabolites of the decayed biomass, was the second most abundant phylum (30.8%). It was found that Nitrosomonas and Nitrobacter sustained a broad population of heterotrophs in the reactor dominated by Alpha- and Gammaproteobacteria and Bacteroidetes, in a 1:4 ratio of total nitrifiers to all heterotrophs.

Bioavailability and dissipation of anthracene from soil with different alkalinity and salinity.

Bioavailability of contaminants, such as anthracene (Anthra), a polycyclic aromatic hydrocarbon (PAHs), and their removal from soil has been related to their extractability with non-exhaustive techniques, such as hydroxypropyl-beta-cyclodextrin (HPCD) or n-butanol. Anthra was extracted with HPCD, n-butanol and by exhaustive ultrasonic extraction method from sterilized and unsterilized alkaline soil of the former lake Texcoco, having pH ranging from pH 8.2 to 10.1 and electrolytic conductivity varying from 1.2 dS m(-1) to 95.2 dS m(-1), respectively. About 24.4 and 37.6% of Anthra was removed biologically from soil as estimated by exhaustive technique after 56 days. The percentage of Anthra that was removed from soil by exhaustive technique was not related to the amount thatwas extractable with HPCD or n-butanol. It was found that the Anthra extractable with n-butanol or HPCD did not correlate well with the removal of the contaminant from soil. In this study, the removal of Anthra from soil could not be predicted by the amount of Anthra that was extracted with n-butanol or HPCD .

Changes in methane oxidation activity and methanotrophic community composition in saline alkaline soils.

The soil of the former Lake Texcoco is a saline alkaline environment where anthropogenic drainage in some areas has reduced salt content and pH. Potential methane (CH4) consumption rates were measured in three soils of the former Lake Texcoco with different electrolytic conductivity (EC) and pH, i.e. Tex-S1 a >18 years drained soil (EC 0.7 dS m(-1), pH 8.5), Tex-S2 drained for ~10 years (EC 9.0 dS m(-1), pH 10.3) and the undrained Tex-S3 (EC 84.8 dS m(-1), pH 10.3). An arable soil from Alcholoya (EC 0.7 dS m(-1), pH 6.7), located nearby Lake Texcoco was used as control. Methane oxidation in the soil Tex-S1 (lowest EC and pH) was similar to that in the arable soil from Alcholoya (32.5 and 34.7 mg CH4 kg(-1) dry soil day(-1), respectively). Meanwhile, in soils Tex-S2 and Tex-S3, the potential CH4 oxidation rates were only 15.0 and 12.8 mg CH4 kg(-1) dry soil day(-1), respectively. Differences in CH4 oxidation were also related to changes in the methane-oxidizing communities in these soils. Sequence analysis of pmoA gene showed that soils differed in the identity and number of methanotrophic phylotypes. The Alcholoya soil and Tex-S1 contained phylotypes grouped within the upland soil cluster gamma and the Jasper Ridge, California JR-2 clade. In soil Tex-S3, a phylotype related to Methylomicrobium alcaliphilum was detected.

Bacterial colonization of a fumigated alkaline saline soil.

After chloroform fumigating an arable soil, the relative abundance of phylotypes belonging to only two phyla (Actinobacteria and Firmicutes) and two orders [Actinomycetales and Bacillales (mostly Bacillus)] increased in a subsequent aerobic incubation, while it decreased for a wide range of bacterial groups. It remained to be seen if similar bacterial groups were affected when an extreme alkaline saline soil was fumigated. Soil with electrolytic conductivity between 139 and 157 dS m(-1), and pH 10.0 and 10.3 was fumigated and the bacterial community structure determined after 0, 1, 5 and 10 days by analysis of the 16S rRNA gene, while an unfumigated soil served as control. The relative abundance of the Firmicutes increased in the fumigated soil (52.8%) compared to the unfumigated soil (34.2%), while that of the Bacteroidetes decreased from 16.2% in the unfumigated soil to 8.8% in the fumigated soil. Fumigation increased the relative abundance of the genus Bacillus from 14.7% in the unfumigated soil to 25.7%. It was found that phylotypes belonging to the Firmicutes, mostly of the genus Bacillus, were dominant in colonizing the fumigated alkaline saline as found in the arable soil, while the relative abundance of a wide range of bacterial groups decreased.

Identification of antibiotic resistance cassettes in class 1 integrons in Aeromonas spp. strains isolated from fresh fish (Cyprinus carpio L.).

Forty-six Aeromonas spp. strains were isolated from fresh fish and investigated for their antimicrobial susceptibility, detection of Class 1 integrons by PCR, and arrangement of gene cassettes. Selected isolates were further characterized by enterobacterial repetitive intergenic consensus-PCR. Twenty isolates were found to carry Class 1 integrons. Amplification of the variable regions of the integrons revealed diverse bands ranging in size from 150 to 1,958 pb. Sequence analysis of the variable regions revealed the presence of several gene cassettes, such as adenylyl transferases (aadA2 and aadA5), dihydrofolate reductases (dfrA17 and dfrA1), chloramphenicol acetyl transferase (catB3), ß-lactamase (oxa2), lincosamide nucleotidil transferase (linF), aminoglycoside-modifying enzyme (apha15), and oxacillinase (bla OXA-10). Two open reading frames with an unknown function were identified as orfC and orfD. The aadA2 cassette was the most common integron found in this study. Interestingly, five integrons were detected in the plasmids that might be involved in the transfer of resistance genes to other bacteria. This is a first report of cassette encoding for lincosamides (linF) resistance in Aeromonas spp. Implications on the incidence of integrons in isolates of Aeromonas spp. from fresh fish for human consumption, and its possible consequences to human health are discussed.

Isolation and phylogenic identification of soil haloalkaliphilic strains in the former Texcoco Lake.

A wide diversity of organisms exists in soil. Well-adapted groups can be found in extreme environments. A great economic and metabolic potential for extremozymes produced by organisms living at extreme environments has been reported. Extreme characteristics such as high salt content and high pH level make the soil of the former Texcoco Lake a unique place which has not been exploited. Therefore, in this study, 66 strains from soil of the former Texcoco Lake were isolated and phylogenetically analyzed using universal oligonucleotide primers. Different genera such as Kocuria, Micrococcus, Nesterenkonia, Halomonas, Salinicoccus, Kurthia, Gracilibacillus, and Bacillus were found. However, only 22 from all isolated strains were identified at specie level.

Characteristics of tomato plants treated with leaf extracts of neem (Azadirachta indica A. Juss. (L.)) and mata-raton (Gliricidia sepium (Jacquin)): a greenhouse experiment.

Extracts of neem (Azadirachta indica A.) and mata-raton (Gliricidia sepium) leaves were used as insect repellent during organic cultivation of tomato plants (Solanum lycopersicum) and were compared with untreated plants or plants treated with lambda-cyhalothrin (chemical treatment). The best developed tomato plants were found in the Gliricidia treatment, while difference between other treatments were small. The number of different species of macrofauna found on tomato plants were similar in different treatments, except for corn rootworm (Diabrotica spp.) found in the Gliricidia treatment, but not in other treatments. It was found that leaf extract of G. sepium stimulated tomato growth and altered the leaf and fruit characteristics. This was most likely due to its action as a growth regulator and/or an inductor of changes in the tomato growth regulation, but not due to its action as an insect repellent. Consequently, leaf extract of G. sepium could be used to stimulate tomato development.

Natronorubrum texcoconense sp. nov., a haloalkaliphilic archaeon isolated from soil of the former lake Texcoco (Mexico).

A new haloalkaliphilic archaeon, strain B4(T), was isolated from the former lake Texcoco in Mexico. The cells were Gram-negative, pleomorphic-shaped, pink to red pigmented and aerobic. Strain B4(T) required at least 2.5 M NaCl for growth, with optimum growth at 3.4 M NaCl. It was able to grow over a pH range of 7.5-10.0 and temperature of 25-50 °C, with optimal growth at pH 9 and 37 °C. Cells are lysed in hypotonic treatment with less than 1.3 M NaCl. The major polar lipids of strain B4(T) were phosphatidylglycerol and methyl-phosphatidylglycerophosphate. Phospholipids were detected, but not glycolipids. The nucleotide sequence of the 16S rRNA gene revealed that the strain B4(T) was phylogenetically related to members of the genus Natronorubrum. Sequence similarity with Natronorubrum tibetense was 96.28 %, with Natronorubrum sulfidifaciens 95.06 % and Natronorubrum sediminis 94.98 %. The G+C content of the DNA was 63.3 mol%. The name of Natronorubrum texcoconense sp. nov. is proposed. The type strain is B4(T) (=CECT 8067(T) = JCM 17497(T)).

Texcoconibacillus texcoconensis gen. nov., sp. nov., alkalophilic and halotolerant bacteria isolated from soil of the former lake Texcoco (Mexico).

A novel Gram-positive, rod-shaped, spore-forming bacterium, designated 13CC(T) was isolated from soil of the former lake Texcoco. The strain was aerobic, catalase-positive and oxidase-negative. It grew at salinities of 0-26% (w/v) NaCl with an optimum at 9-16% (w/v) NaCl. The cells contain peptidoglycan type A1γ, A1γ' with glycine instead of l-alanine and three variations of peptidoglycan type A4γ. The only quinone detected was MK-7. The major fatty acid was anteiso-C(15:0). The polar lipids fraction consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and three different phospholipids. The DNA G+C content was 37.5 mol%. Maximum-likelihood phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 13CC(T) was closely related to members of the genus Bacillus and shared 92.35% similarity with Bacillus agaradhaerens, 92.28% with Bacillus neizhouensis and 92.21% with Bacillus locisalis. It is proposed based on the phenotypic, genotypic and phylogenetic analyses that the novel isolate should be classified as a representative of a new genus and novel species, for which the name Texcoconibacillus texcoconensis gen. nov., sp. nov. is proposed. The type strain of Texcoconibacillus texcoconensis is 13CC(T) ( =JCM 17654(T) =DSM 24696(T)).

Natronobacterium texcoconense sp. nov., a haloalkaliphilic archaeon isolated from soil of a former lake.

A novel haloalkaliphilic archaeon, strain B23(T) was isolated from the former lake Texcoco in Mexico. The strain was Gram-stain-negative, the cells coccoid to ovoid rods, red pigmented and aerobic. Strain B23(T) grew in 1.7-4.3 M NaCl, at pH 6.5-9.5 and at 25-45 °C with optimal growth at 2.6-3.4 M NaCl, pH 7.5-8.5 and 37 °C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain B23(T) was most closely related to Natronobacterium gregoryi SP2(T) with 97.3 % sequence similarity. The polar lipids of strain B23(T) were phosphatidylglycerol and several unidentified phospholipids. The G+C content of the DNA of the strain was 62.5 mol%. Levels of DNA-DNA relatedness between strain B23(T) and Natronobacterium gregoryi DSM 3393(T) was 32.3 %. The name Natronobacterium texcoconense sp. nov. is proposed. The type strain is B23(T) ( = CECT 8068(T) = JCM 17655(T)).

Pyrosequencing analysis of the bacterial community in drinking water wells.

Wells used for drinking water often have a large biomass and a high bacterial diversity. Current technologies are not always able to reduce the bacterial population, and the threat of pathogen proliferation in drinking water sources is omnipresent. The environmental conditions that shape the microbial communities in drinking water sources have to be elucidated, so that pathogen proliferation can be foreseen. In this work, the bacterial community in nine water wells of a groundwater aquifer in Northern Mexico were characterized and correlated to environmental characteristics that might control them. Although a large variation was observed between the water samples, temperature and iron concentration were the characteristics that affected the bacterial community structure and composition in groundwater wells. Small increases in the concentration of iron in water modified the bacterial communities and promoted the growth of the iron-oxidizing bacteria Acidovorax. The abundance of the genera Flavobacterium and Duganella was correlated positively with temperature and the Acidobacteria Gp4 and Gp1, and the genus Acidovorax with iron concentrations in the well water. Large percentages of Flavobacterium and Pseudomonas bacteria were found, and this is of special concern as bacteria belonging to both genera are often biofilm developers, where pathogens survival increases.

Mixing of an anthracene-contaminated soil: a simple but efficient remediation technique?

Contamination of soils with polycyclic aromatic hydrocarbons (PAHs) is a serious problem in petroleum producing countries, such as México, and environment-friendly easy to apply techniques are required to accelerate the removal of the contaminants. Removal of anthracene was monitored in an arable and a pasture soil regularly mixed or amended with organic material, a non-ionic surfactant (Surfynol(®) 485) or earthworms (Eisenia fetida (Savigny, 1826)). In both soils the same results were obtained although the removal of anthracene was faster from the pasture than from the arable soil. The fastest removal of anthracene was obtained when the soil was mixed every 7 days and no contaminant was detected in both soils after 56 days. The second fastest removal of anthracene was obtained when earthworms were added to soil and no contaminant was detected in both soils after 112 days. Application of organic material that served as feed for the earthworms also accelerated the removal of the contaminant compared to the unamended soil, but application of the surfactant inhibited the dissipation of the contaminant. Only 37% of the spiked anthracene was removed from soil when surfactant was applied, while 62% was dissipated in the unamended soil after 112 days. It was found that simply mixing a soil removed anthracene faster than when earthworms were applied, while the application of the surfactant inhibited the removal of anthracene by the autochthonous soil microorganisms.