Impact of Inoculation Protocols, Salinity, and pH on the Degradation of Polycyclic Aromatic Hydrocarbons (PAHs) and Survival of PAH-Degrading Bacteria Introduced into Soil

Degradation of polycyclic aromatic hydrocarbons (PAHs) and survival of bacteria in soil was investigated by applying different inoculation protocols. The soil was inoculated with Sphingomonas paucimobilis BA 2 and strain BP 9, which are able to degrade anthracene and pyrene, respectively. CFU of soil bacteria and of the introduced bacteria were monitored in native and sterilized soil at different pHs. Introduction with mineral medium inhibited PAH degradation by the autochthonous microflora and by the strains tested. After introduction with water (without increase of the pore water salinity), no inhibition of the autochthonous microflora was observed and both strains exhibited PAH degradation.     

Degradation of Aroclor 1221 and survival of strains in soil microcosms

Three bacterial strains able to use different aromatic compounds as the sole carbon and energy source were tested for their potential to degrade Aroclor 1221 in soil microcosms when present in mixed culture. Disappearance of polychlorinated biphenyls (PCBs), occurrence of metabolites, release of chloride, and survival of the laboratory-selected strains were investigated under different conditions. In principle, complete mineralization of various congeners of Aroclor 1221, a technical mixture of PCBs, by the mixed culture was possible. The autochthonous microflora negatively affected the degradation due to formation of a toxic compound from 4-chlorobenzoate. 4-Chlorobenzoate was produced by one of the added strains, Pseudomonas sp. JHK, during degradation of 4-chlorobiphenyl. The unknown metabolite of 4-chlorobenzoate led to a rapid decrease in viable counts of the laboratory-selected strains in the soil microcosm.Correspondence to: J. Havel     

Role of autochthonous filamentous fungi in bioremediation of a soil historically contaminated with aromatic hydrocarbons

Nine fungal strains isolated from an aged and heavily contaminated soil were identified and screened to assess their degradative potential. Among them, Allescheriella sp. strain DABAC 1, Stachybotrys sp. strain DABAC 3, and Phlebia sp. strain DABAC 9 were selected for remediation trials on the basis of Poly R-478 decolorization associated with lignin-modifying enzyme (LME) production. These autochthonous fungi were tested for the abilities to grow under nonsterile conditions and to degrade various aromatic hydrocarbons in the same contaminated soil. After 30 days, fungal colonization was clearly visible and was confirmed by ergosterol determination. In spite of subalkaline pH conditions and the presence of heavy metals, the autochthonous fungi produced laccase and Mn and lignin peroxidases. No LME activities were detected in control microcosms. All of the isolates led to a marked removal of naphthalene, dichloroaniline isomers, o-hydroxybiphenyl, and 1,1'-binaphthalene. Stachybotrys sp. strain DABAC 3 was the most effective isolate due to its ability to partially deplete the predominant contaminants 9,10-anthracenedione and 7H-benz[DE]anthracen-7-one. A release of chloride ions was observed in soil treated with either Allescheriella sp. strain DABAC 1 or Stachybotrys sp. strain DABAC 3, suggesting the occurrence of oxidative dehalogenation. The autochthonous fungi led to a significant decrease in soil toxicity, as assessed by both the Lepidium sativum L. germination test and the Collembola mortality test.     

Biosurfactant Facilitated Biodegradation of Quinalphos at High Concentrations by Pseudomonas aeruginosa Q10

Previous studies indicate that high concentration of pesticides and their associated toxic effects are high at their point source of application. Use of pesticide-degrading bacteria at point sources could augment degradation and thereby reduce toxic effects associated with pesticide persistence in soil. Quinalphos, an organophosphorus insecticide, though ranked “moderately hazardous” in the WHO's acute hazard ranking, still continues to be used extensively in developing countries. The presence of a chloride radical usually makes this pesticide sparingly soluble in water and hence difficult to degrade. The present study aimed to isolate autochthonous bacterial strains capable of utilizing quinalphos as a carbon source. Primary screening of pesticide-contaminated soil by enrichment culture and degradation analysis by UV-VIS spectrophotometry led to the isolation of 12 different bacterial isolates, of which three efficient isolates of Pseudomonas sp, Serratia sp, and Pseudomonas aeruginosa with degradation rate 86%, 82%, 94%, respectively, were selected. GC-MS studies with P.aeruginosa confirmed the formation of 2-hydroxy quinoxaline and phosphorothioic acid as a result of biodegradation. The present study succeeded in isolating autochthonous bacterial strains capable of utilizing high concentrations of quinalphos as a carbon source in a shorter incubation period. This strain also possessed biosurfactant-production ability, which makes quinalphos available to cells at higher concentrations.     

Drought Tolerance and Antioxidant Activities in Lavender Plants Colonized by Native Drought-tolerant or Drought-sensitive <Emphasis Type="Italic">Glomus</Emphasis> Species

This study compared the effectiveness of four arbuscular mycorrhizal (AM) fungal isolates (two autochthonous presumably drought-tolerant Glomus sp and two allochthonous presumably drought-sensitive strains) on a drought-adapted plant (Lavandula spica) growing under drought conditions. The autochthonous AM fungal strains produced a higher lavender biomass, specially root biomass, and a more efficient N and K absorption than with the inoculation of similar allochthonous strains under drought conditions. The autochthonous strains of Glomus intraradices and Glomus mosseae increased root growth by 35% and 100%, respectively, when compared to similar allochthonous strains. These effects were concomitant with an increase in water content and a decline in antioxidant compounds: 25% glutathione, 7% ascorbate and 15% H₂O₂ by G. intraradices, and 108% glutathione, 26% ascorbate and 43% H₂O₂ by G. mosseae. Glutathione and ascorbate have an important role in plant protection and metabolic function under water deficit; the low cell accumulation of these compounds in plants colonized by autochthonous AM fungal strains is an indication of high drought tolerance. Non-significant differences between antioxidant activities such as glutathione reductase (GR), catalase (CAT) and superoxide dismutase (SOD) in colonized plants were found. Thus, these results do not allow the generalization that GR, CAT and SOD were correlated with the symbiotic efficiency of these AM fungi on lavender drought tolerance. Plants colonized by allochthonous G. mosseae (the less efficient strain under drought conditions) had less N and K content than those colonized by similar autochthonous strain. These ions play a key role in osmoregulation. The AM symbiosis by autochthonous adapted strains also produced the highest intraradical and arbuscular development and extraradical mycelial having the greatest fungal SDH and ALP-ase activities in the root systems. Inoculation of autochthonous drought tolerant fungal strains is an important strategy that assured the greatest tolerance water stress contributing to the best lavender growth under drought.     

Effectiveness of autochthonous bacterium and mycorrhizal fungus on Trifolium growth, symbiotic development and soil enzymatic activities in Zn contaminated soil

AIMS: This study investigates how autochthonous micro-organisms [bacterium and/or arbuscular mycorrhizal (AM) fungi] affected plant tolerance to Zn contamination. METHODS AND RESULTS: Zinc-adapted and -nonadapted Glomus mosseae strains protected the host plant against the detrimental effect of Zn (600 microg g(-1)). Zn-adapted bacteria increased root growth and N, P nutrition in plants colonized by adapted G. mosseae and decreased the specific absorption rate (SAR) of Cd, Cu, Mo or Fe in plants colonized by Zn-nonadapted G. mosseae. Symbiotic structures (nodule number and extraradical mycelium) were best developed in plants colonized by those Zn-adapted isolates that were the most effective in increasing plant Zn tolerance. The bacterium also increased the quantity and quality (metabolic characteristics) of mycorrhizal colonization, with the highest improvement for arbuscular vitality and activity. Inocula also enhanced soil enzymatic activities (dehydrogenase, beta-glucosidase and phosphatase) and indol acetic acid (IAA) accumulation, particularly in the rhizosphere of plants inoculated with Zn-adapted isolates. CONCLUSIONS: Glomus mosseae strains have a different inherent potential for improving plant growth and nutrition in Zn-contaminated soil. The bacterium increased the potential of mycorrhizal mycelium as inoculum. SIGNIFICANCE AND IMPACT OF THE STUDY: Mycorrhizal performance, particularly that of the autochthonous strain, was increased by the bacterium and both contributed to better plant growth and establishment in Zn-contaminated soils.     

Growth of Trifolium alpinum: Effects of soil properties, symbionts and pathogens

The lowland cultivation of Trifolium alpinum, a clover species found on acid soils in the Alps and suitable for the restoration of erosion areas at high altitudes, failed repeatedly in previous experiments. Three experiments were carried out in a controlled environment to elucidate the reasons for the failure and to develop possible cultivation strategies. In experiment I, T. alpinum was grown in an autochthonous soil from the Alps (high elevation) and in two allochthonous soils, a grassland soil from the Hercynian mountains (medium elevation), and an arable soil (low elevation), in which the seed propagation of T. alpinum had failed previously. The two allochthonous soils had lower contents of soil organic C and ergosterol, an indicator for fungal biomass, than the autochthonous high-elevation soil, but higher levels of exchangeable Ca and extractable P. Plants grown in the allochthonous soils achieved higher biomass and total N amounts per plant than those from the high elevation soil if inoculated with this autochthonous material to establish rhizobial infection. In the allochthonous high elevation soil, the growth of T. alpinum was P-limited as shown in experiment II. In experiment I, plants grown in the low elevation soil had a lower biomass and smaller number of active leaves at 120 days after emergence than those grown on the medium elevation soil. This difference can be explained by strong colonization with the phytophagous nematode Pratylenchus sp., as demonstrated in experiment III by comparing plant growth either in untreated or in autoclaved low-elevation soil. Successful propagation of T. alpinum at low elevation may be achieved through suitable inoculation with autochthonous soil biota, especially Rhizobia, and avoidance of soils infested by Pratylenchus species by choosing sites with acidic soil and ensuring adequate P-availability.     

Genotypic and phenotypic characterization of industrial autochthonous Saccharomyces cerevisiae for the selection of well-adapted bioethanol-producing strains

In northwestern Argentina, sugarcane-derived industrial fermentation is being extensively used for bioethanol production, where highly adaptive native strains compete with the baker's yeast Saccharomyces cerevisiae traditionally used as starter culture. Yeast populations of 10 distilleries from Tucumán (Argentina) were genotypic and phenotypic characterized to select well-adapted bioethanol-producing autochthonous strains to be used as starter cultures for the industrial production of bioethanol fuel. From the 192 isolates, 69.8% were identified as S. cerevisiae, 25.5% as non-Saccharomyces, and 4.7% as Saccharomyces sp. wild yeasts. The majority of S. cerevisiae isolates (68.5%) were non-flocculating yeasts, while the flocculating strains were all obtained from the only continuous fermentation process included in the study. Simple Sequence Repeat analysis revealed a high genetic diversity among S. cerevisiae genotypes, where all of them were very different from the original baker's strain used as starter. Among these, 38 strains multi-tolerant to stress by ethanol (8%), temperature (42.5 °C) and pH (2.0) were obtained. No major differences were found among these strains in terms of ethanol production and residual sugars in batch fermentation experiments with cell recycling. However, only 10 autochthonous strains maintained their viability (more than 80%) throughout five consecutive cycles of sugarcane-based fermentations. In summary, 10 autochthonous isolates were found to be superior to baker's yeast used as starter culture (S. cerevisiae Calsa) in terms of optimal technological, physiological and ecological properties. The knowledge generated on the indigenous yeast populations in industrial fermentation processes of bioethanol-producing distilleries allowed the selection of well-adapted bioethanol-producing strains.     

Presence and growth of naturalized Escherichia coli in temperate soils from Lake Superior watersheds

The presence of Escherichia coli in water is used as an indicator of fecal contamination, but recent reports indicate that soil populations can also be detected in tropical, subtropical, and some temperate environments. In this study, we report that viable E. coli populations were repeatedly isolated from northern temperate soils in three Lake Superior watersheds from October 2003 to October 2004. Seasonal variation in the population density of soilborne E. coli was observed; the greatest cell densities, up to 3 x 10(3) CFU/g soil, were found in the summer to fall (June to October), and the lowest numbers, < or =1 CFU/g soil, occurred during the winter to spring months (February to May). Horizontal, fluorophore-enhanced repetitive extragenic palindromic PCR (HFERP) DNA fingerprint analyses indicated that identical soilborne E. coli genotypes, those with > or =92% similarity values, overwintered in frozen soil and were present over time. Soilborne E. coli strains had HFERP DNA fingerprints that were unique to specific soils and locations, suggesting that these E. coli strains became naturalized, autochthonous members of the soil microbial community. In laboratory studies, naturalized E. coli strains had the ability to grow and replicate to high cell densities, up to 4.2 x 10(5) CFU/g soil, in nonsterile soils when incubated at 30 or 37 degrees C and survived longer than 1 month when soil temperatures were < or =25 degrees C. To our knowledge, this is the first report of the growth of naturalized E. coli in nonsterile, nonamended soils. The presence of significant populations of naturalized populations of E. coli in temperate soils may confound the use of this bacterium as an indicator of fecal contamination.     

Isolation and characterization of indigenous soil bacteria for bioaugmentation of PAH contaminated soil of semiarid Patagonia, Argentina

The aim of this work was to isolate PAH degrading-bacteria from contaminated Patagonia soil with the ability to tolerate the usual environmental stresses (oligotrophic and dryness conditions). Two approaches were utilized to obtain PAH-degrading bacteria from the Patagonian soil. With a traditional enrichment approach only the PAH- degrading strain 36 was isolated. Using a direct isolation approach three PAH-degrading strains (1A, 22A and 22B) were isolated. The phylogenetic analysis revealed that all isolates belonged to Sphingomonas genus. The PAH degrading activity and the resistance to stress conditions of the strains were determined and compared with those of the exogenous PAH-degrading Sphingomonas paucimobilis 20006FA. The strains 1A, 22A and 36 were phylogenetically closely related between them and with the strain 20006FA. The strain 22B, that showed a different phylogenetic position, was more resistant to C-starvation and drying conditions than other Patagonian strains. The effect of the inoculation of these strains on phenanthrene-induced mineralization and elimination was studied in Patagonian soil artificially contaminated, at different environmental conditions. The results suggest that strain 22B is the most suitable strain for bioaugmentation in PAH-contaminated soils of Central Patagonia, due to its adaptation to the usual environmental conditions. Our results show the importance of a detailed physiological characterization of isolates for autochthonous bioaugmentation strategies success.     

Biostimulation of micro-organisms from sugarcane bagasse pith for the removal of weathered hydrocarbon from soil

AIMS: In this study we studied the biostimulation of micro-organisms associated with sugarcane bagasse pith for the removal of total petroleum hydrocarbon from a soil contaminated with weathered hydrocarbon. METHODS AND RESULTS: Carbon, nitrogen and phosphorus were added at a ratio of 100 : 10 : 1, water content of 40%, and soil : bagasse ratio of 49 : 1. A significant positive difference (P < 0.05) was observed in total petroleum hydrocarbon removal (38 and 48%) by micro-organisms associated with bagasse and native soil micro-organisms, respectively. In addition, total petroleum hydrocarbon removal increased to 60% in a system where both autochthonous soil and bagasse micro-organisms were present. CONCLUSIONS: Micro-organisms from sugarcane bagasse pith can be stimulated for removal of weathered hydrocarbon from contaminated tropical soils, without they being inhibited by indigenous soil micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: Soil of with hydrocarbons can be diminished by stimulation of autochthonous microflora present in soil and agricultural residues. This work contributes to the microbiology of composting, as low amounts of bulking agents for hydrocarbon removal from soil, can be used.     

Grazing on allochthonous vs autochthonous bacteria in river water

The disappearance of bacteria through grazing was studied. Five allochthonous and eight autochthonous bacterial strains, and the bacterioplankton of the Butrón River were tested. There were differences in the susceptibility of different strains. These differences seemed to be related to intrinsic characteristics of the bacteria rather than to their origin.     

Role of Autochthonous Filamentous Fungi in Bioremediation of a Soil Historically Contaminated with Aromatic Hydrocarbons

Nine fungal strains isolated from an aged and heavily contaminated soil were identified and screened to assess their degradative potential. Among them, Allescheriella sp. strain DABAC 1, Stachybotrys sp. strain DABAC 3, and Phlebia sp. strain DABAC 9 were selected for remediation trials on the basis of Poly R-478 decolorization associated with lignin-modifying enzyme (LME) production. These autochthonous fungi were tested for the abilities to grow under nonsterile conditions and to degrade various aromatic hydrocarbons in the same contaminated soil. After 30 days, fungal colonization was clearly visible and was confirmed by ergosterol determination. In spite of subalkaline pH conditions and the presence of heavy metals, the autochthonous fungi produced laccase and Mn and lignin peroxidases. No LME activities were detected in control microcosms. All of the isolates led to a marked removal of naphthalene, dichloroaniline isomers, o-hydroxybiphenyl, and 1,1′-binaphthalene. Stachybotrys sp. strain DABAC 3 was the most effective isolate due to its ability to partially deplete the predominant contaminants 9,10-anthracenedione and 7H-benz[DE]anthracen-7-one. A release of chloride ions was observed in soil treated with either Allescheriella sp. strain DABAC 1 or Stachybotrys sp. strain DABAC 3, suggesting the occurrence of oxidative dehalogenation. The autochthonous fungi led to a significant decrease in soil toxicity, as assessed by both the Lepidium sativum L. germination test and the Collembola mortality test.     

Genomic characterization and selection of wine yeast to conduct industrial fermentations of a white wine produced in a SW Spain winery

Aims: To analyse the diversity of wild yeast in spontaneous fermentations of a white wine and to select the most suitable autochthonous starter yeasts. The selected yeasts would be used for inoculation of industrial fermentations in several years. Methods and Results: Yeasts were characterized by applying electrophoretic karyotyping. This technique was chosen because it can reveal the large‐scale mutations in the yeast genome induced by gross chromosomal rearrangements. This type of mutation is considered one of the main forces behind the rapid evolution of industrial yeasts. A heterogeneous population of yeast strains was observed in the spontaneous fermentations during two consecutive years. Four of the most abundant strains were isolated and tested for microbiological features of industrial importance. The selected autochthonous strains were used as starter yeasts for the following 7 years. In the majority of these experiences, we obtained homogeneous yeast populations, in which the karyotype of one of the inoculated strains – karyotype V – emerged as clearly dominant. Conclusions: The inoculation of the selected strain with karyotype V and a proper handling of the inoculum scaling‐up process led to the substitution of the spontaneous fermentations by controlled fermentations producing a highly satisfactory final product. Significance and Impact of the Study: We monitored the wine yeast population of an industrial system for a total of 9 years. Our work is one of the first examples made at industrial scale showing how molecular techniques can be successfully applied to improve the efficiency of the winemaking process.     

Selection and implantation of yeast strains of genus Saccharomyces at a winery regulated by Appellation Contrôlée "Chacolí de Vizcaya/Bizkaiko Txakolina"

The white wine Chacolía de Vizcaya/Bizkaiko Txakolina is characteristic from The Basque Country region and regulated under Appellation Contr?lée standards (BOPV 14/6/94). The objective of this study was the identification and selection of autochthonous yeast strains, to improve the conditions used to maintain the typical characteristics of this region wines. Yeasts identified as Saccharomyces bayanus isolated around these fields from 1996 to 1998, were subjected to a selective procedure based on enological characteristics and fermentative behaviour. Three of the selected strains were used to inoculate, at winery scale, two grape juice varieties accepted by the Appellation Contr?lée (Hondarrabi Zuri and Folle Blanche). The inoculated strains on the respective vinifications was followed by restriction fragment length polymorphism of mitochondrial DNA (REAmt) method with AluI enzyme, due to their specificity, short outcome, and technological simplicity compared with other molecular typing methods such as: chromosomal karyotyping analyzed by pulsed field gel electrophoresis, Random Amplified Polymorphic DNA-PCR (RAPD-PCR) and restriction fragment length polymorphism using the infrequently cutting enzyme SfiI (REA infrequent). This study demonstrated that strains with different phenotypic traits could show indistinguishable restriction patterns with REAmt, but could be discriminated using other typing methods such as RAPD-PCR, which although showing low reproducibility could be used as complementary to REAmt. Our results demonstrate that in spite of using autochthonous selected strains, the inoculation of musts with a particular strain do not guarantee its predominance and driving fermentation features. Of all yeast strains studied, strain no. 2 showed the best results in sensory testing and at the implantation process. Therefore, it could be used with commercial purposes for the production of Chacolí de Vizcaya/Bizkaiko Txakolina, especially when using musts from Folle Blanche.     

Yeast assessment during alcoholic fermentation inoculated with a natural “pied de cuve” or a commercial yeast strain

The present study has been carried out in an organic winery established in 2003 in the Denomination of Origin “Sierras de Málaga” (Southern Spain) region during the 2007 vintage. The aim of this work was to ascertain the yeast microflora present in the winery and during the vinifications and to obtain a collection of autochthonous S. cerevisiae strains from this area. Yeast populations from three vats containing fermenting musts from different grape varieties were analysed. Two of them were inoculated with a natural “pied de cuve” while the third one was sown with a rehydrated commercial yeast strain. A total of 382 yeasts were isolated and identified, initially by restriction analysis of ribosomal DNA and further by sequencing of this region. Non-Saccharomyces yeasts were found in all three musts but they practically disappeared as the fermentations progressed. Analysis of mitochondrial DNA RFLP revealed 13 different restriction patterns of Saccharomyces cerevisiae strains, five of them similar to those of commercial strains used in the winery. Commercial strains were found even in vats inoculated with a “pied de cuve” generated by spontaneous fermentation of a must sample. The analysis of samples recovered from different winery surfaces and equipments demonstrated that non-Saccharomyces and both commercial and autochthonous Saccharomyces strains were part of the resident microflora in the winery. Biodiversity of autochthonous S. cerevisiae in fermentation vats was low but two of them were able to compete with the commercial ones and they were isolated even at the end of the fermentation.     

Survival of commercial yeasts in the winery environment and their prevalence during spontaneous fermentations

Inoculation of active dry yeasts during the wine-making process has become a common practice in most wine-producing regions; this practice may affect the diversity of the indigenous population of Saccharomyces cerevisiae in the winery. The aim of this work was to study the incidence of commercial yeasts in the experimental winery of Estación de Viticultura e Enoloxía de Galicia (EVEGA) and their ability to lead spontaneous fermentations. To do this, 64 spontaneous fermentations were carried out in the experimental cellar of EVEGA over a period of 7 years. Samples were taken from must and at the beginning, vigorous and final stages of fermentation. A representative number of yeast colonies was isolated from each sample. S. cerevisiae strains were characterised by analysis of mitochondrial DNA restriction patterns. The results showed that although more than 40 different strains of S. cerevisiae were identified, only 10 were found as the dominant strain or in codominance with other strains in spontaneous fermentations. The genetic profiles (mtDNA-RFLPs) of eight of these strains were similar to those of different commercial yeasts that had been previously used in the EVEGA cellar. The remaining two strains were autochthonous ones that were able to reach implantation frequencies as high of those of commercial yeasts. These results clearly indicated that commercial wine yeasts were perfectly adapted to survive in EVEGA cellar conditions, and they successfully competed with the indigenous strains of S. cerevisiae, even during spontaneous fermentations. On the other hand, autochthonous dominant strains that presented desirable oenological traits could be of interest to preserve wine typicity.     

Aerobic biodegradation of propylene glycol by soil bacteria

Propylene glycol (PG) is a main component of aircraft deicing fluids and its extensive use in Northern airports is a source of soil and groundwater contamination. Bacterial consortia able to grow on PG as sole carbon and energy source were selected from soil samples taken along the runways of Oslo Airport Gardermoen site (Norway). DGGE analysis of enrichment cultures showed that PG-degrading populations were mainly composed by Pseudomonas species, although Bacteroidetes were found, as well. Nineteen bacterial strains, able to grow on PG as sole carbon and energy source, were isolated and identified as different Pseudomonas species. Maximum specific growth rate of mixed cultures in the absence of nutrient limitation was 0.014 h^?1 at 4 °C. Substrate C:N:P molar ratios calculated on the basis of measured growth yields are in good agreement with the suggested values for biostimulation reported in literature. Therefore, the addition of nutrients is suggested as a suitable technique to sustain PG aerobic degradation at the maximum rate by autochthonous microorganisms of unsaturated soil profile.     

Cultivation-Based Assessment of Lysogeny Among Soil Bacteria

Lysogeny has long been proposed as an important long-term maintenance strategy for autochthonous soil bacteriophages (phages). Whole genome sequence data indicate that prophage-derived sequences pervade prokaryotic genomes, but the connection between inferred prophage sequence and an active temperate phage is tenuous. Thus, definitive evidence of phage production from lysogenic prokaryotes will be critical in determining the presence and extent of temperate phage diversity existing as prophage within bacterial genomes and within environmental contexts such as soils. This study optimized methods for systematic and definitive determination of lysogeny within a collection of autochthonous soil bacteria. Twenty bacterial isolates from a range of Delaware soil environments (five from each soil) were treated with the inducing agents mitomycin C (MC) or UV light. Six isolates (30%) carried inducible temperate phages as evidenced by an increase in virus direct counts. The magnitude of induction response was highly dependent upon specific induction conditions, and corresponding burst sizes ranged from 1 to 176. Treatment with MC for 30 min yielded the largest induction responses for three of the six lysogens. Morphological analysis revealed that four of the lysogens produced lambda-like Siphoviridae particles, whereas two produced Myoviridae particles. Additionally, pulsed-field gel electrophoresis data indicated that two of the six lysogens were polylysogens, producing more than one distinct type of phage particle. These results suggest that lysogeny is relatively common among soil bacteria.     

Survival and colonisation potential of photoautotrophic microorganisms within a glacierised catchment on Svalbard, High Arctic

The survival and colonisation potential of photoautotrophic microbes (cyanobacteria and microalgae) were investigated in three terrestrial environments within a glacierised catchment on Svalbard: old vegetation-covered soil, recently deglaciated barren soil and subglacial sediments. One-year reciprocal transplant incubations of photoautotrophic microbial communities from the three soil/sediment environments were conducted in order to reveal the autochthonous or allochthonous origin of the present photoautotrophs. The abundance and taxonomic composition of photoautotrophic microbes and their changes over time and between soil/sediment types and physico-chemical characteristics of the soils/sediments were determined. The recovery time of a photoautotrophic community by import of cells was between several months in subglacial and vegetated soils and up to 27 years in proglacial soils. No active growth was recorded in subglacial sediments, whilst positive growth, and so the potential for autochthonous recovery, was found in proglacial and vegetated soils. The most suitable environment for the survival of transplanted microbes was provided in proglacial soil. We show here that the new proglacial substrata can be successfully colonised by photoautotrophic microbes, and that input of allochthonous cells may, in some cases, exceed in situ microbial growth. Whilst the subglacial environment is rather a conduit for photoautotrophic microbes than a place of growth and production, the supply of viable photoautotrophs in it is relatively high and may serve as a significant resource of nutrients for subglacial microbial communities.