Effects of oil spills on microbial heterotrophs in Antarctic soils

Oil spillage on the moist coastal soils of the Ross Sea region of Antarctica can impact on populations of microbial heterotrophs in these soils, as determined by viable plate counts and a most probable number technique. Elevated numbers of culturable hydrocarbon degraders, bacteria and fungi were detected in surface and subsurface soils from oil-contaminated sites, compared with nearby control sites. Culturable yeasts were not detected in soil from coastal control sites, yet reached >10⁵ organisms g^-1 dry weight in contaminated soils. The presence of hydrocarbons in soils resulted in a shift in the genera of culturable filamentous fungi. Chrysosporium dominated control soils, yet Phialophora was more abundant in oil-contaminated soils. Hydrocarbon degraders are most likely bacteria; however, fungi could play a role in degradation of hydrocarbons or their metabolites. Depleted levels of nitrate detected in some contaminated soils and decreased pH may be the result of growth of hydrocarbon degraders. Numbers and diversity of culturable microbes from Antarctic soil varied depending on whether a pristine site or a human-impacted (in this case, by fuel spills) site is studied.     

Plastics select for distinct early colonizing microbial populations with reproducible traits across environmental gradients

Little is known about early plastic biofilm assemblage dynamics and successional changes over time. By incubating virgin microplastics along oceanic transects and comparing adhered microbial communities with those of naturally occurring plastic litter at the same locations, we constructed gene catalogues to contrast the metabolic differences between early and mature biofilm communities. Early colonization incubations were reproducibly dominated by Alteromonadaceae and harboured significantly higher proportions of genes associated with adhesion, biofilm formation, chemotaxis, hydrocarbon degradation and motility. Comparative genomic analyses among the Alteromonadaceae metagenome assembled genomes (MAGs) highlighted the importance of the mannose-sensitive hemagglutinin (MSHA) operon, recognized as a key factor for intestinal colonization, for early colonization of hydrophobic plastic surfaces. Synteny alignments of MSHA also demonstrated positive selection for mshA alleles across all MAGs, suggesting that mshA provides a competitive advantage for surface colonization and nutrient acquisition. Large-scale genomic characteristics of early colonizers varied little, despite environmental variability. Mature plastic biofilms were composed of predominantly Rhodobacteraceae and displayed significantly higher proportions of carbohydrate hydrolysis enzymes and genes for photosynthesis and secondary metabolism. Our metagenomic analyses provide insight into early biofilm formation on plastics in the ocean and how early colonizers self-assemble, compared to mature, phylogenetically and metabolically diverse biofilms.     

Amazon aquatic biodiversity imperiled by oil spills

Oil exploitation poses a significant threat to freshwater biodiversity, and future plans to develop petroleum leases in the Amazon Basin should be seem with caution. A series of oil spills have significantly affected biodiversity and human activities in some Amazonian basins, indicating that disturbances by petroleum activities will increase in the region, particularly in upper basins and river headwaters. Measures are needed to reduce the risk of spills and to minimize their impacts. More fundamentally, changes in decision making are needed that give proper weight to these impacts.     

Methodology for environmental assessments of oil and hazardous substance spills

Scientific assessment of the complex environmental consequences of large spills of oil or other hazardous substances has stimulated development of improved strategies for rapid and valid collection and processing of ecological data. The combination of coastal processes and geological measurements developed by Hayes & Gundlach (1978), together with selected field biological and chemical observations/measurements, provide an ecosystem impact assessment approach which is termed “integrated zonal method of ecological impact assessment.” Ecological assessment of oil and hazardous material spills has been divided into three distinct phases: (1) first-order response studies — conducted at the time of the initial spill event, which gather data to document acute impacts and assist decision-makers in prioritization of cleanup efforts and protection of ecologically sensitive habitats, (2) second-order response studies — conducted two months to one year post-spill, which document any delayed mortality and attempt to identify potential sublethal impacts in sensitive species, and (3) third-order response studies — conducted one to three years post-spill, to document chronic impacts (both lethal and sublethal) to specific indicator species. Data collected during first-order response studies are gathered in a quantitative manner so that the initial assessment may become a baseline for later, more detailed, post-spill scientific efforts. First- and second-order response studies of the “Peck Slip” oil spill in Puerto Rico illustrate the usefulness of this method. The need for contingency planning before a spill has been discussed along with the use of the Vulnerability Index, a method in which coastal environments are classified on a scale of 1–10, based upon their potential susceptibility to oiling. A study of the lower Cook Inlet section of the Alaskan coast illustrates the practical application of this method. Contribution 402, Gulf Breeze Environmental Research Laboratory     

Biofuel cells select for microbial consortia that self-mediate electron transfer

Microbial fuel cells hold great promise as a sustainable biotechnological solution to future energy needs. Current efforts to improve the efficiency of such fuel cells are limited by the lack of knowledge about the microbial ecology of these systems. The purposes of this study were (i) to elucidate whether a bacterial community, either suspended or attached to an electrode, can evolve in a microbial fuel cell to bring about higher power output, and (ii) to identify species responsible for the electricity generation. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output from an initial level of 0.6 W m(-2) of electrode surface to a maximal level of 4.31 W m(-2) (664 mV, 30.9 mA) when plain graphite electrodes were used. This result was obtained with an average loading rate of 1 g of glucose liter(-1) day(-1) and corresponded to 81% efficiency for electron transfer from glucose to electricity. Cyclic voltammetry indicated that the enhanced microbial consortium had either membrane-bound or excreted redox components that were not initially detected in the community. Dominant species of the enhanced culture were identified by denaturing gradient gel electrophoresis and culturing. The community consisted mainly of facultative anaerobic bacteria, such as Alcaligenes faecalis and Enterococcus gallinarum, which are capable of hydrogen production. Pseudomonas aeruginosa and other Pseudomonas species were also isolated. For several isolates, electrochemical activity was mainly due to excreted redox mediators, and one of these mediators, pyocyanin produced by P. aeruginosa, could be characterized. Overall, the enrichment procedure, irrespective of whether only attached or suspended bacteria were examined, selected for organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components.     

Enhanced bioremediation of oil spills in the sea

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Freeze-dried hydrocarbon-utilizing yeasts for possible use in artificial seeding of oil spills

The possible use of freeze-dried cultures of 4 hydrocarbon-utilizing yeasts in artificial seeding of oil spills was evaluated. Life expectancy and rehydration were studied.     

Autochthonous bioaugmentation and its possible application to oil spills

Bioaugmentation for oil spills is a much more promising technique than is biostimulation. However, the effectiveness of bioaugmentation is variable, because the survival and the xenobiotic-degrading ability of introduced microorganisms are highly dependent on environmental conditions. As an alternative, autochthonous bioaugmentation (ABA) is proposed to overcome these difficulties. The ABA method is like a ready-made bioaugmentation technology. In ABA, microorganisms indigenous to the contaminated site or predicted contamination site that are well-characterized and potentially capable of degrading oils are used, and these microorganisms should be enriched under conditions where bioaugmentation will be conducted. It is possible to obtain information in advance on the chemical and physical characteristics of potential oil spill sites and of oils that might be spilled. The application of ABA in the coastal areas of Hokkaido Prefecture, Japan, is considered here, because Hokkaido is located south of Sakhalin Island, Russia, where development of oil fields is in progress. If oil spills in this region were well characterized in advance, ABA could be a feasible technology in the near future.     

Competition for mixed substrates by microbial populations

A model for the growth of an organism on multiple substrates was developed, assuming that each substrate has a competitive inhibition effect on the uptake of other substrates. The model was extended to examine mixed substrates, showing that the coexistence of several species at steady state in continuous cultures is possible, even when all the organisms all strongly prefer the one substrate. The diversity of nutrient sources in a real system may be a key factor in supporting a heterogeneous microbial population.     

Memory shapes microbial populations

Correct decision making is fundamental for all living organisms to thrive under environmental changes. The patterns of environmental variation and the quality of available information define the most favourable strategy among multiple options, from randomly adopting a phenotypic state to sensing and reacting to environmental cues. Cellular memory—the ability to track and condition the time to switch to a different phenotypic state—can help withstand environmental fluctuations. How does memory manifest itself in unicellular organisms? We describe the population-wide consequences of phenotypic memory in microbes through a combination of deterministic modelling and stochastic simulations. Moving beyond binary switching models, our work highlights the need to consider a broader range of switching behaviours when describing microbial adaptive strategies. We show that memory in individual cells generates patterns at the population level coherent with overshoots and non-exponential lag times distributions experimentally observed in phenotypically heterogeneous populations. We emphasise the implications of our work in understanding antibiotic tolerance and, in general, bacterial survival under fluctuating environments.     

Dynamics of the hydrocarbon-degrading Cycloclasticus bacteria during mesocosm-simulated oil spills

We used catalysed reported deposition - fluorescence in situ hybridization (CARD-FISH) to analyse changes in the abundance of the bacterial groups Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes, and of hydrocarbon-degrading Cycloclasticus bacteria in mesocosms that had received polycyclic aromatic hydrocarbons (PAHs) additions. The effects of PAHs were assessed under four contrasting hydrographic conditions in the coastal upwelling system of the Rías Baixas: winter mixing, spring bloom, summer stratification and autumn upwelling. We used realistic additions of water soluble PAHs (approximately 20-30 microg l(-1) equivalent of chrysene), but during the winter period we also investigated the effect of higher PAHs concentrations (10-80 microg l(-1) chrysene) on the bacterial community using microcosms. The most significant change observed was a significant reduction (68 +/- 5%) in the relative abundance of Alphaproteobacteria. The magnitude of the response of Cycloclasticus bacteria (positive with probe CYPU829) to PAHs additions varied depending on the initial environmental conditions, and on the initial concentration of added PAHs. Our results clearly show that bacteria of the Cycloclasticus group play a major role in low molecular weight PAHs biodegradation in this planktonic ecosystem. Their response was stronger in colder waters, when their background abundance was also higher. During the warm periods, the response of Cycloclasticus was limited, possibly due to both, a lower bioavailability of PAHs caused by abiotic factors (solar radiation, temperature), and by inorganic nutrient limitation of bacterial growth.     

Microcomputer package for statistical analysis of microbial populations

We have developed a Pascal system to compare microbial populationsfrom different ecological sites using microcomputers. The valuescalculated are: the coverage value and its standard error, theminimum similarity and the geometric similarity between twobiological samples, and the Lambda test consisting of calculatingthe ratio of the mean similarity between two subsets by themean similarity within subsets. This system is written for AppleII, IBM or compatible computers, but it can work for any computerwhich can use CP/M, if the programs are recompiled for sucha system. Received on December 30, 1987; accepted on June 29, 1987     

Soil microbial populations after wildfire

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

Microbial degradation of oil spills enhanced by a slow-release fertilizer.

The improved cleanup of marine oil spills by stimulating biodegradation through the use of a slow-release fertilizer is reported. A paraffin-supported fertilizer containing MgNH4PO4 as active ingredient was developed and evaluated in laboratory and field experiments using quantitative infrared spectrometry and chromatographic techniques. The biodegradation of Sarir crude oil in the sea was considerably enhanced by paraffin-supported fertilizer. After 21 days 63% had disappeared as compared to 40% in the control area.     

Soil microbial community of abandoned sand fields

Microbiological evaluation of sandy grassland soils from two different stages of secondary succession on abandoned fields (4 and 8 years old fallow) was carried out as a part of research focused on restoration of semi-natural vegetation communities inKiskunság National Park in Hungary. There was an apparent total N and organic C enrichment, stimulation of microbial growth and microbial community structure change on fields abandoned by agricultural practice (small family farm) in comparison with native undisturbed grassland. A successional trend of the microbial community was found after 4 and 8 years of fallow-lying soil. It consisted in a shift of r-survival strategy to more efficient C economy, in a decrease of specific respiration and metabolic activity, forced accumulation of storage bacterial compounds and increased fungal distribution. The composition of microbial phospholipid fatty acids mixture of soils abandoned at various times was significantly different.     

Maladaptation in wild populations of the generalist plant pathogen Pseudomonas syringae

Multihost pathogens occur widely on both natural and agriculturally managed hosts. Despite the importance of such generalists, evolutionary studies of host-pathogen interactions have largely focused on tightly coupled interactions between species pairs. We characterized resistance in a collection of Arabidopsis thaliana hosts, including 24 accessions collected from the Midwest USA and 24 from around the world, and patterns of virulence in a collection of Pseudomonas syringae strains, including 24 strains collected from wild Midwest populations of A. thaliana (residents) and 18 from an array of cultivated species (nonresidents). All of the nonresident strains and half of the resident strains elicited a resistance response on one or more A. thaliana accessions. The resident strains that failed to elicit any resistance response possessed an alternative type III secretion system (T3SS) that is unable to deliver effectors into plant host cells; as a result, these seemingly nonpathogenic strains are incapable of engaging in gene for gene interactions with A. thaliana. The remaining resident strains triggered greater resistance compared to nonresident strains, consistent with maladaptation of the resident bacterial population. We weigh the plausibility of two explanations: general maladaptation of pathogen strains and a more novel hypothesis whereby community level epidemiological dynamics result in adaptive dynamics favoring ephemeral hosts like A. thaliana.     

Microbial degradation of oil spills enhanced by a slow-release fertilizer.

The improved cleanup of marine oil spills by stimulating biodegradation through the use of a slow-release fertilizer is reported. A paraffin-supported fertilizer containing MgNH4PO4 as active ingredient was developed and evaluated in laboratory and field experiments using quantitative infrared spectrometry and chromatographic techniques. The biodegradation of Sarir crude oil in the sea was considerably enhanced by paraffin-supported fertilizer. After 21 days 63% had disappeared as compared to 40% in the control area.