Life Sciences Commons^™

When Is A Microbial Culture "Pure"? Persistent Cryptic Contaminant Escapes Detection Even With Deep Genome Sequencing, Pravin Malla, Kelly P. Nevin, Minita Shrestha, Derek R. Lovley

Derek Lovley

Geobacter sulfurreducens strain KN400 was recovered in previous studies in which a culture of the DL1 strain of G. sulfurreducens served as the inoculum in investigations of microbial current production at low anode potentials (_400 mV versus Ag/AgCl). Differences in the genome sequences of KN400 and DL1 were too great to have arisen from adaptive evolution during growth on the anode. Previous deep sequencing (80-fold coverage) of the DL1 culture failed to detect sequences specific to KN400, suggesting that KN400 was an external contaminant inadvertently introduced into the anode culturing system. In order to evaluate this further, a portion of …

Aromatic Amino Acids Required For Pili Conductivity And Long-Range Extracellular Electron Transport In Geobacter Sulfurreducens, Madeline Vargas, Nikhil S. Malvankar, Pier-Luc Tremblay, Ching Leang, Jessica A. Smith, Pranav Patel, Oona Synoeyenbos-West, Kelly P. Nevin, Derek R. Lovley

Derek Lovley

It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron …

Fluctuations In Species-Level Protein Expression Occur During Element And Nutrient Cycling In The Subsurface, Michael J. Wilkins, Kelly C. Wrighton, Carrie D. Nicora, Kenneth H. Williams, Lee Ann Mccue, Kim M. Handley, Chris S. Miller, Ludovic Giloteaux, Alison P. Montogomery, Derek R. Lovley, Jillian F. Banfield, Philip E. Long, Mary S. Lipton

Derek Lovley

While microbial activities in environmental systems play a key role in the utilization and cycling of essential elements and compounds, microbial activity and growth frequently fluctuates in response to environmental stimuli and perturbations. To investigate these fluctuations within a saturated aquifer system, we monitored a carbon-stimulated in situ Geobacter population while iron reduction was occurring, using 16S rRNA abundances and high-resolution tandem mass spectrometry proteome measurements. Following carbon amendment, 16S rRNA analysis of temporally separated samples revealed the rapid enrichment of Geobacter-like environmental strains with strong similarity to G. bemidjiensis. Tandem mass spectrometry proteomics measurements suggest high carbon flux through …

Engineering Geobacter Sulferreducens To Produce A Highly Cohesive Conductive Matrix With Enhanced Capacity For Current Production, Ching Leang, Nikhil S. Malvankar, Ashley E. Franks, Kelly P. Nevin, Derek R. Lovley

Derek Lovley

The conductive biofilms of Geobacter sulfurreducens have potential applications in renewable energy, bioremediation, and bioelectronics. In an attempt to alter biofilm properties, genes encoding proteins with a PilZ domain were deleted from the G. sulfurreducens genome. A strain, in which the gene GSU1240 was deleted, designated strain CL-1, formed biofilms much more effectively than did the wildtype strain. Increased production of pili and exopolysaccharide were associated with the enhanced biofilm production. When grown with an electrode as the electron acceptor CL-1 produced biofilms that were 6-fold more conductive than wild-type biofilms. The greater conductivity lowered the potential losses in microbial …

Improved Cathode Materials For Microbial Eletrosynthesis, Tian Zhang, Huarong Nie, Timothy S. Bain, Haiyun Lu, Mengmeng Cui, Oona L. Snoeyenbos-West, Ashley E. Franks, Kelly P. Nevin, Thomas P. Russell, Derek R. Lovley

Derek Lovley

Microbial electrosynthesis is a promising strategy for the microbial conversion of carbon dioxide to transportation fuels and other organic commodities, but optimization of this process is required for commercialization. Cathodes which enhance electrode–microbe electron transfer might improve rates of product formation. To evaluate this possibility, biofilms of Sporomusa ovata, which are effective in acetate electrosynthesis, were grown on a range of cathode materials and acetate production was monitored over time. Modifications of carbon cloth that resulted in a positive-charge enhanced microbial electrosynthesis. Functionalization with chitosan or cyanuric chloride increased acetate production rates 6–7 fold and modification with 3-aminopropyltriethoxysilane gave rates …

A Lipid Membrane Intercalating Conjugated Oligoelectrolyte Enables Electrode Driven Succinate Production In Shewanella, Alexander W. Thomas, Logan E. Garner, Kelly P. Nevin, Trevor L. Woodard, Ashley E. Franks, Derek R. Lovley, James J. Sumner, Christian J. Sund, Guillermo C. Bazan

Derek Lovley

An amphiphilic conjugated oligoelectrolyte (COE) that spontaneously intercalates into lipid membranes enables Shewanella oneidensis to use a graphite electrode as the sole electron donor for succinate production. Current consumed in a poised electrochemical system by Shewanella with micromolar concentrations of COE correlates well with the succinate produced via fumarate reduction as determined by HPLC analysis. Confocal microscopy confirms incorporation of the COE into the microbes on the electrode surface. This work presents a unique strategy to induce favorable bioelectronics interactions for the production of reduced microbial metabolites.

Molecular Analysis Of The In Situ Growth Rate Of Subsurface Geobacter Species, Dawn E. Holmes, Ludovic Giloteaux, Melissa Barlett, Milind A. Chavan, Jessica A. Smith, Kenneth H. Williams, Michael Wilkins, Philip Long, Derek Lovley

Derek Lovley

Molecular tools that can provide an estimate of the in situ growth rate of Geobacter species could improve understanding of dissimilatory metal reduction in a diversity of environments. Whole genome microarray analyses of the subsurface isolate, Geobacter uraniireducens, grown under a variety of conditions identified a number of genes that are differentially expressed at different specific growth rates. Expression of two genes encoding ribosomal proteins, rpsC and rplL, were further evaluated with quantitative reverse transcription PCR (qRT-PCR) in cells with doubling times ranging from 6.56 h to 89.28 h. Transcript abundance of rpsC correlated best (r2= 0.90) with specific growth …

The Rnf Complex Of Clostridium Ljungdahlii Is A Proton-Translocating Ferredoxin: Nad+ Oxidoreductase Essential For Autotrophic Growth, Pier-Luc Tremblay, Tian Zhang, Shabir A. Dar, Ching Leang, Derek Lovley

Derek Lovley

It has been predicted that the Rnf complex of Clostridium ljungdahlii is a proton-translocating ferredoxin:NAD+ oxidoreductase which contributes to ATP synthesis by an H+-translocating ATPase under both autotrophic and heterotrophic growth conditions. The recent development of methods for genetic manipulation of C. ljungdahlii made it possible to evaluate the possible role of the Rnf complex in energy conservation. Disruption of the C. ljungdahlii rnf operon inhibited autotrophic growth. ATP synthesis, proton gradient, membrane potential, and proton motive force collapsed in the Rnf-deficient mutant with H2 as the electron source and CO2 as the electron acceptor. Heterotrophic growth was hindered in …

The Genome Of Pelobacter Carbinolicus Reveals Surprising Metabolic Capabilities And Physiological Features, Muktak Aklujkar, Shelley A. Haveman, Raymond Didonato, Olga Chertkov, Cliff S. Han, Miriam L. Land, Peter Brown, Derek Lovley

Derek Lovley

BackgroundThe bacterium Pelobacter carbinolicus is able to grow by fermentation, syntrophic hydrogen/formate transfer, or electron transfer to sulfur from short-chain alcohols, hydrogen or formate; it does not oxidize acetate and is not known to ferment any sugars or grow autotrophically. The genome of P. carbinolicus was sequenced in order to understand its metabolic capabilities and physiological features in comparison with its relatives, acetate-oxidizing Geobacter species.ResultsPathways were predicted for catabolism of known substrates: 2,3-butanediol, acetoin, glycerol, 1,2-ethanediol, ethanolamine, choline and ethanol. Multiple isozymes of 2,3-butanediol dehydrogenase, ATP synthase and [FeFe]-hydrogenase were differentiated and assigned roles according to their structural properties and …

A Genetic System For Clostridium Ljungdahlii: A Chassis For Autotrophic Production Of Biocommodities And A Model Homoacetogen, Ching Leang, Toshiyuki Ueki, Kelly Nevin, Derek R. Lovley

Kelly Nevin

Methods for genetic manipulation of Clostridium ljungdahlii are of interest because of the potential for production of fuels and other biocommodities from carbon dioxide via microbial electrosynthesis or more traditional modes of autotrophy with hydrogen or carbon monoxide as the electron donor. Furthermore, acetogenesis plays an important role in the global carbon cycle. Gene deletion strategies required for physiological studies of C. ljungdahlii have not previously been demonstrated. An electroporation procedure for introducing plasmids was optimized, and four different replicative origins for plasmid propagation in C. ljungdahlii were identified. Chromosomal gene deletion via double-crossover homologous recombination with a suicide vector …

Improved Cathode Materials For Microbial Electrosynthesis, Tian Zhang, Huarong Nie, Timothy S. Bain, Haiyun Lu, Mengmeng Cui, Oona L. Snoeyenbos-West, Ashley E. Franks, Kelly P. Nevin, Thomas P. Russell, Derek Lovley

Derek Lovley

Microbial electrosynthesis is a promising strategy for the microbial conversion of carbon dioxide to transportation fuels and other organic commodities, but optimization of this process is required for commercialization. Cathodes which enhance electrode–microbe electron transfer might improve rates of product formation. To evaluate this possibility, biofilms of Sporomusa ovata, which are effective in acetate electrosynthesis, were grown on a range of cathode materials and acetate production was monitored over time. Modifications of carbon cloth that resulted in a positive-charge enhanced microbial electrosynthesis. Functionalization with chitosan or cyanuric chloride increased acetate production rates 6–7 fold and modification with 3-aminopropyltriethoxysilane gave rates …

Improved Cathode Materials For Microbial Electrosynthesis, Tian Zhang, Huarong Nie, Timothy S. Bain, Haiyun Lu, Mengmeng Cui, Oona L. Snoeyenbos-West, Ashley E. Franks, Kelly Nevin, Thomas P. Russell, Derek R. Lovley

Kelly Nevin

Microbial electrosynthesis is a promising strategy for the microbial conversion of carbon dioxide to transportation fuels and other organic commodities, but optimization of this process is required for commercialization. Cathodes which enhance electrode–microbe electron transfer might improve rates of product formation. To evaluate this possibility, biofilms of Sporomusa ovata, which are effective in acetate electrosynthesis, were grown on a range of cathode materials and acetate production was monitored over time. Modifications of carbon cloth that resulted in a positive-charge enhanced microbial electrosynthesis. Functionalization with chitosan or cyanuric chloride increased acetate production rates 6–7 fold and modification with 3-aminopropyltriethoxysilane gave rates …

Anaerobic Benzene Oxidation By Geobacter Species, Tian Zhang, Timothy S. Bain, Kelly Nevin, Melissa A. Barlett, Derek R. Lovley

Kelly Nevin

The abundance of Geobacter species in contaminated aquifers in which benzene is anaerobically degraded has led to the suggestion that some Geobacter species might be capable of anaerobic benzene degradation, but this has never been documented. A strain of Geobacter, designated strain Ben, was isolated from sediments from the Fe(III)-reducing zone of a petroleum-contaminated aquifer in which there was significant capacity for anaerobic benzene oxidation. Strain Ben grew in a medium with benzene as the sole electron donor and Fe(III) oxide as the sole electron acceptor. Furthermore, additional evaluation of Geobacter metallireducens demonstrated that it could also grow in benzene-Fe(III) …

Comparative Genomic Analysis Of Geobacter Sulfurreducens Kn400, A Strain With Enhanced Capacity For Extracellular Electron Transfer And Electricity Production, Jessica E. Butler, Nelson D. Young, Muktak Aklujkar, Derek Lovley

Derek Lovley

Background A new strain of Geobacter sulfurreducens, strain KN400, produces more electrical current in microbial fuel cells and reduces insoluble Fe(III) oxides much faster than the wildtype strain, PCA. The genome of KN400 was compared to wildtype with the goal of discovering how the network for extracellular electron transfer has changed and how these two strains evolved. Results Both genomes were re-annotated, resulting in 14 fewer genes (net) in the PCA genome; 28 fewer (net) in the KN400 genome; and ca. 400 gene start and stop sites moved. 96% of genes in KN400 had clear orthologs with conserved synteny in …

Interspecies Electron Transfer Via H2 And Formate Rather Than Direct Electrical Connections In Co-Cultures Of Pelobacter Carbinolicus And Geobacter Sulfurreducens, Amelia-Elena Rotaru, Pravin M. Shrestha, Fanghua Liu, Toshiyuki Ueki, Kelly Nevin, Zarath M. Summers, Derek R. Lovley

Kelly Nevin

Direct interspecies electron transfer (DIET) is an alternative to interspecies H2/formate transfer as a mechanism for microbial species to cooperatively exchange electrons during syntrophic metabolism. To understand what specific properties contribute to DIET, studies were conducted with Pelobacter carbinolicus, a close relative of Geobacter metallireducens, which is capable of DIET. P. carbinolicus grew in co-culture with Geobacter sulfurreducens with ethanol as electron donor and fumarate as electron acceptor, conditions under which G. sulfurreducens formed direct electrical connections with G. metallireducens. In contrast to the cell aggregation associated with DIET, P. carbinolicus and G. sulfurreducens did not aggregate. Attempts to initiate …

Promoting Direct Interspecies Electron Transfer With Activated Carbon, Derek Lovley, Fanghua Liu, Amelia-Elena Rotaru, Pravin M. Shrestha, Nikhil S. Malvankar, Kelly P. Nevin

Derek Lovley

Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC's stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation of methanogenesis might be to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens. Metabolism was substantially accelerated when GAC was added to co-cultures of Geobacter metallireducens and Geobacter sulfurreducens grown under conditions previously shown to require DIET. Cells were attached to GAC, but did not aggregate as they do when making biological electrical connections between cells. …

Promoting Direct Interspecies Electron Transfer With Activated Carbon, Fanghua Liu, Amelia-Elena Rotaru, Pravin M. Shrestha, Nikhil S. Malvankar, Kelly Nevin, Derek R. Lovley

Kelly Nevin

Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC's stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation of methanogenesis might be to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens. Metabolism was substantially accelerated when GAC was added to co-cultures of Geobacter metallireducens and Geobacter sulfurreducens grown under conditions previously shown to require DIET. Cells were attached to GAC, but did not aggregate as they do when making biological electrical connections between cells. …

Lack Of Cytochrome Involvement In Long-Range Electron Transport Through Conductive Biofilms And Nanowires Of Geobacter Sulfurreducens, Nikhil S. Malvankar, Mark T. Tuominen, Derek Lovley

Derek Lovley

Two competing models for long-range electron transport through the conductive biofilms and nanowires of Geobacter sulfurreducens exist. In one model electrons are transported via pili that possess delocalized electronic states to function as protein wires with metallic-like conductivity. In the other model electrons are transported by more traditional electron transfer via electron hopping/tunneling between the c-type cytochromes in G. sulfurreducens biofilms and pili. The cytochrome hypothesis was further examined. Quantifying c-type cytochromes in G. sulfurreducens biofilms and pili indicated that there are insufficient cytochromes to account for electron transport through the bulk of the biofilm or pili and demonstrated that …

Electrical Conductivity In A Mixed-Species Biofilm, Nikhil S. Malvankar, Joanne Lau, Kelly Nevin, Ashley E. Franks, Mark T. Tuominen, Derek R. Lovley

Kelly Nevin

Geobacter sulfurreducens can form electrically conductive biofilms, but the potential for conductivity through mixed species biofilms has not been examined. A current-producing biofilm grown from a wastewater sludge inoculum was highly conductive with low charge transfer resistance even though microorganisms other than Geobacteraceae accounted for nearly half the microbial community.

Role Of The Nife Hydrogenase Hya In Oxidative Stress Defense In Geobacter Sulfurreducens, Pier-Luc Tremblay, Derek Lovley

Derek Lovley

Geobacter sulfurreducens, an Fe(III)-reducing deltaproteobacterium found in anoxic subsurface environments, contains 4 NiFe hydrogenases. Hyb, a periplasmically oriented membrane-bound NiFe hydrogenase, is essential for hydrogen-dependent growth. The functions of the three other hydrogenases are unknown. We show here that the other periplasmically oriented membrane-bound NiFe hydrogenase, Hya, is necessary for growth after exposure to oxidative stress when hydrogen or a highly limiting concentration of acetate is the electron source. The beneficial impact of Hya on growth was dependent on the presence of H(2) in the atmosphere. Moreover, the Hya-deficient strain was more sensitive to the presence of superoxide or hydrogen …

Trace Elements Affect Methanogenic Activity And Diversity In Enrichments From Subsurface Coal Bed Produced Water, B. Unal, V. R. Perry, M. Sheth, V. Gomez-Alvarez, K. J. Chin, Klaus R. Nusslein

Klaus R. Nusslein

Microbial methane from coal beds accounts for a significant and growing percentage of natural gas worldwide. Our knowledge of physical and geochemical factors regulating methanogenesis is still in its infancy. We hypothesized that in these closed systems, trace elements (as micronutrients) are a limiting factor for methanogenic growth and activity. Trace elements are essential components of enzymes or cofactors of metabolic pathways associated with methanogenesis. This study examined the effects of eight trace elements (iron, nickel, cobalt, molybdenum, zinc, manganese, boron, and copper) on methane production, on mcrA transcript levels, and on methanogenic community structure in enrichment cultures obtained from …

Chlamydia Pneumoniae-Specific Ige Is Prevalent In Asthma And Is Associated With Disease Severity, David L. Hahn, Allison Schure, Katir K. Patel, Tawanna S. Childs, Eduard Drizik, Wilmore C. Webley

Wilmore C Webley

Background: Several Chlamydia pneumoniae (Cp) biomarkers have been associated with asthma but Cp-specific IgE (Cp IgE) has not been investigated extensively. Our objective was to investigate Cp IgE in community adult asthma patients.

Methods: (1) Prevalence of Cp IgE (measured by immunoblotting) and Cp DNA (by polymerase chain reaction) in peripheral blood, and biomarker associations with asthma severity. (2) Case-control studies of Cp IgE association with asthma using healthy blood donor (study 1) and non-asthmatic clinic patient (study 2) controls.

Results: Of 66 asthma subjects (mean age 40.9 years, range 5–75, 59% male, 45% ever-smokers) 33 (50%) were Cp IgE …

The Prevalence And Identity Of Chlamydia-Specific Ige In Children With Asthma And Other Chronic Respiratory Symptoms, Katir K. Patel, Erica A. Anderson, Paul S. Salva, Wilmore C. Webley

Wilmore C Webley

Background Recent studies have confirmed the presence of viable Chlamydia in the bronchoalveolar lavage (BAL) fluid of pediatric patients with airway hyperresponsiveness. While specific IgG and IgM responses to C. pneumoniae are well described, the response and potential contribution of Ag-specific IgE are not known. The current study sought to determine if infection with Chlamydia triggers the production of pathogen-specific IgE in children with chronic respiratory diseases which might contribute to inflammation and pathology. Methods We obtained BAL fluid and serum from pediatric respiratory disease patients who were generally unresponsive to corticosteroid treatment as well as sera from age-matched control …

The Prevalence And Identity Of Chlamydia-Specific Ige In Children With Asthma And Other Chronic Respiratory Symptoms, Katir K. Patel, Erica A. Anderson, Paul S. Salva, Wilmore C. Webley

Wilmore C Webley

Background Recent studies have confirmed the presence of viable Chlamydia in the bronchoalveolar lavage (BAL) fluid of pediatric patients with airway hyperresponsiveness. While specific IgG and IgM responses to C. pneumoniae are well described, the response and potential contribution of Ag-specific IgE are not known. The current study sought to determine if infection with Chlamydia triggers the production of pathogen-specific IgE in children with chronic respiratory diseases which might contribute to inflammation and pathology.

Methods We obtained BAL fluid and serum from pediatric respiratory disease patients who were generally unresponsive to corticosteroid treatment as well as sera from age-matched control …

Microbial Functional Gene Diversity With A Shift Of Subsurface Redox Conditions During In Situ Uranium Reduction, Yuting Liang, Joy D. Van Nostrand, Lucie A. N′Guessan, Aaron D. Peacock, Ye Deng, Philip E. Long, Tom C. Resch, Liyou Wu, Zhili He, Guanghe Li, Terry C. Hazen, Derek Lovley, Jizhong Zhoua

Derek Lovley

To better understand the microbial functional diversity changes with subsurface redox conditions during in situ uranium bioremediation, key functional genes were studied with GeoChip, a comprehensive functional gene microarray, in field experiments at a uranium mill tailings remedial action (UMTRA) site (Rifle, CO). The results indicated that functional microbial communities altered with a shift in the dominant metabolic process, as documented by hierarchical cluster and ordination analyses of all detected functional genes. The abundance of dsrAB genes (dissimilatory sulfite reductase genes) and methane generation-related mcr genes (methyl coenzyme M reductase coding genes) increased when redox conditions shifted from Fe-reducing to …

Integrative Analysis Of Geobacter Spp. And Sulfate-Reducing Bacteria During Uranium Bioremediation, M. Barlett, K. Zhuang, R. Mahadevan, Derek Lovley

Derek Lovley

Enhancing microbial U(VI) reduction with the addition of organic electron donors is a promising strategy for immobilizing uranium in contaminated groundwaters, but has yet to be optimized because of a poor understanding of the factors controlling the growth of various microbial communities during bioremediation. In previous field trials in which acetate was added to the subsurface, there were two distinct phases: an initial phase in which acetate-oxidizing, U(VI)-reducing Geobacter predominated and U(VI) was effectively reduced and a second phase in which acetate-oxidizing sulfate reducing bacteria (SRB) predominated and U(VI) reduction was poor. The interaction of Geobacter and SRB was investigated …

Biological Conversion Assay Using Clostridium Phytofermentans To Estimate Plant Feedstock Quality, Scott J. Lee, Thomas A. Warnick, Sivakumar Pattathil, Jesus G. Alvelo-Maurosa, Michelle J. Serapiglia, Heather Mccormick, Virginia Brown, Naomi F. Young, Danny J. Schnell, Lawrence B. Smart, Michael G. Hahn, Jeffrey F. Pedersen, Susan Leschine, Samuel P. Hazen

Susan Leschine

Background There is currently considerable interest in developing renewable sources of energy. One strategy is the biological conversion of plant biomass to liquid transportation fuel. Several technical hurdles impinge upon the economic feasibility of this strategy, including the development of energy crops amenable to facile deconstruction. Reliable assays to characterize feedstock quality are needed to measure the effects of pre-treatment and processing and of the plant and microbial genetic diversity that influence bioconversion efficiency. Results We used the anaerobic bacterium Clostridium phytofermentans to develop a robust assay for biomass digestibility and conversion to biofuels. The assay utilizes the ability of …

Comment On “On Electrical Conductivity Of Microbial Nanowires And Biofilms” By S. M. Strycharz-Glaven, R. M. Snider, A. Guiseppi-Elie And L. M. Tender, Energy Environ. Sci., 2011, 4, 4366, Nikhil S. Malvankar, Mark T. Tuominen, Derek Lovley

Derek Lovley

A paper published in Energy and Environmental Science by Strycharz-Glaven et al. suggests that electron transport along the pili and through the conductive biofilms of Geobacter sulfurreducens proceeds via electron superexchange rather than metallic-like conductivity. Multiple lines of evidence disprove the superexchange hypothesis, but are consistent with metallic-like conductivity.

Bioavailability Of Jarosite For Stimulating Acid Mine Drainage Attenuation, Klaus R. Nusslein

Klaus R. Nusslein

Biological reduction of iron-sulfate minerals, such as jarosite, has the potential to contribute to the natural attenuation of acid mine drainage (AMD) sites. Previous studies of AMD attenuation at Davis Mine, an abandoned pyrite mine in Rowe Massachusetts, provided evidence of iron and sulfate reduction by indigenous bacteria. Jarosite is a large component of the sediment at Davis Mine and may play a role in AMD attenuation. In this study, microcosms were constructed with groundwater and sediment from Davis Mine and amended with glycerol, nitrogen and phosphorus (GNP) and naturally formed natrojarosite. Over time, higher total iron, sulfate, pH and …

Desiccation Induces Viable But Non-Culturable Cells In Sinorhizobium Melilioti 1021, Klaus R. Nusslein, Frans J. De Bruijn, Jan Ac Vriezen

Klaus R. Nusslein

Sinorhizobium meliloti is a microorganism commercially used in the production of e.g. Medicago sativa seed inocula. Many inocula are powder-based and production includes a drying step. Although S. meliloti survives drying well, the quality of the inocula is reduced during this process. In this study we determined survival during desiccation of the commercial strains 102F84 and 102F85 as well as the model strain USDA1021. The survival of S. meliloti 1021 was estimated during nine weeks at 22% relative humidity. We found that after an initial rapid decline of colony forming units, the decline slowed to a steady 10-fold reduction in …