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Articles 1 - 30 of 32
Full-Text Articles in Life Sciences
These Are Not The K-Mers You Are Looking For: Efficient Online K-Mer Counting Using A Probabilistic Data Structure, Qingpeng Zhang, Jason Pell, Rosangela Canino-Koning, Adina Chuang Howe, C. Titus Brown
These Are Not The K-Mers You Are Looking For: Efficient Online K-Mer Counting Using A Probabilistic Data Structure, Qingpeng Zhang, Jason Pell, Rosangela Canino-Koning, Adina Chuang Howe, C. Titus Brown
Adina Howe
K-mer abundance analysis is widely used for many purposes in nucleotide sequence analysis, including data preprocessing for de novo assembly, repeat detection, and sequencing coverage estimation. We present the khmer software package for fast and memory efficient online counting of k-mers in sequencing data sets. Unlike previous methods based on data structures such as hash tables, suffix arrays, and trie structures, khmer relies entirely on a simple probabilistic data structure, a Count-Min Sketch. The Count-Min Sketch permits online updating and retrieval of k-mer counts in memory which is necessary to support online k-mer analysis algorithms. On sparse data sets this …
Revealing The Bacterial Butyrate Synthesis Pathways By Analyzing (Meta)Genomic Data, Marius Vital, Adina Chuang Howe, James M. Tiedje
Revealing The Bacterial Butyrate Synthesis Pathways By Analyzing (Meta)Genomic Data, Marius Vital, Adina Chuang Howe, James M. Tiedje
Adina Howe
Butyrate-producing bacteria have recently gained attention, since they are important for a healthy colon and when altered contribute to emerging diseases, such as ulcerative colitis and type II diabetes. This guild is polyphyletic and cannot be accurately detected by 16S rRNA gene sequencing. Consequently, approaches targeting the terminal genes of the main butyrate-producing pathway have been developed. However, since additional pathways exist and alternative, newly recognized enzymes catalyzing the terminal reaction have been described, previous investigations are often incomplete. We undertook a broad analysis of butyrate-producing pathways and individual genes by screening 3,184 sequenced bacterial genomes from the Integrated Microbial …
The Genome And Developmental Transcriptome Of The Strongylid Nematode Haemonchus Contortus, Erich M. Schwarz, Pasi K. Korhonen, Bronwyn E. Campbell, Neil D. Young, Aaron R. Jex, Abdul Jabbar, Ross S. Hall, Alinda Mondal, Adina C. Howe, Jason Pell, Andreas Hofmann, Peter R. Boag, Xing-Quan Zhu, T. Ryan Gregory, Alex Loukas, Brian A. Williams, Igor Antoshechkin, C. Titus Brown, Paul W. Sternberg, Robin B. Gasser
The Genome And Developmental Transcriptome Of The Strongylid Nematode Haemonchus Contortus, Erich M. Schwarz, Pasi K. Korhonen, Bronwyn E. Campbell, Neil D. Young, Aaron R. Jex, Abdul Jabbar, Ross S. Hall, Alinda Mondal, Adina C. Howe, Jason Pell, Andreas Hofmann, Peter R. Boag, Xing-Quan Zhu, T. Ryan Gregory, Alex Loukas, Brian A. Williams, Igor Antoshechkin, C. Titus Brown, Paul W. Sternberg, Robin B. Gasser
Adina Howe
Background The barber's pole worm, Haemonchus contortus, is one of the most economically important parasites of small ruminants worldwide. Although this parasite can be controlled using anthelmintic drugs, resistance against most drugs in common use has become a widespread problem. We provide a draft of the genome and the transcriptomes of all key developmental stages of H. contortus to support biological and biotechnological research areas of this and related parasites. Results The draft genome of H. contortus is 320 Mb in size and encodes 23,610 protein-coding genes. On a fundamental level, we elucidate transcriptional alterations taking place throughout the life …
Potential For Nitrogen Fixation And Nitrification In The Granite-Hosted Subsurface At Henderson Mine, Co, Elizabeth D. Swanner, Alexis S. Templeton
Potential For Nitrogen Fixation And Nitrification In The Granite-Hosted Subsurface At Henderson Mine, Co, Elizabeth D. Swanner, Alexis S. Templeton
Elizabeth D. Swanner
The existence of life in the deep terrestrial subsurface is established, yet few studies have investigated the origin of nitrogen that supports deep life. Previously, 16S rRNA gene surveys cataloged a diverse microbial community in subsurface fluids draining from boreholes 3000 feet deep at Henderson Mine, CO, USA (Sahl et al., 2008). The prior characterization of the fluid chemistry and microbial community forms the basis for the further investigation here of the source of NH4+. The reported fluid chemistry included N2, NH4+ (5–112 μM), NO2− (27–48 μM), and NO3− (17–72 μM). In this study, the correlation between low NH4+ concentrations …
Dryland Residue And Soil Organic Matter As Influenced By Tillage, Crop Rotation, And Cultural Practice, Andrew W. Lenssen, Upendra M. Sainju, Thecan Caesar-Tonthat, Jalal D. Jabro, Robert T. Lartey, Robert G. Evans, Brett L. Allen
Dryland Residue And Soil Organic Matter As Influenced By Tillage, Crop Rotation, And Cultural Practice, Andrew W. Lenssen, Upendra M. Sainju, Thecan Caesar-Tonthat, Jalal D. Jabro, Robert T. Lartey, Robert G. Evans, Brett L. Allen
Andrew W. Lenssen
Novel management practices are needed to increase dryland soil organic matter and crop yields that have been declining due to long-term conventional tillage with spring wheat (Triticum aestivum L.)-fallow system in the northern Great Plains, USA. The effects of tillage, crop rotation, and cultural practice were evaluated on dryland crop biomass (stems + leaves) yield, surface residue, and soil organic C (SOC) and total N (STN) at the 0–20 cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) from 2004 to 2007 in eastern Montana, USA. Treatments were two tillage practices [no-tillage (NT) and conventional tillage (CT)], …
Effects Of Tillage On Microbial Populations Associated To Soil Aggregation In Dryland Spring Wheat System, Andrew W. Lenssen, Thecan Caesar-Tonthat, Anthony J. Caesar, Upendra M. Sainju, John F. Gaskin
Effects Of Tillage On Microbial Populations Associated To Soil Aggregation In Dryland Spring Wheat System, Andrew W. Lenssen, Thecan Caesar-Tonthat, Anthony J. Caesar, Upendra M. Sainju, John F. Gaskin
Andrew W. Lenssen
Tillage may influence the microbial populations involved in soil aggregation.We evaluated the effects of no till (NT) and conventional tillage (CT, tillage depth about 7 cm) continuous spring wheat system on culturable heterotrophic bacterial communities predominant in microaggregates (0.25e0.05 mm) and on soil-aggregating basidiomycete fungi in aggregate-size classes (4.75e2.00, 2.00e0.25, and 0.25e0.05 mm) at 0e20 cm depth of a Williams loam (fine-loamy, mixed, Typic Argiustolls) in dryland Montana, USA. Enzyme-linked immunosorbent assay used to quantify antigenic response to basidiomycete cellwalls,was higher in NT than in CT in 4.75e2.00 mm size class in 2007 and higher in all classes and years …
Management Strategies To Improve Yield And Nitrogen Use Of Spring Wheat And Field Pea In The Semi-Arid Northern Great Plains Usa, Andrew W. Lenssen, Brett Allen, Upendra Sainju, Thecan Caesar, Robert Lartey, Robert Evans
Management Strategies To Improve Yield And Nitrogen Use Of Spring Wheat And Field Pea In The Semi-Arid Northern Great Plains Usa, Andrew W. Lenssen, Brett Allen, Upendra Sainju, Thecan Caesar, Robert Lartey, Robert Evans
Andrew W. Lenssen
Available water and N fertility are primary constraints to crop production in the northern Great Plains of the USA. A field trial was initiated in 2004 to compare four crop rotations in a complete factorial of two tillage and two management systems. Rotations were continuous spring wheat (SW), pea-SW, barley hay-pea-SW, and barley hay-corn-pea-SW. Tillage systems were no till and field cultivator tillage, while management systems were conventional and ecological. Conventional management included broadcast nitrogen fertilizer, standard seeding rates, and short stubble height. Ecological management practices varied by crop, and included banded nitrogen fertilizer for cereals, increased seeding rate, delayed …
Furfural Inhibits Growth By Limiting Sulfur Assimilation In Ethanologenic Escherichia Coli Strain Ly180, Elliot N. Miller, Laura R. Jarboe, Peter C. Turner, Prita Pharkya, Lorraine P. Yomano, Sean W. York, David Nunn, K. T. Shanmugan, Lonnie O. Ingram
Furfural Inhibits Growth By Limiting Sulfur Assimilation In Ethanologenic Escherichia Coli Strain Ly180, Elliot N. Miller, Laura R. Jarboe, Peter C. Turner, Prita Pharkya, Lorraine P. Yomano, Sean W. York, David Nunn, K. T. Shanmugan, Lonnie O. Ingram
Laura R. Jarboe
A wide variety of commercial products can be potentially made from monomeric sugars produced by the dilute acid hydrolysis of lignocellulosic biomass. However, this process is accompanied by side products such as furfural that hinder microbial growth and fermentation. To investigate the mechanism of furfural inhibition, mRNA microarrays of an ethanologenic strain of Escherichia coli (LY180) were compared immediately prior to and 15 min after a moderate furfural challenge. Expression of genes and regulators associated with the biosynthesis of cysteine and methionine was increased by furfural, consistent with a limitation of these critical metabolites. This was in contrast to a …
Silencing Of Nadph-Dependent Oxidoreductase Genes (Yqhd And Dkga) In Furfural-Resistant Ethanologenic Escherichia Coli, Elliot N. Miller, Laura R. Jarboe, L. P. Yomano, S. W. York, K. T. Shanmugam, L. O. Ingram
Silencing Of Nadph-Dependent Oxidoreductase Genes (Yqhd And Dkga) In Furfural-Resistant Ethanologenic Escherichia Coli, Elliot N. Miller, Laura R. Jarboe, L. P. Yomano, S. W. York, K. T. Shanmugam, L. O. Ingram
Laura R. Jarboe
Low concentrations of furfural are formed as a side product during the dilute acid hydrolysis of hemicellulose. Growth is inhibited by exposure to furfural but resumes after the complete reduction of furfural to the less toxic furfuryl alcohol. Growth-based selection was used to isolate a furfural-resistant mutant of ethanologenic Escherichia coli LY180, designated strain EMFR9. Based on mRNA expression levels in the parent and mutant in response to furfural challenge, genes encoding 12 oxidoreductases were found to vary by more than twofold (eight were higher in EMFR9; four were higher in the parent). All 12 genes were cloned. When expressed …
Microbial Development In Distillers Wet Grains Produced During Fuel Ethanol Production From Corn (Zea Mays), R. Michael Lehman, Kurt A. Rosentrater
Microbial Development In Distillers Wet Grains Produced During Fuel Ethanol Production From Corn (Zea Mays), R. Michael Lehman, Kurt A. Rosentrater
Kurt A. Rosentrater
Distillers grains are coproduced with ethanol and carbon dioxide during the production of fuel ethanol from the dry milling and fermentation of corn grain, yet there is little basic microbiological information on these materials. We undertook a replicated field study of the microbiology of distillers wet grains (DWG) over a 9 day period following their production at an industrial fuel ethanol plant. Freshly produced DWG had a pH of about 4.4, a moisture content of about 53.5% (wet mass basis), and 4 x 10(5) total yeast cells/g dry mass, of which about 0.1% were viable. Total bacterial cells were initially …
Delayed-Incubation Method For Microbiological Analysis Of Environmental Specimens And Samples, James S. Dickson, M. H. Brodsky, C. A. Davidson, M. J. Pettis, T. L. Tieso
Delayed-Incubation Method For Microbiological Analysis Of Environmental Specimens And Samples, James S. Dickson, M. H. Brodsky, C. A. Davidson, M. J. Pettis, T. L. Tieso
James S. Dickson
Five laboratories compared the quantitative recovery of heterotrophic bacteria, yeasts and molds, coliforms, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus from a variety of naturally contaminated food and water samples, using traditional incubation procedures and a delayed-incubation method. Refrigeration of inoculated media for up to 3 days prior to incubation was shown to be a viable option for many quantitative analyses, but needs to be validated for each application. Some inoculated media withstood refrigeration for up to 7 days prior to incubation without any detrimental effect on the recovery of target cells, while the incubation of other media for similar …
Cell Surface Charge And Initial Attachment Characteristics Of Rough Strains Of Listeria Monocytogenes, James S. Dickson
Cell Surface Charge And Initial Attachment Characteristics Of Rough Strains Of Listeria Monocytogenes, James S. Dickson
James S. Dickson
The relative negative surface charge and hydrophobicity of four bacterial strains were evaluated by gravity flow and spin column methods. There was no significant difference between the two methods, indicating that spin column chromatography is an acceptable alternative method of determining cell surface charge or hydrophobicity. Six strains of Listeria monocytogenes which exhibited rough colony appearance were evaluated for surface charge and hydrophobicity and their ability to contaminate beef muscle tissue. With one exception, all of the rough strains exhibited greater net negative surface charge and reduced ability to contaminate beef during the initial stages of attachment. Since greater net …
Antimicrobial Effects Of Trisodium Phosphate Against Bacteria Attached To Beef Tissue, James S. Dickson, C. G. Nettles Cutter, G. R. Siragusa
Antimicrobial Effects Of Trisodium Phosphate Against Bacteria Attached To Beef Tissue, James S. Dickson, C. G. Nettles Cutter, G. R. Siragusa
James S. Dickson
Sliced beef tissue was artificially contaminated with Salmonella typhimurium, Listeria monocytogenes and Escherichia coli OI57:H7. The contaminated tissue was immersed in 8, 10 and 12% solutions of trisodium phosphate at 25, 40 and 55°C with contact times of up to 3 min. The concentration of the trisodium phosphate solution was not a significant factor in reducing the populations of the bacteria on either lean or adipose tissue. Reductions in bacterial populations of I to 1.5 loglocycles were obtained on lean tissue contaminated with the gram-negative pathogens, although less reduction in population was seen with L. monocytogenes. Greater reductions in bacterial …
Bacterial Starvation Stress And Contamination Of Beef, James S. Dickson, J. F. Frank
Bacterial Starvation Stress And Contamination Of Beef, James S. Dickson, J. F. Frank
James S. Dickson
Salmonella typhimurium, Listeria monocytogenes, ad Escherichia coli 0157;H7 were starved by suspending washed cells in phosphate buffer for 5 days at 10, 25 or 37 degrees C. Starved bacteria were evaluated for their ability to attach to beef tissue and their sensitivity to acetic acid sanitizing. Starvation stress generally decreased the numbers of bacteria which attached to the tissue when compared to control bacterial cultures grown to late logarithmic growth phase. Starvation temperature was negatively correlated to the numbers of attached bacteria. Starvation slightly increased the sensitivity of attached S. typhimurium and L. monocytogenes cells to acetic acid, but did …
Isolation Of Listeria Spp. From Feces Of Feedlot Cattle, James S. Dickson, G. R. Siragusa, E. K. Daniels
Isolation Of Listeria Spp. From Feces Of Feedlot Cattle, James S. Dickson, G. R. Siragusa, E. K. Daniels
James S. Dickson
Healthy feedlot beef cattle were surveyed for the presence of Listeria spp. in fecal grab samples taken over 3 months. Composite samples were made from 224 individual animals each month. Listeria monocytogenes was isolated from one composite sample (4%) from the first sampling and not from the subsequent two. Listeria innocua was found in composite samples from all three samplings at levels of 17, 9, and 35%, respectively. From the individual samples comprising the Listeria spp.—positive composites, L. monoytogenes was isolated from one sample (3%) in the second sampling but not in the first or third samplings. L. innocua was …
A Computer-Controlled Spray Chill Unit For Red Meat Carcasses, Maynard E. Anderson, James S. Dickson, Mark M. Hulse, Scott T. Drummond, John D. Crouse, Robert T. Marshall
A Computer-Controlled Spray Chill Unit For Red Meat Carcasses, Maynard E. Anderson, James S. Dickson, Mark M. Hulse, Scott T. Drummond, John D. Crouse, Robert T. Marshall
James S. Dickson
A computer controlled and operated spray chill unit which can be used in future research studies for both spray chilling and decontamination of red meat carcasses is described. The unit consists of two parts: (1) an electromechanical system, and (2) a data acquisition/control system. Design concepts for the spray chill system are (1) versatility, (2) rapid change of spray parameters, and (3) computer control of the electromechanical system. An added feature is the computer data collection system for recording information related to each carcass (pH of muscle, surface and internal tissue temperatures, and weights of each half carcass during the …
Microbiological Decontamination Of Food Animal Carcasses By Washing And Sanitizing Systems: A Review, James S. Dickson, Maynard E. Anderson
Microbiological Decontamination Of Food Animal Carcasses By Washing And Sanitizing Systems: A Review, James S. Dickson, Maynard E. Anderson
James S. Dickson
Microbial contamination of animal carcasses is a result of the necessary procedures required to process live animals into retail meat. The contamination can be minimized by good manufacturing processes, but the total elimination of foodborne pathogenic microorganisms is difficult, if not impossible. A variety of methods have been developed to reduce the levels of contaminating bacteria on carcasses, although most of the current methods focus on washing and sanitizing procedures. The commonly used sanitizing agents include hot water, chlorine, and short-chain organic acids. The effectiveness of these compounds varies by the concentration used, the temperature of the sanitizers and contact …
Inhibition Of Listeria Monocytogenes On Beef Tissue By Application Of Organic Acids Immobilized In A Calcium Alginate Gel, James S. Dickson, Gregory R. Siragusa
Inhibition Of Listeria Monocytogenes On Beef Tissue By Application Of Organic Acids Immobilized In A Calcium Alginate Gel, James S. Dickson, Gregory R. Siragusa
James S. Dickson
Organic acids added to calcium alginate gels and immobilized on lean beef tissue inoculated with LLtetia monocytogenes (Lm) reduced the population significantly more than did acid treatment alone. Lactic acid (1.7% v/v) immobilized in alginate reduced counts by 1.3 log,, units vs 0.03 log unit decrease from the acid treatment alone. Acetic acid (2% v/v) reduced counts 1.5 and 0.25 log units, respectively. Over 7 days, Lm proliferated in samples without acid and/or alginate treatment. Differential counts on selective and non-selective agars indicated sublethal cellular injury occurred. Alginate coatings did not enhance acid inhibition on fat tissue. Immobilized agents may …
Acetic Acid Action On Beef Tissue Surfaces Contaminated With Salmonella Typhimurium, James S. Dickson
Acetic Acid Action On Beef Tissue Surfaces Contaminated With Salmonella Typhimurium, James S. Dickson
James S. Dickson
Beef tissue surfaces (lean and fat) were artificially contaminated with Salmonella typhimurium and then sanitized with 2% acetic acid. The reduction in bacterial population by the acid treatment was consistently proportional to the initial inoculum level for both tissue types. Increasing the amount of organic material in the inoculating menstra reduced the bactericidal effects of acetic acid on Salmonella typhimurium on fat tissue, although there was no change in effectiveness on lean tissue. Acid treatment sublethally injured about 65% of the population on both lean and fat tissue, and the residual effects of the acid resulted in a 1 log …
Control Of Salmonella On Beef Tissue Surfaces In A Model System By Pre- And Post-Evisceration Washing And Sanitizing, With And Without Spray Chilling, James S. Dickson, Maynard E. Anderson
Control Of Salmonella On Beef Tissue Surfaces In A Model System By Pre- And Post-Evisceration Washing And Sanitizing, With And Without Spray Chilling, James S. Dickson, Maynard E. Anderson
James S. Dickson
Beef tissue was inoculated with a nalidixic acid resistant strain of Salmonella California and processed under conditions simulating pre- and post-evisceration carcass washing and sanitizing. These treatments, using distilled water to wash and 2% acetic acid to sanitize, reduced the population of salmonellae by as much as 2-log10 cycles when compared to samples which were washed only in distilled water. Increasing the acid temperature to 55°C reduced the bacterial populations further. Spray chilling, when used in series with the pre- and post-evisceration treatments, apparently resulted in recovery of some injured Salmonella.
Contamination Of Beef Tissue Surfaces By Cattle Manure Inoculated With Salmonella Typhimurium And Listeria Monocytogenes, James S. Dickson
Contamination Of Beef Tissue Surfaces By Cattle Manure Inoculated With Salmonella Typhimurium And Listeria Monocytogenes, James S. Dickson
James S. Dickson
Contamination of beef lean and fat tissue surfaces by Salmonella typhimurium and Listeria monocytogenes was evaluated using phosphate buffer or sterilized manure as an inoculation menstruum. Immersion in inoculated phosphate buffer resulted in an increase in numbers of attached cells during the 120 min inoculation for both bacterial species. Tissue immersed in inoculated manure generally showed an increase in cell numbers up to 10 min of immersion with only slight increases in cell numbers from lOto 120 min. Fewer cells attached to either tissue type from the manure inoculum (P<0.05), although actual numerical differences were small.
Attachment Of Salmonella Typhimurium And Listeria Monocytogenes To Glass As Affected By Surface Film Thickness, Cell Density, And Bacterial Motility, James S. Dickson, E. K. Daniels
Attachment Of Salmonella Typhimurium And Listeria Monocytogenes To Glass As Affected By Surface Film Thickness, Cell Density, And Bacterial Motility, James S. Dickson, E. K. Daniels
James S. Dickson
With equal cell densities, surface film thickness did not influence the numbers &Salmonella typhimurium and Listeria monocytogenes cells which attached to glass. Motile L. monocytogenes cells had a greater cell surface charge and generally attached in higher numbers than non-motile cells.
Control Of Salmonella Typhimurium, Listeria Monocytogenes, And Escherichia Coli 0157:H7 On Beef In A Model Spray Chilling System, James S. Dickson
Control Of Salmonella Typhimurium, Listeria Monocytogenes, And Escherichia Coli 0157:H7 On Beef In A Model Spray Chilling System, James S. Dickson
James S. Dickson
Simulated water spray chilling cycles were modified to include acetic acid as a sanitizer. The modified cycles were tested for effectiveness in reducing levels of S. typhimutium, L. monocyfogenes, and E. coli 0157:H7 on beef lean and fat tissue. Reductions of up to 3 log cycles were obtained for all three bacterial species on fat tissue. Reduction was less on lean tissue with the same treatments, although the modified cycles reduced populations when compared to the control cycle.
Storage And Bacterial Contamination Effects On Myofibrillar Proteins And Shear Force Of Beef, James S. Dickson, John D. Crouse, M. Koohmaraie
Storage And Bacterial Contamination Effects On Myofibrillar Proteins And Shear Force Of Beef, James S. Dickson, John D. Crouse, M. Koohmaraie
James S. Dickson
Thirty-two steaks from the longissimus muscle, fifth rib to third lumbar vertebra, were obtained from youthful carcass beef. Half were sterilized by ultraviolet light and all vacuum packaged and stored for 1, 14, 28 or 57 days at 2°C. After storage, steaks were examined for microbial populations, myofibril fragmentation index (MFI), cooking characteristics and shear force (SF). Aerobic and anaerobic counts decreased during storage. Psychrotrophic counts were low throughout. Sterilization had no effect on SF or MFI. Cooking loss tended (P < 0.09) to increase with time of storage. SF values decreased and MFI values increased through day 14, but remained relatively constant after that. Results of SDS-PAGE, SF and MFI indicate major changes in proteolysis of myofibrils and tenderness were completed by day 14.
Attachment Of Salmonella Typhimurium And Listeria Monocytogenes To Beef Tissue: Effects Of Inoculum Level, Growth Temperature And Bacterial Culture Age, James S. Dickson
Attachment Of Salmonella Typhimurium And Listeria Monocytogenes To Beef Tissue: Effects Of Inoculum Level, Growth Temperature And Bacterial Culture Age, James S. Dickson
James S. Dickson
The effects of inoculum level, growth temperature and culture age on the attachment of Salmonella typhimurium and Listeria monocytogenes to beef tissue surfaces were evaluated. An increase in inoculum level resulted in an increase in the number of attached cells for both bacteria which was proportional to the increase in inoculum. Bacteria grown at 23°C attached in higher numbers flVO5) to fat tissue than bacteria grown at 37°C or at 37°C followed by 24 h at 5°C. Growth temperature did not affect attachment to lean tissue for either bacterium. Overnight cultures of both bacteria attached in greater numbers 0VO.05) to …
Surface Moisture And Osmotic Stress As Factors That Affect The Sanitizing Of Beef Tissue Surfaces, James S. Dickson
Surface Moisture And Osmotic Stress As Factors That Affect The Sanitizing Of Beef Tissue Surfaces, James S. Dickson
James S. Dickson
The use of osmotic stress or desiccation in combination with 2% acetic acid reduced the numbers of Salmonella typhimurium or Listeria monocytogenes on beef tissue to a greater degree than the acid alone. Bacteria were osmotically stressed by NaCl, CaCl2, or sucrose solutions. Pre-washing with 20% NaCl followed by sanitizing with acetic acid reduced the numbers of S. typhimurium an additional 1.5-to 2-log cycles compared with acetic acid alone. Similar reductions were seen by allowing the tissue surfaces to dry before the application of the acid. Desiccation in combination with acetic acid was also effective in reducing the numbers of …
Transfer Of Listeria Monocytogenes And Salmonella Typhimurium Between Beef Tissue Surfaces, James S. Dickson
Transfer Of Listeria Monocytogenes And Salmonella Typhimurium Between Beef Tissue Surfaces, James S. Dickson
James S. Dickson
Beef tissue surfaces were inoculated with either Listeria monocytogenes or Salmonella typhimurium and placed in contact with uninoculated tissue surfaces. The transfer of bacteria from one surface to another was determined under conditions designed to simulate contamination during meat processing. Bacterial transfer decreased when the initial inoculum was allowed to adsorb to the base tissue prior to contact with the second tissue. The type of base tissue was a factor (P<0.05), with a greater transfer from fat with contact times of less than 1 min and a greater transfer from lean with longer contact times.
Comparison Of Homogenization By Blending Or Stomaching On The Recovery Of Listeria Monocytogenes From Beef Tissues, James S. Dickson
Comparison Of Homogenization By Blending Or Stomaching On The Recovery Of Listeria Monocytogenes From Beef Tissues, James S. Dickson
James S. Dickson
Homogenization by blending or stomaching was compared for the recovery of Listeria monocytogenes from inoculated intact beef tissue. There were no differences in numbers of recovered bacteria (P > 0.10) attributable to either homogenization time or method. Fewer viable bacteria (PcO.05) were recovered in phosphate buffer than either buffered peptone water or 2% trisodium citrate buffer. Tween 80 increased the numbers of bacteria recovered from fat tissue (PcO.05). Stomaching is an acceptable method for homogenizing samples for Listeria analysis.
Attachment And Proliferation Of Bacteria On Meat, James S. Dickson, King-Thom Chung, John D. Crouse
Attachment And Proliferation Of Bacteria On Meat, James S. Dickson, King-Thom Chung, John D. Crouse
James S. Dickson
The attachment of bacteria (Serratia marcescens, Staphylococcus aureus, Streptococcus faecalis, Salmonella arizonae, Pseudomonas aeruginosa, and Listeria monocytogenes), to lean muscle tissue and fat tissue was investigated. The number of cells attached to the meat was directly proportional to the initial cell concentrations present. There was no significant difference in the number of cells attached between the lean muscle tissue and fat tissues among the organisms tested. All bacteria tested except P. aeruginosa proliferated better on the lean muscle tissues than on the fat tissue at ambient temperature for 72 h. No significant attachment competition to tissue samples was seen between …
An Electrochemical Method Of Measuring The Oxidation Rate Of Ferrous To Ferric Iron With Oxygen In The Presence Of Thiobacillus Ferrooxidans, David J. Oliver, B. Pesic, P. Wichlacz
An Electrochemical Method Of Measuring The Oxidation Rate Of Ferrous To Ferric Iron With Oxygen In The Presence Of Thiobacillus Ferrooxidans, David J. Oliver, B. Pesic, P. Wichlacz
David J. Oliver
The oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+ < 0.001M, T < 25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression: [equation image] Below pH = 2.2, the oxidation rate is independent of H+ Concentration.