College of Engineering

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The College of Engineering at Montana State University will serve the State of Montana and the nation by fostering lifelong learning, integrating learning and discovery, developing and sharing technical expertise, and empowering students to be tomorrow's leaders.

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10 Steps to Implementing Health in All Policies in Rural Communities
(Western Transportation Institute, 2024-08) Comey, Danika; Madsen, Matthew
This toolkit serves as a guiding document for frontier, rural, and micro-urban communities to implement a Health in All Policies (HiAP) framework in rural America. Too often, rural America is overlooked when it comes to public health and policy work. This tool will guide public health practitioners, community planners, elected officials, healthcare providers, and those who are interested in improving community and public health by analyzing and improving local policy in rural communities. Barriers to accessing healthcare services are well documented in rural communities. Rural populations often face greater challenges accessing healthcare services compared to their urban peers such as long distances to primary care, lower insurance coverage rates, higher health needs, and higher rates of poverty [1–4]. Incorporating a HiAP framework in rural areas is an effective way to decrease health inequities and disparities between urban and rural communities.
A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core
(2017-05) D'Andrilli, Juliana; Foreman, Christine M.; Sigl, Michael; Priscu, John C.; McConnell, Joseph R.
Englacial ice contains a significant reservoir of organic material (OM), preserving a chronological record of materials from Earth's past. Here, we investigate if OM composition surveys in ice core research can provide paleoecological information on the dynamic nature of our Earth through time. Temporal trends in OM composition from the early Holocene extending back to the Last Glacial Maximum (LGM) of the West Antarctic Ice Sheet Divide (WD) ice core were measured by fluorescence spectroscopy. Multivariate parallel factor (PARAFAC) analysis is widely used to isolate the chemical components that best describe the observed variation across three-dimensional fluorescence spectroscopy (excitation–emission matrices; EEMs) assays. Fluorescent OM markers identified by PARAFAC modeling of the EEMs from the LGM (27.0–18.0 kyr BP; before present 1950) through the last deglaciation (LD; 18.0–11.5 kyr BP), to the mid-Holocene (11.5–6.0 kyr BP) provided evidence of different types of fluorescent OM composition and origin in the WD ice core over 21.0 kyr. Low excitation–emission wavelength fluorescent PARAFAC component one (C1), associated with chemical species similar to simple lignin phenols was the greatest contributor throughout the ice core, suggesting a strong signature of terrestrial OM in all climate periods. The component two (C2) OM marker, encompassed distinct variability in the ice core describing chemical species similar to tannin- and phenylalanine-like material. Component three (C3), associated with humic-like terrestrial material further resistant to biodegradation, was only characteristic of the Holocene, suggesting that more complex organic polymers such as lignins or tannins may be an ecological marker of warmer climates. We suggest that fluorescent OM markers observed during the LGM were the result of greater continental dust loading of lignin precursor (monolignol) material in a drier climate, with lower marine influences when sea ice extent was higher and continents had more expansive tundra cover. As the climate warmed, the record of OM markers in the WD ice core changed, reflecting shifts in carbon productivity as a result of global ecosystem response..
A 3-D constitutive model for finite element analyses of agarose with a range of gel concentrations
(Elsevier BV, 2020-11) Wang, Xiaogang; June, Ronald K.; Pierce, David M.
Hydrogels have seen widespread application across biomedical sciences and there is considerable interest in using hydrogels, including agarose, for creating in vitro three-dimensional environments to grow cells and study mechanobiology and mechanotransduction. Recent advances in the preparation of agarose gels enable successful encapsulation of viable cells at gel concentrations as high as 5%. Agarose with a range of gel concentrations can thus serve as an experimental model mimicking changes in the 3-D microenvironment of cells during disease progression and can facilitate experiments aimed at probing the corresponding mechanobiology, e.g. the evolving mechanobiology of chondrocytes during the progression of osteoarthritis. Importantly, whether stresses (forces) or strains (displacements) drive mechanobiology and mechanotransduction is currently unknown. We can use experiments to quantify mechanical properties of hydrogels, and imaging to estimate microstructure and even strains; however, only computational models can estimate intra-gel stresses in cell-seeded agarose constructs because the required in vitro experiments are currently impossible. Finite element modeling is well-established for (computational) mechanical analyses, but accurate constitutive models for modeling the 3-D mechanical environments of cells within high-stiffness agarose with varying gel concentrations are currently unavailable. In this study we aimed to establish a 3-D constitutive model of high-stiffness agarose with a range of gel concentrations. We applied a multi-step, physics-based optimization approach to separately fit subsets of model parameters and help achieve robust convergence. Our constitutive model, fitted to experimental data on progressive stress-relaxations, was able to predict reaction forces determined from independent experiments on cyclical loading. Our model has broad applications in finite element modeling aimed at interpreting mechanical experiments on agarose specimens seeded with cells, particularly in predicting distributions of intra-gel stresses. Our model and fitted parameters enable more accurate finite element simulations of high-stiffness agarose constructs, and thus better understanding of experiments aimed at mechanobiology, mechanotransduction, or other applications in tissue engineering.
A 3D computer model analysis of three hypothetical biofilm detachment mechanisms
(2007-08) Chambless, Jason D.; Stewart, Philip S.
Three hypothetical mechanisms of detachment were incorporated into a three-dimensional computer model of biofilm development. The model integrated processes of substrate utilization, substrate diffusion, growth, cell advection, and detachment in a cellular automata framework. The purpose of this investigation was to characterize each of the mechanisms with respect to four criteria: the resulting biofilm structure, the existence of a steady state, the propensity for sloughing events, and the dynamics during starvation. The three detachment mechanisms analyzed represented various physical and biological influences hypothesized to affect biofilm detachment. The first invoked the concept of fluid shear removing biomass that protrudes far above the surface and is therefore subjected to relatively large drag forces. The second pathway linked detachment to changes in the local availability of a nutrient. The third pathway simulated an erosive process in which individual cells are lost from the surface of a biofilm cell cluster. The detachment mechanisms demonstrated diverse behaviors with respect to the four analysis criteria. The height dependant mechanism produced flat, steady state biofilms that lacked sloughing events. Detachment based on substrate limitation produced significant sloughing events. The resulting biofilm structures included distinct, hollow clusters separated by channels. The erosion mechanism produced neither a non-zero steady state nor sloughing events. A mechanism combining all three detachment mechanisms produced mushroom-like structures. The dynamics of biofilm decay during starvation were distinct for each detachment mechanism. These results show that detachment is a critical determinant of biofilm structure and of the dynamics of biofilm accumulation and loss.
A 3D model of antimicrobial action on biofilms
(2005) Hunt, Stephen Michael; Hamilton, Martin A.; Stewart, Philip S.
A three-dimensional cellular automata model of biofilm dynamics was adapted to simulate the protection from killing by antimicrobial agents afforded to microorganisms in the biofilm state. The model incorporated diffusion and simultaneous utilization of a single substrate, growth and displacement of cells, detachment, and killing by an antimicrobial agent. The rate of killing was assumed to be directly proportional to the local concentration of substrate available to the microorganisms. Some of the features predicted by this model included development of dynamic, heterogeneous biofilm structures, gradients in substrate concentration leading to regions of substrate depletion in the interior of large cell clusters, variable killing by an antimicrobial agent from one simulation to the next, greater killing of cells at the periphery of cell clusters compared to those cells which were more deeply embedded, and reduced overall antimicrobial susceptibility of cells in the biofilm. These simulations show that substrate limitation can contribute to the protection from antimicrobial agents in biofilms but cannot explain the long-term persistence of biofilm viability that is often observed in practice.
A Case Study Comparison of Undergraduate Education and Engineering Majors’ Understanding of Community Engineering
(Informa UK Limited, 2024-06) Vo, Tina; Hammack, Rebekah; Gannon, Paul; Lux, Nicholas; Wiehe, Blake; Moonga, Miracle; LaMeres, Brock
As we prepare teachers to provide students with opportunities within STEM education, authentic experiences should guide the instruction. Unfortunately, due to the novel integration of engineering into national reform documents, there is a dearth of documentation on elementary preservice teachers’ engineering ideas as they align with student goals (e.g. enrolling in an engineering program). As teachers must provide authentic science experiences to help frame the work of scientists for students, creating authentic engineering experiences should frame the work of engineers. Thus, it is important to foundationally investigate how elementary preservice teachers’ ideas about engineering reflect those of novice engineers. This research uses multiple case study to investigate and compare teaching and engineering majors’ understanding of engineering within their communities. Additionally, while there were some similarities across groups, engineering majors were more likely to speak to the science behind the artifacts represented in the photo novellas they authored, and the preservice teachers found a larger variety and diversity of engineering elements. Findings indicate that these groups have fundamentally different perspectives on engineering and how it is manifested within the communities. This has implications for upper tiers of education as elementary teachers lay broad engineering foundations, while middle, high school, and community colleges must methodically highlight engineering disciplines to provide more authentic experiences, highlighting the connections between engineering, science, and math.
A Comprehensive Study of Walmart Sales Predictions Using Time Series Analysis
(Sciencedomain International, 2024-06) C., Cyril Neba; F., Gerard Shu; Nsuh, Gillian; A., Philip Amouda; F., Adrian Neba; Webnda, F.; Ikpe, Victory; Orelaja, Adeyinka; Sylla, Nabintou Anissia
This article presents a comprehensive study of sales predictions using time series analysis, focusing on a case study of Walmart sales data. The aim of this study is to evaluate the effectiveness of various time series forecasting techniques in predicting weekly sales data for Walmart stores. Leveraging a dataset from Kaggle comprising weekly sales data from various Walmart stores around the United States, this study explores the effectiveness of time series analysis in forecasting future sales trends. Various time series analysis techniques, including Auto Regressive Integrated Moving Average (ARIMA), Seasonal Auto Regressive Integrated Moving Average (SARIMA), Prophet, Exponential Smoothing, and Gaussian Processes, are applied to model and forecast Walmart sales data. By comparing the performance of these models, the study seeks to identify the most accurate and reliable methods for forecasting retail sales, thereby providing valuable insights for improving sales predictions in the retail sector. The study includes an extensive exploratory data analysis (EDA) phase to preprocess the data, detect outliers, and visualize sales trends over time. Additionally, the article discusses the partitioning of data into training and testing sets for model evaluation. Performance metrics such as Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE) are utilized to compare the accuracy of different time series models. The results indicate that Gaussian Processes outperform other models in terms of accuracy, with an RMSE of 34,116.09 and an MAE of 25,495.72, significantly lower than the other models evaluated. For comparison, ARIMA and SARIMA models both yielded an RMSE of 555,502.2 and an MAE of 462,767.3, while the Prophet model showed an RMSE of 567,509.2 and an MAE of 474,990.8. Exponential Smoothing also performed well with an RMSE of 555,081.7 and an MAE of 464,110.5. These findings suggest the potential of Gaussian Processes for accurate sales forecasting. However, the study also highlights the strengths and weaknesses of each forecasting methodology, emphasizing the need for further research to refine existing techniques and explore novel modeling approaches. Overall, this study contributes to the understanding of time series analysis in retail sales forecasting and provides insights for improving future forecasting endeavors.
A New Approach for Identifying Safety Improvement Sites on Rural Highways: A Validation Study
(MDPI AG, 2024-02) Dhakal, Bishal; Al-Kaisy, Ahmed
The research presented in this paper examines a new proposed approach for identifying safety improvement sites on rural highways. Unlike conventional approaches, the proposed approach does not require crash history, but rather utilizes classified variables for traffic volume, geometric features, and roadside characteristics that do not require access to exact data or extensive technical expertise. The research validates the performance of the proposed approach using field data from a large sample of rural two-lane highway segments in the state of Oregon including traffic, roadway, and crash data. A mathematical model for the prediction of the EB expected number of crashes using multivariate regression analysis is developed and used as the network screening criterion. The model’s independent variables include roadway geometry, roadside characteristics, and traffic exposure, while the dependent variable is the EB expected number of crashes. Using observed crash history as a reference, the performance of the proposed approach was compared to two of the well-established methods in practice, namely, the Empirical Bayes (EB) and the potential for safety improvement (PSI) methods. The study results suggest that by using crash density for highway segments, the performance of the proposed method was lower than that of the EB and PSI methods. This is despite the high R-square value of the predictive model used in the proposed method. However, when using crash frequencies for highway segments, the performance of the proposed method was found comparable to the well-established EB and PSI methods.
A Novel Network Screening Methodology for Rural Low-Volume Roads
(Scientific Research Publishing, Inc., 2023-01) Al-Kaisy, Ahmed; Raza, Sajid
Low-volume roads (LVRs) are an integral part of the rural transportation network providing access to remote rural areas and facilitating the movement of goods from farms to markets. These roads pose unique challenges for highway agencies including those related to safety management on the highway network. Specifically, traditional network screening methods using crash history can be effective in screening rural highways with higher traffic volumes and more frequent crashes. However, these traditional methods are often ineffective in screening LVR networks due to low traffic volumes and the sporadic nature of crash occurrence. Further, many of the LVRs are owned and operated by local agencies that may lack access to detailed crash, traffic and roadway data and the technical expertise within their staff. Therefore, there is a need for more efficient and practical network screening approaches to facilitate safety management programs on these roads. This study proposes one such approach which utilizes a heuristic scoring scheme in assessing the level of risk/safety for the purpose of network screening. The proposed scheme is developed based on the principles of US Highway Safety Manual (HSM) analysis procedures for rural highways and the fundamentals in safety science. The primary application of the proposed scheme is for ranking sites in network screening applications or for comparing multiple improvement alternatives at a specific site. The proposed approach does not require access to detailed databases, technical expertise, or exact information, making it an invaluable tool for small agencies and local governments (e.g. counties, townships, tribal governments, etc.).
A Review on Recent Progress of Biodegradable Magnetic Microrobots for Targeted Therapeutic Delivery: Materials, Structure Designs, and Fabrication Methods
(ASME International, 2024-08) Cao, Yang; Nunez Michel, Karen; Alimardani, Farzam; Wang, Yi
Targeted therapeutic delivery employs various technologies to enable precise delivery of therapeutic agents (drugs or cells) to specific areas within the human body. Compared with traditional drug administration routes, targeted therapeutic delivery has higher efficacy and reduced medication dosage and side effects. Soft microscale robotics have demonstrated great potential to precisely deliver drugs to the targeted region for performing designated therapeutic tasks. Microrobots can be actuated by various stimuli, such as heat, light, chemicals, acoustic waves, electric fields, and magnetic fields. Magnetic manipulation is well-suited for biomedical applications, as magnetic fields can safely permeate through organisms in a wide range of frequencies and amplitudes. Therefore, magnetic actuation is one of the most investigated and promising approaches for driving microrobots for targeted therapeutic delivery applications. To realize safe and minimally invasive therapies, biocompatibility and biodegradability are essential for these microrobots, which eliminate any post-treatment endoscopic or surgical removals. In this review, recent research efforts in the area of biodegradable magnetic microrobots used for targeted therapeutic delivery are summarized in terms of their materials, structure designs, and fabrication methods. In the end, remaining challenges and future prospects are discussed.
Abandoned well CO2 leakage mitigation using biologically induced mineralization: Current progress and future directions
(2013-02) Cunningham, Alfred B.
Methods of mitigating leakage or re-plugging abandoned wells before exposure to CO2are of high potential interest to prevent leakage of CO2 injected for geologic carbon sequestration in depleted oil and gas reservoirs where large numbers of abandoned wells are often present. While CO2resistant cements and ultrafine cements are being developed, technologies that can be delivered via low viscosity fluids could have significant advantages including the ability to plug small aperture leaks such as fractures or delamination interfaces. Additionally there is the potential to plug rock formation pore space around the wellbore in particularly problematic situations. We are carrying out research on the use of microbial biofilms capable of inducing the precipitation of crystalline calcium carbonate using the process of ureolysis. This method has the potential to reduce well bore permeability, coat cement to reduce CO2â€“related corrosion, and lower the risk of unwanted upward CO2 migration. In this spotlight, we highlight research currently underway at the Center for Biofilm Engineering (CBE) at Montana State University (MSU) in the area of ureolytic biomineralization sealing for reducing CO2 leakage risk. This research program combines two novel core testing systems and a 3-dimensional simulation model to investigate biomineralization under both radial and axial flow conditions and at temperatures and pressures which permit CO2 to exist in the supercritical state.This combination of modeling and experimentation is ultimately aimed at developing and verifying biomineralization sealing technologies and strategies which can successfully be applied at the field scale for carbon capture and geological storage (CCGS) projects.
ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios
(Springer, 2010-02) Yang, Qing; Lim, Alvin; Li, Shuang; Fang, Jian; Agrawal, Prathima
Multi-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.
Accelerated Gibbs sampling of normal distributions using matrix splittings and polynomials
(2017-11) Fox, Colin; Parker, Albert E.
Standard Gibbs sampling applied to a multivariate normal distribution with a specified precision matrix is equivalent in fundamental ways to the Gauss-Seidel iterative solution of linear equations in the precision matrix. Specifically, the iteration operators, the conditions under which convergence occurs, and geometric convergence factors (and rates) are identical. These results hold for arbitrary matrix splittings from classical iterative methods in numerical linear algebra giving easy access to mature results in that field, including existing convergence results for antithetic-variable Gibbs sampling, REGS sampling, and generalizations. Hence, efficient deterministic stationary relaxation schemes lead to efficient generalizations of Gibbs sampling. The technique of polynomial acceleration that significantly improves the convergence rate of an iterative solver derived from a symmetric matrix splitting may be applied to accelerate the equivalent generalized Gibbs sampler. Identicality of error polynomials guarantees convergence of the inhomogeneous Markov chain, while equality of convergence factors ensures that the optimal solver leads to the optimal sampler. Numerical examples are presented, including a Chebyshev accelerated SSOR Gibbs sampler applied to a stylized demonstration of low-level Bayesian image reconstruction in a large 3-dimensional linear inverse problem.
Accumulation of a biofilm of k. pneumoniae and p. aeruginosa
(1989-12) Siebel, M. A.; Characklis, William G.
The accuracy of oxygen flux measurements using microelectrodes
(1998-12) Rasmussen, Kjetil; Lewandowski, Zbigniew
An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a flat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the oxygen profiles above and within the graphite felt. From the shape of the oxygen profile we evaluated the oxygen flux to the graphite felt. This provided us with two sets of data, the true oxygen flux, calculated from polarization current, and the oxygen flux estimated from microelectrode measurements. Comparing these two fluxes, for different flow velocities, showed that the fluxes evaluated from the polarization current were different from those evaluated from the oxygen profiles. The differences were likely caused by the presence of the microelectrode in the mass boundary layer and/or by the simplifying assumptions accepted in computational procedures employed to calculate oxygen fluxes. For low flow velocities, between zero and 1.0 cm s−1, the differences were velocity sensitive; the higher the flow velocity, the bigger the difference. For higher flow velocities, between 1 cm s−1 and 3 cm s−1, the flux of oxygen estimated from the microelectrode measurements was consistently approximately 80% higher than the true oxygen flux estimated from the polarization current.
Actin recruitment to the Chlamydia inclusion is spatiotemporally regulated by a mechanism that requires host and bacterial factors
(2012-10) Chin, E.; Kirker, Kelly R.; Zuck, Meghan; James, Garth A.; Hybiske, K.
The ability to exit host cells at the end of their developmental growth is a critical step for the intracellular bacterium Chlamydia. One exit strategy, extrusion, is mediated by host signaling pathways involved with actin polymerization. Here, we show that actin is recruited to the chlamydial inclusion as a late event, occurring after 20 hours post-infection (hpi) and only within a subpopulation of cells. This event increases significantly in prevalence and extent from 20 to 68 hpi, and actin coats strongly correlated with extrusions. In contrast to what has been reported for other intracellular pathogens, actin nucleation on Chlamydia inclusions did not â€˜flashâ€™, but rather exhibited moderate depolymerization dynamics. By using small molecule agents to selectively disrupt host signaling pathways involved with actin nucleation, modulate actin polymerization dynamics and also to disable the synthesis and secretion of chlamydial proteins, we further show that host and bacterial proteins are required for actin coat formation. Transient disruption of either host or bacterial signaling pathways resulted in rapid loss of coats in all infected cells and a reduction in extrusion formation. Inhibition of Chlamydia type III secretion also resulted in rapid loss of actin association on inclusions, thus implicating chlamydial effector proteins(s) as being central factors for engaging with host actin nucleating factors, such as formins. In conclusion, our data illuminate the host and bacterial driven process by which a dense actin matrix is dynamically nucleated and maintained on the Chlamydia inclusion. This late stage event is not ubiquitous for all infected cells in a population, and escalates in prevalence and extent throughout the developmental cycle of Chlamydia, culminating with their exit from the host cell by extrusion. The initiation of actin recruitment by Chlamydia appears to be novel, and may serve as an upstream determinant of the extrusion mechanism
Action of antimicrobial substances produced by different oil reservoir Bacillus strains against biofilm formation
(2008-03) Korenblum, E.; Sebastián, G. V.; Paiva, M. M.; Coutinho, C. M. L. M.; Magalhães, F. C. M.; Peyton, Brent M.; Seldin, L.
Microbial colonization of petroleum industry systems takes place through the formation of biofilms, and can result in biodeterioration of the metal surfaces. In a previous study, two oil reservoir Bacillus strains (Bacillus licheniformis T6-5 and Bacillus firmus H2O-1) were shown to produce antimicrobial substances (AMS) active against different Bacillus strains and a consortium of sulfate-reducing bacteria (SRB) on solid medium. However, neither their ability to form biofilms nor the effect of the AMS on biofilm formation was adequately addressed. Therefore, here, we report that three Bacillus strains (Bacillus pumilus LF4-used as an indicator strain, B. licheniformis T6-5, and B. firmus H2O-1, and an oil reservoir SRB consortium (T6lab) were grown as biofilms on glass surfaces. The AMS produced by strains T6-5 and H2O-1 prevented the formation of B. pumilus LF4 biofilm and also eliminated pre-established LF4 biofilm. In addition, the presence of AMS produced by H2O-1 reduced the viability and attachment of the SRB consortium biofilm by an order of magnitude. Our results suggest that the AMS produced by Bacillus strains T6-5 and H2O-1 may have a potential for pipeline-cleaning technologies to inhibit biofilm formation and consequently reduce biocorrosion.
Action of chlorhexidine digluconate against yeast and filamentous forms in an early-stage candida albicans biofilm
(2002-11) Suci, Peter A.; Tyler, Bonnie J.
An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded into the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t-test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.
Action of glutaraldehyde and nitrite against sulfate-reducing bacterial biofilms
(2002-12) Gardner, Lawrence Robert; Stewart, Philip S.
A continuous flow reactor system was developed to evaluate the efficacy of antimicrobial treatments against sulfate-reducing bacterial biofilms. An annular reactor operating at a nominal dilution rate of 0.5 h-1 was fed one-tenth strength Postgate C medium diluted in 1.5% NaCl and was inoculated with a mixed culture enriched from oilfield-produced water on the same medium. Thin biofilms developed in this reactor after 2 days of operation. The activity of these biofilms resulted in approximately 50 mg S l-1 of sulfide at steady state prior to biocide treatment. Biocide efficacy was quantified by recording the time required for sulfide production to recover following an antimicrobial treatment. In a control experiment in which pure water was applied, the time required to reach 10 mg S l-1 sulfide after the treatment was 1.7±1.2 h, whereas the time to reach this level of sulfide after a pulse dose of 500 mg l-1 glutaraldehyde was delayed to 61±11 h. Nitrite treatment suppressed sulfide production as long as the nitrite concentration remained above 15 mg N l-1. Sulfide production recovered more rapidly after nitrite treatment than it did after glutaraldehyde treatment. Gardner, L.R., P.S. Stewart, "Action of Glutaraldehyde and Nitrite Against Sulfate-Reducing Bacterial Biofilms," J. Industrial Microbiol. Biotech. 29(6):354 (2002).
Activity and stability of a recombinant plasmid-borne tce degradative pathway in biofilm cultures
(1998-08) Sharp, Robert R.; Bryers, James D.; Jones, Wallace E.
The activity and stability of the TCE degradative plasmid TOM31c in the transconjugant host Burkholderia cepacia 17616 was studied in selective and non-selective biofilm cultures. The activity of plasmid TOM31c in biofilm cultures was measured by both TCE degradative studies and the expression of the Tom pathway. Plasmid loss was measured using continuous flow, rotating annular biofilm reactors, and various analytical and microbiological techniques. The probability of plasmid loss in the biofilm cultures was determined using a non-steady-state biofilm plasmid loss model that was derived from a simple mass balance, incorporating results from biofilm growth and plasmid loss studies. The plasmid loss model also utilized Andrew's inhibition growth kinetics and a biofilm detachment term. Results from these biofilm studies were compared to similar studies performed on suspended cultures of Burkholderia cepacia 17616-TOM31c to determine if biofilm growth has a significant effect on either plasmid retention or Tom pathway expression (i.e., TCE degradation rates). Results show that the activity and expression of the Tom pathway measured in biofilm cultures was significantly less than that found in suspended cultures at comparable growth rates. The data obtained from these studies fit the plasmid loss model well, providing plasmid loss probability factors for biofilm cultures that were equivalent to those previously found for suspended cultures. The probability of plasmid loss in the B. cepacia 17616-TOM31c biofilm cultures was equivalent to those found in the suspended cultures. The results indicate that biofilm growth neither helps nor hinders plasmid stability. In both the suspended and the biofilm cultures, plasmid retention and expression could be maintained using selective growth substrates and/or an appropriate plasmid-selective antibiotic.