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Deciphering Genetic Contributions to Antibiotic Persistence: Insights from Multi-Gene Knockout Studies
No full textAntibiotic resistance is a critical global health challenge, complicating efforts to treat bacterial infections effectively. Antibiotic persistence plays a significant role in driving resistance. Persisters are a subpopulation of non-dividing bacterial cells that often evade lethal antibiotic treatment. Once antibiotics are removed, these cells resurrect, resuming growth and may lead to relapsing infections. Notably, the progeny of persister cells exhibit a heightened tendency to acquire mutations or incorporate antibiotic resistance genes, further compounding the challenge of antibiotic resistance. In our recent study, we knocked out seven hypothetical genes and observed a significant reduction in persister levels. Compared to the wild type, mutants exhibited 4-6-fold fewer persisters after 3 hours and 10-15-fold fewer persisters after 6 hours of lethal ampicillin treatment. However, at 24 hours and beyond (48 and 72 hours), no significant difference in survival was detected between the mutants and the wild type. These findings align with our previous hypothesis that individual cells within a clonal population use distinct survival strategies, resulting in multiple persister genotypes. The seven genes may function in a single pathway or in multiple pathways, contributing to persister survival during the medium-term phase of antibiotic exposure. To investigate further, we constructed double and triple gene knockouts. While most of the mutants showed no growth defects, one double mutant did. Triple mutants exhibited significantly reduced persister levels at 3 hours compared to the wild type. Utilizing the Minimum Inhibitory Concentration (MIC) Agar Dilution Test, we quantitatively demonstrated that several mutants exhibit increased antibiotic sensitivity compared to the wild type. This assay precisely measures the effects of even minimal antibiotic concentrations on bacterial growth, yielding critical insights that other methods we tried could not provide. We show that in some cases, conventional antibiotic strip tests lacked the sensitivity needed to detect subtle reductions in MIC for some mutants, a limitation overcome by the Agar Dilution Test. Researchers often compare MIC values between wild-type and mutant strains to assess the impact of specific genetic alterations, and our findings highlight that the Agar Dilution Test can offer a more precise and sensitive alternative to strip tests in certain contexts
Impact of Natural Feed Additives and Monensin Sodium on Growth Performance in Feedlot Cattle
No full textThe objective of this dissertation was to investigate how phytogenic feed additives and a pulse feeding monensin sodium strategy would affect growth performance in the receiving and finishing feedlot phases. Three randomized complete block design feedlot experiments and one pooled analysis were conducted to determine the effects of the feed additives and management strategies used in newly weaned and finishing beef cattle. The objective of these experiments were 1) determine if a blend of capsicum oleoresin, clove essential oil, and garlic essential oil (CCG) influences cattle performance, sera metabolites or health outcomes during the feedlot receiving phase; 2) determine if CCG influences growth performance and carcass traits during the finishing phase; 3) pool data from 4 studies to determine the effects of supplementation of CCG on growth performance of steers and intact-bulls; and 4) evaluate the effects of pulse feeding monensin sodium on growth performance, carcass characteristics, and liver abscesses in feedlot cattle. Experiment 1 used Charolais × Angus steers (n = 256; iBW = 273 ± 26 kg) in a 56 d receiving trial. Steers were allotted to 1 of 32 pens (n = 8 steers; 8 pens/treatment) and assigned to treatments: no test product (MON); CCG at 125 mg/steer/d (CCG125); CCG at 250 mg/steer/d (CCG250); or CCG at 500 mg/steer/d (CCG500). MON and CCG500 had greater DMI (quadratic effect; P = 0.01). However, CCG did not improve ADG, nor G:F (P ≥ 0.15). On d 14, CCG500 had elevated NEFA compared to the other treatments (P ≤ 0.05). Ceruloplasmin was decreased (P = 0.04) in steers from CCG250 and CCG500. There was no effect of supplementation on health outcomes (P ≥ 0.12). Experiment 2 used Charolais × Angus steers (n = 96; iBW = 391 ± 34.0 kg) in a 144 d feedlot finishing trial. Steers were weighed and allotted to 1 of 14 pens (6 to 7 steers; 7 pens/treatment) and assigned to 1 of 2 treatments: control diet without the test product (CON) or a diet including CCG at 500 mg/steer daily (CCG). There were no differences (P ≥ 0.10) in any growth performance outcomes from d 1 to 35, 36 to 70, or 71 to 98. From d 99 to 144 steers from CCG tended to have 5% greater average daily gain (P = 0.09) and 8% improved feed conversion (G:F) (P = 0.01). No differences (P ≥ 0.15) were noted for cumulative growth performance measures. No differences were noted for any carcass measurements or categorical carcass outcomes, nor lung or liver health outcomes (P ≥ 0.15). For study 3, data was pooled from experiments in South Dakota (n = 2) and Oklahoma (n = 2), and 1701 steers and 341 intact bulls were used with an iBW of 320 kg (SEM = 1.3) and enrolled into 64 pens (32 pens per treatment) with 6 to 80 head per pen. Within each study, pens were assigned to 1 of 2 treatments: 1) non-supplemented control (CON); 2) supplemented with 500 mg/steer daily of CCG. Receiving and finishing period were analyzed separately and combined No statistical differences were observed for any growth performance measurements during the receiving period (P ≥ 0.16). However, during the finishing period, supplemented steers had improved G:F by 2.3% (P = 0.04) and tended to have a greater ADG by 1.7% (P = 0.07). When the data was analyzed combined, steers that were supplemented with CCG had improved G:F by 2.8% (P = 0.02) and ADG tended to be 2.0% greater (P = 0.07). Experiment 4 used Charolais × Angus steers (n = 64; initial shrunk BW = 450 kg) in a 165 -d finishing feedlot trial. Steers were allotted in 1 of 10 pens (n = 6 to 7 steers; 5 pens/treatment). Treatments were 1) continuous monensin sodium feeding (MON) 2) pulse feeding monensin sodium (PF). The monensin sodium feeding regimen for PF entailed a 28-d administration period, followed by a subsequent 28-d withholding period without monensin. There were no differences (P ≥ 0.11) in any growth performance outcomes from d 1 to 111, and 140 to 165. However, from d 112 to 139, MON steers tended to have greater ADG (P = 0.09), and improved G:F (P = 0.02). No differences were noted for cumulative growth performance (P ≥ 0.59). No differences were noted for any carcass measurements or categorical carcass outcomes, nor liver health outcomes (P ≥ 0.34). The results from the studies in this dissertation suggest that supplementation with CCG positively influences growth performance in beef steers and intact bulls fed diets containing monensin sodium. Furthermore, this response is consistent across multiple phases of growth and management conditions. Additionally, pulse feeding monensin sodium did not compromise overall growth performance or carcass characteristics compared to continuous supplementation. Notably, comparable performance was achieved using only half the total monensin sodium dosage provided to the MON group. These findings indicate potential for both strategies to enhance production efficiency. Further research is warranted to investigate interactions with diet composition, cattle type, and management systems to optimize their application in commercial feedlot settings
Belowground Response of C3 and C4 Grass Dominated Plant Communities to Future Larger and Less Frequent Rainfall Events
No full textData description: Month: Time of data collection from 2020 to 2022. Plant community: C3 plant community and C4 plant community. Treatment: ambient treatment and manipulated treatment. AMF: Arbuscular Mycorrhizal Fungi concentration (ng C g-1 Soil). F: Fungi concentration (ng C g-1 Soil). GP: Gram-Positive bacteria concentration (ng C g-1 Soil). GN: Gram-Negative bacteria concentration (ng C g-1 Soil). Actinomycetes: concentration (ng C g-1 Soil). Saprophytes: concentration (ng C g-1 Soil). F:B: The ratio of Fungi concentration over sum of Gram-Positive and Gram-Negative bacteria concentration. GP:GN: The ratio of Gram-Positive bacteria concentration over Gram-Negative bacteria concentration.
File type: zip/application (Contains .xlxs & .txt files)File size: 14K
Cover Cropping Strategies for Improving Weed Suppression
Full text linkCover crops (CCs) play an essential role in sustainable agriculture by providing multiple ecosystem services. However, adoption remains low due to concerns about economic returns, management complexity, and potential yield reductions in cash crops. Applying CCs uniformly across fields without accounting for spatial variability can result in inconsistent outcomes. A precision cover cropping system (PCCS), which incorporates site-specific management zones (MZs), offers a more targeted approach to improving performance while minimizing costs and uncertainties. This study explores the interaction between CCs and field variability through complementary field and greenhouse experiments. The field experiment demonstrates that field heterogeneity significantly influences CC effectiveness, particularly weed suppression. Varying seeding rates of cereal rye revealed that both CC biomass and suppression efficacy varied across MZs, highlighting the limitations of uniform applications. The greenhouse experiment evaluates how different CC species affect soil properties under controlled conditions. Results show species-specific effects on soil characteristics, emphasizing the importance of aligning species selection with site-specific agronomic goals. Overall, this research highlights the need for a precision-based approach to CC management, where MZs are used to tailor species selection, seeding rates, and operational practices based on field-specific characteristics
Design and Optimization of the Injection Molding Process of Glass Fiber Reinforced Polymeric Car Fender Using Computational Simulation
Full text linkThe increasing demand for lightweight and energy-efficient materials in the automotive industry has accelerated the adoption of fiber-reinforced polymer composites. This research presents the design and optimization of the injection molding process for glass fiber-reinforced polymer (GFRP) car fenders using computational simulation. The effects of various gate types and locations on key process parameters, including fiber orientation, volumetric shrinkage, shear rate, and fill time, were investigated using Finite Element Analysis (FEA), Autodesk Moldflow Insight 2024, and MATLAB-based Multi-Criteria Decision-Making (MCMD) techniques. Simulations were conducted across multiple configurations involving three, four, and five gates, with several variations in location. Among all, the four-gate configuration at Location 2 exhibited the most optimal performance. This location demonstrated the lowest shrinkage, stable and consistent fiber orientation, and a manageable shear rate, indicating superior dimensional accuracy and process stability. Fiber orientation was predicted using the Folgar-Tucker model, and the Tsai-Wu criterion was implemented to assess stress distribution without directly estimating mechanical strength. The results determine the crucial role of gate placement in influencing material behavior during molding and reducing common flaws. A simulation-driven method for optimizing injection molding settings is presented in this paper, enabling increased production efficiency, reduced trial-and-error, and improved quality control. The study presents a valuable approach for enhancing the production of GFRP car components by integrating process simulation and decision-making frameworks. These findings can inform future mold design strategies in the automotive sector, leading to improved quality control, reduced trial-and-error processes, and enhanced production efficiency
What Do We Get Out of Our Entertainment? Empirically Determining the Differences Between Narrative Engagement and Flow Using Video Games
Full text linkImmersion is an important aspect of entertainment media because it both drives the use of media and heightens one’s experience with that media (Nilsson et al., 2016). There are three core aspects of immersion. These aspects are (1) narrative engagement, (2) flow, and (3) enjoyment. This study set out to determine whether these aspects are statistically distinct from one another when observed in video games. The result indicated that these aspects were distinct from one another when examined through a structural equation model. This indicates that creating an overarching immersion variable that combines the different aspects of immersion may not be beneficial as it would leave out aspects of immersion. However, measures used in an attempt to influence narrative engagement and flow, narrative richness and gamification failed to have any impact. Therefore, future research should be done on how to better manipulate richness and gamification in an effort to influence narrative engagement and flow
Effect of Six-Day Germination on Chemical Composition, Functional, and Nutritional Properties of Pea Varieties
Full text linkPulses, particularly peas, have long been a crucial source of protein in vegetarian and cost-effective diets worldwide. They have gained popularity in Western diets as more people turn to plant-based proteins as alternatives to animal products. Peas are known for their high protein content; however, their use in food products has been limited due to factors like poor solubility and digestibility. Germination improves the nutritional profile of peas by enhancing protein content and digestibility. The objective of this study was to determine the effects of six days of germination on the nutritional composition and functional properties of different varieties of peas. In this study, germinated pea seeds were milled into flour, and nutritional composition and functional properties were determined. Germination caused variations in nutritional composition across pea varieties and days. Most varieties showed increases in moisture and protein content over time. In-vitro protein digestibility also varied significantly with both day and variety. Insoluble and soluble dietary fiber percentages increased, with soluble fiber changing significantly. Ash content decreased across all varieties, and fat content fluctuated during germination. The B- vitamins changed significantly, with thiamine and niacin generally increasing while folic acid decreased. Riboflavin and pyridoxine content fluctuate across varieties, reflecting varied effects of germination. Germination significantly impacted the functional properties of pea flours. Antioxidant activity increased significantly, with the AGA variety showing the highest ability, reflecting enhanced activity from the release of bioactive compounds. Protein content increased, while amylose and total starch fluctuated. The effect of germination on amylose and total starch varied depending on the variety. Changes in pasting properties were observed, with peak viscosity increasing, while setback and final viscosities generally decreased. Gel strength increased at first but decreased by day 6, reflecting changes in starch during germination. Significant changes were observed in protein structure, including shifts in secondary structures such as increased random coils and β-turns, along with protein aggregation in some varieties. Functional properties such as water absorption, foaming capacity, and emulsification capacity also varied over time. These findings demonstrate the substantial impact of germination on the nutritional and functional qualities of peas
Identification of Gut Bacterial Symbionts from Atlantic Salmon That Are Involved in Metabolizing Feed Ingredients Derived from Soybean Meal
Full text linkIn the aquaculture industry, plant-based protein sources have emerged as an economically and environmentally sustainable replacement for traditional animal protein sources. Yet, due to reduced digestibility, the presence of anti-nutritional factors, as well as an increased risk of inflammation of the digestive system, the inclusion of plant-based protein ingredients must be limited, especially in the diets of carnivorous fishes. To gain further insight on how to adapt the fish digestive tract to more effectively utilize or tolerate plant-based protein ingredients, slurry from cultured Atlantic Salmon (Salmo salar) was used as a proxy in an in vitro model system to identify candidate gut bacterial species from fish that can metabolize plant-based protein sources. The study revealed nine candidate bacterial species that could be enriched in cultures supplemented with soybean-based ingredients, which was indicative of their capacity to metabolize soy-based compounds. To elucidate their functional capabilities, we subsequently focused on building partial genomes of these enriched candidate bacteria. Among the various metabolic pathways uncovered, the capacity to utilize carbohydrate-type anti-nutritional factors was identified. In addition, the potential to express secretory systems that have been previously found in pathogens was deemed of particular interest. Using metatranscriptomics, the genes responsible for these functions were confirmed to be expressed in cultures grown in the presence of soybean-based ingredients. By elucidating the mechanisms underlying microbial utilization plant protein sources, this research provides a foundation for developing strategies to modulate the gut microbiome towards enhancing the digestibility of plant-based diets for salmonids
Pressure-Related Discrepancies in Landsat 8 Level 2 Collection 2 Surface Reflectance Products and Their Correction
No full textDairy and Food Science Student Newsletter, November 5, 2025
No full texthttps://openprairie.sdstate.edu/dairy_student-news/1020/thumbnail.jp