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Decomposition of Microbial Necromass Is Divergent at the Individual Taxonomic Level in Soil
Get PDFThe turnover of microbial biomass plays an important part in providing a significant source of carbon (C) to soil organic C. However, whether the decomposition of microbial necromass (non-living microbial biomass) in the soil varies at the individual taxa level remains largely unknown. To fill up these gaps, we compared the necromass decomposition of bacterial and archaeal taxa by separating live microbial biomass with 18O-stable isotope probing from dead microbial biomass in soil. Our results showed that most of the microbial necromass at the operational taxonomic unit level (88.51%), which mainly belong to Acidobacteria, Actinobacteria, Gemmatimonadetes, and Proteobacteria, decomposed significantly after 30 days. In addition, there were great variations in necromass decomposition within each phylum, such as the decomposition of operational taxonomic units in Proteobacteria that ranged from 51% (Beijerinckia) to 92% (Nitrosospira). More importantly, the necromass decomposition was not related to the chemical composition of the cell wall but might positively correlate with the guanine–cytosine content of DNA and negatively correlated with genome size. This study provided a new insight that the decomposition of microbial necromass in soil was divergent at the individual taxonomic level and could not be fully explained by previously proposed mechanisms
Short-term canopy and understory nitrogen addition differ in their effects on seedlings of dominant woody species in a subtropical evergreen broadleaved forest
Get PDFAs atmospheric nitrogen (N) deposition continues to increase, information on how N deposition affects seedling performance of tree species is critical for predicting forest regeneration. In this study, we examined the effects of canopy N addition at 25 and 50 kg ha−1 year−1 of N (CAN25 and CAN50), and understory N addition at 25 and 50 kg ha−1 year−1 of N (UAN25 and UAN50) on the survival, physiology, and growth of seedlings of two dominant woody species (Schima superba and Ardisia quinquegona) that were transplanted into a subtropical evergreen broadleaved forest. At two years after transplanting, understory N additon greatly decreased seedling height and biomass production for both species, especially at 50 kg ha−1 year−1 of N. N-addition treatments, however, had only minor effects on seedling survival and biomass allocation. UAN50 decreased leaf light-saturated photosynthesis (Asat) in the dry season and increased stem N concentration; UAN25 increased intrinsic water-use efficiency (WUEi); and CAN50 increased concentrations of N and P in the roots and stems of S. superba seedlings. Both UAN25 and UAN50 generally increased stem and leaf N concentrations and the leaf N/P ratio in A. quinquegona seedlings. UAN50 decreased whole-plant N-use efficiency of both species, and CAN50 reduced whole-plant N- and P-use efficiencies of S. superba seedlings. Overall, S. superba seedlings performed better than A. quinquegona seedlings in terms of height, biomass, Asat, and WUEi. Our results indicate that N deposition can profoundly influence the seedling growth of woody species, and that seedling height, basal diameter and biomass are more sensitive to the understory addition of N than to the canopy addition of N, i.e., the traditional use of understory addition of N to simulate atmospheric N deposition may overestimate the effects of N deposition on seedling performance
Competition and Innovation in Markets with Technology Leaders
Get PDFIn this article, we consider technology leaders (which are innovators) and technology followers (which are non-innovators) to provide a new theoretical explanation for the well-cited empirical evidence of an inverted-U relationship between competition and aggregate innovation. We consider a two-stage game with a deterministic Research and Development (R&D) process, where the leaders first determine their R&D investments simultaneously and then all leaders and followers determine their outputs simultaneously. We show that the inverted-U relationship between competition and aggregate innovation occurs if competition is affected by the number of technology followers. However, the presence of more technology leaders decreases individual R&D investments while increasing aggregate R&D investments. If the total number of firms remains the same but the composition of technology leaders and followers changes in favor of leaders (followers), individual R&D investments decrease (increase) but aggregate R&D investments increase (decrease). The relationship between competition and R&D investments can be U-shaped if the intensity of competition is measured by product substitutability. Contrary to the standard expectation, the presence of more firms may reduce welfare
Challenges Black Women Face with Promotional Opportunities to Executive-Level Administration Positions in an HBCU
No full textThis qualitative research study examined the challenges that Black women face at an HBCU when aspiring to be promoted into executive-level administration. The study focused on challenges that were faced in the 19th century and compared them to the challenges that are faced today in the 21st century. The study looked at challenges such as lack of mentoring and training provided, opportunities that are available, relationships that are important to form, and the race and gender that keeps Black women behind. This study was accomplished by obtaining personal perspectives and lived experiences of those currently serving in the roles of executive-level administrators. The overall summary for this study was provided by personal perceptions, insights, and recommendations from participants from a southeastern HBCU. The findings of this study encourage the building of relationships within the community, faculty, and executive-level administrators. Among the major findings, this study indicated that Black women do not receive the mentoring that could be beneficial in obtaining promotions, and neither is the opportunity available to them as is available to men or other races. This study provides implications for Black women in executive-level administration positions that can improve relationships, mentoring and provide more training for arising Black females. This study highlighted important information related to the experiences and challenges of Black women who desire to be promoted to executive-level administrators. One recommendation for further research is to duplicate this research study with target populations that were not represented in this study’s results
Performance Evaluation of a Pilot Scale Dean Flow UV System: Fundamentals and Applications
No full textMitigating the risk of introducing an adventitious contaminant during upstream processes of liquid foods manufacturing is critical. Although the inactivation of microorganisms in water and high transmittance liquid foods have been studied extensively, the efficiency of the process is rather poor for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in opaque fluids using a pilot-scale Dean Flow UV system. Simulated fluids inoculated with MS2 bacteriophage were used to test the system’s efficiency and assess the boundary conditions. A mathematical model was developed as a function of optical attenuation coefficients (abs. coefficient: 6.5 to 17 cm-1) and flow rates (31.70, 63.40, 95.10 gph). It was observed that REF scaled up linearly as an inverse function of flow rate and absorbance (R2 \u3e 0.99, p \u3c 0.05), indicating efficient mixing in the reactor. The algorithm was further tested and validated against independent experiments using S. Typhimurium and B. cereus. The predicted and experimental inactivation results were in close agreement, p\u3e0.05 which demonstrated that the developed model can predict the REF, thus microbial inactivation in simulated fluids within the model boundary conditions. The system was improved for its transmittance and penetration efficiency and tested against WM inoculated with B. cereus. The REF delivered in WM was quantified at flow rates of 11.88, 23.77, and 47.55 gph. Among all the experimental flow rates, at 47.55 gph, the highest REF rate was observed attributed to the turbulence and Dean effect shown by high Reynolds and Dean number. Microbial inactivation studies conducted at 47.55 gph showed 0.91 ± 0.15 and 2.14 ± 0.19 log reduction per pass for B. cereus and T1 phage. It was envisaged that linear inactivation trends were observed, which demonstrates high mixing during each pass. A lower EEO value signifies the higher electrical efficiency of the system. No significant alteration in volatile profile and lipid peroxidation (p\u3e0.05) was observed at UV-C fluence of 60 mJ/cm2, sufficient to inactivate \u3e6-log of B. cereusand \u3e12-log of T1 phage. This demonstrated the efficiency of UV-C to inactivate a range of pathogens without altering the quality of WM
Integration of Sanitation Practices and Fungicide Applications for Assuring Better Postharvest Shelf Life of Cut Flowers and Greenery
No full textBotrytis blight, boxwood blight and Volutella blight caused by Botrytis cinerea Pers. Fr. [teleomorph Botryotinia fuckeliana (de Bary) Whetzel], Calonectria pseudonaviculata Lombard, Wingf, & Crous, and Pseudonectria foliicola Lambard & Crous, respectively are becoming more problematic in ornamental plant production, reducing the quantity, quality, and marketability of susceptible plants. These pathogens can be mechanically transmitted through air, water splash, cutting tools and equipment, worker gloves, shoes, and clothes. These pathogens can cause disease in ornamental plants in both field and postharvest conditions. Sometimes, these pathogens remain inactive during harvesting of ornamental flowers or greenery, but cause infection during transportation, storage, and retail/wholesale shop. These pathogens not only affect the plants but also cause significant loss in postharvest life of cut flowers and greenery. The objective of this study was to evaluate the efficacy of sanitizers, biorational products, and fungicides in managing the pre and postharvest foliar diseases of cut flowers and greenery. In this current study, isofetamid, fluxapyroxad + pyraclostrobin, and biofungicide Aureobasidium pullulans strain DSM 14940 and DSM 14941 were the most effective treatments in reducing the postharvest botrytis blight on bigleaf hydrangea cut flowers. Similarly, (ODD + DoD + DdD + DB)AC [Simple Green D Pro 5], 2 propanol + DDAC [0.12% (KleenGrow)], and DBAC + DEAC [GreenShield] were the most effective in reducing the plant to plant transfer of boxwood blight and Volutella blight when pruned with contaminated Felco 19 shears. In addition to the three effective treatments above, acetic acid [2.5% (Vinegar)], 2-propanol + DDAC (0.06%), sodium hypochlorite [Clorox] and potassium peroxymonosulfate + NaCl [2% (Virkon)] were effective in reducing postharvest boxwood blight whereas DBAC + DBAC [Lysol All-purpose Cleaner], ethanol [70% (Ethyl alcohol)] and DDAC +DBAC [Simple Green D Pro 3 plus] were effective in reducing Volutella blight disease severity, AUDPC, and maintained better quality and longer postharvest shelf life of boxwood cuttings. Additionally, we also identified the causal agent for bending (meltdown) of zinnia cut flower stem. The morphological, molecular, and phylogenetic analysis, as well as pathogenicity test, determined that Fusarium commune Skovgaard, Rosendahl, O’Donnell & Nirenberg is the causal agent of zinnia meltdown in Tennessee
CRISPR Genome Editing of Transcription Factors Related to Aluminum Toxicity in Tomato (Solanum lycopersicum)
No full textThe objective of this study is to set up the CRISPR/Cas9 system for tomatoes in the Plant Biotech Lab at Tennessee State University. Two transcription factors were selected as these genes were shown changes at transcript and protein abundance levels in response to treatments of Al toxicity stress in tomatoes (Solanum lycoperisicum). The selected genes were found specifically expressed in roots in Tomato eFP browser. The online-based tool CRISPR P v2.0 was used for guide RNA (gRNA) design. For gRNA design, two gRNAs were selected based on the number of on & off target sites, location (gene exon, intron, UTR, or intergenic), preferred restriction endonuclease site, and GC content (30-80%). The p201N vector with 2X35S promoter and kanamycin resistance genes was used to prepare the CRISPR/Cas9 construct. The two gRNAs were assembled onto the p201N Cas9 vector using NEBuilder DNA assembly. The CRISPR/Cas9 constructs were first transformed into Top 10 E. coli competent cells provided with the NEBuilder DNA assembly kit. Positive colonies grown on an agar plate supplemented with 50mg/L kanamycin were selected and plasmids were extracted and sequenced. Plasmids containing the gRNA sequences were used to transform Agrobacterium tumefaciens AGL1 strain using the electroporation method. Tomato ‘Money Maker’ seeds were germinated, and cotyledons were used for inoculation of the A. tumefaciens AGL1 harboring the p201N Cas9-gRNAs constructs. Positive T0 plants with genome integrated with the Cas9 & gRNA constructs were screened using PCR with primers specific for these sequences. Rooted plants were transplanted into the potting mix and self-pollinated to produce seeds. Seedlings in the T1 generation. were genotyped for segregation of Cas9 and mutations on targeted and non-targeted regions