Browsing by Subject "essential"

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    cis- and trans-acting transcriptional activators: characterization of single nucleotide polymorphisms and a novel two-component system of Staphylococcus aureus
    (2014-03) Hall, Jeffrey W.
    Staphylococcus aureus is a major opportunistic pathogen and a common cause of hospital- and community-acquired infections. Furthermore, infections of livestock animals by S. aureus results in billion dollar losses to agriculture producers annually. Over the last five decades antibiotic resistance has dramatically increased in S. aureus and highly pathogenic strains have emerged that threaten human and animal health. Characterization of highly pathogenic strains and novel transcriptional mechanisms and pathways is of utmost importance as it will provide a critical evolutionary understanding of the transcriptional changes that led to the emergence of successfully infectious S. aureus strains and may identify novel targets for antibacterial development. The overarching goal of research described in this thesis was to characterize and understand how novel cis- and trans-acting factors affect gene expression in S. aureus. To that end, the work and data presented investigate the effect of promoter based single nucleotide polymorphisms (SNPs) of the hla gene, encoding α-toxin, on gene transcription and gene product expression. The cis-acting SNPs increased the binding affinity of the promoter to the trans-acting transcription factor SarZ. Furthermore, the S. aureus RF122 strain had increased transcriptional expression of several positive regulators and decreased transcription of negative regulators of hla, which resulted in a dramatic increase in α-toxin expression and likely contributes to the increased mastitis pathogenesis of RF122. Additionally, the essentiality of the yhcSR two-component system was confirmed in the hospital-acquired methicillin resistant S. aureus WCUH29 strain. The YhcSR TCS was identified to transcriptionally activate the lacABCDE and opuCABC operons involved in cellular metabolism and osmoregulatory mechanisms, respectively. In an effort determine if a relationship existed between YhcSR and pathogenesis, studies revealed that the YhcSR TCS transcriptionally regulated, in a positive manner, the sspABC and crtOPQMN operons, encoding exported proteases and staphyloxanthin biosynthesis, which contribute to the survival of S. aureus in human blood. The data indicate that the YhcSR TCS system is an essential trans-acting global regulator in S. aureus.
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    Interrelationships between Soybean Seed Quality Characteristics
    (2016-10) Pfarr, Matthew
    The quality of a protein for animal growth is partially determined by the relative abundance of essential amino acids. Those essential amino acids supplied in the lowest quantity relative to the animal’s requirement limit growth. Examination of soybean protein across genetic sources and environments has indicated that the abundance of potentially limiting amino acids within soybean protein may be influenced by the seed protein concentration. Our objective was to evaluate the effects of seed protein concentration on relative amino acid abundance under controlled environments in order to better understand the biological basis of this apparent relationship. This was accomplished through the use of source-sink treatments that altered seed protein concentration within environments. Increasing the source-to-sink ratio through partial pod removal and open environment treatments significantly increased seed protein; however, the resulting protein was disproportionately enriched in the amino acids glutamic acid and arginine at the expense of the limiting amino acids lysine, cysteine, methionine, threonine, and tryptophan. Defoliation treatments gave the opposite response to pod removal, resulting in a more favorable amino acid balance but with a lower seed protein concentration. Alternatively, the shade treatment increased protein concentration, but the relative concentration of the limiting amino acids was not reduced. This indicates that limiting amino acid abundance is not solely dependent on seed protein percentage and that limiting amino acids may be supplied by the vegetative tissue under C-limited conditions. The ultimate goal of soybean seed improvement is to increase yield while also increasing or maintaining seed protein concentration and the balance of the limiting amino acids. Meeting two of these goals was achieved through the current source-sink treatments as the open environment treatment increased seed yield and protein concentration while shade increased protein concentration and maintained limiting amino acid balance. Meeting all three goals concurrently for soybean improvement was not achieved in the current experiment and may be difficult.