Date of Award

2023-05-01

Degree Name

Doctor of Philosophy

Department

Biological Sciences

Advisor(s)

Anthony Darrouzet-Nardi

Abstract

Microbial processes such as soil enzyme production are a major driver of decomposition and a current topic of interest in arctic soils due to the effects of climate warming. Despite the advances in understanding soil enzymes, there are still knowledge gaps regarding the role of enzymes in decomposition. In this dissertation, I addressed three of those gaps in the following chapters: (Ch.2) to explore the location of enzymes within the soil matrix, (Ch.3) to identify peptides matched to soil enzymes produced by microorganisms for organic matter decomposition, and (Ch.4) understand the longevity of enzymes in the soil after microbial production. For this project, I examined the soils from Utqiaġvik (Barrow), located in the North Slope of Alaska, north of the Arctic circle. Chapters 2, 3, and 4 measured the activities of potential hydrolytic and oxidative enzymes. Chapter 2 focused on various separation techniques to determine the location of enzymes in the soil matrix. Chapter 3 enhances protein extraction techniques used in proteomics to remove humic substances and achieve improved data without humic interference. With the optimized method, I examine the proteins from the soil samples to enable the identification of soil enzymes. In addition, I examined the association between the peptides seen in the proteome and the activity of enzymes. In chapter 4, enzyme activity was monitored weekly to assess the decline in activity after the eradication of microbial organisms by chloroform (CHCl3) fumigation. Additional microscopy techniques were implemented in this chapter to confirm cellular death after chloroform fumigation. My findings demonstrate that, in chapter 2, soil enzymes tend to be predominantly linked with larger organic matter particles. Enzyme activity was not detected in the soil pore water, suggesting that enzymes have a limited persistence in the soil pore water over an extended period. Chapter 3 determined that using FASP (filter-aided sample preparation) for soil enzyme extractions during proteomics yields higher peptide counts. Following this, I identified our typically assayed soil enzyme in the proteome and two additional enzymes with a high peptide count (β-galactosidase and arylsulfatase), and was able to measure substantial enzyme activity for each of these. Finally, in chapter 4, I observed that soil enzymes have a prolonged lifespan following their production. While the exact timeframe was not determined, my results indicate their longevity extends beyond 12 weeks. Overall, this dissertation provides evidence that a variety of microbes produce soil enzymes that have a relatively long lifespan and are most likely associated with large organic matter particles they decompose.

Language

en

Provenance

Recieved from ProQuest

File Size

p.

File Format

application/pdf

Rights Holder

Jane Karen Martinez

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