DeAngelis, Kristen

Job Title

Assistant Professor, Department of Microbiology

Last Name

DeAngelis

First Name

Kristen

Discipline

Microbiology

Introduction

I am a microbiologist trained in microbial ecology and bioinformatics. My research is focused on microbial traits and emergent properties of microbial communities. Climate change is the most pressing issue facing people today, and our work seeks to understand microbial feedbacks with climate, and applying this understanding to improve lignocellulosic biofuels production.

Show all metadata

Search Results

Now showing 1 - 10 of 20

Open Access
Microbiology 562: D. Batch Fermentation Module
(2017-01-01) DeAngelis, Kristen; Prado, Cecilia
In this module, we set up a fermentation of grains by yeast with hops to brew beer (D1). We make media and pour plates to grow and identify microbial contaminants (D2). Two weeks after setting up the primary fermentation, we prime and condition the fermentation (D3). While we wait for the priming and conditioning to finish, we do a bioinformatics analysis of microbial communities turning ethanol (a product of fermentation) to n-caproic acid, (D4), to illustrate the power of metagenomic sequencing in resolving microorganisms and their potential physiology. Then we identify and examine the microbial contaminants cultured in the primary fermentation (D5). When the beer is finished, we perform a sensory analysis (D6) followed by a field trip to the Berkshire Brewing Company in South Deerfield, MA, where we will tour their brewing facilities and microbiology lab.
Open Access
Integrative Experience: Soil Microbes and the Sustainability of Organic Agriculture
(2020-01-07) DeAngelis, Kristen; Domeignoz Horta, Luiz
This curriculum describes a one-unit course designed to fulfill the University of Massachusetts requirement for Integrative Experience as part of the Gen Ed curriculum for undergraduates.
Open Access
Multi-time series RNA-seq analysis of Enterobacter lignolyticus SCF1 during growth in lignin-amended medium
(2017) Orellana, Roberto; Chaput, Gina; Markillie, Lye Meng; Mitchell, Hugh; Gaffrey, Matt; Orr, Gayla; DeAngelis, Kristen
The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors. Enterobacter lignolyticus SCF1 is a facultative anaerobic Gammaproteobacteria isolated from tropical rain forest soil collected in El Yunque forest, Puerto Rico under anoxic growth conditions with lignin as sole carbon source. Whole transcriptome analysis of SCF1 during E.lignolyticus SCF1 lignin degradation was conducted on cells grown in the presence (0.1%, w/w) and the absence of lignin, where samples were taken at three different times during growth, beginning of exponential phase, mid-exponential phase and beginning of stationary phase. Lignin-amended cultures achieved twice the cell biomass as unamended cultures over three days, and in this time degraded 60% of lignin. Transcripts in early exponential phase reflected this accelerated growth. A complement of laccases, aryl-alcohol dehydrogenases, and peroxidases were most up-regulated in lignin amended conditions in mid-exponential and early stationary phases compared to unamended growth. The association of hydrogen production by way of the formate hydrogenlyase complex with lignin degradation suggests a possible value added to lignin degradation in the future.
Open Access
Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia
(2012) DeAngelis, Kristen; Fortney, Julian L.; Borglin, Sharon; Silver, Whendee L.; Simmons, Blake A.; Hazen, Terry C.
Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To investigate how TEAs affect decomposition, we cultivated feedstock-adapted consortia (FACs) derived from two tropical forest soils collected from the ends of a rainfall gradient: organic matter-rich tropical cloud forest (CF) soils, which experience sustained low redox, and iron-rich tropical rain forest (RF) soils, which experience rapidly fluctuating redox. Communities were anaerobically passed through three transfers of 10 weeks each with switchgrass as a sole carbon (C) source; FACs were then amended with nitrate, sulfate, or iron oxide. C mineralization and cellulase activities were higher in CF-FACs than in RF-FACs. Pyrosequencing of the small-subunit rRNA revealed members of the Firmicutes, Bacteroidetes, and Alphaproteobacteria as dominant. RF- and CF-FAC communities were not different in microbial diversity or biomass. The RF-FACs, derived from fluctuating redox soils, were the most responsive to the addition of TEAs, while the CF-FACs were overall more efficient and productive, both on a per-gram switchgrass and a per-cell biomass basis. These results suggest that decomposing microbial communities in fluctuating redox environments are adapted to the presence of a diversity of TEAs and ready to take advantage of them. More importantly, these data highlight the role of local environmental conditions in shaping microbial community function that may be separate from phylogenetic structure. IMPORTANCE After multiple transfers, we established microbial consortia derived from two tropical forest soils with different native redox conditions. Communities derived from the rapidly fluctuating redox environment maintained a capacity to use added terminal electron acceptors (TEAs) after multiple transfers, though they were not present during the enrichment. Communities derived from lower-redox soils were not responsive to TEA addition but were much more efficient at switchgrass decomposition. Though the communities were different, diversity was not, and both were dominated by many of the same species of clostridia. This reflects the inadequacy of rRNA for determining the function of microbial communities, in this case the retained ability to utilize TEAs that were not part of the selective growth conditions. More importantly, this suggests that microbial community function is shaped by life history, where environmental factors produce heritable traits through natural selection over time, creating variation in the community, a phenomenon not well documented for microbes.
Open Access
Up Against The Wall: The Effects of Climate Warming on Soil Microbial Diversity and The Potential for Feedbacks to The Carbon Cycle
(2013) Pold, Grace; DeAngelis, Kristen
Earth’s climate is warming, and there is evidence that increased temperature alters soil C cycling, which may result in a self-reinforcing (positive), microbial mediated feedback to the climate system. Though soil microbes are major drivers of soil C cycling, we lack an understanding of how temperature affects SOM decomposition. Numerous studies have explored, to differing degrees, the extent to which climate change may affect biodiversity. While there is ample evidence that community diversity begets ecosystem stability and resilience, we know of keystone species that perform functions whose effects far outweigh their relative abundance. In this paper, we first review the meaning of microbial diversity and how it relates to ecosystem function, then conduct a literature review of field-based climate warming studies that have made some measure of microbial diversity. Finally, we explore how measures of diversity may yield a larger, more complete picture of climate warming effects on microbial communities, and how this may translate to altered carbon cycling and greenhouse gas emissions. While warming effects seem to be ecosystem-specific, the lack of observable consistency between measures is due in some part to the diversity in measures of microbial diversity.
Open Access
Metagenomes of tropical soil-derived anaerobic switchgrass-adapted consortia with and without iron
(2013) DeAngelis, Kristen; D'Haeseleer, Patrick; Chivian, Dylan; Simmons, Blake; Arkin, Adam P.; Mavromatis, Konstantinos; Malfatti, Stephanie; Tringe, Susannah; Hazen, Terry C.
Tropical forest soils decompose litter rapidly with frequent episodes of anoxia, making it likely that bacteria using alternate terminal electron acceptors (TEAs) such as iron play a large role in supporting decomposition under these conditions. The prevalence of many types of metabolism in litter deconstruction makes these soils useful templates for improving biofuel production. To investigate how iron availability affects decomposition, we cultivated feedstock-adapted consortia (FACs) derived from iron-rich tropical forest soils accustomed to experiencing frequent episodes of anaerobic conditions and frequently fluctuating redox. One consortium was propagated under fermenting conditions, with switchgrass as the sole carbon source in minimal media (SG only FACs), and the other consortium was treated the same way but received poorly crystalline iron as an additional terminal electron acceptor (SG + Fe FACs). We sequenced the metagenomes of both consortia to a depth of about 150 Mb each, resulting in a coverage of 26× for the more diverse SG + Fe FACs, and 81× for the relatively less diverse SG only FACs. Both consortia were able to quickly grow on switchgrass, and the iron-amended consortium exhibited significantly higher microbial diversity than the unamended consortium. We found evidence of higher stress in the unamended FACs and increased sugar transport and utilization in the iron-amended FACs. This work provides metagenomic evidence that supplementation of alternative TEAs may improve feedstock deconstruction in biofuel production.
Open Access
Evidence supporting dissimilatory and assimilatory lignin degradation in Enterobacter lignolyticus SCF1
(2013) DeAngelis, Kristen; Sharma, Deepak; Varney, Rebecca; Simmons, Blake; Isern, Nancy G.; Markillie, Lye Meng; Nicora, Carrie; Norbeck, Angela D.; Taylor, Ronald C.; Aldrich, Joshua T.; Robinson, Errol W.
Lignocellulosic biofuels are promising as sustainable alternative fuels, but lignin inhibits access of enzymes to cellulose, and by-products of lignin degradation can be toxic to cells. The fast growth, high efficiency and specificity of enzymes employed in the anaerobic litter deconstruction carried out by tropical soil bacteria make these organisms useful templates for improving biofuel production. The facultative anaerobe Enterobacter lignolyticus SCF1 was initially cultivated from Cloud Forest soils in the Luquillo Experimental Forest in Puerto Rico, based on anaerobic growth on lignin as sole carbon source. The source of the isolate was tropical forest soils that decompose litter rapidly with low and fluctuating redox potentials, where bacteria using oxygen-independent enzymes likely play an important role in decomposition. We have used transcriptomics and proteomics to examine the observed increased growth of SCF1 grown on media amended with lignin compared to unamended growth. Proteomics suggested accelerated xylose uptake and metabolism under lignin-amended growth, with up-regulation of proteins involved in lignin degradation via the 4-hydroxyphenylacetate degradation pathway, catalase/peroxidase enzymes, and the glutathione biosynthesis and glutathione S-transferase (GST) proteins. We also observed increased production of NADH-quinone oxidoreductase, other electron transport chain proteins, and ATP synthase and ATP-binding cassette (ABC) transporters. This suggested the use of lignin as terminal electron acceptor. We detected significant lignin degradation over time by absorbance, and also used metabolomics to demonstrate moderately significant decreased xylose concentrations as well as increased metabolic products acetate and formate in stationary phase in lignin-amended compared to unamended growth conditions. Our data show the advantages of a multi-omics approach toward providing insights as to how lignin may be used in nature by microorganisms coping with poor carbon availability.
Open Access
Changes in substrate availability drive carbon cycle response to chronic warming
(2017) Pold, Grace; Grandy, A. Stuart; Melillo, Jerry M.; DeAngelis, Kristen
As earth's climate continues to warm, it is important to understand how the capacity of terrestrial ecosystems to retain carbon (C) will be affected. We combined measurements of microbial activity with the concentration, quality, and physical accessibility of soil carbon to microorganisms to evaluate the mechanisms by which more than two decades of experimental warming has altered the carbon cycle in a Northeast US temperate deciduous forest. We found that concentrations of soil organic matter were reduced in both the organic and mineral soil horizons. The molecular composition of the carbon was altered in the mineral soil with significant reductions in the relative abundance of polysaccharides and lignin, and an increase in lipids. Mineral-associated organic matter was preferentially depleted by warming in the top 3 cm of mineral soil. We found that potential extracellularenzyme activity per gram of soil at a common temperature was generally unaffected by warming treatment. However, by measuring potential extracellular enzyme activities between 4 and 30 °C, we found that activity per unit microbial biomass at in-situ temperatures was increased by warming. This was associated with a tendency for microbial biomass to decrease with warming. These results indicate that chronic warming has reduced soil organic matter concentrations, selecting for a smaller but more active microbial community increasingly dependent on mineral-associated organic matter.
Open Access
Complete genome sequence of the lignin-degrading bacterium Klebsiella sp. strain BRL6-2
(2014) Woo, Hannah L.; Ballor, Nicholas R.; Hazen, Terry C.; Fortney, Julian L.; Simmons, Blake; Davenport, Karen Walston; Goodwin, Lynne; Ivanova, Natalia; Kyrpides, Nikos C.; Mavromatis, Konstantinos; Woyke, Tanja; Jansson, Janet; Kimbrell, Jeff; DeAngelis, Kristen
In an effort to discover anaerobic bacteria capable of lignin degradation, we isolated Klebsiella sp. strain BRL6-2 on minimal media with alkali lignin as the sole carbon source. This organism was isolated anaerobically from tropical forest soils collected from the Bisley watershed at the Ridge site in the El Yunque National Forest in Puerto Rico, USA, part of the Luquillo Long-Term Ecological Research Station. At this site, the soils experience strong fluctuations in redox potential and are characterized by cycles of iron oxidation and reduction. Genome sequencing was targeted because of its ability to grow on lignin anaerobically and lignocellulolytic activity via in vitro enzyme assays. The genome of Klebsiella sp. strain BRL6-2 is 5.80 Mbp with no detected plasmids, and includes a relatively small arsenal of genes encoding lignocellulolytic carbohydrate active enzymes. The genome revealed four putative peroxidases including glutathione and DyP-type peroxidases, and a complete protocatechuate pathway encoded in a single gene cluster. Physiological studies revealed Klebsiella sp. strain BRL6-2 to be relatively stress tolerant to high ionic strength conditions. It grows in increasing concentrations of ionic liquid (1-ethyl-3-methyl-imidazolium acetate) up to 73.44 mM and NaCl up to 1.5 M.
Open Access
Enzyme activities of aerobic lignocellulolytic bacteria isolated from wet tropical forest soils
(2014) Woo, Hannah L.; Hazen, Terry C.; Simmons, Blake A.; DeAngelis, Kristen
Lignocellulolytic bacteria have promised to be a fruitful source of new enzymes for next-generation lignocellulosic biofuel production. Puerto Rican tropical forest soils were targeted because the resident microbes decompose biomass quickly and to near-completion. Isolates were initially screened based on growth on cellulose or lignin in minimal media. 75 Isolates were further tested for the following lignocellulolytic enzyme activities: phenol oxidase, peroxidase, β-d-glucosidase, cellobiohydrolase, β-xylopyranosidase, chitinase, CMCase, and xylanase. Cellulose-derived isolates possessed elevated β-d-glucosidase, CMCase, and cellobiohydrolase activity but depressed phenol oxidase and peroxidase activity, while the contrary was true of lignin isolates, suggesting that these bacteria are specialized to subsist on cellulose or lignin. Cellobiohydrolase and phenol oxidase activity rates could classify lignin and cellulose isolates with 61% accuracy, which demonstrates the utility of model degradation assays. Based on 16S rRNA gene sequencing, all isolates belonged to phyla dominant in the Puerto Rican soils, Proteobacteria, Firmicutes, and Actinobacteria, suggesting that many dominant taxa are capable of the rapid lignocellulose degradation characteristic of these soils. The isolated genera Aquitalea, Bacillus, Burkholderia, Cupriavidus, Gordonia, and Paenibacillus represent rarely or never before studied lignolytic or cellulolytic species and were undetected by metagenomic analysis of the soils. The study revealed a relationship between phylogeny and lignocellulose-degrading potential, supported by Kruskal–Wallis statistics which showed that enzyme activities of cultivated phyla and genera were different enough to be considered representatives of distinct populations. This can better inform future experiments and enzyme discovery efforts.