Biology Education

Soils are the largest organic carbon reservoir in terrestrial ecosystems, storing carbon as organic matter derived from decomposed plant, microbial, and animal residues that resist microbial decomposition. Recent research has revealed that organic molecules adsorbed onto soil mineral nanoparticles, such as iron and aluminum oxides, form the most stable and persistent pool of organic carbon in soils. However, the environmental factors driving the formation and destabilization of mineral-associated organic matter (MAOM) remain poorly understoodIn boreal and subarctic regions, climate change is causing trees and shrubs to encroach upon tundra ecosystems, leading to significant decreases in soil organic carbon stocks. While most studies have focused on the organic layers of soils—primarily composed of particulate plant residues—there is limited knowledge about how changes in vegetation types affect organic carbon stored in the mineral soil layers as MAOM.

Objectives
This project aims to understand how the progression of trees and shrubs affects MAOM processes in subarctic soils. To achieve this, we will utilize a natural ecotone from dwarf birch forest to tundra in the Swedish subarctic as our study site. By employing a new probe system, we will quantify MAOM formation and destabilization rates across this gradient. We will then compare these rates with various plant parameters (such as species composition, and tree density), soil parameters (including organic matter stocks, pH, moisture, and temperature), and microbial parameters (bacterial and fungal community diversity and composition). This project aims to identify the abiotic and biotic drivers influencing MAOM processes in subarctic mineral soils.

Methodology

• Analyze MAOM probes to determine stabilization and destabilization rates.
• Assess plant parameters to evaluate their influence on MAOM processes.
• Measure soil parameters to determine their effect on MAOM processes.
• Examine soil microbial parameters to understand their role in MAOM processes.

Skills and techniques acquired

• Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy.
• Stable isotope tracing using ¹³C and ¹⁵N isotopes.
• Soil organic matter fractionation techniques.
• Bacterial and fungal metabarcoding to determine soil microbial community composition.
• Advanced statistical analysis and data visualization.

Application process

• Flexible starting date,
• 45-60 cr
• Interested candidates should contact Dr. François Maillard at francois.maillard@biol.lu.se.

Ectomycorrhizal fungi form symbiotic relationships with trees, playing a pivotal role in forest ecosystems by enhancing plant nutrient uptake in exchange for carbon from photosynthesis. Unlike most mycorrhizal fungi that transfer inorganic nutrients to their host plants, ectomycorrhizal fungi have the unique ability to acquire nutrients—particularly nitrogen—directly from soil organic matter. This process allows them to bypass the typical nutrient mineralization pathways in soils.
In boreal forests, where nutrients predominantly exist in organic forms, the capacity of ectomycorrhizal fungi to access organic nitrogen is especially critical. However, despite their ecological importance, there is limited understanding of the efficiency and mechanisms of organic nitrogen acquisition among the diverse species of ectomycorrhizal fungi. This knowledge gap stems from their high diversity; ectomycorrhizal symbiosis has evolved independently over 80 times, resulting in up to 20,000 different species.

Objectives
The project aims to phenotype a diverse collection of ectomycorrhizal fungi in vitro, encompassing over 50 different genera. By assessing their growth performance on various organic nitrogen sources, quantifying enzyme production that facilitates nutrient acquisition, and analyzing modifications of organic matter induced by fungal activity, this project seeks to evaluate the efficiencies and mechanisms used by ectomycorrhizal fungi for organic nitrogen acquisition. Ultimately, this work will connect the functional diversity of ectomycorrhizal fungi with soil biogeochemical cycles.

Methodology

• Cultivation of fungi: Grow cultures on media containing different organic nitrogen sources.
• Biomass measurement: Quantify fungal growth and nitrogen uptake.
• Enzyme assays: Use fluorometric and colorimetric methods to measure enzyme activity.
• Spectroscopy analysis: Employ Fourier-transform infrared spectroscopy (FTIR) to characterize
  changes in organic matter.
• Data interpretation: Analyze results to determine nutrient acquisition strategies among
  various fungal taxa.

Skills and techniques acquired

• Fungal microbiology: Sterile techniques, media preparation, and high-throughput in vitro
  phenotyping.
• Enzymology: Performing and interpreting enzyme assays.
• Spectroscopy: Utilizing FTIR spectroscopy for organic matter characterization.
• Data Analysis: Statistical analysis and scientific interpretation of experimental data.

 Application process

• Flexible starting date,
• 45-60 cr
• Interested candidates should contact Dr. François Maillard at francois.maillard@biol.lu.se.

Songbirds rely on an endogenous program to follow species-specific routes and schedule their migrations to the annual cycle. Due to competition, birds are often under time stress to complete their migrations, especially in spring when they are heading to the breeding areas. How birds are affected by parasites on migration and in particular, if fueling and expression of migratory activity potentially leading to slower migration speeds decrease in sick birds compared to healthy birds is not well known. We have collected fueling and activity data from a number of migratory songbird species in controlled experiments, from which we have blood samples that will be analyzed with respect to prevalence of avian malaria parasites. We hypothesize that migratory songbirds are affected by chronic avian malaria infections and will show decreased levels of fueling and migratory activity recorded by films.

We aim to test the hypothesis that songbirds can adjust their schedule of migratory fueling, migration activity and orientation to parasite load by exploring already collected data potentially in combination with new data collected during the study period. We are looking for a dedicated master’s student to conduct the avian malaria genotyping and analyses of behavioural and ecophysiological data collected in controlled experiments. There is a possibility to collect additional experimental data during spring or autumn.

Labwork and potential fieldwork starts: Autumn 2024/Spring 2025.

If understanding how songbirds are affected by parasites on migration excites you, then this may be your master’s project.

Please, contact Susanne Åkesson (migration phenotype, behavioural data) or Helena Westerdahl (genetics) for more information.

Professor Susanne Åkesson, Department of Biology
susanne.akesson@biol.lu.se

Professor Helena Westerdahl, Department of Biology
helena.westerdahl@biol.lu.se

The evolutionary ecology of cognition and memory in Caenorhabditis worms

We have two MSc projects (45-60 credits each) to investigate the evolution and ecology of cognition and transgenerational epigenetic memory in Caenorhabditis worms. With as few as c.a. 300 neurons, worms demonstrate a wide range of learning capabilities; they can associate olfactory cues with stress, learn to avoid pathogens, and can transmit their learned memory to their offspring (how convenient!). However, the regulation of their cognitive capacity remains unclear, and the ecology that facilitates the evolution of epigenetic memory inheritance is unknown.

Project 1: Being good at learning may seem universally beneficial. But is it? First, you can make mistakes. Second, there may be physiological costs associated with learning, forming memories, and keeping your nervous system in peak condition. Our recent results indicate that learning is regulated by the RNA interference (RNAi) pathway, but the capacity for RNAi-regulated learning may come with a potential fitness cost. This MSc project aims to investigate the costs of the active process of learning and memory inheritance using several RNAi mutants of Caenorhabditis elegans. 

Project 2: C. elegans worms learn to avoid pathogenic food (Pseudomonas bacteria) and can transmit the learned avoidance through epigenetic mechanisms (in this case, non-coding RNAs) to naïve progeny that have never encountered the pathogen. Such epigenetic memory inheritance has important implications in evolution, but its ecological relevance remains unclear – can other Caenorhabditis species that occupy different ecological niches inherit pathogenic memories? And how does worms’ microbial environment affect their response to pathogenic learning? This MSc project is part of a larger study, where we aim to investigate learning and epigenetic memory inheritance across Caenorhabditis species, as well as explore the interactions between the worms’ microbial environment and epigenetic memory inheritance.

Starting date: flexible

Required qualifications: Strong interests in evolutionary biology. No specific experience required.

Who are we?

We are three groups of researchers based in Lund University (Hwei-yen Chen), Uppsala University (Martyna Zwoinska), and Halmstad University (Martin Lind). Our shared interests include plasticity, cognition, life-history, and aging. Drop us a line if you’re interested in our projects, or if you would like to develop your own project with us!

Hwei-yen Chen, hwei-yen.chen@biol.lu.se

Martin Lind, martin.lind@hh.se

Martyna Zwoinska, martyna.zwoinska@ebc.uu.se

Cancers are bad, but why do they occur?

The prevalence of cancer, or malignant neoplasia, varies across and within species. Theories argue that life-history trade-off underpins this variation and predict a negative correlation between lifespan and neoplasia prevalence, and a positive correlation between fertility and neoplasia prevalence.

This is because neoplasia increases mortality risk, and tumor suppression is important for survival. Therefore, organisms that invest more resources in survival could evolve better defense against neoplastic growth, leading to the evolution of longer lifespan and lower neoplasia prevalence. On the other hand, because resources are limited, organisms evolve to ‘trade off’ resources among traits (such as between survival and reproduction) to maximize their overall fitness. If fitness is increased by channeling more resources to reproduction (e.g., by increasing fertility) at the cost of lower resources for somatic maintenance, optimization of resource allocation could result in a concomitant increase in fertility and in neoplasia prevalence.

For this project, we will take advantage of the long-lived and short-lived selection lines of Drosophila melanogaster that are already available. We will examine neoplasia prevalence (in the intestine) in long-lived versus short-lived Drosophila melanogaster, and we will disentangle the genes underlying neoplasia defense and lifespan regulation using transcriptome analysis.

What you will learn: You will learn about evolutionary medicine and life-history evolution. You will gain experience on fly maintenance, molecular biology techniques, and bioinformatics skills (optional; if time allows and if you are interested).

Required qualifications: Interested in evolutionary biology and evolutionary applications. Willing to learn handle small insects and work in a lab setting. No other specific experience required.

Duration: 45-60 credits

Starting date: flexible

Contact: Hwei-yen Chen, hwei-yen.chen@biol.lu.se

The most well-known life-history trade-off involves the survival cost of reproduction – reproduction (e.g., fertility, number of eggs) is commonly ‘costly’ in terms of future survival (i.e., longevity), so that we often observe a negative correlation between fertility and longevity.
At the heart of this trade-off is stem cell capacity – while stem cell maintenance is crucial for longevity (e.g., for tissue regeneration to repair damage), stem cell differentiation is required for fertility (i.e., to produce gametes). However, the role of stem cell capacity in life-history trade-off has not been investigated.
In this project, we will manipulate stem cell capacity in Drosophila melanogaster flies by controlling their oxygen-sensing conditions (e.g., by keeping them under different oxygen concentrations or by using transgenic flies), and we will investigate whether and how fertility, longevity, and (potentially) tissue repair differ between flies with high or low stem cell capacity.

What you will learn: You will learn about life-history evolution and molecular cell biology. You will gain experience on fly maintenance, animal crossing (!), fitness assays, and molecular biology techniques (op<onal; if <me allows and if you are interested).

Duration: 45-60 credits
Starting date: Fexible
Required qualifications: Strong interests in life-history evolution and molecular cell biology. Willing to learn handle small insects and work in a lab seCng. No other specific experience required.

Contact:
Hwei-yen Chen, hwei-yen.chen@biol.lu.se
Emma Hammarlund, emma.hammarlund@med.lu.se
Courtney Stairs, courtney.stairs@biol.lu.se