Role of UDP-Glycosyltransferase (ugt) Genes in Detoxification and Glycosylation of 1-Hydroxyphenazine (1-HP) in Caenorhabditis elegans.

Caenorhabditis elegans is a useful model organism to study the xenobiotic detoxification pathways of various natural and synthetic toxins, but the mechanisms of phase II detoxification are understudied. 1-Hydroxyphenazine (1-HP), a toxin produced by the bacterium Pseudomonas aeruginosa, kills C. elegans. We previously showed that C. elegans detoxifies 1-HP by adding one, two, or three glucose molecules in N2 worms. Our current study evaluates the roles that some UDP-glycosyltransferase (ugt) genes play in 1-HP detoxification. We show that ugt-23 and ugt-49 knockout mutants are more sensitive to 1-HP than reference strains N2 or PD1074. Our data also show that ugt-23 knockout mutants produce reduced amounts of the trisaccharide sugars, while the ugt-49 knockout mutants produce reduced amounts of all 1-HP derivatives except for the glucopyranosyl product compared to the reference strains. We characterized the structure of the trisaccharide sugar phenazines made by C. elegans and showed that one of the sugar modifications contains an N-acetylglucosamine (GlcNAc) in place of glucose. This implies broad specificity regarding UGT function and the role of genes other than ogt-1 in adding GlcNAc, at least in small-molecule detoxification.

Computational analysis of variation in C. elegans ugts.

Caenorhabditis elegans are free-living nematodes with a relatively short life cycle and a wealth of genomic information across multiple databases. Uridine diphosphate-glycosyltransferases (UGTs) are a family of enzymes involved in Phase II modification of xenobiotics in C. elegans , which is the addition of a sizeable water-soluble molecule to a xenobiotic to allow for its excretion out of a cell. Little is known about the variation in UGTs across wild isolates and how that might affect their innate immune response. We analyzed the diversity in ugt genes across C. elegans isolates from different geographical locations from the Caenorhabditis elegans Natural Diversity Resource (CaeNDR) database. This was accomplished using whole genome data and data identifying genome regions as hyper-divergent for each isotype. We implemented three steps to identify ugt genes and make inferences based on their variation. First, we created a catalog of UGTs in the N2 reference strain and used them to create a phylogenetic tree that depicts the relationships between the UGT protein sequences. We then quantified ugt variation using the strains from the CaeNDR database and used their data to remove hyper-divergent ugt genes. The third step was to catalog the occurrence of minor allele frequency (MAF) > 0.05 for all the ugts to compare how that aligned with genes classified as hyper-divergent by CaeNDR. Of the 67 ugt genes analyzed, 18 were hyper-divergent. This research will help improve our understanding of ugt variation in C. elegans .

Postgraduate perspectives on mentoring undergraduate researchers for talent development.

Undergraduate research experiences are critical for the talent development of the STEM research workforce, and research mentors play an influential role in this process. Given the many life science majors seeking research experiences at universities, graduate and postdoctoral researchers (i.e., postgraduates) provide much of the daily mentoring of undergraduate researchers. Yet, there remains little research on how postgraduates contribute to talent development among undergraduate researchers. To begin to address this knowledge gap, we conducted an exploratory study of the experiences of 32 postgraduates who mentored life science undergraduate researchers. We identified four factors that they perceived as enabling undergraduate researcher talent development: undergraduate researcher characteristics, research project characteristics, and mentoring implementation as well as outcomes for both the postgraduate and undergraduate. We then describe a team-based approach to postgraduate mentoring of undergraduate researchers that attends to these factors to provide an example that practitioners can adapt or adopt for their own research groups.

A Plate Based Assay for Determination of the Median Lethal Dose of 1-Hydroxyphenazine in Caenorhabditis elegans.

Caenorhabditis elegans is an ideal model organism for studying the xenobiotic detoxification pathways of various natural and synthetic toxins. We developed a new workflow to study the effects of 1-hydroxyphenazine (1-HP), a toxin produced by the bacterium Pseudomonas aeruginosa, on the survival of C. elegans. Prior research has demonstrated that C. elegans can detoxify 1-HP through the general mechanism of O-glycosylation. As part of the Vertically Integrated Projects (VIP) undergraduate research team, we have developed a workflow for a plate-based toxicity assay to determine the median lethal dose (LD50) of 1-HP. This was achieved through a toxin exposure method in which the worms were exposed to varying concentrations of 1-HP. The death rates were measured using a fluorescent bead assay. This workflow can be used to test C. elegans responses to different toxins and also the response of different mutant strains to a toxin of interest.

"Where's My Mentor?!" Characterizing Negative Mentoring Experiences in Undergraduate Life Science Research.

Undergraduate research experiences in science, technology, engineering, and mathematics fields are championed for promoting students' personal and professional development. Mentorship is an integral part of undergraduate research, as effective mentorship maximizes the benefits undergraduates realize from participating in research. Yet almost no research examines instances in which mentoring is less effective or even problematic, even though prior research on mentoring in workplace settings suggests negative mentoring experiences are common. Here, we report the results of a qualitative study to define and characterize negative mentoring experiences of undergraduate life science researchers. Undergraduate researchers in our study reported seven major ways they experienced negative mentoring: absenteeism, abuse of power, interpersonal mismatch, lack of career support, lack of psychosocial support, misaligned expectations, and unequal treatment. They described some of these experiences as the result of absence of positive mentoring behavior and others as actively harmful behavior, both of which they perceive as detrimental to their psychosocial and career development. Our results are useful to mentors for reflecting on ways their behaviors might be perceived as harmful or unhelpful. These findings can also serve as a foundation for future research aimed at examining the prevalence and impact of negative mentoring experiences in undergraduate research.

Volunteered or Voluntold? The Motivations and Perceived Outcomes of Graduate and Postdoctoral Mentors of Undergraduate Researchers.

Graduate students and postdoctoral researchers (postgraduates) in the life sciences frequently mentor undergraduate researchers, especially at research universities. Yet there has been only modest investigation of this relationship from the postgraduate perspective. We conducted an exploratory study of the experiences of 32 postgraduate mentors from diverse institutions, life sciences disciplines, and types of research to examine their motivations for mentoring and their perceived outcomes. Although some postgraduates reported feeling pressured to mentor undergraduate researchers, all expressed personal motivations, including both agentic (self-focused) and communal (community-focused) motivations. These postgraduates reported benefits and costs of mentoring that had both vocational and psychosocial elements. Given that our results indicated that even postgraduates who engaged in mentoring at the request of their faculty advisors had their own motivations, we conducted a second phase of analysis to determine the extent to which our results aligned with different theories of motivation (self-determination theory, social cognitive career theory, expectancy-value theory, social exchange theory). We end by proposing a model of postgraduate mentoring of undergraduate researchers that integrates the theories supported by our findings.