Ten simple rules for succeeding as an underrepresented STEM undergraduate

Undergraduate students from underrepresented backgrounds (e.g., Black, Indigenous, and people of color [BIPOC], members of the Deaf community, people with disabilities, members of the 2SLGBTQIA+ community, from low-income backgrounds, or underrepresented genders) continue to face exclusion and marginalization in higher education. In this piece, authored and edited by a diverse group of Science, Technology, Engineering, and Mathematics (STEM) scholars, we present 10 simple rules for succeeding as an underrepresented STEM undergraduate student, illuminating the “hidden curriculum” of STEM specifically as it relates to the underrepresented undergraduate experience. Our rules begin by encouraging students to embrace their own distinct identities and scientific voices and explain how students can overcome challenges unique to underrepresented students throughout their undergraduate degrees. These rules are derived from a combination of our own experiences navigating our undergraduate STEM degrees and the growing body of literature on improving success for underrepresented students.     

Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co‐occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar g_s temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.     

The Role of Microsite Conditions in Restoring Trembling Aspen (Populus tremuloides Michx) from Seed

Encouraging natural regeneration of Populus tremuloides Michx (trembling aspen) from seed is a largely unexplored means for reintroducing the species into reclamation areas. We evaluated the effects of microsite (surface contour and substrate type) on aspen seedling establishment and growth on a reclaimed coal mine. The 4.6 ha study site was divided into six 48 m‐wide strips that had 15 or 40 cm capping material salvaged from a nearby forest floor added to the mine surface. We surveyed 126 m long transects located in the center of each strip for microsite conditions, and the presence and height of aspen seedlings. We found that aspen seedlings generally preferred mineral‐organic substrates and concave microsites. To facilitate the regeneration of aspen by seed, we suggest that land managers increase small‐scale roughness and microtopographic diversity on reclaimed sites .     

Evidence that Early Carboniferous ostracods colonised coastal flood plain brackish water environments

A study of the stable isotope composition (δ¹⁸O, δ¹³C) of biogenic (ostracod, mollusc) and authigenic carbonates in the Ballagan Formation, Lower Carboniferous of Scotland, coupled with evidence from sedimentology and associated fossil fauna and flora, supports the argument that this formation was deposited in a coastal flood plain setting, in brackish (0.5 < 30‰ NaCl) and hypersaline (> 40‰ NaCl) waters, but in the absence of persistent normal marine conditions. The oxygen isotope data from the Ballagan Formation divide into three clusters: a diagenetic field defined by low δ¹⁸O (< − 11‰ VPDB); an intermediary field (δ¹⁸O − 11‰ to − 9‰) composed of a mixture of known primary and secondary (diagenetic) carbonates; and samples within the range of − 9‰ to − 4‰ which, as far as we can ascertain, are largely unaltered. No samples give typical Early Carboniferous δ¹⁸O marine values. Average marine carbonates from Europe have δ¹⁸O between − 4‰ to − 3‰. The Ballagan Formation carbonates were probably deposited in evaporated freshwater and/or brackish water. This conclusion is supported by the presence of evaporites (gypsum, anhydrite, halite pseudomorphs) and common desiccation-cracked mudstone surfaces throughout the Ballagan Formation, suggesting conditions of fluctuating salinity in ephemeral bodies of water. The stable isotope data support the notion that the ostracod assemblages of the Ballagan Formation were colonising brackish water and hypersaline ecologies on a coastal flood plain during the Early Carboniferous, a stage of development that may have encouraged their colonisation of fully non-marine (limnetic) environments during the later Carboniferous. The ostracods include cytherellacean and kloedenellacean species known from marginal marine sites elsewhere, but probably tolerant of brackish water, podocopid species such as ‘Bythocypris’ aequalis that may have been adapted for brackish water settings on coastal flood plains (ephemeral lakes and lagoons), and paraparchitacean-dominated assemblages that may signal harsh (hypersaline or desiccating) environments.     

Mycobacteriosis in zebrafish (Danio rerio) research facilities

The Zebrafish International Resource Center was established to support the zebrafish research community, and includes a diagnostic service. One of the most common diseases that we have diagnosed is mycobacteriosis, which represented 18% of the diagnostic cases submitted from November 1999 to June 2003. We describe here the severity of the disease and associated pathological changes of 24 diagnostic cases from 14 laboratories. Identifications of the bacteria are provided for seven of these cases. For two cases in which culture of the organism was not successful, these identifications were based on ribosomal DNA (rDNA) sequence analysis obtained directly from infected tissues. Biochemical characteristics and rDNA sequence analysis from cultures are reported for the other isolates. Two severe outbreaks from different facilities on different continents were associated with an organism identified as Mycobacterium haemophilum based on rDNA sequence from tissues. Another severe outbreak was associated with an organism most closely related to Mycobacterium peregrinum. These species are recognized pathogens of humans, but this is the first report of them from fish. Bacteria identified as Mycobacterium chelonae or M. abscessus were recovered from fish in cases categorized as moderate disease or as an incidental finding. These findings indicate that species of Mycobacterium previously undescribed from fish (i.e., M. haemophilum and M. peregrinum) may pose significant health problems in zebrafish research facilities, whereas species and strains that are already recognized as common in fish usually cause limited disease on a population basis in zebrafish.     

Elf5 is essential for early embryogenesis and mammary gland development during pregnancy and lactation

Elf5 is an epithelial-specific ETS factor. Embryos with a null mutation in the Elf5 gene died before embryonic day 7.5, indicating that Elf5 is essential during mouse embryogenesis. Elf5 is also required for proliferation and differentiation of mouse mammary alveolar epithelial cells during pregnancy and lactation. The loss of one functional allele led to complete developmental arrest of the mammary gland in pregnant Elf5 heterozygous mice. A quantitative mRNA expression study and Western blot analysis revealed that decreased expression of Elf5 correlated with the downregulation of milk proteins in Elf5(+/-) mammary glands. Mammary gland transplants into Rag(-/-) mice demonstrated that Elf5(+/-) mammary alveolar buds failed to develop in an Elf5(+/+) mammary fat pad during pregnancy, demonstrating an epithelial cell autonomous defect. Elf5 expression was reduced in Prolactin receptor (Prlr) heterozygous mammary glands, which phenocopy Elf5(+/-) glands, suggesting that Elf5 and Prlr are in the same pathway. Our data demonstrate that Elf5 is essential for developmental processes in the embryo and in the mammary gland during pregnancy.