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ABSTRACT Heavy metals (HMs) are known to modify bacterial communities both in the laboratory and in situ . Consequently, soils in HM-contaminated sites such as the U.S. Environmental Protection Agency (EPA) Superfund sites are predicted to have altered ecosystem functioning, with potential ramifications for the health of organisms, including humans, that live nearby. Further, several studies have shown that heavy metal-resistant (HMR) bacteria often also display antimicrobial resistance (AMR), and therefore HM-contaminated soils could potentially act as reservoirs that could disseminate AMR genes into human-associated pathogenic bacteria. To explore this possibility, topsoil samples were collected from six public locations in the zip code 35207 (the home of the North Birmingham 35th Avenue Superfund Site) and in six public areas in the neighboring zip code, 35214. 35027 soils had significantly elevated levels of the HMs As, Mn, Pb, and Zn, and sequencing of the V4 region of the bacterial 16S rRNA gene revealed that elevated HM concentrations correlated with reduced microbial diversity and altered community structure. While there was no difference between zip codes in the proportion of total culturable HMR bacteria, bacterial isolates with HMR almost always also exhibited AMR. Metagenomes inferred using PICRUSt2 also predicted significantly higher mean relative frequencies in 35207 for several AMR genes related to both specific and broad-spectrum AMR phenotypes. Together, these results support the hypothesis that chronic HM pollution alters the soil bacterial community structure in ecologically meaningful ways and may also select for bacteria with increased potential to contribute to AMR in human disease. IMPORTANCE Heavy metals cross-select for antimicrobial resistance in laboratory experiments, but few studies have documented this effect in polluted soils. Moreover, despite decades of awareness of heavy metal contamination at the EPA Superfund site in North Birmingham, Alabama, this is the first analysis of the impact of this pollution on the soil microbiome. Specifically, this work advances the understanding of the relationship between heavy metals, microbial diversity, and patterns of antibiotic resistance in North Birmingham soils. Our results suggest that polluted soils carry a risk of increased exposure to antibiotic-resistant infections in addition to the direct health consequences of heavy metals. Our work provides important information relevant to both political and scientific efforts to advance environmental justice for the communities that call Superfund neighborhoods home. 

Many microbial photoautotrophs depend on heterotrophic bacteria for accomplishing essential functions. Environmental changes, however, could alter or eliminate such interactions. We investigated the effects of changing pCO2 on gene transcription in co-cultures of 3 strains of picocyanobacteria (Synechococcus strains CC9311 and WH8102 and Prochlorococcus strain MIT9312) paired with the ‘helper’ bacterium Alteromonas macleodii EZ55. Co-culture with cyanobacteria resulted in a much higher number of up- and down-regulated genes in EZ55 than pCO2 by itself. Pathway analysis revealed significantly different transcription of genes involved in carbohydrate metabolism, stress response, and chemotaxis, with different patterns of up- or down-regulation in co-culture with different cyanobacterial strains. Gene transcription patterns of organic and inorganic nutrient transporter and catabolism genes in EZ55 suggested resources available in the culture media were altered under elevated (800 ppm) pCO2 conditions. Altogether, changing transcription patterns were consistent with the possibility that the composition of cyanobacterial excretions changed under the two pCO2 regimes, causing extensive ecophysiological changes in both members of the co-cultures. Additionally, significant downregulation of oxidative stress genes in MIT9312/EZ55 cocultures at 800 ppm pCO2 were consistent with a link between the predicted reduced availability of photorespiratory byproducts (i.e., glycolate/2PG) under this condition and observed reductions in internal oxidative stress loads for EZ55, providing a possible explanation for the previously observed lack of “help” provided by EZ55 to MIT9312 under elevated pCO2. If similar broad alterations in microbial ecophysiology occur in the ocean as atmospheric pCO2 increases, they could lead to substantially altered ecosystem functioning and community composition.

 

ABSTRACT Microalgal cultures are often maintained in xenic conditions, i.e., with associated bacteria, and many studies indicate that these communities both are complex and have significant impacts on the physiology of the target photoautotroph. Here, we investigated the structure and stability of microbiomes associated with a diverse sampling of diatoms during long-term maintenance in serial batch culture. We found that, counter to our initial expectation, evenness diversity increased with time since cultivation, driven by a decrease in dominance by the most abundant taxa in each culture. We also found that the site from which and time at which a culture was initially collected had a stronger impact on microbiome structure than the diatom species; however, some bacterial taxa were commonly present in most cultures despite having widely geographically separated collection sites. Our results support the conclusion that stochastic initial conditions (i.e., the local microbial community at the collection site) are important for the long-term structure of these microbiomes, but deterministic forces such as negative frequency dependence and natural selection exerted by the diatom are also at work. IMPORTANCE Natural microbial communities are extremely complex, with many more species coexisting in the same place than there are different resources to support them. Understanding the forces that allow this high level of diversity has been a central focus of ecological and evolutionary theory for many decades. Here, we used stock cultures of diatoms, which were maintained for years in continuous growth alongside populations of bacteria, as proxies for natural communities. We show that the bacterial communities remained relatively stable for years, and there is evidence that ecological forces worked to stabilize coexistence instead of favoring competition and exclusion. We also show evidence that, despite some important regional differences in bacterial communities, there was a globally present core microbiome potentially selected for in these diatom cultures. Understanding interactions between bacteria and diatoms is important both for basic ecological science and for practical science, such as industrial biofuel production. 

ABSTRACT We previously developed and assessed “The Art of Microbiology,” a course-based undergraduate research experience (CURE) which uses agar art to spur student experimentation, where we found student outcomes related to science persistence. However, these outcomes were not correlated with specific activities and gains were not reported from more than one class. In this study, we explored which of the three major activities in this CURE—agar art, experimental design, or poster presentations—affected student engagement and outcomes associated with improved understanding of the nature of science (NOS). The Art of Microbiology was studied in three microbiology teaching laboratories: at a research university with either the CURE developer (18 students) or a CURE implementer (39 students) and at a community college with a CURE implementer (25 students). Our quasi-experimental mixed methods study used pre/post-NOS surveys and semi-structured class-wide interviews. Community college students had lower baseline NOS responses but had gains in NOS similar to research university students post-CURE. We surveyed research university students following each major activity using the Assessing Student Perspective of Engagement in Class Tool (ASPECT) survey but did not find a correlation between NOS and activity engagement. Of the three activities, we found the highest engagement with agar art, especially in the CURE developer class. Interviewed students in all classes described agar art as a fun, relevant, and low-stakes assignment. This work contributes to the evidence supporting agar art as a curricular tool, especially in ways that can add research to classrooms in and beyond the research university. 

Many biological functions are leaky, and organisms that perform them contribute some of their products to a community “marketplace” in which nonperforming individuals may compete for them. Leaky functions are partitioned unequally in microbial communities, and the evolutionary forces determining which species perform them and which become beneficiaries are poorly understood. Here, we demonstrate that the market principle of comparative advantage determines the distribution of a leaky antibiotic resistance gene in an environment occupied by two “species”—strains ofEscherichia coligrowing on mutually exclusive resources and thus occupying separate niches. Communities comprised of antibiotic-resistant cells were rapidly invaded by sensitive cells of both types. While the two phenotypes coexisted stably for 500 generations, in 15/18 replicates, antibiotic sensitivity became fixed in one species. Fixation always occurred in the same species despite both species being genetically identical except for their niche-defining mutation. In the absence of antibiotic, the fitness cost of resistance was identical in both species. However, the intrinsic resistance of the species that ultimately became the sole helper was significantly lower, and thus its reward for expressing the resistance gene was higher. Opportunity cost of resistance, not absolute cost or efficiency of antibiotic removal, determined which species became the helper, consistent with the economic theory of comparative advantage. We present a model that suggests that this market-like dynamic is a general property of Black Queen systems and, in communities dependent on multiple leaky functions, could lead to the spontaneous development of an equitable and efficient division of labor.

 

Anxiety can impact overall performance and persistence in college. Student response systems (SRSs), real-time active-learning technologies used to engage students and gauge their understanding, have been shown to elicit anxiety for some students. Kahoot! is an SRS technology that differs from others in that it involves gamification, the use of gamelike elements. Recent studies have explored the impact of active-learning strategies on student anxiety across different institutions, but there is little known about how Kahoot! impacts student perceived anxiety, especially in comparison with other active-learning strategies. In two complementary yet parallel studies of introductory biology courses at a western research-intensive institution ( n = 694) and a southeastern research-intensive institution ( n = 60), we measured students’ perceived anxiety. We then explored how students were influenced by nongraded Kahoot! play and other elements of instruction. Using previously developed and course-specific pre- and post-course surveys, we found students at both universities agreed that nongraded Kahoot! play caused less anxiety compared with other pedagogical practices, such as working in small groups or reading the textbook. After playing Kahoot!, lower-performing students demonstrated greater engagement and lower levels of anxiety compared with their peers, suggesting that Kahoot! may be a particularly engaging active-learning strategy for these students. 

[ABSTRACT] Educators need to create an informed scientifically aware citizenry, especially in the era of the COVID-19 pandemic, where public health measures have focused on increasing adoption of safe behaviors for reducing the transmission of COVID-19. Non-major science students make up an important, yet understudied, part of our public, given that they constitute tomorrow’s voters, workers, consumers, and policy-makers. Expecting that non-majors may benefit from a module connecting COVID-19 to community education, we implemented a novel E-service-learning module in light of the transition from an in-person course to an online platform. Our 4-week module included expert-led lectures, assigned digital infographics about COVID-19 safety precautions, and a required post-reflection assignment summarizing their learning gains. Out of 112 enrolled students, 87 consented to have their reflections analyzed and 8 students chose to participate in additional one-on-one online interviews. In an effort to determine which parts of our module garnered the most student commentary, we grouped post-reflection and interview data into four categories: service-learning infographic, service-learning guest lectures, information on COVID-19, and the broader implications of COVID-19. While 13% of students explicitly referenced infographics in their reflections, a far greater proportion (37%) explicitly referenced learning gains related to the expert-led lectures. Based on these findings, we encourage other educators to continue to explore the impact of E-service-learning content and assignments to help maximize learning in an online classroom environment during the COVID-19 pandemic and beyond. 

Course-based undergraduate research experiences (CUREs) often involve a component where the outcomes of student research are broadly relevant to outside stakeholders. We wanted to see if building courses around an environmental justice issue relevant to the local community would impact students’ sense of civic engagement and appreciation of the relevance of scientific research to the community. In this quasi-experimental study, we assessed civic engagement and scientific identity gains ( N = 98) using pre- and post-semester surveys and open-ended interview responses in three different CUREs taught simultaneously at three different universities. All three CURES were focused on an environmental heavy metal pollution issue predominantly affecting African–Americans in Birmingham, Alabama. While we found increases in students’ sense of science efficacy and identity, our team was unable to detect meaningful changes in civic engagement levels, all of which were initially quite high. However, interviews suggested that students were motivated to do well in their research because the project was of interest to outside stakeholders. Our observations suggest that rather than directly influencing students’ civic engagement, the “broadly relevant” component of our CUREs engaged their pre-existing high levels of engagement to increase their engagement with the material, possibly influencing gains in science efficacy and science identity. Our observations are consistent with broader community relevance being an important component of CURE success, but do not support our initial hypothesis that CURE participation would influence students’ attitudes toward the civic importance of science.