Extensive horizontal gene transfer in cheese-associated bacteria.

Acquisition of genes through horizontal gene transfer (HGT) allows microbes to rapidly gain new capabilities and adapt to new or changing environments. Identifying widespread HGT regions within multispecies microbiomes can pinpoint the molecular mechanisms that play key roles in microbiome assembly. We sought to identify horizontally transferred genes within a model microbiome, the cheese rind. Comparing 31 newly sequenced and 134 previously sequenced bacterial isolates from cheese rinds, we identified over 200 putative horizontally transferred genomic regions containing 4733 protein coding genes. The largest of these regions are enriched for genes involved in siderophore acquisition, and are widely distributed in cheese rinds in both Europe and the US. These results suggest that HGT is prevalent in cheese rind microbiomes, and that identification of genes that are frequently transferred in a particular environment may provide insight into the selective forces shaping microbial communities

Biotic Interactions Shape the Ecological Distributions of Staphylococcus Species.

Many metagenomic sequencing studies have observed the presence of closely related bacterial species or genotypes in the same microbiome. Previous attempts to explain these patterns of microdiversity have focused on the abiotic environment, but few have considered how biotic interactions could drive patterns of microbiome diversity. We dissected the patterns, processes, and mechanisms shaping the ecological distributions of three closely related Staphylococcus species in cheese rind biofilms. Paradoxically, the most abundant species (S. equorum) is the slowest colonizer and weakest competitor based on growth and competition assays in the laboratory. Through in vitro community reconstructions, we determined that biotic interactions with neighboring fungi help resolve this paradox. Species-specific stimulation of the poor competitor by fungi of the genus Scopulariopsis allows S. equorum to dominate communities in vitro as it does in situ Results of comparative genomic and transcriptomic experiments indicate that iron utilization pathways, including a homolog of the S. aureus staphyloferrin B siderophore operon pathway, are potential molecular mechanisms underlying Staphylococcus-Scopulariopsis interactions. Our integrated approach demonstrates that fungi can structure the ecological distributions of closely related bacterial species, and the data highlight the importance of bacterium-fungus interactions in attempts to design and manipulate microbiomes.ImportanceDecades of culture-based studies and more recent metagenomic studies have demonstrated that bacterial species in agriculture, medicine, industry, and nature are unevenly distributed across time and space. The ecological processes and molecular mechanisms that shape these distributions are not well understood because it is challenging to connect in situ patterns of diversity with mechanistic in vitro studies in the laboratory. Using tractable cheese rind biofilms and a focus on coagulase-negative staphylococcus (CNS) species, we demonstrate that fungi can mediate the ecological distributions of closely related bacterial species. One of the Staphylococcus species studied, S. saprophyticus, is a common cause of urinary tract infections. By identifying processes that control the abundance of undesirable CNS species, cheese producers will have more precise control on the safety and quality of their products. More generally, Staphylococcus species frequently co-occur with fungi in mammalian microbiomes, and similar bacterium-fungus interactions may structure bacterial diversity in these systems

Want to change perspectives on social justice? Academic courses and social movements matter

Background: Ending systemic racism and other interrelated forms of oppression depends on institutional change, as well as changing individuals’ hearts and minds. The present study examines first the impact of a course focusing on social justice and second the impact of 2020, with the COVID-19 pandemic, a critical stage of the Black Lives Matter Movement, and increasing awareness of racism and classism. Method: Participants were 139 WCU students (87% female identified, 36% BIPOC): 101 were enrolled in 2017-2019, and 38 in 2020. Measures included the White Privileges Attitudes Scale (Pinterits, Poteat, & Spanierman, 2009) in its original form as well as an adapted form to measure attitudes about middle class privilege, and the Coping with Discrimination Scale (Wei, Alvarez, Ku, Russell, & Bonett, 2010). Results and Implications: A repeated measures MANCOVA revealed significant change from pre- to post-course in student ratings for awareness of White privilege, willingness to confront White privilege, willingness to confront middle class privilege, and interest in advocating for education about discrimination. A GLM comparing pre-course scores for students in 2017-2019 versus those in 2020, revealed significant differences for awareness of White privilege, remorse about White privilege, awareness of middle-class privilege, willingness to confront middle class privilege, remorse about middle class privilege, interest in advocating for education about discrimination, interest in resisting discrimination, and detachment from discrimination. If we are interested in changing perspectives about issues of social justice, academic courses can matter, but social conditions and movements may matter more

The Irreversible Loss of a Decomposition Pathway Marks the Single Origin of an Ectomycorrhizal Symbiosis

Microbial symbioses have evolved repeatedly across the tree of life, but the genetic changes underlying transitions to symbiosis are largely unknown, especially for eukaryotic microbial symbionts. We used the genus Amanita, an iconic group of mushroom-forming fungi engaged in ectomycorrhizal symbioses with plants, to identify both the origins and potential genetic changes maintaining the stability of this mutualism. A multi-gene phylogeny reveals one origin of the symbiosis within Amanita, with a single transition from saprotrophic decomposition of dead organic matter to biotrophic dependence on host plants for carbon. Associated with this transition are the losses of two cellulase genes, each of which plays a critical role in extracellular decomposition of organic matter. However a third gene, which acts at later stages in cellulose decomposition, is retained by many, but not all, ectomycorrhizal species. Experiments confirm that symbiotic Amanita species have lost the ability to grow on complex organic matter and have therefore lost the capacity to live in forest soils without carbon supplied by a host plant. Irreversible losses of decomposition pathways are likely to play key roles in the evolutionary stability of these ubiquitous mutualisms.Organismic and Evolutionary Biolog

Polo-Like Kinase 1 Directs Assembly of the HsCyk-4 RhoGAP/Ect2 RhoGEF Complex to Initiate Cleavage Furrow Formation

To complete cell division with high fidelity, cytokinesis must be coordinated with chromosome segregation. Mammalian Polo-like kinase 1, Plk1, may function as a critical link because it is required for chromosome segregation and establishment of the cleavage plane following anaphase onset. A central spindle–localized pool of the RhoGEF Ect2 promotes activation of the small GTPase RhoA, which drives contractile ring assembly at the equatorial cortex. Here, we have investigated how Plk1 promotes the central spindle recruitment of Ect2. Plk1 phosphorylates the noncatalytic N terminus of the RhoGAP HsCyk-4 at the central spindle, creating a phospho-epitope recognized by the BRCA1 C-terminal (BRCT) repeats of Ect2. Failure to phosphorylate HsCyk-4 blocks Ect2 recruitment to the central spindle and the subsequent induction of furrowing. Microtubules, as well as the microtubule-associated protein (MAP) Prc1, facilitate Plk1 phosphorylation of HsCyk-4. Characterization of a phosphomimetic version of HsCyk-4 indicates that Plk1 promotes Ect2 recruitment through multiple targets. Collectively, our data reveal that formation of the HsCyk-4-Ect2 complex is subject to multiple layers of regulation to ensure that RhoA activation occurs between the segregated sister chromatids during anaphase.</p

Tapping the Geoscience Two-Year College Student Reservoir: Factors that Influence Student Transfer Intent and Physical Science Degree Aspirations

Colleges and universities are facing greater accountability to identify and implement practices that increase the number of two-year college (2YC) students who transfer to four-year institutions (4YC) and complete baccalaureate degrees. This is particularly true for physical science and geoscience disciplines, which have the lowest STEM degree completion rates of students transferring from 2YCs (Wilson, 2014a). A better understanding of how academic engagement experiences contribute to increased 2YC student interest in these disciplines and student intent to transfer is critical in strengthening the transfer pathway for the physical sciences and geosciences. The purpose of this study was to gain understanding of the influence that background characteristics, mathematics preparation, academic experiences (e.g. faculty-student interaction, undergraduate research experiences, and field experiences), and academic advisor engagement have on 2YC student intentions to transfer to a four-year institution (4YC) with physical science or geoscience degree aspirations. Incorporating the conceptual frameworks of student engagement and transfer student capital (Laanan et al., 2010), this study used Astin’s (1993; 1999) input-environment-outcomes (I-E-O) model to investigate what factors predict 2YC students’ intent to transfer to a 4YC and pursue physical science or geoscience degrees. This study used a quantitative research approach with data collected from 751 student respondents from 24 2YCs. Results from three sequential multiple regression models revealed advisor interaction, speaking with a transfer advisor, and visiting the intended 4YC were significant in increased 2YC student transfer intent. Student-faculty interaction and faculty and academic advisors discussing career opportunities in the physical sciences were significant in leading to increased 2YC student intent to pursue physical science degrees or geoscience degrees. The results also substantiated the significant role that field-based experiences have in increasing student intent in pursuing geoscience related majors. Surprisingly, developmental math placement was not found to be a significant predictor of transfer intent nor intent to pursue physical science or geoscience degrees. These findings reveal that developing practices focused on transfer student capital acquisition can strengthen the pipeline of physical science and geoscience degrees and supports the suggestion that 2YCs can serve as an intervention point to broaden participation in STEM related degrees