The emergence of bacterial pathogens resistant to all known antibiotics is a global health crisis. Adding to this problem is that major pharmaceutical companies have shifted away from antibiotic discovery due to low profitability. As a result, the pipeline of new antibiotics is essentially dry and many bacteria now resist the effects of most commonly used drugs. To address this global health concern, citizen science through the Small World Initiative (SWI) was formed in 2012. As part of SWI, students isolate bacteria from their local environments, characterize the strains, and assay for antibiotic production. During the 2015 fall semester at Bowling Green State University, students isolated 77 soil‐derived bacteria and genetically characterized strains using the 16S rRNA gene, identified strains exhibiting antagonistic activity, and performed an expanded SWI workflow using transposon mutagenesis to identify a biosynthetic gene cluster involved in toxigenic compound production. We identified one mutant with loss of antagonistic activity and through subsequent whole‐genome sequencing and linker‐mediated PCR identified a 24.9 kb biosynthetic gene locus likely involved in inhibitory activity in that mutant. Further assessment against human pathogens demonstrated the inhibition of Bacillus cereus, Listeria monocytogenes, and methicillin‐resistant Staphylococcus aureus in the presence of this compound, thus supporting our molecular strategy as an effective research pipeline for SWI antibiotic discovery and genetic characterization.

Ice-nucleating particles (INPs) associated with fresh waters are a neglected, but integral component of the water cycle. Abundant INPs were identified from surface waters of both the Maumee River and Lake Erie with ice nucleus spectra spanning a temperature range from −3 to −15 °C. The majority of river INPs were submicron in size and attributed to biogenic macromolecules, inferred from the denaturation of ice-nucleation activity by heat. In a watershed dominated by row-crop agriculture, higher concentrations of INPs were found in river samples compared to lake samples. Further, ice-nucleating temperatures differed between river and lake samples, which indicated different populations of INPs. Seasonal analysis of INPs that were active at warmer temperatures (≥−10 °C; INP −10 ) showed their concentration to correlate with river discharge, suggesting a watershed origin of these INPs. A terrestrial origin for INPs in the Maumee River was further supported by a correspondence between the ice-nucleation signatures of river INPs and INPs derived from the soil fungus Mortierella alpina. Aerosols derived from turbulence features in the river carry INP −10 , although their potential influence on regional weather is unclear. INP −10 contained within aerosols generated from a weir spanning the river, ranged in concentration from 1 to 11 INP m −3 , which represented a fold-change of 3.2 over average INP −10 concentrations sampled from aerosols at control locations.

In nutrient-poor habitats, competition for limited resources is thought to select for organisms with an enhanced ability to scavenge nutrients and utilize them efficiently. Such adaptations characterize the cyanobacterium Prochlorococcus , the most abundant photosynthetic organism in the nutrient-limited open ocean.

The marine cyanobacterium Prochlorococcus numerically dominates the phytoplankton community of the nutrient-limited open ocean, establishing itself as the most abundant photosynthetic organism on Earth. This ecological success has been attributed to lower cell quotas for limiting nutrients, superior resource acquisition, and other advantages associated with cell size reduction and genome streamlining. In this study we tested the prediction that Prochlorococcus outcompetes its rivals for scarce nutrients, and that this advantage leads to its numerical success in nutrient-limited waters. Strains of Prochlorococcus and its sister genus Synechococcus grew well in both mono- and co-culture when nutrients were replete. However, in nitrogen-limited medium Prochlorococcus outgrew Synechococcus, but only when heterotrophic bacteria were also present. In the nitrogen-limited medium, the heterotroph Alteromonas macleodii outcompeted Synechococcus for nitrogen, but only if stimulated by exudate released by Prochlorococcus, or if a proxy organic carbon source was provided. Analysis of a nitrate reductase mutant Alteromonas suggested that Alteromonas outcompetes Synechococcus for nitrate, during which co-cultured Prochlorococcus grows on ammonia or other available nitrogen species. We propose that Prochlorococcus can stimulate antagonism between heterotrophic bacteria and potential phytoplankton competitors through a metabolic cross-feeding interaction, and this stimulation could contribute to the numerical success of Prochlorococcus in the nutrient-limited regions of the ocean.