Freshwater iron mats are dynamic geochemical environments with broad ecological diversity, primarily formed by the iron-oxidizing bacteria. The community features functional groups involved in biogeochemical cycles for iron, sulfur, carbon, and nitrogen. Despite this complexity, iron mat communities provide an excellent model system for exploring microbial ecological interactions and ecological theories in situ. Syntrophies and competition between the functional groups in iron mats, how they connect cycles, and the maintenance of these communities by taxons outside bacteria (the eukaryota, archaea, and viruses) have been largely unstudied. Here, we review what is currently known about freshwater iron mat communities, the taxa that reside there, and the interactions between these organisms, and we propose ways in which future studies may uncover exciting new discoveries. For example, the archaea in these mats may play a greater role than previously thought as they are diverse and widespread in iron mats based on 16S rRNA genes and include methanogenic taxa. Studies with a holistic view of the iron mat community members focusing on their diverse interactions will expand our understanding of community functions, such as those involved in pollution removal. To begin addressing questions regarding the fundamental interactions and to identify the conditions in which they occur, more laboratory culturing techniques and coculture studies, more network and keystone species analyses, and the expansion of studies to more freshwater iron mat systems are necessary. Increasingly accessible bioinformatic, geochemical, and culturing tools now open avenues to address the questions that we pose herein.

The immune system is critical in defending against infection from pathogenic microorganisms. Individuals with weakened immune systems, such as the elderly, are more susceptible to infections and developing autoimmune and inflammatory diseases. The gut microbiome contains a plethora of bacteria and other microorganisms, which collectively plays a significant role in immune function and homeostasis. Gut microbiota are considered to be highly influential on host health and immune function. Therefore, dysbiosis of the microbiota could be a major contributor to the elevated incidence of multiple age-related pathologies. While there seems to be a general consensus that the composition of gut microbiota changes with age, very little is known about how diet and exercise might influence the aging microbiome. Here, we examine the current state of the literature regarding alterations to the gut microbiome as hosts age, drawing particular attention to the knowledge gaps in addressing how diet and exercise influence the aging microbiome. Further, we will demonstrate the need for more controlled studies to investigate the roles that diet and exercise play driving the composition, diversity, and function of the microbiome in an aging population.

Two global cycles, iron and sulfur, are critically interconnected in estuarine environments by microbiological actors. To this point, the methods of laboratory study of this interaction have been limited. Here we propose a methodology for co-culturing from numerous coastal environments, from the same source inocula, iron-oxidizing and sulfatereducing bacteria. The use of same source inocula is largely beneficial to understand real-world interactions that are likely occurring in situ. Through the use of this methodology, the ecological interactions between these groups can be studied in a more controlled environment. Here, we characterize the oxygen and hydrogen sulfide concentrations using microelectrode depth profiling in the co-cultures of iron-oxidizing bacteria and sulfate-reducing bacteria. These results suggest that while oxygen drives the relationship between these organisms and sulfate-reducers are reliant on iron-oxidizers in this culture to create an anoxic environment, there is likely another environmental driver that also influences the interaction as the two remain spatially distinct, as trends in FeS precipitation changed within the anoxic zone relative to the presence of Fe(III) oxyhydroxides. Understanding the relationship between iron-oxidizing and sulfate-reducing bacteria will ultimately have implications for understanding microbial cycling in estuarine environments as well as in processes such as controlling microbially influenced corrosion.

The issue of antibiotic resistance among bacterial pathogens is often misunderstood. Here, we present an activity that debunks misconceptions regarding microorganisms, such as bacterial pathogens, and addresses how antibiotics work. We propose this activity be incorporated into middle or high school classrooms addressing both this real-world issue and elements from the Next Generation Science Standards. Students are encouraged to use hands-on experiences toward hypothesis development and testing to better understand how antibiotic resistance is spread among bacterial pathogens and commensals. Over half of the students who participated in this activity self-reported that they were likely to share the information they learned outside of their classroom, reflecting real-time impacts on science stewardship in students. This activity also presents students with an issue that has clear action items they can undertake to effect positive change.