Higher-order interaction inhibits bacterial invasion of a phototroph-predator microbial community

The composition of an ecosystem is thought to be important for determining its resistance to invasion. Studies of natural ecosystems, from plant to microbial communities, have found that more diverse communities are more resistant to invasion. It is thought that more diverse communities resist invasion by more completely consuming the resources necessary for invaders. Here we show that Escherichia coli can successfully invade cultures of the alga Chlamydomonas reinhardtii (phototroph) or the ciliate Tetrahymena thermophila (predator), but cannot invade a community where both are present. The invasion resistance of the algae-ciliate community arises from a higher-order (3-way) interaction that is unrelated to resource consumption. We show that the mechanism of this interaction is the algal inhibition of bacterial aggregation which leaves bacteria vulnerable to ciliate predation. This mechanism requires both the algae and the ciliate to be present and provides an example of invasion resistance through a trait-mediated higher-order interaction. In a separate project we explore how the environment determines evolutionary trajectory when there exists a trade-off between beneficial traits. We select Escherichia coli for faster migration through a porous environment, a process which depends on both motility and growth. Evolving faster migration in rich medium results in slow growth and fast swimming, while evolution in minimal medium results in fast growth and slow swimming. Given that both fast growth and fast swimming would enhance migration rate, this result suggests that there is a trade-off between these two phenotypes and that the direction of evolution depends on the environment

Closed microbial communities self-organize to persistently cycle carbon

Cycles of nutrients (N, P, etc.) and resources (C) are a defining emergent feature of ecosystems. Cycling plays a critical role in determining ecosystem structure at all scales, from microbial communities to the entire biosphere. Stable cycles are essential for ecosystem persistence because they allow resources and nutrients to be regenerated. Therefore, a central problem in ecology is understanding how ecosystems are organized to sustain robust cycles. Addressing this problem quantitatively has proved challenging because of the difficulties associated with manipulating ecosystem structure while measuring cycling. We address this problem using closed microbial ecosystems (CES), hermetically sealed microbial consortia provided with only light. We develop a technique for quantifying carbon cycling in hermetically sealed microbial communities and show that CES composed of an alga and diverse bacterial consortia self-organize to robustly cycle carbon for months. Comparing replicates of diverse CES, we find that carbon cycling does not depend strongly on the taxonomy of the bacteria present. Moreover, despite strong taxonomic differences, self-organized CES exhibit a conserved set of metabolic capabilities. Therefore, an emergent carbon cycle enforces metabolic but not taxonomic constraints on ecosystem organization. Our study helps establish closedmicrobial communities as model ecosystems to study emergent function and persistence in replicate systems while controlling community composition and the environment. © 2021 National Academy of Sciences. All rights reserved

Evaluated Community Fire Safety Interventions in the United States: A Review of Current Literature

The purpose of the study was to assess the state of fire prevention research, provide an updated synthesis of evaluated fire prevention programs, and discuss the role of fire fighters and data systems in prevention efforts. The review included all evaluations of U.S. based fire prevention interventions published between January 1998 and September 2004 and any earlier articles about U.S. fire prevention interventions not included in two prior review articles. We retrieved information from each identified study including evaluation findings, involvement of fire service personnel and use of existing data systems. We identified twelve articles: seven reported on smoke alarm interventions, three on multi-faceted programs, and two other programs. Five programs involved fire service personnel in the design, implementation, and/or evaluation, and three used existing data systems. Studies reviewed suggest that canvassing and smoke alarm installations are the most effective means of distributing alarms and increasing the functional status of distributed alarms. The functionality of smoke alarms, an issue noted in earlier reviews, remains a problem. Programs involving partnerships with fire departments have indicated success in preventing fires and deaths, improving smoke alarm ownership and functional status, and improving children’s fire safety knowledge. Using existing data systems to target and to evaluate interventions was effective. In the years since prior reviews, some improvements in the rigor of evaluation designs have been made, but there is still a need for high quality evaluations that will inform fire injury prevention efforts

Review of Carbur\u27s restaurant, which was established in 1977 and has survived th

Review of Carbur\u27s restaurant, which was established in 1977 and has survived the changes the Old Port has seen since that time