Biology and potential biogeochemical impacts of novel predatory flavobacteria

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010Predatory bacteria are ubiquitous in aquatic environments and may be important players in the ecology and biogeochemistry of microbial communities. Three novel strains belonging to two genera of marine flavobacteria, Olleya and Tenacibaculum, were cultured from coastal sediments and found to be predatory on other bacteria on surfaces. Two published species of the genus Tenacibaculum were also observed to grow by lysis of prey bacteria, raising the possibility that predation may be a widespread lifestyle amongst marine flavobacteria, which are diverse and abundant in a variety of marine environments. The marine flavobacterial clade is known to include species capable of photoheterotrophy, scavenging of polymeric organic substances, pathogenesis on animals, the degradation and lysis of phytoplankton blooms and, now, predation on bacterial communities. Strains from the two genera were found to exhibit divergent prey specificities and growth yields when growing predatorily. Olleya sp. predatory cells accumulated to an order of magnitude greater cell densities than Tenacibaculum sp. cells on equivalent prey cell densities. Experiments were conducted to constrain the potential of the novel isolates to affect prey communities under more environmentally relevant conditions. An investigation of the minimum number of predatory cells needed to generate clearings of prey cells found that the inoculation of individual predatory flavobacteria cells can ultimately result in dense lytic swarms. In some cases, the susceptibility of particular prey species to lysis by a flavobacterial predator was found to vary based on the growth state of the prey cells or the presence of their spent growth media. A novel methodology for the experimental study of biofilms was used to assess the impact of exposure to predatory marine flavobacteria on the release of macronutrients from prey biofilms. The Olleya sp. predator had a stimulative effect on macronutrient release while the Tenacibaculum sp. did not, further suggesting the two groups of predators are adapted to different ecological niches.Support by the National Science Foundation (NSF) Division of Molecular and Cellular Biosciences Grant (MCB- 0348425), the MIT Student Assistance Fund, the Woods Hole Oceanographic Institution (WHOI) Academic Programs Office, WHOI Coastal Ocean Institute (COI) and WHOI Ocean Venture Fund grant, COI and the WHOI Ocean Life Institute

Sports teams as complex adaptive systems: manipulating player numbers shapes behaviours during football small-sided games

Small-sided and conditioned games (SSCGs) in sport have been modelled as complex adaptive systems. Research has shown that the relative space per player (RSP) formulated in SSCGs can impact on emergent tactical behaviours. In this study we adopted a systems orientation to analyse how different RSP values, obtained through manipulations of player numbers, influenced four measures of interpersonal coordination observed during performance in SSCGs. For this purpose we calculated positional data (GPS 15 Hz) from ten U-15 football players performing in three SSCGs varying in player numbers (3v3, 4v4 and 5v5). Key measures of SSCG system behaviours included values of (1) players’ dispersion, (2) teams’ separateness, (3) coupling strength and time delays between participants’ emerging movements, respectively. Results showed that values of participants’ dispersion increased, but the teams’ separateness remained identical across treatments. Coupling strength and time delay also showed consistent values across SSCGs. These results exemplified how complex adaptive systems, like football teams, can harness inherent degeneracy to maintain similar team spatial–temporal relations with opponents through changes in inter-individual coordination modes (i.e., players’ dispersion). The results imply that different team behaviours might emerge at different ratios of field dimension/player numbers. Therefore, sport pedagogists should carefully evaluate the effects of changing RSP in SSCGs as a way of promoting increased or decreased pressure on players

Physical, Psychological and Emotional Benefits of Green Physical Activity: An Ecological Dynamics Perspective

© 2015 Springer International Publishing Switzerland Increasing evidence supports the multiple benefits to physical, psychological and emotional wellbeing of green physical activity, a topic of increasing interest in the past decade. Research has revealed a synergistic benefit of green physical activity, which includes all aspects of exercise and physical activity in the presence of nature. Our theoretical analysis suggests there are three distinct levels of engagement in green physical activity, with each level reported to have a positive effect on human behaviours. However, the extent to which each level of green physical activity benefits health and wellbeing is assumed to differ, requiring confirmation in future research. This elucidation of understanding is needed because previous literature has tended to focus on recording empirical evidence rather than developing a sound theoretical framework to understand green physical activity effects. Here we propose an ecological dynamics rationale to explain how and why green physical activity might influence health and wellbeing of different population groups. This framework suggests a number of unexplored, interacting constraints related to types of environment and population groups, which shape reported levels of benefit of green physical activity. Further analysis is needed to clarify the explicit relationship between green physical activity and health and wellbeing, including levels of engagement, types of environmental constraints, levels of physical activity, adventure effects, skill effects and sampling of different populations

Emergence of contact injuries in invasion team sports : an ecological dynamics rationale

The incidence of contact injuries in team sports is considerable, and injury mechanisms need to be comprehensively understood to facilitate the adoption of preventive measures. In Association Football, evidence shows that the highest prevalence of contact injuries emerges in one-on-one interactions. However, previous studies have tended to operationally report injury mechanisms in isolation, failing to provide a theoretical rationale to explain how injuries might emerge from interactions between opposing players. In this position paper, we propose an ecological dynamics framework to enhance current understanding of behavioural processes leading to contact injuries in team sports. Based on previous research highlighting the dynamics of performer–environment interactions, contact injuries are proposed to emerge from symmetry-breaking processes during on-field interpersonal interactions among competing players and the ball. Central to this approach is consideration of candidate control parameters that may provide insights on the information sources used by players to reduce risk of contact injuries during performance. Clinically, an ecological dynamics analysis could allow sport practitioners to design training sessions based on selected parameter threshold values as primary and/or secondary preventing measures during training and rehabilitation sessions

Numerical relations and skill level constrain co-adaptive behaviors of agents in sports teams

Similar to other complex systems in nature (e.g., a hunting pack, flocks of birds), sports teams have been modeled as social neurobiological systems in which interpersonal coordination tendencies of agents underpin team swarming behaviors. Swarming is seen as the result of agent co-adaptation to ecological constraints of performance environments by collectively perceiving specific possibilities for action (affordances for self and shared affordances). A major principle of invasion team sports assumed to promote effective performance is to outnumber the opposition (creation of numerical overloads) during different performance phases (attack and defense) in spatial regions adjacent to the ball. Such performance principles are assimilated by system agents through manipulation of numerical relations between teams during training in order to create artificially asymmetrical performance contexts to simulate overloaded and underloaded situations. Here we evaluated effects of different numerical relations differentiated by agent skill level, examining emergent inter-individual, intra- and inter-team coordination. Groups of association football players (national - NLP and regional-level - RLP) participated in small-sided and conditioned games in which numerical relations between system agents were manipulated (5v5, 5v4 and 5v3). Typical grouping tendencies in sports teams (major ranges, stretch indices, distances of team centers to goals and distances between the teams' opposing line-forces in specific team sectors) were recorded by plotting positional coordinates of individual agents through continuous GPS tracking. Results showed that creation of numerical asymmetries during training constrained agents' individual dominant regions, the underloaded teams' compactness and each team's relative position on-field, as well as distances between specific team sectors. We also observed how skill level impacted individual and team coordination tendencies. Data revealed emergence of co-adaptive behaviors between interacting neurobiological social system agents in the context of sport performance. Such observations have broader implications for training design involving manipulations of numerical relations between interacting members of social collectives

High-risk pooling for mitigating risk selection incentives in health insurance markets with sophisticated risk equalization:an application based on health survey information

Background: Despite sophisticated risk equalization, insurers in regulated health insurance markets still face incentives to attract healthy people and avoid the chronically ill because of predictable differences in profitability between these groups. The traditional approach to mitigate such incentives for risk selection is to improve the risk-equalization model by adding or refining risk adjusters. However, not all potential risk adjusters are appropriate. One example are risk adjusters based on health survey information. Despite its predictiveness of future healthcare spending, such information is generally considered inappropriate for risk equalization, due to feasibility challenges and a potential lack of representativeness. Methods: We study the effects of high-risk pooling (HRP) as a strategy for mitigating risk selection incentives in the presence of sophisticated– though imperfect– risk equalization. We simulate a HRP modality in which insurers can ex-ante assign predictably unprofitable individuals to a ‘high risk pool’ using information from a health survey. We evaluate the effect of five alternative pool sizes based on predicted residual spending post risk equalization on insurers’ incentives for risk selection and cost control, and compare this to the situation without HRP. Results: The results show that HRP based on health survey information can substantially reduce risk selection incentives. For example, eliminating the undercompensation for the top-1% with the highest predicted residual spending reduces selection incentives against the total group with a chronic disease (60% of the population) by approximately 25%. Overall, the selection incentives gradually decrease with a larger pool size. The largest marginal reduction is found moving from no high-risk pool to HRP for the top 1% individuals with the highest predicted residual spending. Conclusion: Our main conclusion is that HRP has the potential to considerably reduce remaining risk selection incentives at the expense of a relatively small reduction of incentives for cost control. The extent to which this can be achieved, however, depends on the design of the high-risk pool.</p

High-risk pooling for mitigating risk selection incentives in health insurance markets with sophisticated risk equalization:an application based on health survey information

Background: Despite sophisticated risk equalization, insurers in regulated health insurance markets still face incentives to attract healthy people and avoid the chronically ill because of predictable differences in profitability between these groups. The traditional approach to mitigate such incentives for risk selection is to improve the risk-equalization model by adding or refining risk adjusters. However, not all potential risk adjusters are appropriate. One example are risk adjusters based on health survey information. Despite its predictiveness of future healthcare spending, such information is generally considered inappropriate for risk equalization, due to feasibility challenges and a potential lack of representativeness. Methods: We study the effects of high-risk pooling (HRP) as a strategy for mitigating risk selection incentives in the presence of sophisticated– though imperfect– risk equalization. We simulate a HRP modality in which insurers can ex-ante assign predictably unprofitable individuals to a ‘high risk pool’ using information from a health survey. We evaluate the effect of five alternative pool sizes based on predicted residual spending post risk equalization on insurers’ incentives for risk selection and cost control, and compare this to the situation without HRP. Results: The results show that HRP based on health survey information can substantially reduce risk selection incentives. For example, eliminating the undercompensation for the top-1% with the highest predicted residual spending reduces selection incentives against the total group with a chronic disease (60% of the population) by approximately 25%. Overall, the selection incentives gradually decrease with a larger pool size. The largest marginal reduction is found moving from no high-risk pool to HRP for the top 1% individuals with the highest predicted residual spending. Conclusion: Our main conclusion is that HRP has the potential to considerably reduce remaining risk selection incentives at the expense of a relatively small reduction of incentives for cost control. The extent to which this can be achieved, however, depends on the design of the high-risk pool.</p

Attractive Stepping Stones Landscapes:Preference for Stone Height Variation Appears to Be Age Independent

An earlier study on the attractiveness of stepping stones configurations revealed that children like variation in stone height better than variation in stone size or gap width. In the present study, we conducted two experiments to examine whether this preference is found also in young and older adults. In Experiment 1, participants stepped freely in a standardized configuration, and three configurations with either height, size or gap width variation. Most interestingly, adults judged playgrounds with variation in stone height as most fun and beautiful, suggesting that the preference for variation in height is indeed age independent. In Experiment 2, we compared the configuration with only height variation with three configurations in which variation in height was combined with variation in stone size or gap width, or both. Although we found no significant differences among the configurations in the older adults, young adults judged the combination of height with size and gap width variation as more fun and esthetically appealing than the configuration with only height variation. The implications of our findings for playground research and designers are discussed.</p