Biofilm-Mediated Fragmentation and Degradation of Microcrystalline Cellulose by Cellulomonas flavigena KU (ATCC 53703).

Cellulomonas flavigena KU (ATCC 53703) produces an extracellular matrix involved in the degradation of microcrystalline cellulose. This extracellular material is primarily composed of the gel-forming, ß-1,3-glucan known as curdlan and associated, cellulose-degrading enzymes. In this study, the effects of various forms of nutrient limitation on cellulose attachment, cellular aggregation, curdlan production, and biofilm formation were investigated throughout a 7-day incubation period by using phase-contrast microscopy. Compared to cultures grown in non-limiting media, nitrogen-limitation promoted early attachment of C. flavigena KU cells to the cellulose surface, and cellulose attachment was congruent with cellular aggregation and curdlan production. Over the course of the experiment, microcolonies of attached cells grew into curdlan-producing biofilms on the cellulose. By contrast, bacterial cells grown on cellulose in non-limiting media remained unattached and unaggregated throughout most of the incubation period. By 7 days of incubation, bacterial aggregation was ninefold greater in N-limited cultures compared to nutritionally complete cultures. In a similar way, phosphorus- and vitamin-limitation (i.e., yeast extract-limitation) also resulted in early cellulose attachment and biofilm formation. Furthermore, nutrient limitation promoted more rapid and efficient fragmentation and degradation of cellulose, with cellulose fragments in low-N media averaging half the size of those in high-N media after 7 days. Two modes of cellulose degradation are proposed for C. flavigena KU, a "planktonic mode" and a "biofilm mode". Similar observations have been reported for other curdlan-producing cellulomonads, and these differing cellulose degradation strategies may ultimately prove to reflect sequential stages of a multifaceted biofilm cycle important in the bioconversion of this abundant and renewable natural resource.

How to develop young physical activity leaders? A Delphi study.

The International Society for Physical Activity and Health advocates for increased capability of the physical activity workforce as a key ingredient to a system-based approach. Young leader programmes are gaining traction globally as peers are a primary influence on young people and positive role models are important for increasing or maintaining physical activity. Yet, there is limited understanding of 'what works' for training young physical activity leaders. This study aims to develop a consensus on how to identify and support young people to become physical activity leaders. An iterative three-phased mixed methods Delphi consensus approach. A rapid review focused on the feasibility, acceptability and impact of existing young leader physical activity training (phase one); focus groups (n = 3) and interviews (n = 6) with 15 practitioners and young leaders to examine young physical activity leader training needs (phase two); and a three-round questionnaire process (phase three). Stakeholders (n = 43) from across the public, voluntary and education sectors, academics and young leaders completed all questionnaires. A consensus was reached for 75 statements related to: young leader traits prior to and following training, recruitment methods, training content, delivery format and context, relationships, incentives, and skill development. The Delphi process, combining insight from multi-sectoral stakeholders, identified a range of factors that underpin young leader training programmes. These factors should be applied to develop a curriculum and comprehensive training programme to provide young leaders with the required capability to be effective within their roles, and ultimately support an increase in physical activity amongst children and young people.