Although molecular data have revealed the vast scope of microbial diversity, two fundamental questions remain unanswered even for well-defined natural microbial communities: how many bacterial types co-exist, and are such types naturally organized into phylogenetically discrete units of potential ecological significance? It has been argued that without such information, the environmental function, population biology and biogeography of microorganisms cannot be rigorously explored. Here we address these questions by comprehensive sampling of two large 16S ribosomal RNA clone libraries from a coastal bacterioplankton community. We show that compensation for artefacts generated by common library construction techniques reveals fine-scale patterns of community composition. At least 516 ribotypes (unique rRNA sequences) were detected in the sample and, by statistical extrapolation, at least 1,633 co-existing ribotypes in the sampled population. More than 50% of the ribotypes fall into discrete clusters containing less than 1% sequence divergence. This pattern cannot be accounted for by interoperon variation, indicating a large predominance of closely related taxa in this community. We propose that such microdiverse clusters arise by selective sweeps and persist because competitive mechanisms are too weak to purge diversity from within them.

The genomic diversity and relative importance of distinct genotypes within natural bacterial populations have remained largely unknown. Here, we analyze the diversity and annual dynamics of a group of coastal bacterioplankton (greater than 99% 16 S ribosomal RNA identity to Vibrio splendidus ). We show that this group consists of at least a thousand distinct genotypes, each occurring at extremely low environmental concentrations (on average less than one cell per milliliter). Overall, the genomes show extensive allelic diversity and size variation. Individual genotypes rarely recurred in samples, and allelic distribution did not show spatial or temporal substructure. Ecological considerations suggest that much genotypic and possibly phenotypic variation within natural populations should be considered neutral.

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Abstract:The study aimed to evaluate co-benefits in term of GHG reduction, and avoided landfill costs by implementing a community-based management (CBM) program for municipal solid waste (MSW). Two towns of peri-urban settlement in Thailand were investigated in case studies to compare eco-performance between the towns with and without implementation of the CBM program. MSW mass flows together with MSW utilization records were analyzed based on data in year 2013. Climate co-benefits from waste utilization activities were examined. Results from the study indicated that waste banks in the CBM program can effectively divert most of recyclables from entering landfills. The performance of "waste bank-recyclable recovery program" recycling rate from the case study with CBM is 172.20 kg per member per year, which is about 926% higher than average CBMs with MSW recycling in Thailand, and the success of CBM can be attributed to its curbside pickup service and fair-pricing of recyclables. The study also found that if the town decided to divert wastes from landfilling, carbon intensity of the MSW system would be 0.47 tons of CO2-eq per ton of collected MSW. The landfilling cost would be approximately 7.41 USD per ton of MSW as landfilling cost. With CBM programs, current MSW reutilization rate has achieved 9.68% of generated waste, and 16.80% of GHG emission has been avoided, along OPEN ACCESSSustainability 2015, 7 7418 with a reduction in landfill costs of 11.57%. Two scenarios of waste utilization in Thailand were explored and compared, in terms of which scenarios yielded the highest co-benefits. The study demonstrates that by allowing local mechanism and community involvement programs to develop with operational waste banks, the efficiency of collecting recycling wastes increased. A similar system can be applied to other communities in other countries.

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