engleski

Comparison of bacterial communities on limnic vs. coastal marine particles reveals profound differences in colonization

Marine and limnic particles are hotspots of organic matter mineralization significantly affecting biogeochemical element cycling. Fluorescence-in-situ-hybridization and pyrosequencing of 16S rRNA genes were combined to investigate bacterial diversity and community composition on limnic and coastal marine particles >5 and >10 μm, respectively. Limnic particles were more abundant (average: 1×107 L-1), smaller in size (average areas: 471 vs. 2, 050 μm2), and more densely colonized (average densities: 7.3 vs. 3.6 cells 100 μm-2) than marine ones. Limnic particle-associated (PA) bacteria harbored Alphaproteobacteria and Betaproteobacteria, and unlike previously suggested sizeable populations of Gammaproteobacteria, Actinobacteria and Bacteroidetes. Marine particles were colonized by Planctomycetes and Betaproteobacteria additionally to Alphaproteobacteria, Bacteroidetes and Gammaproteobacteria. Large differences in individual particle colonization could be detected. High- throughput sequencing revealed a significant overlap of PA and free-living (FL) bacteria highlighting an underestimated connectivity between both fractions. PA bacteria were in 14/21 cases more diverse than FL bacteria, reflecting a high heterogeneity in the particle microenvironment. We propose that a ratio of Chao1 indices of PA/FL<1 indicates the presence of rather homogeneously colonized particles. The identification of different bacterial families enriched on either limnic or marine particles demonstrates that, despite the seemingly similar ecological niches, PA communities of both environments differ substantially.

Bacterial community composition; Ecological niches; FISH; Free-living bacteria; imnic and marine particles; Particle-associated bacteria; Tag pyrosequencing

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