TY  - JOUR
A1  - Ionescu, Danny
A1  - Bizic-Ionescu, Mina
A1  - Khalili, Arzhang
A1  - Malekmohammadi, Reza
A1  - Morad, Reza Mohammad
A1  - de Beer, Dirk
A1  - Grossart, Hans-Peter
T1  - A new tool for long-term studies of POM-bacteria interactions: overcoming the century-old Bottle Effect
JF  - Scientific reports
N2  - Downward fluxes of particulate organic matter (POM) are the major process for sequestering atmospheric CO2 into aquatic sediments for thousands of years. Budget calculations of the biological carbon pump are heavily based on the ratio between carbon export (sedimentation) and remineralization (release to the atmosphere). Current methodologies determine microbial dynamics on POM using closed vessels, which are strongly biased towards heterotrophy due to rapidly changing water chemistry (Bottle Effect). We developed a flow-through rolling tank for long term studies that continuously maintains POM at near in-situ conditions. There, bacterial communities resembled in-situ communities and greatly differed from those in the closed systems. The active particle-associated community in the flow-through system was stable for days, contrary to hours previously reported for closed incubations. In contrast to enhanced respiration rates, the decrease in photosynthetic rates on particles throughout the incubation was much slower in our system than in traditional ones. These results call for reevaluating experimentally-derived carbon fluxes estimated using traditional methods.
Y1  - 2015
U6  - https://doi.org/10.1038/srep14706
SN  - 2045-2322
VL  - 5
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bizic-Ionescu, Mina
A1  - Zeder, Michael
A1  - Ionescu, Danny
A1  - Orlic, Sandi
A1  - Fuchs, Bernhard M.
A1  - Grossart, Hans-Peter
A1  - Amann, Rudolf
T1  - Comparison of bacterial communities on limnic versus coastal marine particles reveals profound differences in colonization
JF  - Environmental microbiology
N2  - 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 >10m respectively. Limnic particles were more abundant (average: 1x10(7)l(-1)), smaller in size (average areas: 471 versus 2050m(2)) and more densely colonized (average densities: 7.3 versus 3.6 cells 100m(-2)) than marine ones. Limnic particle-associated (PA) bacteria harboured 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 Chao 1 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.
Y1  - 2015
U6  - https://doi.org/10.1111/1462-2920.12466
SN  - 1462-2912
SN  - 1462-2920
VL  - 17
IS  - 10
SP  - 3500
EP  - 3514
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -