TY  - JOUR
A1  - Corno, Gianluca
A1  - Salka, Ivette
A1  - Pohlmann, Kirsten
A1  - Hall, Alex R.
A1  - Grossart, Hans-Peter
T1  - Interspecific interactions drive chitin and cellulose degradation by aquatic microorganisms
JF  - Aquatic microbial ecology : international journal
N2  - Complex biopolymers (BPs) such as chitin and cellulose provide the majority of organic carbon in aquatic ecosystems, but the mechanisms by which communities of bacteria in natural systems exploit them are unclear. Previous degradation experiments in artificial systems predominantly used microcosms containing a single bacterial species, neglecting effects of interspecific interactions. By constructing simplified aquatic microbial communities, we tested how the addition of other bacterial species, of a nanoflagellate protist capable of consuming bacteria, or of both, affect utilization of BPs. Surprisingly, total abundance of resident bacteria in mixed communities increased upon addition of the protist. Concomitantly, bacteria shifted from free-living to aggregated morphotypes that seemed to promote utilization of BPs. In our model system, these interactions significantly increased productivity in terms of overall bacterial numbers and carbon transfer efficiency. This indicates that interactions on microbial aggregates may be crucial for chitin and cellulose degradation. We therefore suggest that interspecific microbial interactions must be considered when attempting to model the turnover of the vast pool of complex biopolymers in aquatic ecosystems.
KW  - Aggregation
KW  - Flagellate grazing
KW  - Ecological interactions
KW  - Microbial carbon transfer
KW  - Polymer degradation
KW  - System ecology
Y1  - 2015
U6  - https://doi.org/10.3354/ame01765
SN  - 0948-3055
SN  - 1616-1564
VL  - 76
IS  - 1
SP  - 27
EP  - +
PB  - Institute of Mathematical Statistics
CY  - Oldendorf Luhe
ER  - 
TY  - JOUR
A1  - Kleeberg, Andreas
A1  - Hupfer, Michael
A1  - Gust, Giselher
A1  - Salka, Ivette
A1  - Pohlmann, Kirsten
A1  - Grossart, Hans-Peter
T1  - Intermittent riverine resuspension effects on phosphorus transformations and heterotrophic bacteria
JF  - Limnology and oceanography
N2  - Intermittent riverine resuspension (IRR), a common phenomenon, was applied to investigate its effects on sedimentary resources availability and bacteria in the water column. This lab experiment used organic-rich lowland river sediment in a newly designed erosion chamber, the Benthic Water Column Simulator, generating well-defined ratios of shear velocity u* to turbulence intensity. Eight consecutive resuspension events, 1-8, were initiated at u* = 1.1 cm s(-1). Sedimentary and phosphorus entrainment decreased from 20.4 g m(-2) h(-1) and 111.6 mg m(-2) h(-1) at event 1 to 1.31 g m(-2) h(-1) and 18.7 mg m(-2) h(-1) at event 8, suggesting an exhaustion of particulate and dissolved sediment constituents. Entrainment of particle-associated (PA) bacteria (132.7 x 10(9)-251.1 x 10(9) cells m(-2) h(-1)) was strongly correlated to that of particles. Free-living (FL) bacteria (-27.6 x 10(9)-36.4 x 10(9) cells m(-2) h(-1)) were fractionally entrained. Numbers of PA bacteria remained low after each event, whereas those of FL bacteria strongly increased 5-15 h after an event because of growth due to increased availability of dissolved organic carbon and inorganic nutrients following each event. FL bacteria community structure also changed during IRR. The systematic changes over consecutive IRR cycles show a strong effect in all considered parameters that elude the typical single-event, steady-state experiments. IRR should thus be considered in two respects: experimental protocols on riverine water quality should be revised. In ecosystem modeling, IRR should be considered to better predict extent and effect of resuspension. Only IRR adequately reflects the natural interplay between hydrodynamics and organisms in rivers.
Y1  - 2013
U6  - https://doi.org/10.4319/lo.2013.58.2.0635
SN  - 0024-3590
SN  - 1939-5590
VL  - 58
IS  - 2
SP  - 635
EP  - 652
PB  - Wiley
CY  - Waco
ER  -