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Comparison of cell-specific activity between free-living and attached bacteria using isolates and natural assemblages

Gropssar, HP
; 
Tang, KW
; 
Kiorboe, T
; 
Ploug, H
Abstract
Marine snow aggregates are microbial hotspots that support high bacterial abundance and activities. We conducted laboratory experiments to compare cell-specific bacterial protein production (BPP) and protease activity between free-living and attached bacteria. Natural bacterial assemblages attached to model aggregates (agar spheres) had threefold higher BPP and two orders of magnitude higher protease activity than their free-living counterpart. These observations could be explained by preferential colonization of the agar spheres by bacteria with inherently higher metabolic activity and/or individual bacteria increasing their metabolism upon attachment to surfaces. In subsequent experiments, we used four strains of marine snow bacteria isolates to test the hypothesis that bacteria could up- and down-regulate their metabolism while on and off an aggregate. The protease activity of attached bacteria was 10-20 times higher than that of free-living bacteria, indicating that the individual strains could increase their protease activity within a short time (2 h) upon attachment to surfaces. Agar spheres with embedded diatom cells were colonized faster than plain agar spheres and the attached bacteria were clustered around the agar-embedded diatom cells, indicating a chemosensing response. Increased protease activity and BPP allow attached bacteria to quickly exploit aggregate resources upon attachment, which may accelerate remineralization of marine snow and reduce the downward carbon fluxes.
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2007-01-01
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Biological Sciences Peer-Reviewed Articles
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Virginia Institute of Marine Science
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https://doi.org/10.1111/j.1574-6968.2006.00520.x
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https://scholarworks.wm.edu/handle/internal/17605
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