Depth distribution of active bacteria and bacterial activity in lake sediment

• Published in: FEMS microbiology ecology Vol. 46; no. 1; pp. 31 - 38
• Main Authors: Haglund, Ann-Louise, Lantz, Peter, Törnblom, Erik, Tranvik, Lars
• Format: Journal Article
• Language: English
• Published: Oxford, UK Elsevier B.V 01.10.2003; Blackwell Publishing Ltd; Blackwell
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Bacterium; Biological and medical sciences; Cell-specific production; Economic plant physiology; Freshwater; Fundamental and applied biological sciences. Psychology; Metabolically active bacterium; Microbial ecology; Production; Sediment; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Various environments (extraatmospheric space, air, water); Bacterium; Sediment; Metabolically active bacterium; Cell-specific production; Production; Biotope; Incorporation; Staining; Thymidine; Leucine; Lake sediments; Metabolism; Profile; Depth; Freshwater environment; Nucleoid; Lakes; Bacteria; Ecological abundance
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1016/S0168-6496(03)00190-9

The bacterial activity in sediments is often low considering the generally high bacterial abundance. Still, a large fraction of bacteria have been found active even in deep sediments. These findings suggest that sediment bacteria have comparatively low cell-specific production. We studied bacterial activity and the active fraction of bacteria in a lake sediment profile. Bacterial production and metabolism were measured by thymidine and leucine incorporation and by microcalorimetry. In addition to counts of total bacteria, we estimated the nucleoid-containing fraction of the bacteria by adding a destaining step to the DAPI staining method, and the live fraction using the Live/Dead Baclight bacterial viability kit. The bacterial activity and abundance decreased with sediment depth, while the proportion of active bacteria remained similar at all depths. Between 57 and 63% of the bacteria were scored viable, and 13–52% were scored as nucleoid-containing cells. Consequently, there was no accumulation of dead bacterial cells in deeper sediments. Cell-specific production of sediment bacteria may be severely underestimated if the active fraction of the sediment bacterial community is not considered during enumeration.