Aquatic Sciences Meeting, Albuquerque 2001

CS20 Microbial Dynamics

Date: Friday, February 16, 2001, Time: 11:00:00 AM

Location: Ruidoso/Pecos

Arnosti, C, , Univ. North Carolina, Dept. of Marine Sciences, Chapel Hill, USA, arnosti@email.unc.edu

TIMESCALES OF MICROBIAL ENZYMATIC RESPONSES TO HIGH MOLECULAR WEIGHT SUBSTRATES

The ability of heterotrophic microbial communities to use high molecular weight (HMW) organic matter as substrates depends on production of the extracellular enzymes required to hydrolyze these macromolecules to lower molecular weights. Although mechanisms of enzyme induction and production have been investigated in pure culture, the timescales of exoenzyme response among sedimentary microbial communities are not well constrained. In order to investigate exoenzymatic response to HMW substrates, replicate sediment samples were homogenized, and half received a low pulse of one of two HMW polysaccharide substrates. After this pulse was completely hydrolyzed to monomers, a follow-up pulse (2x initial pulse) was added to all sediments. Hydrolysis of pullulan (glucose polysaccharide), was equally rapid in both sets of sediments. For chondroitin sulfate (mixed polysaccharide), however, hydrolysis rates in pre-pulsed sediments were ca. 150% of the rates in unpulsed sediments, perhaps due to longer timescales of enzyme induction. For both substrates, enhancement of activity was measurable in extracts of 0.2-micron filtered porewater following exposure to HMW substrates, so some of the enzymes produced in response to substrate addition are released from the cells.

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Aquatic Sciences Meeting, Albuquerque 2001

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