Keith, S. C. University of North Carolina at Chapel Hill, skeith@marine.unc.edu
Arnosti, C. C. University of North Carolina at Chapel Hill, arnosti@marine.unc.edu

 
BACTERIAL EXTRACELLULAR ENZYMATIC ACTIVITY IN A RIVERINE- COASTAL WATER TRANSECT: VARIATIONS OF POLYSACCHARIDE HYDROLYSIS RATES WITH SUBSTRATE AND SIZE CLASS
 
Extracellular hydrolysis initiates bacterial remineralization of organic macromolecules; a major portion of those macromolecules in marine settings are carbohydrates. To investigate spatial and temporal patterns in enzymatic activity, we measured potential hydrolysis rates of four polysaccharides, laminarin, pullulan, xylan, and fucoidan, in a transect along the Delaware River-Bay -shelf in summer, fall, and winter. Potential hydrolysis rates for all four polysaccharides, which differ in monomer composition, linkage position, and anomeric linkage, were vastly different. Rates were variable for each substrate in time and space, and were significantly higher overall than has been suggested by measurements using simple substrate analogs such as MUF-glucose. Most enzymatic activity was generated by the larger particulate size class (>0.45 um), but the small particulate / free-living bacteria (0.2-0.45 um) and free enzyme (<0.2 um) size classes each accounted for all activity for specific substrates, times and locations. Our results clearly reflect a temporally and spatially dynamic bacterial population. The data reported here also support earlier studies showing that bacterial extracellular hydrolysis of macromolecules can be rapid. The suite of substrates used uncovers variability in microbial enzyme activity which would not be revealed through the use of standard simple substrate proxies.
 
Day: Thursday, Feb. 4
Time: 02:15 - 02:30pm
Location: Sweeney Center
 
Code: SS33TH0215S