Zimmer, R. K.. University of California, zf@biology.ucla.edu
Decho, A. K.. University of South Carolina, decho@sophe.sc.edu
Browne, K. A.. University of California, kab@protos.lifesci.ucla.edu

Waterborne chemical cues are critical in mediating interactions among marine organisms, yet mechanisms controlling the extinction of these signals have not been described. In this study, we chose glycyl-glycyl-L-arginine (GGR) to examine the rates and mechanisms of peptide uptake by a natural assemblage of marine bacteria. GGR is a potent synthetic analog of the natural cue inducing settlement by oyster and barnacle larvae. Kinetic parameters for the microbial uptake and colloidal adsorption of glycine, L-arginine, and GGR were determined from the decay of 14C-radiolabeled substrates and from high performance liquid chromatography (HPLC) analyses. The bacterial uptake rate constant was 3.5-fold smaller for GGR than for its component amino acids at all substrate concentrations (1 - 1,000 nM). Nonspecific adsorption of GGR onto colloids had a similar rate constant. HPLC analyses did not indicate any build up of the potential proteolytic products of GGR during experiments. Our results show that the tripeptide GGR is taken up by marine bacteria at significantly lower rates than are its component amino acids. The slow utilization of GGR by bacteria and low adsorption to colloids could provide at least one rationale -- signal persistence -- for the selection of basic peptides as chemical cues in marine environments.
Day: Thursday, Feb. 4
Time: 11:15 - 11:30am
Location: Hilton of Santa Fe
Code: SS16TH1115H