|
Hmelo, L.,
Van Mooy, B.
, Kinetic constraints on acylated homoserine lactone-based quorum sensing in marine environments
, Aquatic Microbial Ecology, in press
Quorum sensing (QS) via acylated homoserine lactones (AHLs) was
discovered in the ocean, yet AHLs are expected to be very short-lived at seawater
pH due to rapid abiotic degradation. Quorum quenching, the enzymatic degradation of AHLs, is also
likely. To better understand the potential for QS to regulate behaviors of marine bacteria, we
investigated the degradation of a variety of AHL molecules in several types of saltwater media. We did
this by incubating AHLs and tracking their concentration using HPLC/electrospray-ionization
mass-spectrometry (HPLC/ESI-MS). AHL concentrations decreased with time, and degradation rate
coefficients were calculated by applying a first-order rate law. The rate of abiotic degradation
showed strong dependence on acyl chain length and the presence of 3-oxo
substitutions on the acyl chain. We found that the rate of abiotic degradation of AHLs in artificial seawater was much slower than
that predicted by an oft-cited equation that takes only pH into account. However, AHLs degraded
more rapidly in natural seawater than in artificial seawater, an observation we found to be due
to quorum quenching enzyme activity. By applying calculated degradation rates in a simple
steady-state calculation, we suggest that despite the observed quorum quenching activity, AHLs are likely
to be viable signals in organic particles and in other microbial ‘hotpsots' in marine environments.
|
|
