Pseudoalteromonas spp. Serve as Initial Bacterial Attractants in Mesocosms of Coastal Waters but Have Subsequent Antifouling Capacity in Mesocosms and when Embedded in Paint

Abstract

ABSTRACTThe purpose of the present study was to determine if the monoculture antifouling effect of several pigmented pseudoalteromonads was retained inin vitromesocosm systems using natural coastal seawater and when the bacteria were embedded in paint used on surfaces submerged in coastal waters.Pseudoalteromonas piscicidasurvived on a steel surface and retained antifouling activity for at least 53 days in sterile seawater, whereasP. tunicatasurvived and had antifouling activity for only 1 week. However, during the first week, allPseudoalteromonasstrains facilitated rather than prevented bacterial attachment when used to coat stainless steel surfaces and submerged in mesocosms with natural seawater. The bacterial density on surfaces coated with sterile growth medium was 105cells/cm2after 7 days, whereas counts on surfaces precoated withPseudoalteromonaswere significantly higher, at 106to 108cells/cm2. However, after 53 days, seven of eightPseudoalteromonasstrains had reduced total bacterial adhesion compared to the control.P. piscicida,P. antarctica, andP. ulvaeremained on the surface, at levels similar to those in the initial coating, whereasP. tunicatacould not be detected. Larger fouling organisms were observed on all plates precoated withPseudoalteromonas; however, plates coated only with sterile growth medium were dominated by a bacterial biofilm. Suspensions of aP. piscicidastrain and aP. tunicatastrain were incorporated into ship paints (Hempasil x3 87500 and Hempasil 77500) used on plates that were placed at the Hempel A/S test site in Jyllinge Harbor. For the first 4 months, no differences were observed between control plates and treated plates, but after 5 to 6 months, the control plates were more fouled than the plates with pseudoalteromonad-based paint. Our study demonstrates that no single laboratory assay can predict antifouling effects and that a combination of laboratory and real-life methods must be used to determine the potential antifouling capability of new agents or organisms.