Effects of bacteria on the growth of an amoeba infecting the gills of turbot

We analysed the influence of various bacteria on the in vitro growth of tro phozoites of a Platyamoeba strain isolated from diseased gill tissues of cu ltured turbot. Little or no growth was shown by amoebae cultured in the pre sence of (1) the turbot-pathogenic bacteria Vibrio anguillarum, Aeromonas s almonicida or Streptococcus sp., (2) Pasteurella piscicida or Vibrio vulnif icus (pathogenic for some fishes but not turbot), or (3) the non-pathogenic 'environmental' bacteria Vibrio campbelli, Vibrio fluvialis or Pseudomonas dondorofii. The only bacteria which were successfully utilized as food sou rces were Aeromonas hydrophila (pathogenic for some fishes but not turbot) and the non-pathogens Vibrio natriegens, Pseudomonas nautica and Escherichi a coil. These results suggest that the colonization of the gills of culture d turbot by the epizoic amoeba Platyamoeba may be an indicator of faecal co ntamination.