Carbon load in aquatic ecosystems affects the diversity and biomass of water biofilm consortia and the persistence of the pathogen Campylobacter jejuni within them

The influence of carbon load on autochthonous water microflora population d istribution and diversity, and on the persistence of Campylobacter jejuni, was examined with a two-stage aquatic biofilm model. Serine was chosen sinc e it is a carbon source utilised by C. jejuni and concentrations were chose n to reflect upper limits of amino acid load reported in surface mater. The total viable count of the autochthonous biofilm microflora increased with increasing serine concentration (10-fold and 20-fold with 5 nM and 5 mu M s erine, respectively), as did the counts of the microflora in the planktonic phase. Differences in biofilm species distribution as determined by cultur e were small with changes in temperature or the addition of serine; but was markedly affected by serine as determined by light microscopy, becoming mo re luxuriant and dominated by long filamentous cells. The addition of serin e to the water significantly and progressively reduced the persistence of C , jejuni, which decreased by 25% and 50% with serine concentrations of 5 nM and 5 mu M respectively. We have demonstrated that carbon load affects the species diversity and den sity of both the planktonic and biofilm phase of aquatic autochthonous micr oflora. Although the survival of C. jejuni in water in a culturable form wa s sufficient for this to be an important vehicle for its transmission, carb on load significantly influenced survival; an increase in serine concentrat ion significantly reduced survival.