This is corroborated by the values shown in Table 1, where cultivable Acidovorax sp. and Sphingomonas selleck chemicals sp. numbers are 6.55 × 106 and 1.06 × 106 CFU cm-2 suggesting that these two microorganisms could be metabolically active in the biofilm despite the poor nutrient concentration of the medium (filtered tap water). Another possible explanation for the lower numbers of cultivable L. pneumophila when biofilms were formed in co-culture

with Sphingomonas sp., can be related to the structure of the biofilm. Figure 2 shows a 32 days-old biofilm formed by L. pneumophila and L. pneumophila associated with Sphingomonas sp. The biofilm formed in the presence of Sphingomonas sp. had a different morphology, and although the thickness of the biofilm has not been measured, the presence of microcolonies suggests the presence of thicker structures where anaerobic zones might occur. Wadowsky et al. [33] have demonstrated that in anaerobic conditions L. pneumophila loses cultivability and if biofilms formed by L. pneumophila and Sphingomonas sp. have indeed anaerobic zones, then it is possible that L. pneumophila located in those places has become uncultivable. It would therefore be interesting to undertake further research

to measure the thickness of different parts of the biofilm and the respective concentration of oxygen and relate those results to the cultivability of cells from those regions. However, the selleckchem fact that the numbers quantified by the use of a PNA probe remained constant, might indicate that these cells may still be viable and can probably recover cultivability in favorable conditions. This work clearly demonstrates that L. pneumophila can be negatively or positively influenced by other microorganisms present in drinking water. It is important to note that this study was carried out under particular conditions and it will be important to perform more experiments in the future, in particular to study the effect of other drinking water bacteria, the formation of biofilms under dynamic conditions and Carnitine palmitoyltransferase II the incorporation

of a disinfectant, such as chlorine. It is known that other bacteria can influence the growth of L. pneumophila either in nutrient-poor environments, such as drinking water, or in rich artificial media. Toze et al. [51] have demonstrated that some bacteria commonly present in heterotrophic biofilms, such as Pseudomonas sp. and Aeromonas sp., can inhibit the growth of L. pneumophila while Wadowsky and Yee [49] demonstrated that Flavobacterium breve can support the satellite growth of this pathogen on BCYE agar without L-cysteine. A curious result was obtained by Temmerman et al. [52] who demonstrated that dead cells can also support the growth of this pathogen. Although the mechanisms responsible for the influence of different microorganisms on L. pneumophila survival are unknown there is one aspect of L. pneumophila microbial ecology that has been already well-established: L.