Abstract
Legionella
species are frequently detected in hot water systems, attached to the surface as a biofilm. In this work, the dynamics of
Legionella
spp. and diverse bacteria and eukarya associated together in the biofilm, coming from a pilot scale 1 system simulating a real hot water system, were investigated throughout 6 months after two successive heat shock treatments followed by three successive chemical treatments. Community structure was assessed by a fingerprint technique, single-strand conformation polymorphism (SSCP). In addition, the diversity and dynamics of
Legionella
and eukarya were investigated by small-subunit (SSU) ribosomal cloning and sequencing. Our results showed that pathogenic
Legionella
species remained after the heat shock and chemical treatments (
Legionella pneumophila
and
Legionella anisa
, respectively). The biofilm was not removed, and the bacterial community structure was transitorily affected by the treatments. Moreover, several amoebae had been detected in the biofilm before treatments (
Thecamoebae
sp.,
Vannella
sp., and
Hartmanella vermiformis
) and after the first heat shock treatment, but only
H. vermiformis
remained. However, another protozoan affiliated with Alveolata, which is known as a host cell for
Legionella
, dominated the eukaryal species after the second heat shock and chemical treatment tests. Therefore, effective
Legionella
disinfection may be dependent on the elimination of these important microbial components. We suggest that eradicating
Legionella
in hot water networks requires better study of bacterial and eukaryal species associated with
Legionella
in biofilms.