ABSTRACT1. In France, the distribution of the native white-clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. To conserve this indigenous species, it is necessary to characterize its habitat preferences.2. Seven brooks in the Deux-Se`vres De´partement (western France) containing wild populations of A. pallipes were studied to determine its ranges of tolerance to 19 physical and chemical water parameters. On two brooks, the Se`vre Nantaise and the Verdonnie`re, sites with and without A. pallipes were compared. Each site was sampled twice monthly from November 2002 to November 2004.3. It was found that the white-clawed crayfish was able to tolerate wide ranges of values of some of the measured parameters. The Magot site harboured the largest A. pallipes population (17.5 crayfish m À2 ) and had dissolved oxygen concentrations as low as 4.93 mg L À1 , while water temperature rose above 208C for several consecutive days during summer and nitrate concentrations were always found to be above 30 mg L À1. These unusual findings could call into question the status of A. pallipes as a bioindicator of good water quality.4. Principal component analyses (PCA) suggested that an increase of organic matter was a discriminant factor for the presence or absence of A. pallipes. In addition, sites with and without crayfish on the Se`vre Nantaise brook showed showed significant differences (p50:05) in total organic carbon (TOC), and those on the Verdonnie`re brook in turbidity and total suspended solids (TSS).

ABSTRACTFree-living amoebae are protozoa found in soil and water. Among them, some are pathogenic and many have been described as potential reservoirs of pathogenic bacteria. Their cell cycle is divided into at least two forms, the trophozoite and the cyst, and the differentiation process is named encystment. As cysts are more resistant to disinfection treatments than trophozoites, many studies focused on encystment, but until recently, little was known about cellular, biochemical, and molecular modifications operating during this process. Important signals and signaling pathways at play during encystment, as well as cell responses at the molecular level, have been described. This review summarizes our knowledge and focuses on new findings.

ABSTRACTLegionellaspecies are frequently detected in hot water systems, attached to the surface as a biofilm. In this work, the dynamics ofLegionellaspp. 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 ofLegionellaand eukarya were investigated by small-subunit (SSU) ribosomal cloning and sequencing. Our results showed that pathogenicLegionellaspecies remained after the heat shock and chemical treatments (Legionella pneumophilaandLegionella 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 (Thecamoebaesp.,Vannellasp., andHartmanella vermiformis) and after the first heat shock treatment, but onlyH. vermiformisremained. However, another protozoan affiliated with Alveolata, which is known as a host cell forLegionella, dominated the eukaryal species after the second heat shock and chemical treatment tests. Therefore, effectiveLegionelladisinfection may be dependent on the elimination of these important microbial components. We suggest that eradicatingLegionellain hot water networks requires better study of bacterial and eukaryal species associated withLegionellain biofilms.

Aims:  (i) To develop an analytical tool in order to evaluate the effectiveness of anti‐Legionella treatment in biofilm and (ii) study the fate of Legionella populations in water and biofilm after applying a heat shock treatment. Methods and Results:  A pilot‐scale unit simulating a hot water system was built and designed by the Scientific and Technical Building Centre (CSTB, France). At the end of the contamination period, a stable cultivable Legionella spp. concentration of 5 × 105 CFU l−1 was obtained. Two heat shock treatments (70°C for 30 min) were applied. The results showed that the first treatment had a transitional effect on the abatement of Legionella concentrations, while the second treatment had no detectable effect on Legionella populations in water and biofilm. The DAPI (4′,6′‐diamidino‐2‐phenylindole), Legionella PCR and GVPC (glycocolle vancomycin pyrophosphate cycloheximide) counts measured in the dead leg water of the Test Loop were 1, 2 and 2 log units higher than results found in the Test Loop water. Moreover, Legionella spp. count in tap water was about 104 GU l−1. These analyses revealed that they are responsible for the rapid recolonization as well as the uncomplete destroyed biofilm. In addition, a resistance test was conducted and showed that Legionella in the second heat shock treatment was not thermo‐resistant but thermo‐acclimated. Conclusion:  Thermal disinfection does not seem to be efficient enough to eliminate Legionella when it is used as a curative treatment. Significance and Impact of the Study:  This work could help water managers for a better management of water network and for a better control of Legionella.

Vermamoeba vermiformis is a free-living amoeba (FLA) widely distributed in the environment, known to colonize hot water networks and to be the reservoir of pathogenic bacteria such as Legionella pneumophila. FLA are partly resistant to biocides, especially in their cyst form. The control of V. vermiformis in hot water networks represents an important health issue, but there are very few data on their resistance to disinfection treatments. The sensitivity of cysts of two strains of V. vermiformis to three disinfectants frequently used in hot water networks (chlorine, heat shock, peracetic acid (PAA) mixed with hydrogen peroxide (H2O2)) was investigated. In vitro, several concentrations of biocides, temperatures and exposure times according to the French regulation were tested. Cysts were fully inactivated by the following conditions: 15 mg/L of chlorine for 10 min; 60 °C for 30 min; and 0.5 g/L equivalent H2O2 of PAA mixed with H2O2 for 30 min. For the first time, the strong efficacy of subtilisin (0.625 U/mL for 24 h), a protease, to inactivate the V. vermiformis cysts has been demonstrated. It suggests that novel approaches may be efficient for disinfection processes. Finally, V. vermifomis cysts were sensitive to all the tested treatments and appeared to be more sensitive than Acanthamoeba cysts.