TY - JOUR

T1 - Growth kinetics of environmental Legionella pneumophila isolated from industrial wastewater

AU - Caicedo, C.

AU - Verstraete, W.

AU - Rosenwinkel, K. H.

AU - Nogueira, R.

N1 - Funding Information: We thank Mrs. Karen Kock and Dr. Corinna Lorey from the Institute for Sanitary Engineering and Waste Management, Leibniz University Hannover, for performing the qPCR and FISH analyses, respectively. We are grateful to Mrs. Claudia Helle for her support during the growth experiments. This work was conducted with financial support from the industrial sector (Grant No.: CA-60451429).

PY - 2020/2

Y1 - 2020/2

N2 - Wastewater treatment plants are environmental niches for Legionella pneumophila, the most commonly identified causative agent of severe pneumonia known as Legionnaire’s disease. In the present study, Legionella pneumophila’s concentrations were monitored in an industrial wastewater treatment plant and environmental isolates were characterized concerning their growth kinetics with respect to temperature and their inhibition by organic acids and ammonium. The results of the monitoring study showed that Legionella pneumophila occurs in activated sludge tanks operated with very different sludge retention times, 2.5 days in a complete-mix reactor, and 10 days in a membrane bioreactor, indicating that this bacterium can grow at different rates, despite the same wastewater temperature of 35 °C. The morphology of Legionella cells is different in both reactors; in the membrane bioreactor, the bacteria grow in clusters, while in the complete-mix reactor, filaments predominate demonstrating a faster growth rate. Legionella pneumophila concentrations in the complete-mix reactor and in the membrane bioreactor were within the range 3 × 101 to 4.8 × 103 GU/mL and 3 × 102 to 4.7 × 103 GU/mL, respectively. Environmental Legionella pneumophila SG2–14 isolates showed distinct temperature preferences. The lowest growth rate was observed at 28 °C, and the highest 0.34 d−1 was obtained at 42 °C. The presence of high concentrations of organic acids and ammonium found in anaerobically pre-treated wastewater caused growth inhibition. Despite the increasing research efforts, the mechanisms governing the growth of Legionella pneumophila in wastewater treatment plants are still unclear. New innovative strategies to prevent the proliferation of this bacterium in wastewater are in demand.

AB - Wastewater treatment plants are environmental niches for Legionella pneumophila, the most commonly identified causative agent of severe pneumonia known as Legionnaire’s disease. In the present study, Legionella pneumophila’s concentrations were monitored in an industrial wastewater treatment plant and environmental isolates were characterized concerning their growth kinetics with respect to temperature and their inhibition by organic acids and ammonium. The results of the monitoring study showed that Legionella pneumophila occurs in activated sludge tanks operated with very different sludge retention times, 2.5 days in a complete-mix reactor, and 10 days in a membrane bioreactor, indicating that this bacterium can grow at different rates, despite the same wastewater temperature of 35 °C. The morphology of Legionella cells is different in both reactors; in the membrane bioreactor, the bacteria grow in clusters, while in the complete-mix reactor, filaments predominate demonstrating a faster growth rate. Legionella pneumophila concentrations in the complete-mix reactor and in the membrane bioreactor were within the range 3 × 101 to 4.8 × 103 GU/mL and 3 × 102 to 4.7 × 103 GU/mL, respectively. Environmental Legionella pneumophila SG2–14 isolates showed distinct temperature preferences. The lowest growth rate was observed at 28 °C, and the highest 0.34 d−1 was obtained at 42 °C. The presence of high concentrations of organic acids and ammonium found in anaerobically pre-treated wastewater caused growth inhibition. Despite the increasing research efforts, the mechanisms governing the growth of Legionella pneumophila in wastewater treatment plants are still unclear. New innovative strategies to prevent the proliferation of this bacterium in wastewater are in demand.

KW - Activated sludge

KW - Growth kinetics

KW - Industrial wastewater

KW - Inhibition

KW - Legionella pneumophila

UR - http://www.scopus.com/inward/record.url?scp=85070198035&partnerID=8YFLogxK

U2 - 10.1007/s13762-019-02482-5

DO - 10.1007/s13762-019-02482-5

M3 - Article

AN - SCOPUS:85070198035

VL - 17

SP - 625

EP - 632

JO - International Journal of Environmental Science and Technology

JF - International Journal of Environmental Science and Technology

SN - 1735-1472

IS - 2

ER -