Implantation d'Escherichia coli en pilote expérimental et influence des compétitions de flore

Abstract

Implantation in seawater and (or) sediment of bacterial flora and the influence of such flora upon the survival and growth of an Escherichia coli of human origin have been the object of experimental pilot studies. The selected pilot plant permitted work on large volumes of seawater and sediment, and maintenance of the structure of the latter. Diverse experiments were carried out in the presence or absence of seawater and (or) sediment bacterial flora during 13 days. Escherichia coli bacteria were introduced in the seawater experimental system at concentrations of 1 to 3 X 10(5) colony-forming units (cfu) per 100 mL. In sterile sediment, E. coli bacteria first went through a proliferative phase and then implanted themselves (3 X 10(4) cfu/100 g at 0 days and 4 X 10(5) cfu/100 g at 13 days). Diffusion in the supernatant sterile seawater of organic matter released from sediment allowed the strain to proliferate (8 X 10(6) cfu/100 mL at 1 day) and survive for a few days (1 X 10(4) cfu/100 mL at 6 days), prior to an ultimate decreasing phase (1 cfu/100 mL at 13 days). In the presence of the seawater indigenous flora, an immediate decrease (2 X 10(3) cfu/100 mL at 6 days), without a growth or even a survival phase, evidenced a selection pressure. In a nonsterile sediment, in the presence or absence of seawater indigenous flora, E. coli bacteria implanted themselves quickly (5 X 10(4) cfu/100 g at 1 day) and survived (1 X 10(4) cfu/100 g at 13 days). In the supernatant seawater, a decrease was observed from the 1st day.(ABSTRACT TRUNCATED AT 250 WORDS)