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 × 105 colony-forming units (cfu) per 100 mL. In sterile sediment, E. coli bacteria first went through a proliferative phase and then implanted themselves (3 × 104 cfu/100 g at 0 days and 4 × 105 cfu/100 g at 13days). Diffusion in the supernatant sterile seawater of organic matter released from sediment allowed the strain to proliferate (8 × 106 cfu/100 mL at 1 day) and survive for a few days (1 × 104 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 × 103 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 × 104 cfu/100 g at 1 day) and survived (1 × 104 cfu/100 g at 13 days). In the supernatant seawater, a decrease was observed from the 1st day. Our results show that a state of equilibrium was reached, with E. coli bacteria disappearing from the seawater under the pressure selection created by the indigenous marine flora (an important role of the organic matter), and with a considerable survival in the sediment, whatever the conditions might be. Key words: Escherichia coli, bacterial flora, seawater, sediment, competition. [Translated by the Journal]
Proteomic method to extract, concentrate, digest and enrich peptides from fossils with coloured (humic) substances for mass spectrometry analyses
