ASSESSMENT OF THE EFFECTS OF SULFATE AND NITRATE ON THE TEMPORAL EVOLUTION OF KLEBSIELLA OXYTOCA AND STAPHYLOCOCCUS AUREUS ABUNDANCE UNDER SHAKING CONDITIONS, IN AQUATIC MICROCOSM Évaluation de l'influence du nitrate et du sulfate sur l'évolution temporelle d'abondance de Klebsiella oxytoca et Staphylococcus aureus sous conditions agitées en milieu aquatique en microcosme

Most chemicals in natural aquatic media can be assimilated by bacteria. The impact of various environmental conditions on this microbial process is not always clear. This study aimed at investigating changes in the abundance of Klebsiella oxytoca and Staphylococcus aureus under different shaking conditions, in aquatic microcosms containing nitrate and sulfate. Sodium chloride solution (8.5 g NaClL ‑1 ), and nitrate and sulfate solutions (0.005, 0.05, 0.5 and 5 gL ‑1 ) containing bacteria were supplemented with tryptic peptone at a final concentration of 10 gL ‑1 . The solutions were incubated under shaking conditions (300, 350 and 400 revmin ‑1 ). Bacteriological analyses were performed hourly over a 6‑h period. During the first 3 h of incubation, results showed that the highest values of the apparent cell growth rates (CAGRs) with K 2 SO 4 in pure cultures, at a shaking speed 400 revmin ‑1 , were 0.656 h ‑1 for S. aureus, and 0.364 h ‑1 for K. oxytoca. In mixed culture, the CAGR was 0.235 h ‑1 for S. aureus, and 0.388 h ‑1 for K. oxytoca, both recorded at 300 revmin ‑1 . With KNO 3 in pure culture solutions, the CAGR was 0.353 h ‑1 for S. aureus at 300 revmin ‑1 , and 0.367 h ‑1 for K. oxytoca at 350 revmin ‑1 . In mixed culture it was 0.454 h ‑1 for S. aureus and 0.393 h ‑1 for K. oxytoca, both recorded at 350 revmin ‑1 . The highest value of the apparent cell inhibition rate (CAIR) for S. aureus was 0.520 h ‑1 in K 2 SO 4 (5 gL ‑1 , 400 revmin ‑1 ),