Influence of different concentrations of nitrogen and phosphorous on Aeromonas spp. growth.

This paper evaluates the influence of nitrogen and phosphorous on the growth of Aeromonas previously isolated from irrigation water. Three strains respectively of three species of Aeromonas (A. hydrophila, A. caviae, A. sobria) (nine strains) were individually inoculated in a microcosm added with ammonium, nitrate and phosphate using different combinations (NH4-N + NO3-N and NH4-N + NO3-N + PO4-P) and concentrations (NH4-N: from 20 to 2500 microg l-1; NO3-N: from 200 to 22000 microg l-1; PO4-P: from 20 to 1200 microg l-1). A positive correlation was found between bacterial growth and NH4-N charge, but not a strict correlation with NO3-N. The addition of PO4-P at concentrations from 20 to 200 microg l-1 stimulated the bacterial growth; inversely, concentrations of 500 and 1200 microg l-1 were inhibitory. Ammonium, nitrate and phosphate influence in different way Aeromonas growth; so, their various concentrations can partially explain the different recovery of these bacteria from aquatic environments. There is discordance in literature about the influence of environmental parameters on Aeromonas growth in aquatic ecosystems. Therefore, this study contributes to a better understanding about interactions of some chemical parameters and Aeromonas growth, which are at the basis of the varied relationship described for environmental factors governing aeromonads densities.