Heterogeneity of population of microorganisms grown in presence of iron oxide maghemite nanoparticles

In this work y-Fe203 MNPs were obtained by laser target evaporation and water based suspensions were prepared. Maximum permissive dose of iron in water (MPD) is 0.3 mg/L. It was found that 100 MPD dose of iron induces formation of non-typical colonies after 72 or 96 hours exposition: against a background of small black colonies large white colonies appeared due to a disruption in tyrosine synthesis. Multiple re-cloning of the white colonies grown with MNPs showed that they retained their properties both under standard conditions (temperature of 24 C) and at the temperatures up to 37 C. E.nigrum grown with MNPs demonstrated very scant extension of small colonies at the cultivation temperature of 24 C, their growth was completely blocked at 37 C. Significant changes in the structure of the population were noted. First of all, large cells with pronounced aggregation were observed among the black colonies. These aggregates consisted of large cells connected to each other by matrix. In the white colonies the appearance of very long threadlike cells connecting different groups of the cells establishing an intercellular communication was evident. Fe203 MNPs induce an increase in the heterogeneity of the population, expressed as a change in morpho-physiological states.