Iron is regarded as essential to virtually all microorganisms, although the
role of this nutrient on biofilm formation by many bacterial species is
unknown or poorly explored. This is the case of Staphylococcus
epidermidis, a major inhabitant of the human skin, which has also
become an important nosocomial pathogen. Interestingly, biofilm
formation has been regarded as a pivotal feature in both commensal and
clinical isolates. Recent results from our group have pointed out iron
uptake as an important mechanism for S. epidermidis biofilms survival.
The present work was therefore aimed at elucidating the effect of iron
availability in S. epidermidis biofilm formation.To achieve that, biofilm
formation of three S. epidermidis isolates was evaluated when cultured in
medium presenting different iron availability levels. Interestingly, under
physiological iron concentrations, biofilm formation and planktonic growth
were not affected but supraphysiological concentrations displayed an
inhibitory effect both on biofilm and planktonic growth. Importantly, biofilm
formation and planktonic growth was also inhibited by chelation of the
iron present in the culture medium, which was completely restored after
iron addition in a dose-dependent manner. Our findings provide clear
evidence that iron plays a pivotal role on S. epidermidis biofilm formation,
and this seems to be primarily related with its effect on the bacterial
growth rate. Additionally, the iron concentration range supporting
bacterial growth and further biofilm development was found to be very
narrow, a feature that may be explored in the future for biofilm control
purposes
