S. marcescens strains associated with transfusion reactions form biofilms under platelet storage conditions, and initial biofilm formation correlates with missed detection of contaminated platelet concentrates by the BacT/ALERT system.

No abstract

The present study examined the impact of transferrin on Bacillus thuringiensis biofilms. Three commercial strains, an environmental strain (33679), the type strain (10792), and an isolate from a diseased insect (700872), were cultured in iron restricted minimal medium. All strains produced biofilm when grown in vinyl plates at 30°C. B. thuringiensis 33679 had a biofilm biomass more than twice the concentration exhibited by the other strains. The addition of transferrin resulted in slightly increased growth yields for 2 of the 3 strains tested, including 33679. In contrast, the addition of 50 μg/mL of transferrin resulted in an 80% decrease in biofilm levels for strain 33679. When the growth temperature was increased to 37°C, the addition of 50 μg/mL of transferrin increased culture turbidity for only strain 33679. Biofilm levels were again decreased in strain 33679 at 37°C. Growth of B. thuringiensis cultures in polystyrene resulted in a decrease in overall growth yields at 30°C, with biofilm levels significantly decreased for 33679 in the presence of transferrin. These findings demonstrate that transferrin impacts biofilm formation in select strains of B. thuringiensis. Identification of these differences in biofilm regulation may be beneficial in elucidating potential virulence mechanisms among the differing strains.

Bacillus amyloliquefaciens is a biocontrol agent whose genome has been sequenced. Within the genome of B. amyloliquefaciens are genes associated with iron chelation, but these genes are not found within all sequenced strains. The impact of iron availability on the B. amyloliquefaciens physiology was examined in this study. B. amyloliquefaciens ATCC 23843 was cultured under ironreplete and iron-deplete conditions for 48 hours, at 37˚C. Final growth yields were dependent on iron concentration. Cultures grown in the absence of detectable iron were restricted in growth, but reached their highest yields at 48 hours. Iron restriction was confirmed by the presence of iron chelators in the filtrates. In contrast, B. amyloliquefaciens ATCC 23843 cultures grown with ferric ammonium citrate as the iron source research reached the highest yields at 24 hours. Iron chelator production was not detected in the ferric ammonium samples. A significant decrease in turbidity was observed for these cultures, which coincided with elevated spore production in B. amyloliquefaciens ATCC 23843. A decrease in turbidity was also observed on blood agar, where hemolysis was readily evident. We propose that iron impacts numerous physiological responses and further studies will elucidate the complex regulatory mechanisms governed by iron availability.