Abstract 1987 Elucidating the Mechanism of Biofilm Desorption Upon Coliphage Infection and Nutrient Deprivation

Biofilm is a collection of microorganisms that adheres to a surface and continues to grow in the presence of nutrients. The genetic diversity within biofilm makes it difficult to control biofilm growth. Although physical, chemical, and biological methods are used to disrupt biofilms, it is always a challenge to determine an effective method to treat biofilms. Bacteriophages are effective against biofilms. However, a clear comparison between the anti-biofilm effect of a DNA phage versus that of an RNA phage needed attention. Furthermore, the effect of nutrient deprivation on an established biofilm is less studied. We undertook this study to compare the biofilm desorption abilities of T4 (a DNA coliphage), and MS2 (an RNA coliphage). In addition, this study employs quantitative RT-PCR to test the expression of the genes responsible for biofilm formation. Natural biofilms were formed from the microorganisms residing in the recreational water samples. The pure-culture E. coli biofilms were formed from two different strains of E. coli; 11303 E. coli (T4 host), and C3000 E. coli (MS2 host). All C3000 E. coli biofilms were allowed to form in the presence of 0.15% solution of Ampicillin and Streptomycin diluted 1:1000 with Tryptic Soy Broth. The presence of ampicillin and streptomycin aided with successful MS2 phage infection. The established natural biofilms and pure-culture E. coli biofilms were separately treated with Tryptic Soy Broth, Phosphate Buffered Saline, T4 phage suspension, and MS2 phage suspension. Biofilm desorption was assessed by measuring the optical density of treated natural biofilms, and by biofilm assays performed with treated pure culture E. coli biofilms. Results show similar biofilm desorption abilities between T4 and MS2 coliphages. Surprisingly, both natural and pure-culture biofilms were significantly desorbed upon nutrient deprivation. We tested the expression of the waaC gene which codes for an enzyme that forms lipopolysaccharide. While the expression of waaC gene was downregulated upon nutrient deprivation in 11303 E. coli biofilm, this expression was induced upon nutrient deprivation of C3000 E. coli biofilm that was formed in the presence of ampicillin and streptomycin antibiotics. T4 phage infection resulted in higher waaC transcripts in 11303 E. coli. Whereas, C3000 E. coli biofilm infected with MS2 phage had reduction in waaC gene expression. Our results thus far indicate a possibility of a presence of distinct biofilm desorption mechanisms upon coliphage treatment and from lack of nutrients.