Observation of a Peak in T4 Phage Development in Escherichia coli Biofilm Grown on Millipore Filters for Four Days

Abstract

Escherichia coli biofilms are aggregate communities of stationary cells that are known to be inefficient in producing T4 bacteriophage progeny. Previous publications have shown a peak in viral titers in four-day old biofilms infected with T4 phage. A novel method of studying phage infectivity in biofilms grown on LB agar was devised. T4 phage infectivity of E. coli biofilms grown in LB broth was compared to infectivity on LB agar. A peak in infectivity at day four was observed for both cultures. Viability of each biofilm was assessed using spread plates to enumerate the population of cells. A large peak in biofilm viability was observed for both broth and agar cultures at day four, which corresponds to the spike in phage titres. Moreover, viability of the biofilms decreased after infection with T4 phage, suggesting that biofilms are perhaps more capable of producing T4 phage progeny at day four because they are more proliferative at that age. These results indicate that the observations seen in phage infections of biofilms grown in LB broth are reproducible in infections of biofilms grown on LB agar. However, the latter method to culture biofilms produces low cell viability counts, suggesting that the method must be further validated and optimized before concluded as reliable.