Submitted to: International Congress of Virology
Publication Type: Abstract only
Publication Acceptance Date: 6/13/2002
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Most detailed studies of phage infection focus on a few model coliphages and host strains in rich, well-aerated medium. However, interest is rapidly growing in a range of natural and applied effects of phage for bacterial control, from the oceans to the barnyard to human therapy. Our particular focus is on T-even phage infection of various E. coli under anaerobic and nutrient-restricted conditions - a topic of particular interest since T-even phages are key components in the therapeutic cocktails used against enteric bacteria. We have found that most of the phages tested still infect the same subset of E. coli hosts under conditions of anaerobic fermentation (as in the rumen) and anaerobic respiration (as in the colon). However, the infection parameters are very different, and lysis inhibition times as long as 27 hours have been observed. Also, there is a general assumption that T-even phages do not infect stationary-phase cells, even aerobically. Surprisingly, we find that after E. coli has been incubated in Luria broth or M9 for up to 20 days, T4 still injects efficiently and makes stable infective centers that are able to form plaques when plated up to 24 hours later. In this "hibernation" mode, phages are only formed after nutrients are added to the infected cells; most of the same few "lag phase" proteins are made as in uninfected cells before host protein synthesis is terminated and all the cells convert to making phage. This is in sharp contrast to the immediate termination of host transcription and translation in anaerobic cells. These sorts of variations in infection patterns under various conditions help explain how very virulent phages like T4 coexist so effectively and ubiquitously with their hosts in nature. They also suggest that phages selected for therapeutic use should also be analyzed under conditions approaching those of the human or animal body.